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Quantum key distribution (QKD)1,2 has the potential to enable secure communication and information transfer3. In the laboratory, the feasibility of point-to-point QKD is evident from the early proof-of-concept demonstration in the laboratory over 32 centimetres4; this distance was later extended to the 100-kilometre scale5,6 with decoy-state QKD and more recently to the 500-kilometre scale7-10 with measurement-device-independent QKD. Several small-scale QKD networks have also been tested outside the laboratory11-14. However, a global QKD network requires a practically (not just theoretically) secure and reliable QKD network that can be used by a large number of users distributed over a wide area15. Quantum repeaters16,17 could in principle provide a viable option for such a global network, but they cannot be deployed using current technology18. Here we demonstrate an integrated space-to-ground quantum communication network that combines a large-scale fibre network of more than 700 fibre QKD links and two high-speed satellite-to-ground free-space QKD links. Using a trusted relay structure, the fibre network on the ground covers more than 2,000 kilometres, provides practical security against the imperfections of realistic devices, and maintains long-term reliability and stability. The satellite-to-ground QKD achieves an average secret-key rate of 47.8 kilobits per second for a typical satellite pass-more than 40 times higher than achieved previously. Moreover, its channel loss is comparable to that between a geostationary satellite and the ground, making the construction of more versatile and ultralong quantum links via geosynchronous satellites feasible. Finally, by integrating the fibre and free-space QKD links, the QKD network is extended to a remote node more than 2,600 kilometres away, enabling any user in the network to communicate with any other, up to a total distance of 4,600 kilometres.

This paper describes the scientific objectives and payloads of Tianwen-1, China’s first exploration mission to Mars. An orbiter, carrying a lander and a rover, lifted-off in July 2020 for a journey to Mars where it should arrive in February 2021. A suite of 13 scientific payloads, for in-situ and remote sensing, autonomously commanded by integrated payload controllers and mounted on the orbiter and the rover will study the magnetosphere and ionosphere of Mars and the relation with the solar wind, the atmosphere, surface and subsurface of the planet, looking at the topography, composition and structure and in particular for subsurface ice. The mission will also investigate Mars climate history. It is expected that Tianwen-1 will contribute significantly to advance our scientific knowledge of Mars.

This study explored an infrared/laser dual-mode compound detection mode. To be specific, the infrared system and laser radar were combined in common path, and the target at a far distance can be recognized, tracked and located using infrared-guided laser-detection mode. The combination of the two single-mode detection techniques, namely, infrared passive imaging and laser active detection, can complement their own advantages, thereby achieving the acquisition of multi-dimensional information of the target such as the azimuth angle, the pitch angle, the velocity, and the range. To enhance the laser’s coherent detection efficiency, a piezoelectric-driven double-sided fast-steering mirror was innovatively developed, which realized emission, receiving, and registration of laser with the use of two reflection sides of a mirror. This study proposed the system indexes and overall architecture in accordance with actual application requirements, and developed an infrared/laser compound detection prototype. The pointing range, the scanning velocity of the system, the infrared target detection, and recognition as well as the range and velocity measurement performances of the linear frequency modulation (LFM) continuous wave laser were examined in depth. Finally, an outdoor scaled experiment at a range of 40 m was designed. The experimental results proved that the designed system can meet the expectations in performance.

Mars surface composition detector (MarSCoDe) is a scientific instrument suite onboard the Mars rover of the “Tianwen-1” mission, which uses laser-induced breakdown spectroscopy and shortwave infrared spectroscopy to detect the composition of soils and rocks at the surface of Mars. The optical head unit (OHU) is the core hardware of MarSCoDe, containing a Cassegrain telescope and other optical modules for lasers generation and signals transmission. The unit lacks thermal control resources and is located outside the rover’s cabin, which will directly face the Martian surface drastic temperature changes. We introduce the optomechanical designs that realize the lightweight and high thermal stability of the OHU optical system, especially the designs and implementations of the semiopen primary mirror based on silicon carbide and the fully closed optical bench based on carbon fiber-reinforced polymer. Meanwhile, the advantages and difficulties of silicon carbide, long carbon fiber-reinforced silicon carbide composites, and carbon fiber-reinforced polymer materials used for small and compact optomechanical systems are discussed. Subsequently, the environmental adaptability of the telescope system of OHU was studied through analytical and experimental methods, which show that it can achieve the required optical performance over a temperature range of approximately 100°C.

Mars Surface Composition Detector (MarSCoDe) is a scientific payload onboard the Mars rover of China’s Tianwen-1 mission. With the capability of 1.6∼7 m remote detection and analysis, MarSCoDe instrument suite consists of a two dimensional pointing mirror and an optical head outside the rover cabin, a Laser Induced Breakdown Spectroscopy (LIBS) spectrometer and a Short Wave Infrared (SWIR) spectrometer collectively covering 240∼2400 nm and a master controller unit inside the rover body, calibration target sets, optical fibers and power cables connecting the internal and external units. Combining the techniques of active LIBS, passive SWIR and micro-imaging, MarSCoDe provides functions including elemental composition discrimination and quantitative determination, classification of rock and soil characteristics, sample texture imaging and characterization of plasma-excited area. This paper introduces MarSCoDe mainly in terms of scientific objectives, design requirements, assembly and implementation, spectral and radiation calibration, and performance verification. The LIBS laser irradiance on the target can soundly exceed 10 MW/mm2, and the performance of the LIBS module operated at different temperatures has been tested. The field of view of the SWIR spectrometer is 36.5 mrad. The micro-imager can extract the central pixel area of 320 × 320 and 1024 × 1024, and the former is binned into 64 × 64. The 2D pointing mirror has a wide forward detection range and a narrow backward calibration range, with the pointing pitch accuracy better than 0.133°.

The main objective of this study is to develop a Hapke photometric model that is suited for Chang’E-1 (CE-1) Interference Imaging Spectrometer (IIM) data. We first divided the moon into three areas including ‘maria’, ‘new highland’ and old ‘highland’ with similar photometry characteristic based on the Hapke parameters of the moon derived from Lunar Reconnaissance Orbiter Camera (LROC) Wide Angle Camera (WAC) multispectral data. Then, we selected the sample data in the ‘maria’ area and obtained a new set of Hapke model’s parameters that can best fit these data. Result shows that photometric correction using Hapke model with these new derived parameters can eliminate the effect of variations in viewing and luminating geometry, especially ‘opposition surge’, more efficiently than the empirical model. The corrected mosaic shows no significant artifacts along the tile boundaries, and more detailed information of the image can be exhibited due to a better correction of ‘opposition surge’ at small phase angle (g

In the experiment of quantum key distribution in free space, the polarization degradation and the propagation directions of the four polarization-encoded quantum light beams vary relative to each other and reduce the service life of the terminals, which severely limits their practical application. In order to solve the above problems, we report research on real-time polarization compensation methods for dynamic quantum communication terminals. The difference from Micius is that our proposed system emits quantum lights through the same optical fiber to ensure high-precision coaxiality, and uses a set of wave plates to compensate for both the polarization degradation caused by single-mode fiber and the polarization change caused by optical elements. We introduce our polarization compensation methods in detail and present a design for a dynamic polarization compensation scheme and experimental device. The final experimental polarization extinction ratio of our dynamic optical system is greater than 30 dB after real-time polarization compensation, which meets quantum communication requirements. The successful implementation of this method can effectively improve terminal service life and provide a foundation for the practical applications of quantum communication.

We report a pulsed wavelength-agile laser near 765 nm, which was frequency doubled from an erbium-doped fiber amplifier for oxygen A-band spectroscopy. A single frequency distributed feedback laser around 1529.6 nm was employed as the seed. After three stages of amplification, its average power was boosted to 610 mW and was then frequency doubled via a 15-mm-long MgO:PPLN crystal with the highest conversion efficiency of 34%. Thanks to the short crystal length expanding the acceptance bandwidth, a power difference of only 36% for the second harmonic output was achieved within the whole wavelength tuning range benefitting low-noise remote sensing. The measured oxygen transmission spectra using a 0.5-meter-long gas cell with multiple passes were mostly in good agreement with the calculations from HITRAN 2012 database indicating the capability of our laser for oxygen A-band related remote sensing.

Shortwave infrared (SWIR) imaging technology attracts more and more attention by its fascinating ability of penetrating haze and smoke. For application of spaceborne remote sensing, spatial resolution of SWIR is lower compared with that of visible light (VIS) wavelength. It is difficult to balance between the spatial resolution and signal to noise ratio (SNR). Some conventional methods, such as enlarging aperture of telescope, image motion compensation, and analog time delay and integration (TDI) technology are used to gain SNR. These techniques bring in higher cost of satellite, complexity of system or other negative factors. In this paper, time delay and digital accumulation (TDDA) method is proposed to achieve higher spatial resolution. The method can enhance the SNR and non-uniformity of system theoretically. A prototype of SWIR imager consists of opto-mechanical, 1024 × 128 InGaAs detector, and electronics is designed and integrated to prove TDDA method. Both of measurements and experimental results indicate TDDA method can promote SNR of system approximated of the square root of accumulative stage. The results exhibit that non-uniformity of system is also improved by this approach to some extent. The experiment results are corresponded with the theoretical analysis. Based on the experiments results, it is proved firstly that the goal of 1 m ground sample distance (GSD) in orbit of 500 km is feasible with the TDDA stage of 30 for SWIR waveband (0.9–1.7 μm).

We have developed an amplified frequency double-shifting loop with a bidirectionally operated acousto-optic modulator as the in-loop frequency shifter to generate a frequency-stepped pulse train (FSPT) with frequency spacing twice as much as its operation frequency. Based on this configuration, a FSPT with 51 equidistant optical frequencies and 800 MHz frequency spacing around 1572 nm was generated, covering the whole R16 absorption peak of C O 2 for direct spectral measurement in the time domain. The retrieved transmission curve from a C O 2 gas cell with concentration of 4.02% is in good agreement with the calculated Voigt lineshape from the HITRAN database. The maximal relative errors between the measured and calculated results are within 0.5% for each optical frequency, indicating its great potential for practical C O 2 monitoring.

We have demonstrated, to the best of our knowledge, the first photon-counting shallow-water bathymetric Lidar based on a fiber-laser-pumped green laser. An Ytterbium-doped, fiber master oscillator power amplifier is developed as the fundamental laser, delivering 2.3 W pulses with widths of 450 ps at 500 kHz and bandwidths of 0.04 nm centered at 1064.1 nm. Its wavelength is frequency doubled to 532 nm, located within the transparent window of water, with an average power of 0.95 W. A coaxial transmitting and receiving photon-counting shallow-water bathymetric Lidar is constructed based on the fiber-laser-pumped green laser. Subsequent daytime shipborne experiments in Thousand-Island Lake show that the largest slope distance of ~3.1 m, more than twice as much as the Secchi depth (~1.5 m), can be achieved indicating its capability of practical shallow-water bathymetry.

A plane wave aspheric surfaces test is simpler and easier to assemble than a spherical wave test. An optical system combining Dall with Offner null compensation using a plane wave is proposed for measuring large-aperture and large-relative-aperture aspheric concave surfaces. One back compensation lens and one front compensation lens are used in the system, which can realize a high-precision null test. Based on the third-order aberration theory, the normalized theoretical parameters are calculated by formula derivation, and then are optimized after analysis. The design characteristic is compared with the classical plane wave Offner null test. A prototype experiment of the proposed method is carried out with a parabolic mirror of 500 mm diameter, at relative aperture 1/1, showing that RMS surface error of λ / 40 can be obtained.

We report a comprehensive design procedure for passively Q -switched monolithic Nd : YAG / Cr 4 + : YAG microchip lasers to realize operation conditions of the pulse repetition rate (PRR) > 100 kHz and pulse width (PW) < 400 ps , simultaneously. Crucial parameters including effective pump power and waist diameter of the pump laser, doping concentration and thickness of the Nd:YAG crystal, initial transmittance ( T 0 ) of the Cr 4 + : YAG crystal, as well as the reflectivity of the output coupler are all considered during the design process. Two single-longitudinal-mode-operated lasers are designed and constructed according to the numerical results. The lengths and doping concentrations of Nd:YAG for both microchips are optimized to be 0.5 mm and 2%, respectively. A PRR up to 170 kHz and PW of ∼ 370 ps are measured under the pump power of 2.6 W for a microchip with T 0 of 0.85. A slightly lower PRR of 118 kHz with a shorter PW of ∼ 320 ps is also achieved under the same pump power for another microchip with T 0 of 0.8. The related pulse energies for the two microchips are ∼ 2.1 µ J and ∼ 1.8 µ J , respectively. To the best of our knowledge, these results are among the highest PRRs achieved for passively Q -switched Nd : YAG / Cr 4 + : YAG microchips with PWs < 400 ps .

Terahertz communication is recognized as a transformational technology that can meet the future demands of point-to-point communication. The study of terahertz atmospheric transmission characteristics is important for guiding the terahertz communication window selection process. In this report, based on the modified ITU-R P.676-10 model, we determined that the terahertz communication windows above 100 GHz were located at the bands at approximately 140, 220, 340, 410, and 460 GHz, which is verified by recent experiments. We also verified the feasibility of indoor point-to-point communication by the 110 m transmission experiment through the communication window around 460 GHz.

To explore the reliability and validity of radiofrequency (RF) ablation in treating uterine fibroids.We evaluated 63 patients who underwent hysterectomy to treat multiple fibroids. Thirty patients immediately underwent abdominal hysterectomy after the fibroids were ablated under direct vision. Thirty-three patients first experienced trans-vaginal ablation with the guidance of a baseline ultrasound. We performed abdominal or trans-vaginal hysterectomy 72 h later. The tissues in the centre of the ablated lesion (group A), at the edge of the ablated lesion (group B), 1 cm away from the ablated edge (group C) and the control group were sampled. We observed ultra-structure changes by transmission electron microscopy and detected survivin expression with Western blot analysis.According to transmission electron microscopy, the ultra-structure of fibroid cells in groups A and B was damaged. However, in group C, the ultra-structure was normal. Compared with the control group, survivin expression was significantly decreased. Meanwhile survivin expression was significantly increased with the distance to the ablated centre (p 0.05).Radiofrequency ablation caused permanent and irreversible damage to fibroid cells and decreased survivin expression, which provided reliable clinical evidence for the success of radiofrequency ablation treating uterine fibroids.

We perform decoy-state quantum key distribution between a low-Earth-orbit satellite and multiple ground stations located in Xinglong, Nanshan, and Graz, which establish satellite-to-ground secure keys with similar to kHz rate per passage of the satellite Micius over a ground station. The satellite thus establishes a secure key between itself and, say, Xinglong, and another key between itself and, say, Graz. Then, upon request from the ground command, Micius acts as a trusted relay. It performs bitwise exclusive OR operations between the two keys and relays the result to one of the ground stations. That way, a secret key is created between China and Europe at locations separated by 7600 km on Earth. These keys are then used for intercontinental quantum-secured communication. This was, on the one hand, the transmission of images in a one-time pad configuration from China to Austria as well as from Austria to China. Also, a video conference was performed between the Austrian Academy of Sciences and the Chinese Academy of Sciences, which also included a 280 km optical ground connection between Xinglong and Beijing. Our work clearly confirms the Micius satellite as a robust platform for quantum key distribution with different ground stations on Earth, and points towards an efficient solution for an ultralong-distance global quantum network.

Coupling of scattering light in space into a single-mode fiber is a key technology in the process of developing the Laser Doppler Velocity Radar. In order to make sure that the radar can get the longest detect distance, we have discussed the method of determining the key parameters of the receiver/transmitter common-path optical system based on the singlemode fiber coupling, from the points of laser radar detect distance equation, principle of single-mode fiber coupling efficiency reach maximum, and considerations of laser transmitter. In the engineering development process of an laser Doppler velocity radar, we have designed the optical system which fulfills the requirement of detect distance bigger than 3Km, then given out simulation results of single-mode fiber coupling efficiency versus lens spherical aberration, fiber defocus and fiber tilt. The tolerance analysis result indicates that the coupling efficiency will bigger than 52% under the usual levels of optical manufacture and assembly. At last we designed specialized equipment for testing the single-mode fiber coupling efficiency of the system we developed, the results showed that after mechanical vibration and thermal experiments, the single-mode coupling efficiency is 55.9%, and in the operating temperature range of 20±3°C, the lowest coupling efficiency is 45%, which is still bigger than 35% as the system required to make sure the detect distance bigger than 3Km.

Space-based laser altimetry, which measures the planetary surface topography based on time-of-flight ranging, is an important technology for earth and deep space exploration. The development history and current status were sorted out systematically and development in three directions was proposed, including multi-beam observation, underwater terrain observation of offshore and islands and laser active multispectral detection. It was suggested that some key technologies should be developed, including infrared single photon detection, ultra-narrowband optical filtering, multiphoton resolution detection, single-photon data on-board preprocessing and high conversion efficiency laser and nonlinear optical frequency conversion, to promote the further development of Chinese space laser altimetry technology.

In the Chinese moon exploration project “ChangE-3”, the laser telemeter and lidar are important equipments on the lunar landing vehicle. A low-thrust vernier rocket engine works during the soft landing, whose plume may influence on the laser equipments. An experiment has first been accomplished to evaluate the influence of the plume on the propagation characteristics of infrared laser under the vacuum condition. Combination with our theoretical analysis has given an appropriate assessment of the plumeʼs effects on the infrared laser hence providing a valuable basis for the design of lunar landing systems.

Objectives Amelogenins are proposed to be responsible for enamel matrix derivative (EMD)-induced periodontal regeneration; however, heterogeneity of amelogenins makes it challenging to purify the full-length proteins. This study has been carried out to express and purify a recombinant full-length human amelogenin protein (rHhAm175) in the eukaryotic yeast Pichia pastoris, and further compare biological responses of human periodontal ligament fibroblasts (PDLFs) to rHhAm175 and porcine EMD (pEMD). Materials and methods Human cDNA encoding a 175-amino acid amelogenin was subcloned into the pPIC3.5K vector. The rHhAm175 expressed in P. pastoris GS115 (Mut+) was purified and characterized. We examined cell attachment, migration and proliferation responses of human PDLFs to rHhAm175 and pEMD respectively, and characterized associated changes of proliferation-related intracellular signalling molecules, including extracellular signal response kinase (ERK) and Akt kinases/protein kinase B (Akt/PKB) kinases. Results The purified rHhAm175 was confirmed to be molecular mass 22 021.13 Da, phosphorylated human amelogenin, and alone significantly promoted proliferation and migration of human PDLFs to an extent comparable to that of pEMD. Cell attachment was increased over the first 60 min incubation with rHhAm175 or pEMD. Both rHhAm175 and pEMD induced PDLF mitogenesis via extracellular signal response kinase (ERK1/2), but not by Akt kinases/protein kinase B (Akt/PKB). Conclusions rHhAm175 modulated cell activities of human PDLFs, to a comparable extent as porcine EMD. These data suggest that rHhAm175 might be used to induce periodontal tissue regeneration.

A series of Ir-supported catalysts were prepared by incipient impregnation method. The activity of Ir catalyst for the simultaneous removal of soot and NOx in the presence of rich-oxygen and H2O as well as SO2 has been studied, and the effects of calcination temperature, calcination time, calcination atmosphere, loading, carrier and precursor on its catalytic performance has also been investigated. Ir catalyst exhibits a high activity. With the calcination temperature increasing, Ir catalytic activity increases firstly and then decreases, and the optimal calcination temperature is 900°C. With the calcination time prolonged, Ir catalytic activity also increases firstly and then decreases, and the optimal calcination time is 3h. The optimal calcination atmosphere is 1.5vol.% H2/N2. Support material and precursor have a little effect on the catalytic activity, and the order is Ir/TiO2 > Ir/ZrO2 > Ir/SiO2 > Ir/Al2O3 > Ir/ZSM-5 and IrCl (CO)[P(C6H5)3]2/ZrO2 > H2IrCl6·6H2O/ZrO2 > IrCl4·4H2O/ZrO2.

The design and operation of the Laser Altimeter of CE-1 Payloads System are presented in this paper. The paper includes the design of the system and spacecraft-level laser, the description of the emitting-system and receiving system, and the testing of the laser altimeter. The CE-1 laser altimeter is the first Chinese deep-space probe using a laser. It has one beam and operates at 1 Hz, with a nominal accuracy of 5 m. The laser altimeter has operated successfully in lunar orbit since November 28, 2007. It has obtained 9120 thousand data values about the lunar altitude.

More than 3 million range measurements from the Chang’E-1 Laser Altimeter have been used to produce a global topographic model of the Moon with improved accuracy. Our topographic model, a 360th degree and order spherical harmonic expansion of the lunar radii, is designated as Chang’E-1 Lunar Topography Model s01 (CLTM-s01). This topographic field, referenced to a mean radius of 1738 km, has an absolute vertical accuracy of approximately 31 m and a spatial resolution of 0.25° (∼7.5 km). This new lunar topographic model has greatly improved previous models in spatial coverage, accuracy and spatial resolution, and also shows the polar regions with the altimeter results for the first time. From CLTM-s01, the mean, equatorial, and polar radii of the Moon are 1737103, 1737646, and 1735843 m, respectively. In the lunar-fixed coordinate system, this model shows a COM/COF offset to be (−1.777, −0.730, 0.237) km along the x, y, and z directions, respectively. All the basic lunar shape parameters derived from CLTM-s01 are in agreement with the results of Clementine GLTM2, but CLTM-s01 offers higher accuracy and reliability due to its better global samplings.

In this paper, we report an abnormal laser deflection phenomena based on quadratic electro-optic effect in copper doped KTN crystal. Cu:KTa0.62Nb0.38O3 block with size a×b×c = 2.8mm×2.6mm×12.5mm was used as beam deflection element. 75mrad beam deflection angle were observed under 1KV voltage when the laser beam across the c direction of the sample at room temperature. The special features of our experiment are that the direction of laser beam deflect perpendicular to the electric field direction, and the angular size and direction of the deflection beam remain unchanged when the electric field direction reverse. We believe that the interaction of graded refractivity and electro-optic effect leads to these special features. Besides of the special deflection mode, the deflection efficiency of our experiment also reached the world advanced level.

Testing the predictions of galaxy formation scenarios on mildly- and non-linear regimes requires the detection from space of ultra-low surface brightness features both around galaxies (dwarf satellites) and in the cosmic web (filaments). The requirements of such a space mission imply innovative concepts for fast, wide-field, distortion-free telescopes. Several optical designs, based on freeform mirrors, are presented and compared here to address these stringent constraints on space-borne, wide field drift-scanning imaging. An optimal solution is presented, showing that a telescope with f /2, 4° × 2° FoV, with a 50 cm pupil can achieve the required exquisite image quality, free of distortion, with an optimal SNR in the detection of ultra-low surface brightness.

Photon counting lidar has an ultra-high sensitivity which can be hundreds even thousands of times higher than the linear detection lidar. It can significantly increase the system’s capability of detection rang and imaging density, saving size and power consumings in airborne or space-borne applications. Based on Geiger-mode Si avalanche photodiodes (Si-APD), a prototype photon counting lidar which used 8 APDs coupled with a 1×8-pixel fiber array has been made in June, 2011. The experiments with static objects showed that the photon counting lidar could operate in strong solar background with 0.04 receiving photoelectrons on average. Limited by less counting times in moving platforms, the probability of detection and the 3D imaging density would be lower than that in static platforms. In this paper, a latest fiber array coupled multi-channel photon counting, 3D imaging, airborne lidar system is introduced. The correlation range receiver algorithm of photon counting 3D imaging is improved for airborne signal photon events extraction and noise filter. The 3D imaging experiments in the helicopter shows that the false alarm rate is less than 6×10 -7 , and the correct rate is better than 99.9% with 4 received photoelectrons and 0.7MHz system noise on average.

We design a kind of imaging LiDAR with sixteen channels, which consists of a fiber laser source, dual scanning galvanometers, range measurement circuits and information processing circuits etc. The image LiDAR provides sixteen range measurements for one laser shot and the distance accuracy of each channel is about 4cm. This paper provides a calibrate method to correct point cloud images captured with the multi-channel LiDAR. The method needs to construct different slanted planes to cover the imaging field, and establish precise plane equations in the known ground coordinates, then fit planes with point clouds data and calculate correction parameters of all channels through the error model. The image accuracy is better than 5cm processed by this calibration method.

In the day time of the Moon surface, the strong illumination from high altitude and high albedo rate radical craters will introduce the illumination effect on observing the nearby low altitude, low albedo rate and shallow small slop rate area seriously, and even can “hide” the later area from the light. Based on the lunar global topography model obtained by Chang’E-1 mission, and by comparing with the lunar gravity model, a volcano named “YUTU Mountain” has been identified. It is a volcano with diameter of ∼300 km and height of ∼2 km located at (14°N, 308°E) in Oceanus Procellarum. Besides, the DEM of another volcano named “GUISHU Mountain” in the same area has been improved. This new discovery will benefit the study of lunar magmatism and volcanism evolution in the nearside of the Moon.

We report a novel burst-mode-operated sub-nanosecond fiber Master Oscillator, Power Amplifier (MOPA) system incorporating direct seed-packet shaping without external modulators. A fast digital-to-analog converter with 1 Gsps sampling rate and 16 bit resolution was developed to control the pulse amplitudes and sequences of a distributed feedback semiconductor seed laser to realize packet-shaped burst mode operation. Optical pulses with durations as short as 700 ps and peak power as high as 1 W can be generated from the seed by applying proper reverse voltages after positive electrical pulses to the laser driver to cancel the residual charges at its gate electrode. The average power of the laser can be amplified to nearly 40 W with FWHM spectral linewidth of ~0.12 nm after three stages of polarization maintaining fiber amplifiers. Different packet shapes including ramp-off, Gaussian, square and double rectangle can be produced from the fiber MOPA by finely pre-shaping the seed pulse bursts. It is believed that such a laser has provided a cost-effective solution to the generation of pulse bursts with arbitrary packet shapes for different practical applications including material micromachining and nonlinear frequency conversion.

We have experimentally demonstrated a high power linearly polarized, dual wavelength frequency-modulated continuous-wave (FMCW) fiber laser with master-oscillator power-amplifier (MOPA) configuration, which is specially designed for simultaneous coherent distance and speed measurements. Two single longitudinal mode laser diodes working at 1550.12 and 1554.13 nm are employed as the seeds of the fiber MOPA. The wavelengths of the seeds are externally modulated by two acousto-optic frequency shifters (AOFSes) with a symmetrical sawtooth wave from 330–460 MHz in the frequency domain. The modulation periodicities for the two seeds are 26 and 26.3 μs, respectively, by which the distance ambiguity can be eliminated and therefore the detection range can be extended to a great extent. The seeds are then amplified independently to reduce their power differences during frequency modulation. After being coupled and boosted with three successive fiber amplifiers, an output power of 12.1 W is recorded from the FMCW laser with a power instability 18 dB and

Photon counting laser radar is the most sensitive and efficiency detection method of direct-detection laser radar. With the use of Geiger-mode avalanche photodiode (APD) or other single photon detectors, every laser photon could be sufficiently used for ranging and three-dimensional imaging. The average energy of received laser signal could be as low as a single photon, or even less than one. This feature of photon counting laser radar enables ranging under conditions of long range, low laser pulse energy, and multi-pixel detection, while receiver size, mass, power, and complexity of laser radar are reduced. In this paper, a latest multi-channel photon counting 3D imaging laser radar system using fiber array coupled Geiger-mode avalanche photodiode (APD) is introduced. Detection model based on Poisson statistics of a photon counting laser radar is discussed. A laser radar system, working under daylight condition with ultra-low signal level (less than single photon per pulse), has been designed and analyzed with the detection model and photon counting three-dimensional imaging theory. A passively Q-switched microchip laser is used to transmit short sub-nanosecond laser pulses at 532nm. The output laser is divided into 1×8 laser spots, which correspond to 8 Geiger-mode avalanche photodiodes coupled by a 1×8-pixel fiber array. A FPGA based time-to-digital converter (TDC), which is designed by delay line interpolation technology, is used for multi-hit signal acquisition. The algorithm of photon counting three-dimensional imaging is developed for signal photon events extraction and noise filter. Three-dimensional images under daylight conditions were acquired and analyzed. The results show that system could operate at strong solar background. The ranging accuracy of the system is 6.3cm (σ) while received laser pulse signal level is only 0.04 photoelectrons on average. The advantages and feasibility of photon counting laser radar working at daylight have been demonstrated experimentally.

As an active remote sensor technology, the terrestrial laser scanner is widely used for direct generation of a three-dimensional (3D) image of an object in the fields of geodesy, surveying, and photogrammetry. In this article, a new laser scanner using array avalanche photodiodes, as designed by the Shanghai Institute of Technical Physics of the Chinese Academy of Sciences, is introduced for rapid collection of 3D data. The system structure of the new laser scanner is first presented, and a mathematical model is further derived to transform the original data to the 3D coordinates of the object in a user-defined coordinate system. The performance of the new laser scanner is tested through a comprehensive experiment. The result shows that the new laser scanner can scan a scene with a field view of 30° × 30° in 0.2 s and that, with respect to the point clouds obtained on the wall and ground floor surfaces, the root mean square errors for fitting the two planes are 0.21 and 0.01 cm, respectively. The primary advantages of the developed laser scanner include: (i) with a line scanning mode, the new scanner achieves simultaneously the 3D coordinates of 24 points per single laser pulse, which enables it to scan faster than traditional scanners with a point scanning mode and (ii) the new scanner makes use of two galvanometric mirrors to deflect the laser beam in both the horizontal and the vertical directions. This capability makes the instrument smaller and lighter, which is more acceptable for users.

The pulsed laser range finding has been extensively applied in space exploration, military use and industry, due to its advantages over other methods of non-contact ranging in simplicity, non-cooperativeness of objects, long detecting range and short range acquisition time. The integration of its receiver channel will be beneficial to weight-lightening, miniaturization and mass production of the laser range finder. A transimpedance amplifier for receiver channel of pulsed range finder is designed using 0.6-μm CMOS technology in this work. It consists of transimpedance pre-amplifier, R-2R resistors ladder variable attenuator and post-amplifier. A regulated cascade circuit (RGC) is used to isolate the input capacitor from input node of transimpedance pre-amplifier, reducing the bandwidth suppression caused by large input capacitor. R-2R variable attenuator is implemented for digital gain control, achieving a total gain control range of 42dB with 7 steps and 6dB per step. Simulation shows that the circuit achieves a bandwidth of 83 MHz with the presence of a 5-pF input capacitor, and a maximum transimpedance of 125.5dBΩ, meeting the requirement of high-precision pulsed laser range finder.

Because infrared system detects the radiation energy of the target, it has the ability to work all day that the visible-light detection system cannot achieve, at the same time, infrared system is a passive detection system, does not need active detection technology such as radar, which requires large radiation power or a larger expandable antenna. It is more suitable for airborne applications, therefore, infrared imaging based on the aircraft and aerostat platform, has been an important means of monitoring the ground. However, due to detector limitations, the spatial resolution of current infrared cameras or spectrographs and the total field coverage of view are generally not satisfied the customer's requirements. This paper proposes an airborne infrared camera imaging method based on multi-planar arrays, using frame-type imaging array. In order to provide large ground coverage together with good spatial resolution, the mirror is drove to scan rapidly by the galvanometer. The scanning mirror works at staring imagery mode. During multi-planar detectors exposure and imaging, the mirror moves to the staring position. There is more than 10 % overlapping sensor foot prints between two adjacent frames, and the functions of image matching algorithms are used to ensure the seamless butting. This imaging method improves the system integration time, and effectively improves the sensitivity of infrared systems; frame-type imaging solves the serious image distortion caused by the platform attitude.

For a direct-detection 3D imaging ladar, the use of Geiger-mode avalanche photodiode (APD) could greatly enhance the detection efficiency of the receiver since each range measurement requires only one detected photon. Single photon sensitivity of the detector offers significant advantages in reducing receiver size, mass and power and reducing laser complexity. This paper studies the 3D imaging ladar using APDs which are actively quenched and gated to operate at Geiger-mode to detect short weak laser echo pulse. The detection model of this detector as well as the detection probability and false alarm probability for this ladar is analyzed and discussed. The analysis shows that the major factors influencing system design are the background light noise and the dead time of the Geiger-mode APD. Then the noise which affects the false alarm probability is analyzed and calculated and the measures to extract the weak signal echo from a high noise background are put forward. The research also shows that using a detector array instead of a single detector could reduce the false alarm probability by orders of magnitude. Finally a 3D imaging brassboard system which utilizes Geiger-mode APDs, a fast pulse, high repetition rate laser, and an optical scanner is described, and some experimental results obtained by this system are presented and analyzed. The results suggest that if the background light noise is sufficiently suppressed, 3D images of the targets could be successfully taken by the ladar using Geiger-mode APDs.

landing on the moon, Mars or other planets safely is of great significance for the success of space exploration. Compared with the previous cameras and human vision to look for a safe landing area, LIDAR can quickly detect the undesired zone with gravels,craters,scarps and other dangerous features. A type of laser scanner, which is designed by Shanghai Institute of Technical Physics of the Chinese Academy of Sciences (SITP) for safe landing on planets, is introduced. The single laser beam is expanded to linear beams through a cylindrical lens and the scanning direction is controlled by two-dimensional tilt mirrors. The reflected laser beams gather at avalanche diode detectors of the focal plane of telescope. The signal of every cell is processed individually and the planetary surface can be achieved by the fast two-dimensional scanning. At present, the designed linear array LIDAR is under prototype development, this paper describes its principle, and detection capability of single cell LIDAR for dangerous terrain.

A ground-based long-wave hyperspectral imaging spectrometer (LWHIS) is designed and simulated. The spectrometer is based on a focal plane array detector with a spectral response that covers the range 7700 to 9300 nm. Optical system of this instrument is all-reflective and provides up to 30 continuous spectral channels with 54 nm of dispersion per pixel. The entrance aperture is 20 mm and feeds an F/2 telescope front end. The telescope has a 11-deg field of view with 256 spatially resolved elements (detector pixel size is 30 μm). To get high enough signal noise rate (SNR), no concern about the electronic part, first, the cool stop of the detector is used as soon as possible, and second, background thermal radiance of the opto-mechanical system seen by the focal plane must be suppressed. Thus, the entire instrument is set in a vacuum chamber and the opto-mechanical subsystem is cooled by liquid nitrogen. The background thermal radiance verse different cases is discussed. Based on the radiation simulation and analysis, if the opto-mechanical subsystem of the spectrometer within the vacuum chamber is cooled blew 100 Kelvin, significant performance gains can be realized. The design and simulation provides an example for illustrating the design principles specific and radiation simulation to this type of system.

Laser coherent detection makes use of the coherence of laser to pick up weak laser signal by an optical LO (local oscillator) signal. Compared to direct detection, coherent detection has higher sensitivity and could get the frequency difference between incident signal and LO. Traditional coherent detection systems are composed of free space optical components; the systems were complicated and hard to adjust. We built an all-fiber MOPA heterodyne laser detection system by DFB laser, AO frequency Shifter, polarization beam splitters, polarization maintaining couplers and balanced photo receivers. Because the coherence of laser beams is relative to the alignment of polarizations states, our system uses double-balanced structure. The balanced detection structure greatly reduces the relative intensity noise of the LO. In the article, the theory of coherent detection and the double balanced coherent detection are presented; the design of detection electronic circuits is also discussed. The high coherent efficiency of fiber-optic detection system and high sensitivity of coherent detection are proved by experiment. Some problems caused by fiber optics are also introduced.

Based on the digital array radar (DAR), conformal array, sparse array, multi-input multi-output (MIMO) system and Ubiquitous radar, a new radar system-the Opportunistic digital array radar (ODAR) has been proposed in recent years. The concept, principle and characteristics of the ODAR are presented in this paper. Furthermore, the challenges are also analyzed from the aspects of the random element distributing, digital beam forming, signal transmission synchronization and adaptively intelligent decision, etc. The Genetic Arithmetic (GA) is exploited to carry out the beam shaping optimization of 3-D randomly distributed elements. The simulation results indicate that the method is feasible. The mathematics models of phase perturbation are preformed to implement the clock synchronization and adaptive beam steering. The adaptive synchronization design of signal transmission is adopted to improve the synchronization precision. The phase perturbation module is built to analyze the influence on ODAR specification by optical fibre or wireless links. (4 pages)

This paper introduces a skill but practical optical model of developing wide field of view push-broom hyperspectral imager. Usually, the field of view of a push-broom hyperspectral imaging sensor is less than 30 degrees, and it can not meet the requirement for typical earth observation mission. This paper addresses the difficulty of developing wide field of view imaging sensor and presents an optical model of wide field of view hyperspectal imager. The optical model of hyperspectral imager is composed of a large field of view lens, a long entrance slit, two spectrometers and two area detector arrays and has a cross-track field of view of 60 degrees. The lens images a ground belt onto the long entrance slit, the slit acts as a field stop and allow only light from a linear belt in the scene to enter the imager. The light passing through the long slit is divided two equal parts using a special skill and it is separated and imaged on the area detector arrays by the two spectrometer. The analysis shows that the wide field of view hyperspectral imager doesn't drop down the spatial resolution.

A compact, actively Q-switched Nd:YAG laser has been developed for laser altimeter in China Chang'E lunar explorer. It passed all space-flight environmental tests at subsystem and satellite successfully, and will be launched in October, 2007. This paper will present it's configuration, specification, and the result of lifetime test.

To explore the feasibility and efficacy of radiofrequency ablation in treating uterine fibroids. Ninety patients with multiple uterine fibroids, who had undergone hysterectomy were included in the study. After the uterus was resected, the temperature of 60, 80, 100°C were adopted to ablate the in vitro fibroid with each temperature dealing with 30 patients. Simultaneously, 5 patients were included, whose in vivo fibroid were ablated with the temperature of 100°C before the fibroids were removed after laparotomy. After the fibroids were ablated, the smooth muscle in the ablated center (group A), the ablated edge (group B) and 1 cm away from the ablated edge (group C) were taken. Then, the samples were stained with hematoxylin and eosin (HE) to examine the histopathological changes, and immunohistochemistry was performed to detect the expression of estrogen receptor (ER) and progesterone receptor (PR). After radiofrequency ablation, the ablated lesions were round, toast tan, and dry on gross appearance. There were no obvious tissue carbonization and there were distinct boundary from periphery tissue. In vitro: On automated analysis, the average optical density of ER and PR in group A, B, and C was lower than the control group (P 0.05). In vivo: Compared with the control group, the average optical density of ER and PR were significantly different among group A, B, and C (P

The method for designing beam expander of near infrared laser altimeter is discussed in the paper. By designing the beam expander with 632.8nm and 1064nm respectively and integrating it with 632.8nm design but compensating the chromatic aberration with 1064nm design with gasket and finally testing the result with 1064nm laser, the beam expander with requirement magnification is integrated. With a simulate detector and a Continuous-Wave (CW) 1064nm laser, an infinite light with divergence of the Field-of-View (FOV) of the telescope is produced. By acquiring the image of this infinite lignt and the laser transmitter at a 4m collimator's focal plane using a CCD camera and adjusting the relative azimuth and pitching of the transmitter and receiver, the alignment of the two subsystems is finished with the decentration less than 5%.

We propose a novel wavelength-locking-free differential absorption lidar system for CO2 sensing. The ON-line wavelength laser was wavelength modulated around a specific CO2 absorption line to ensure that the emission from the ON-line laser hit the atmospheric CO2 absorption line peak twice a cycle. In the meantime, the intensity of the ON-line and OFF-line wavelength lasers were sinusoidally intensity modulated to enhance the SNR of the back-scattered signal. As a consequence, the system configuration was simplified and the measurement error caused by the deviation of CO2 absorption coefficient from the long-time ON-line wavelength drifting was completely eliminated. Furthermore, a more precise calibration method was developed which could simultaneously calibrate the offset and precision of the lidar detector. This method could be applied to other differential-absorption-based lidar systems. The result showed that a measurement precision of 0.525% for the column concentration was achieved in 1 s time interval through a path of 780m. We recorded the CO2 concentration variation for 12 hours starting from mid-night, the result showed that the course of the concentration derived from the DIAL was in good agreement with that of the in situ CO2 sensor only when the status of atmosphere was stable.

An abnormal laser deflection phenomenon in a copper-doped KTa1−xNbxO3 (Cu:KTN) crystal is demonstrated in this Letter. A near-50 mrad beam deflection angle was observed when a voltage of 1.2 kV was applied to a Cu:KTN block with size of 2.8 mm × 1.2 mm × 7.5 mm at room temperature. The special features of this deflection phenomenon are that the laser beam deflection direction is perpendicular to the electric field direction, and the beam deflection angle remains unchanged when the electric field direction is reversed. The operating principle of the phenomenon is investigated and the origin of the deflection phenomenon is attributed to an interaction between the graded refractivity effect and the quadratic electro-optic effect of the crystal.

There is an extensive application requirement of airborne 3D imager in city planning today. An airborne 3D imager has been developed and it is introduced first in this paper. Some solutions in the imager to improve the efficiency and accuracy of 3D imaging for city planning are specially analyzed. After some flight missions of the imager for city planning it provided lots of data of i®digital cityi¯. Through information and image processing a series of images with a scale of 1:10000 are produced. Some typical images and 3D city models of several Chinese cities are given finally.

The real-time acquiring and processing technology of three- dimension (3D) geosciences information is an important field of modern remote sensing. The Airborne Scanning Laser Ranging-Imager Sensor (ASLRIS) is a new generation of remote sensing and mapping system for providing 3D geosciences information. The system integrates the laser altimeter, IR imager, Differential Global Positioning System (DGPS) and Inertial Reference System (INS), by which Digital Elevation Model (DEM) and Georeferenced Image (GI) can be generated quickly and effectively without ground control point. The scanning laser rangefinder and the passive infrared scanning imager share the telescope and the scanning mirror. A suitable optical scanning mode is important to satisfy the demand of high-speed scanning and high-resolution laser ground sampling with limited repetitive rate of laser. The optical scanning of conical mode is studied emphatically comparing to the linear optical scanning mode in this paper, which two have been applied to the ASLRIS. The configuration, fundamental, specification and character of conical scanning technology are analyzed respectively. The principles to harmonize the conditions among scanning rate, optical aperture, scanning efficiency, platform flight height and repetitive rate of laser are specially studied. Finally the field test results of the ASLRIS are given.