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A tunable passively mode-locked fiber laser with cylindrical vector beams (CVB) generation in a linear cavity was presented. The mode-locking mechanism is based on the nonlinear multimode interference effect of the graded-index multimode fiber (GIMF). The Sagnac loop mirror works as a filter. An ultra-broadband long-period fiber grating (UBLPFG) with a high conversion efficiency < 90% from 1004 nm to 1068 nm is used to covert fundamental mode to higher-order modes. The laser can achieve a continuously tunable wavelength range from 1032.344 nm to 1042.556 nm by changing the reflection spectrum of the Sagnac loop mirror thermally. When the laser operates at the central wavelength of 1042.556 nm, the output pulse trains have a period of 92.08 ns with pulse duration of 1.15 ns. The slope efficiency of the laser is about 4.73% with the mode-locking threshold of 167.7 mW. The purity of the radially and azimuthally polarized beams is measured to be higher than 93.8%.

We use the full vector beams propagation method (VFE-BPM) to simulate the nonlinear propagation process of the cylindrical vector beams (CVBs). We have shown that the CVBs have poor transverse stability which causes which causes the breakup due to the ring-shaped beam field. Then, we use the approximate analytic theory to qualitative analyze the variations of the numerically calculated instability growth rates, which shows excellent agreement with the simulated results.

In this paper, a new design of an electrothermal micromirror integrated with piezoresistive sensors is proposed. The micromirror is composed of four electrothermal bimorph actuators and four piezoresistive position sensors. In order to reduce the influence of temperature on piezoresistance, silicon dioxide can be used to thermally isolate the piezoresistive sensors from the silicon substrate. The optimized micromirror has a square mirror plate of 1800 * 1800 μm2 and a footprint of 4040 * 4040 μm2 , leading to a fill factor of 20%. The simulation results show that the optical fields of view of the micromirror are about 7° in the tilt and tip directions and the maximum piston displacement is close to 600 μm. The simulation results also show that the sensitivity and resolution of the piezoresistive sensors under a 3 V bias voltage are 2.88 mV/° and 0.4 μrad for the tip-tilt motion, respectively, and 0.056 mV/μm and 1.2 nm for the piston motion, respectively.

A novel design for speckle reduction based on a rotating ball lens is investigated. In addition, a standardized speckle measurement method is also developed and the parameters mainly accord with characteristics of human eye. This method could open up an avenue to the practical speckle measurement application.

We have experimentally demonstrated the generation of DSR in normal and anomalous dispersion regimes by using a chirped fiber Bragg grating (CFBG) for dispersion management. The dispersions of our proposed laser are calculated to be around +5.34 ps2 and -2.66 ps2 with different directions of CFBG. By properly adjusting the polarization state and pump power, we can achieve two kinds of square pulses with different shapes at the fundamental frequency of 3.58 MHz and 3.583 MHz, respectively. The width of square pulse can be tuned from 1.65 ns to 5.43 ns in normal dispersion regime. The width of square pulse can be tuned from 1 ns to 2.7 ns in anomalous dispersion regime.

Facial component and landmark detection have many applications in many facial analysis tasks. In this paper, a semisupervised method for this task is proposed to detect facial components and landmarks. Different from other facial detectors algorithms, our model without extra input solve the occlusion problem by detecting the visible facial components. Firstly, we propose a data augmentation method based on the Deep Convolutional Generative Adversarial Network to generate a large amount of semi-supervised training data. Then, a semi-supervised learning model based on Region-based CNN is responsible for multi-task facial component and landmark detection by training on the generated semi-supervised training data. During training, facial component regions and landmarks are used as supervised training data, while unsupervised training data only contains component bounding box. Experimental results illustrate that the proposed model can handle multi-task facial detection, and outperforms the state-of-the-art algorithms.

Color gamut is an important parameter for display system. Wider gamut means that the system can display more colors. In this article, we designed an experiment to measure the color discrimination ability of human eyes in a certain range under different light sources such as LCD, LED, OLED and laser display, which has different center wavelength and spectrum-width. In our experiment, a Xenon lamp projector and a RGB laser projector were used to run the testing program. Eight volunteers` results showed that the gamut of RGB laser display is 49.48% larger than that of ordinary Xenon lamp display, and the standard deviation of the result was 8.7%.

Many kinds of display technology such as LCD, OLED, quantum dot and laser display are developing rapidly. The final purpose of display technology is to achieve wider color gamut. Traditional method uses planar chromaticity diagram in CIEXYZ space to describe color gamut. This method did not use uniform color space and cannot deal with the situation of display systems with four or more primaries. In our previous work, we have already established a theory based on Macadam’s theory to calculate the stereoscopic color gamut for RGB laser display systems. In this letter, we extend this theory to display systems with four or more primaries. By using our algorithm, we calculate the stereoscopic color gamut of multi-primary display system. We set a four primary display system as an example. The center wavelength of the primary are set as 467nm, 520nm, 532nm and 630nm, white point is set as D65(x=0.3127, y=0.3290), and color gamut has been calculated in CIELAB color space. Results show that when the ratio of the intensity of four primary is 1.0000：0.7490： 0.4316：1.5000, the largest gamut is obtained, whose value is 2.1030*106. These results can be used in engineering to optimize the intensity of the primaries in four primaries display systems.

Laser display technology has developed rapidly in the past decade because it has advantages of high color saturation, high conversion efficiency, long life span and the capability to show real objects accurately. Many new laser technologies such as ALPD (Advanced Laser Phosphor Display) solution, Two Primary and three Primary Laser Display solutions have been studied for handling wide-gamut standard of Rec.2020 to reproduce the natural object colors faithfully. Different kinds of laser source including LD (laser diodes), diode-pumped solid-state laser, LD pumped Phosphor, VCSEL (Vertical-cavity surface-emitting laser) and fiber laser have been utilized in these solution. They have different center wavelengths and different linewidths which influence the color gamut and the speckle contrast of different display systems. In this paper, we calculate the color solid volume of laser display systems, and systematically investigate the color gamut conditions among display systems with different spectral linewidth selecting and different combination of three primaries. The color gamut of Rec.2020 is set as an object of comparison, in which the center wavelength of three primaries is set as Red=630nm, Green=532nm and Blue=467nm with spectral line width=1 nm. White balanced point is set as D65(x=0.3127, y=0.3291) and curve of color gamut as a function of spectral linewidth is calculated in CIELAB space. Our results would give researchers working on laser display a reference to choose suitable laser source with center wavelength and linewidth to keep a balance between laser speckle and color saturation.

In this work, by combining the wavelength- and time-division multiplexing technologies, we demonstrate a multiplexing time-bin entangled photon pair source based on a silicon nanowire waveguide and distribute entangled photons into 3(time) × 14(wavelength) channels independently. The indistinguishability of photon pairs in each time channel is confirmed by a fourfold Hong-Ou-Mandal quantum interference.

A 978 nm single mode passively mode-locked all-fiber laser delivering square-wave pulses was demonstrated using a figure-8 cavity and a 75 cm commercial double-clad ytterbium-doped fiber. We found the three-level system near 978 nm was able to operate efficiently under clad pumping, simultaneously oscillation around 1030 nm well inhibited. The optimized nonlinear amplifying loop mirror made the mode locking stable and performed the square-pulses shaping. To the best of our knowledge, it is the first time to report the square-wave pulse fiber laser operating at 980 nm. The spectral width of the 978 mode-locked square pulses was about 4 nm, far greater than that of the mode-locked square pulses around 1060 nm reported before, which would be helpful to deeply understand the various square-wave pulses’ natures and forming mechanisms. Compared with modulated single-mode or multimode 980 nm LDs, this kind of 980 nm square-wave sources having higher brightness, more steeper rising and falling edge and shorter pulse width, might have potential applications in pumping nanosecond ytterbium or erbium fiber lasers and amplifiers.

The ultimate goal of quantum information science is to build a global quantum network, which enables quantum resources to be distributed and shared between remote parties. Such a quantum network can be realized using only fiber elements, thus deriving the advantages of low transmission loss, low cost, scalability, and integrability through mature fiber communication techniques such as dense wavelength division multiplexing. Hence high-quality entangled-photon sources based on fibers are in high demand. Here we report multiplexed polarization- and time-bin-entangled photon-pair sources based on the dispersion-shifted fiber operating at room temperature. The associated high quality of entanglement is characterized using interference, Bell’s inequality, and quantum state tomography. The simultaneous presence of both types of entanglement in multi-channel pairs of a 100-GHz dense wavelength division multiplexing device indicates a great capacity in distributing entangled photons over multiple users. Our design provides a versatile platform and takes a big step toward constructing an all-fiber quantum network.

Based on a few-mode fiber Bragg grating as polarization-selective output coupler and topological insulators Bi2Te3 as the saturable absorber, we propose a passively Q-switched fiber laser with cylindrical vector beam output. Both radially and azimuthally polarized beams can be readily generated, and the output polarization can be switchable through tuning the polarization controllers inside the laser cavity. The laser operates at the wavelength of 1557.5 nm with a 3 dB linewidth of less than 0.04 nm. The repetition rate of the Q-switched laser can be tuned from 31.54 kHz to 49.40 kHz when the pump power increases from 103.5 mW to 139.5 mW.

We demonstrate a thulium-doped all fiber actively mode-locked laser by synchronously pumping without electronic modulator. A mode-locked fiber laser operating at 1550 nm based on nonlinear polarization rotation (NPR) is innovatively utilized as the pulsed pump. Through cavity length matching, stable mode-locking that operate at 1891.25 nm is achieved with a spectral width of 0.52 nm at 3 dB. The repetition rate is 11.59 MHz with an estimated pulse duration less than 125 ps.

We demonstrated an all fiber actively mode-locked laser emitting cylindrical vector beam. A few-mode fiber Bragg grating is adopted to achieve mode selecting and spectrum filtering. An offset splicing of single-mode fiber with fourmode fiber is utilized as a mode coupler in the laser cavity. A LiNbO3 Mach-Zehnder modulator is used to achieve active mode locking in the laser. The laser operates at 1547nm with 30 dB spectrum width of 0.3nm. The emitted modelocked pulses have a duration of 1ns and repetition of 12.06MHz. Both radially and azimuthally polarized beams have been obtained with very good modal symmetry by adjusting the polarization in the laser cavity.

A stable mode-locked fiber laser employing graphene as a saturable absorber is presented. One monolayer graphene can obtain mode-locking when the cavity is around 12m, but when the cavity decreases to 6m, no stable pulses can be formed. In order to solve this problem, cascade of two monolayer graphenes is used and stable mode locked pulses with a frequency of 44.53MHz, a bandwidth of 2.4nm, a pulse width of 43.89ps and an average power of 19.10mW have been directly obtained from the laser. Our results show the atomic-layer graphene may be a promising satrurable absorber for stable pulses formation of fiber laser.

We have proposed and demonstrated a nanosecond square-wave fiber laser working in the 1060nm band. The passively mode-locked fiber laser based on the nonlinear optical loop mirror has a peak power clamping effect which leads to the generation of nanosecond square-wave pulses. To investigate the spectrum width of the nanosecond square-wave pulse laser, we added couplers with different coupling ratio to the bidirectional ring of the figure-8 fiber laser and analyzed the laser output. The results show that a higher output coupling ratio leads to stronger peak power clamping effect, and the peak power of the square-wave pulse gets lower and the corresponding spectrum band width is narrower.

For better performance of laser coupling in inertial confinement fusion (ICF), beam shaping of the focus spot is required. Among all the beam smoothing methods, the multi frequency modulation smoothing by spectral dispersion (MultiFM-SSD) proposed by LLE has the advantages of the faster smoothing and better operability. Strong frequency modulation to amplitude modulation conversion(FM-to-AM) will take place because of the complex spectrum imposed by the multi frequency modulators applied in the Multi FM-SSD method. The FM-to-AM effect is studied with numerical simulation including the polarization mode dispersion and group velocity dispersion. The results reveal that the modulation frequencies and bandwi dths of multi modulators will influence the contrast degree of the FM-to-AM effect. The compensation of the FM-to-AM with arbitrary waveform generator (AWG) is also numerically simulated. The FM-to-AM effect is effectively suppressed, i.e. the non-unifo rmity of the pulse decreases substantially, by applying multiple intensity and phase compensation (the compensation function is obtained via G-S algorithm). Keywords: FM to AM,MultiFM, modulation frequency, effective modulation frequency

We have demonstrated a passively mode-locked fiber laser with a composite cavity structure for repetition rate control. An optical delay line is used to control the length so that the lengths of the main cavity and the sub-ring cavity are accurately co-prime. Using this method we have obtained 46th harmonic pulses with a fundamental repetition of 17.39MHz. The fundamental mode-locking is substantially suppressed. The SNR of rf spectrum is higher than 45 dB. Stable 800MHz repetition rate mode-locked pulses in duration of 14.27 ps are generated. The detuning phenomenon appears when two cavity’s lengths are not matched. A larger pump power is required to maintain the oscillation.

A passively mode-locked ytterbium-doped all fiber laser has been demonstrated based on the nonlinear polarization rotation technique in a all normal dispersion cavity. By optimizing the coupling ratio and position of the output coupler, stable mode-locked pulses is generated with an average power of 200 mW at a repetition rate of 3.3 MHz, and corresponding to single pulse energy of 60 nJ. The slope efficiency of power is as high as 68%.

This paper is focused on the research of SSD and CPP carried out on TIL. A bulk phase modulator with 9.2-GHz modulation frequency is adopted in SSD. The output spectrum of the phase modulator is stable and the residual amplitude modulation is small. FM-to-AM effect caused by free-space propagation after using smoothing by spectral dispersion is theoretically and experimentally studied. Results indicate inserting a dispersion grating in places with larger beam aperture alleviates the FM-to-AM effect, suggesting minimizing free-space propagation and adopting image relay. Experiments indicate when the number of color cycles (N c ) adopts 1, imposing of SSD with 4.26 times diffraction limit (TDL) did not lead to pinhole closure in the spatial filters of the preamplifier with 20 TDL and main amplifier with 26 TDL. Experimental results also indicate SSD didn’t influence the load capacity of the laser facility. The contrast of the 440-μm diameter focal spot with 95% energy included using SSD and CPP drops to 0.47, comparing to 1.71 not using SSD and CPP. When the pulse width of the third harmonic wave is 1 ns and the energy is 1115 J, no damage is found in CPP and other final optics. The experiments solves some key technical problems using SSD and CPP on high-power laser facilities, and provides a flexible platform for the laser-plasma interaction experiments.

The effect of stimulated Brillouin scattering is considered and found to be important in high power optical fibers especially when amplifier is used. Numerical simulation has been done to show how the effect of stimulated Brillouin scattering is affects the amplified spontaneous emission and the signal. Found the difference between just decrease the Brillouin signal and decrease the NF, and give a method to decrease it through change the pump method.

Direct laser driven ICF system requires a high degree of uniformity in laser energy in order to avoid Rayleigh-Taylor instability. In all-fiber laser driven ICF system, millions of fibers are fixed around the target chamber. We suggest the fibers are arranged in bundles with a single lens coupling the output of a bundle. If the arrangement is optimized, top-flat intensity profile is acquired near the focus of the lens. Least square method is used here in determining the optimum values of relative parameters. Factors on the irradiation nonuniformity are also analyzed here by numerical simulations.

Stacking chirped pulse has been studied on its shape ability. When it propagates in single-mode fiber, the nonlinear effects become very significant because of high peak power. By numerical solving the nonlinear Schrodinger equation the simulation results indicate that stacking chirped pulse has different transmission characteristic from chirped pulse because of its special spectrogram distribution. In the paper, the dispersion length and the nonlinear length are modified for stacking chirped pulse. Even the SPM effects dominate over GVD effects in propagation, GVD effects should not be ignored or be treated as perturbation. More details about pulse evolution are discussed: as the stacking chirped pulse propagating, the pulse width changes little while the detail structure becomes unorganized and peak power decreases; the spectrum are significantly broadened because of the intense SPM effects.

We present a numerical model for generating cylindrical vector beams (CVBs) through an ytterbium-doped few-mode fiber laser. A practical numerical model based on propagation rate equations with consideration of propagating modes competition between LP 01 and LP 11 . To optimize the output power of LP 11 while depress LP 01 , we analyze the dependence of this competition on resonant wavelength, pump power, ytterbium doped fiber (YDF) length, doping concentration and distribution. We also propose an effect method to completely depress the generation of LP 01 .

We proposed and demonstrated an all-fiber laser to generate cylindrical vector beams at 1030 nm. The cylindrical vector beams were obtained by exciting high order mode operating in the few-mode fiber inside the laser system, which was implemented through adjusting the angle and transversal dimension of a couple of fiber collimators. The radial and azimuthal polarization beams can be switchable conveniently just by applying twist and pressure to the few-mode fiber.

We experimentally demonstrate coherent beam combination of two double-clad fiber lasers using mutual injectionlocking in an external cavity coupling structure. The configuration employs a corner cube as a mutual injection component to couple the two lasers. A beam splitter acts as the output coupler and far field intensity has been observed at the lens focus plane. We observe interferential fringes with the contrast ratio of 0.5, and a combination efficiency of 80% is achieved. The total output power exceeds 11 W. We present simulative discussion here on the influence of multitransversal modes of element beam. The multi-mode operation degrades the quality of the output beam of main peak power, fringe contrast ratio, and other parameters. The configuration has the potential to scale to more lasers without much structural modification.

We have demonstrated an all-fiber passively mode-locked ytterbium fiber laser operating with a rectangular spectrum profile. Mode-locking is achieved by adopting nonlinear polarization rotation (NPR) in an all fiber ring cavity with normal dispersion. The 3 dB bandwidth of the spectrum is 8.6 nm, the signal-to-noise ratio (SNR) is more than 40 dB, and the rising and falling band edges are very steep. The mode-locking pulse train is stable and has a repetition of 13.4 MHz. We believe that the laser is operating in the gain-guided soliton state, which means soliton formation is induced purely by the existence of gain and gain dispersion. This kind of mode-locked fiber laser with the rectangular spectrum has potential applications in optical-based ultra-high-speed signal collection system, optical frequency combs generation and supercontinuum light source.

Supercontinuum(SC) source has found numerous applications, such as DWDM, frequency metrology, optical coherence tomography, and optical measurement. We demonstrate an all-fiber supercontimuun source generated in highly nonlinear fiber (HNLF). The HNLF is pumped by our mode-locked fiber laser with pulse width and peak power, 21.1ps and kW, respectively. An ultra-broadband supercontinuum extends from 1000 nm to 1750 nm is obtained, and the spectrum is flat with the amplitude variation less than 4dB except around the fiber zero dispersion wavelength. The spectrum of our supercontinuum source can extend beyond 1750 nm, but due to the limitation of the measured range of optical spectrum analyzer (AQ6317B), the spectrum of the supercontinuum source beyond 1750 nm is not yet obtained in our lab now. The spectral broadening mechanism of smoothed supercontinnum is considered by the higher-order soliton fission and their blue-shifted dispersive wave. Keywords: supercontinuum generation , all-fiber laser system , highly nonlinear dispersion-shifted fiber , mode-locked fiber laser , erbium-doped fiber amplifier, higher-order soliton fission

In this paper, we theoretically present a novel method applying nonlinear amplifying loop mirror to generate square pulse. From our analysis, the generated square pulse is steady and flat. We give the criteria for steady power and point out that there would be a stable region around the certain steady power. With the steady power given, the temporal width and other properties of square pulse will be determined. We also find that due to the steady power and stable region, the laser could give a multi-square-pulse output by adjusting the controlling light. An example of initially Gaussian pulse is discussed to support the idea. By adjusting transmission characteristics of the nonlinear amplifying loop mirror we will get different steady power, and then we can control power, temporal width and other properties of the generated square pulse by tuning the controlling light and choosing proper optical components. We also give a restriction for choosing optical components.

In this paper, we report the gain-switching operation in Yb 3+ -doped DFB fiber laser. Our DFB fiber laser operates with single longitudinal mode and single polarization state under cw pump, however, the DFB fiber laser will operate with gain-switching mode if it is pump by pulse of certain duration. Detail experimental results are given in the paper. We believe this king of pulse source is useful in optical sensor.

In this paper, we report the experimental study of erbium-doped mode-locked fiber laser using semiconductor saturable absorber mirror (SESAM). Two configuration erbium-doped mode-locked fiber lasers, single wavelength operation and multi-wavelength operation, are study systematically. In single wavelength operating configuration, the fiber laser can operate harmonic mode-locking of 31 MHz repetition rate, which is two times of the fundamental repetition rate in our setup. In multi-wavelength operation, the output spectrum range from 1550 nm to 1556 nm with interval of 0.8 nm. The self-starting passive mode-locked laser is constructed in a Fabry-Perot configuration using the saturable absorber mirror as the back reflector of the cavity. Fiber Bragg grating and Chirped Bragg grating are used as the other reflector. Both of our mode-locked lasers are very compact, the output pulse train is stable, which has potential applications in high speed optical communication and optical sensor.

For the growing web intrusion issues, we propose a new method for intrusion detection. In this paper, statistical learning theory (SLT) is introduced to intrusion detection and a method based on support vector machine (SVM) is presented. Theory of SVM is introduced first, and then in data pretreatment, we propose a method of reducing the dimension of primal data sets and a method of transforming eigenvalue from characters to numbers. In virtue of the network data sets which appear variable, small and with high dimension, we introduce the Sequential Minimal Optimization (SMO) algorithm which is especially for large scale problems. The testing result based on the DARPA data show that the method is effective and efficient.

We will describe recent results in all-optical packet switching with all-optical header processing using Fabry-Perot laser diodes (FP-LD). First, we will report an all-optical header processor and control signal generator using a single FP-LD with a special two-intensity-level control signal and a novel self-routing address format for the data packets. We then show that the special control signal can be generated by direct modulation of a DFB laser with square electrical pulses thus simplifying implementation. We will demonstrate that a single Fabry-Perot laser diode can also serve as an all-optical on/off switch with all-optical header processing. The header rate is 5 Gb/s and the payload rate is 10 Gb/s. The all-optical on/off switch can also be realized by using a FP-LD as the header processor only and executing the packet switching at a separate stage. The two-stage implementation of all-optical on/off switch eliminates the residue header bits problems if only a single FP-LD is used. Finally, we propose an all-optical packet-switched ring network which can be constructed from the all-optical on/off switches demonstrated.

A temperature-tunable polarization interference filter (PIF) made of YVO 4 crystal has been presented and applied for wavelength monitoring of a distributed feedback (DFB) laser in a dense wavelength-division-multiplexing (DWDM) optical communication system. This novel device offers a flexible way to monitor the operating wavelength of the transmitter over a wide capture range. Monitoring resolution of 0.02 nm can be obtained by measuring the temperature variation of the filter while its transmission value is kept at a constant value.

A diode-pumped, compact, wavelength tunable, single frequency Er3:Yb3 codoped DBR fiber laser is reported.An output power of 2.4mW for 75mW of 980nm diode pump power and a slope efficiency of 6% at 1 557.O5nmwere obtained. Linewidth of the laser was estimated at 1557.O5nm to be less than 1MHz. Also, the laser can betuned to wavelengths between 1557nm to 156mm and operates single mode throughout this range.Keywords: wavelength tunable, single frequency, fiber laser

The self-injection locking single frequency Yb-doped fiber ring laser is reported. The system shows compact, stable and tunable. In the primary experiment, the Self-injection locking single frequency fiber ring laser with wavelength 1.05325)mum, power exceeding 3.5mW,line-width less than 36 MHz was manufactured. The laser shows stability, low threshold and high power. No mode-hopping was observed within 2 hours. The single polarization output can be obtained when use single polarization fiber.

For the passive fiber probe, the dependence of the probes' transmission efficiencies on the parameters such as fiber probe shape, taper length, tip diameter and incident wavelength are analyzed with the coupled local-mode theory. It shows that the transmission efficiency of a parabolic fiber probe is about an order of magnitude higher than that of the conical fiber probe. With the increase of the incident wavelength, the transmission efficiency of fiber probes decrease. The images of phase grating by conical fiber probe and by parabolic fiber probe are compared. The Nd:YVO4 frequency-doubling laser with a miniature structure is used as light source in the experiment of SNOM, which provides higher transmission efficiency and make it fascinating in some SNOM's applications. As for active fiber probe, the ASE fiber probe is proposed. It has a wide spectrum of 6nm and may greatly reduce the coherent noise in SNOM image. It may improve the output photon flux several times higher than that of passive fiber probe. Meanwhile, the guide-wave reflection properties in fiber taper are investigated.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.