Search

The fabrication and manipulation of tunable micro- and macro-domain silver nanowires (AgNWs) remains challenging. In this letter, we explored the dispersion, orientation, reorientation, order param...

A diode-pumped Tm:YAP crystal model was built and analyzed to present an analytical solution of the heat equation for a thin-slab geometry crystal. Using Matlab, the temperature distributions of Tm:YAP crystal at different plane were calculated and shown under different pumping and cooling condition. The calculation results show that the temperature distribution is greatly dependent on the thickness of the Tm:YAP crystal and characteristics of pump light, such as pump power and spot size. The thermal focal length produced by temperature gradient was also calculated and the results show that the thermal lens effect was enhanced with the increase of the pump power density while the size and doping concentration of Tm:YAP crystal is assumed stationary. And at last, a stable laser resonator is designed and analyzed according to the calculation result of thermal lens.

To quantitatively analyze the influence of vehicle platform vibration on the vehicle laser radar (LIDAR) measurement accuracy, the modal, harmonic response, and random vibration are analyzed using finite-element software. On this basis, combined with the optical path structure of LIDAR, the deformation of mirror caused by vibration is analyzed. The results show that the maximum deflection of the laser output angle resulting from the mirror deformation is about 0.0001 deg, which is much less than the 0.00573 deg (0.1 mrad) that is required by the performance of the vehicle LIDAR.

Based on the homodyne detection, a compact and cost-effective all-fiber laser Doppler vibrometer (LDV) with high resolution is presented. For the signal processing, the discrimination algorithm combined with the nonorthogonal correction is applied. The algorithm corrects the quadrature imbalance and other nonlinearity. In the calibration experiment, with the glass pasted on a piezoceramic transducer (PZT), the velocity resolution of 62 nm/s at 4 kHz and displacement resolution of 2.468 pm are achieved. For the LDV-based acousto-optic communication, the minimum detectable sound pressure level (SPL) reached 0.12 Pa under the hydrostatic air-water surface. The results demonstrate that the designed homodyne LDV has a low system background noise and can offer high precision in the vibration measurement.

Thermal effect is a key problem to obtain high average power output from the Fe:ZnSe crystal. Main parameters of micro-channel structure heat sink, such as channel depth, width and duty cycle are designed and optimized to improve the dissipation capability. And on these basis, a thin-slab and composite Fe:ZnSe model is constructed and the temperature distribution of the Fe:ZnSe is analyzed and discussed.

In this paper, a 1550 nm five-channel all-fiber homodyne laser Doppler vibrometer with high sensitivity and good signal probing probability is presented. Under the anechoic tank, standing on an airborne platform above the water surface 3 m away, the calibration experiments of the designed system are conducted. The minimum detectable sound pressure level is up to 101.73 dB re 1 µPa at 10 kHz under the hydrostatic water surface condition, and the time distribution of the final outputs are consistent with that of the underwater sound transducer. For the hydrodynamic detection capability, with the help of a 1064 nm high-pulse-energy laser whose pulse energy is 6J, pulse duration is about 8 ns, and repetition rate is 1 Hz, the system performance is tested in Qiandao Lake. And the signal probing probability of the whole sensing system is up to 59.77%.

A thin layer of single-walled carbon nanotubes (SWCNTs) exhibiting optical anisotropy is prepared by electroactively elongating SWCNT agglomerates. SWCNTs are doped into a reactive mesogen (RM) solution, and the composite solution is spin-coated on an interdigitated-electrode substrate. The spherical shaped SWCNT agglomerates observed in the solution of thin layers are electroactively elongated and aligned along the direction of the external electric field. After elongating the SWCNT agglomerates, the transparency of RM-SWCNT thin composite layers increases by about 14%. In addition, the elongated SWCNT agglomerates present significant optical anisotropy such that an incident light with a polarization direction parallel and perpendicular to the elongated direction of SWCNTs is absorbed and transmitted, respectively. The electroactively elongating strategy adopted to realize the optical anisotropy of SWCNT agglomerates suggests a new way to fabricate an optically anisotropic SWCNT thin layer.

It is very difficult to make a liquid crystal display (LCD) that is flexible. However, for an optically re-writable LCD (ORWLCD), only the spacers and the substrates need to be flexible because the driving unit and the display unit are separate and there are no electronics in the display part of ORWLCD. In this paper, three flexible-spacer methods are proposed to achieve this goal. A cholesteric liquid crystal colored mirror with a polarizer behind it is used as the colored reflective backboard of an ORWLCD. Polyethersulfone substrates and flexible spacers are used to make the optically re-writable cell insensitive to mechanical force.

In consideration of low power density of electric excitation claw-pole synchronous alternator (EECA) and some difficulties in magnetic field regulation of permanent magnet claw-pole synchronous alternator (PMCA), a novel hybrid excitation brushless claw-pole alternator (HEBCA) is proposed in this paper. Its structure and field control principle are described. Three dimensional finite element analysis is used to obtain the no-load magnetic field distributions and field control capability under different field currents. The result shows that the flux of the prototype machine can be adjusted over a wide range with a relatively low field current.

Tm:YAG ceramics with a quasi-three-level system are sensitive to temperature. The optical and thermodynamic properties of Tm:YAG ceramics can change with changing temperature, and this affects the output power stability and beam quality of lasers. Thus temperature control is a key and difficult problem for Tm:YAG lasers, especially for high power laser output. In combination with slab structure and grad-doping techniques for composite ceramics, the temperature distributions of Tm:YAG ceramics are analyzed. It is found that the temperature difference of a rationally designed grad-doping Tm:YAG ceramic can be reduced significantly with the same absorption pump power, which results in higher output power and beam quality.

An all-fiber compact homodyne laser Doppler vibrometry for the future-generation seafloor topographic survey in turbid water has been developed. By means of this setup, we display the experiment results obtained in the anechoic tank.

Three advanced detection methods are proposed to realize high spatial resolution detection. Compared with the parameters of the GLAS, all of the three methods are superior in terms of spatial resolution, power consumption, and sensitivity.

The paper present three different all-fiber heterodyne Laser Doppler Vibrometry (HLDV) for acousto-optic communication according to the theory of the coherent detection. A line width of 1 kHz single mode continuous fiber laser and one telescope with a 30mm aperture are used in all of three HLDV. The first HLDV is made up with one acousto-optic frequency shifter (AOFS) and one balanced detector, the second one is made up with two AOFSs and two balanced detectors, and the third one is made up with two AOFSs and one balanced detector. The corresponding vibration measurements on the piezoelectric ceramic were performed and the results were compared in view of the noise floor and the spectrum distribution under 1kHz. For the low-frequency vibration measurement, the HLDV with two AOFSs and two balanced detectors shows a good application potential.

A novel all-fiber heterodyne Laser Doppler Vibrometry (LDV) for acousto-optic communication has been developed in this paper. A line width of 1 kHz single mode continuous fiber laser, two acousto-optic frequency shifters (AOFS), two balanced photodetectors and one telescope with 30 mm aperture were used in this LDV. Using the above system setup, the 6 kHz signal can be reconstructed by detecting the vibration of a glass sticking on the piezoceramic transducer (PZT). The proposed vibration measurement technique proved to be very accurate and potential to acquire the acoustic signal by experimental results.

A laser Doppler Vibrometer (LDV) with a configuration of all fiber is developed according to the theory of the heterodyne detection. The system can be applied in an effective and high-sensitivity way to acquire the real-time acoustical signals through glass 20 meters away.

To observe the short-term efficacy of autogenous bone pate and Palva graft for obliterating huge remnant mastoid cavity in canal wall down approach.Retrospective analysis clinical data of twenty-one cholesteatomatous cases operated by one surgeon from 2004 to 2007. In twelve cases, simultaneous III type tympanoplasty (Sheehy, P. O. P) was performed. Other 9 cases had undergone mastoidectomy elsewhere before the admission. Six of them were still draining with huge remnant mastoid cavity, and the rest three patients had relapsed cholesteatomas with intermittent draining and huge mastoid cavity. Normal saline solution perfusion was used to measure the volume of remnant mastoid cavity. The criterion of huge remnant mastoid cavity is more than 8 ml.Of twelve primary cases with III type tympanoplasty, 11 patients maintained a small, dry, and healthy mastoid cavity after twenty-seven days. The average increase of hearing level of them was 17.5dB, and the air-bone gap is less than 20 dB. Of one patient, bone pate was infected and was discharged. A dry mastoid cavity was achieved until fifty-five days after surgery. The patient is keeping a big air-bone gap caused by displacement of ossicle chain prosthesis. Just eighteen days later, other nine cases of revision mastoidectomy achieved a small, dry, and healthy mastoid cavity, with lightly improved hearing level.Obliteration of a canal wall down huge mastoid cavity by Palva graft with autologous bone pate is a reliable and effective technique that results in a small, dry, low-maintenance mastoid cavity. The short-term efficacy of simultaneous III tympanoplasty is satisfactory if patient selection is suitable.

Laser Doppler vibrometer (LDV) has a potential application prospect in remote sensing. Based on the correlation theories of heterodyne detection, a LDV system with a configuration of all fiber and heterodyne techniques is developed to detect the sound signal through the vibration of glass. Experimental results show that the LDV system has an ability to acquire the real-time speech signal 25 m away through glass. While, the system signal-to-noise ratio (SNR) value decreases with the increase of the glass thickness and the detection distance.

A high spatial resolution, high velocity resolution all-fiber laser Doppler vibrometry (LDV) based on heterodyne detection for vibration measurements is reported. A linewidth of 1-kHz single-mode continuous fiber laser, polarization-preserving fiber, and a telescope with 30-mm aperture are used in this LDV. With the inphase-quadrature circuit and the digital differentiating discriminator, a high velocity resolution of 96.9 nm/s and a high displacement resolution of 2.5 pm are obtained simultaneously with a glass attached to a piezoceramic transducer. These values correspond to the measurement uncertainties of vibration velocity and displacement within 4.14% and 4.6%, respectively.

A 1550-nm all-fiber monostatic lidar system based on linear chirp amplitude modulation and heterodyne detection for the measurements of range and velocity is presented. The signal processing method is given, after which the relationship between the peak frequency values in the final signal spectrum, the target's range, and the line-of-sight velocity is obtained in the presence of the fiber end-face-reflected signal plaguing many monostatic lidar systems. The range of an electric fan as well as the line-of-sight fan speed of different levels is tested. This proposed system has a potential application for the space-borne landing system.

In this paper, a 1550 nm all fiber monostatic laser range finder system based on linear chirp modulation and heterodyne detection is presented. The fiber end face signal is used as a range starting indicator. The transmitted laser power is 5 mW with a laser pulse length of 131 micros and a linear chirp bandwidth of 40 MHz. The telescope with an aperture of 3 cm couples the return light into a single mode fiber. Better than 14 cm distance accuracy and 26 dB SNR can be achieved for a wood target at a distance of about 43 m by using the above system setup. Several experiments with different system parameters are conducted. The system performance is tested under variable laser pulse length, linear chirp bandwidth, local oscillator power, and background noise. Finally, an application of the linear chirp modulation heterodyne laser range finder in a spaceborne ranging system is proposed.