Eye-safe,single-frequency pulsed all-fiber laser for Doppler wind lidar

A single-frequency pulsed erbium-doped fiber(EDF) laser with master-oscillator power-amplifier configuration at 1 533 nm is developed. A short-cavity,erbium-doped phosphate glass fiber laser is utilized as a seeder laser with a linewidth of 5 kHz and power of 40 mW. The seeder laser is modulated to be a pulse laser with a repetition rate of 10 kHz and pulse duration of 500 ns. The amplifier consists of two pre-amplifiers and one main amplifier. The detailed characteristics of the spectrum and linewidth of the amplifiers are presented. A pulse energy of 116 μJ and a linewidth of 1.1 MHz are obtained. This laser can be a candidate transmitter for an all-fiber Doppler wind lidar in the boundary layer.     

High-energy dissipative soliton with MHz repetition rate from an all-fiber passively mode-locked laser

We experimentally demonstrate pulse energy enhancement in an all-fiber passively mode-locked laser operating in the large normal dispersion regime. By increasing the laser cavity length as well as its net cavity dispersion, the proposed laser, which is mode-locked by nonlinear polarization rotation, generates highly chirped dissipative solitons with pulse energies up to 9.4 nJ. The fundamental repetition rate is 2.3 MHz, and the pulse duration is 35 ps. Such low repetition rate as well as wide pulse width makes this mode-locked all-fiber laser a suitable oscillator to directly seed a fiber amplifier, which can be used as compact sources for high-power applications.     

基于光参量振荡器的重频人眼安全激光器技术研究

 对KTP-OPO的相位匹配进行了理论分析和计算,并绘制了角度调谐曲线。基于光参量振荡器,选用KTP非线性晶体,在1.57μm人眼安全激光波段进行了实验研究。将脉冲氙灯侧面泵浦Nd∶YAG 1.064 μm激光应用于腔内KTP-OPO设计中,在工作频率5 Hz时,输出激光能量32 mJ,脉冲宽度7.22 ns,光 光转换效率为41%。这一结果使重频远距离人眼安全激光测距成为可能。     

Dark pulses with tunable repetition rate emission from fiber ring laser

We demonstrated the experimental observation of the dark pulses with tunable repetition rate from an erbium-doped fiber ring laser. A considerable length of high nonlinear fiber is incorporated into the fiber ring laser to enhance the nonlinear intensity. In our experiment, both bright and dark pulses can be observed under the conditions of appropriately setting of the device in the cavity. Further study showed that the dark pulse is formed due to the cross coupling between two different lasing wavelengths. Particularly, dark pulse-train with multiple repetition rates was observed from the laser cavity and the repetition rate switchable operation can be realized by simply adjusting the polarization controller (PC) in the cavity. The operation of multiple repetition rates of dark pulses was further experimentally investigated and detected as a result of pulse splitting of each component with different wavelength.     

Single-frequency high-energy Yb-doped pulsed all-fiber laser

A single-frequency pulsed all-fiber laser with a master oscillator power amplifier configuration is presented. While maintaining the properties of single mode, linear polarization, and narrow linewidth, a single-pulse energy of 260 μJ and over 500-W peak power is experimentally demonstrated at 1 kHz by employing tensile strain gradient and pulse-shape control methods. In addition, approximately 55 dB of optical signal to noise ratio is also achieved.     

High repetition rate, tunable, Q-switched diode pumped Tm:YLF laser

The aim of work was to characterize a simple oscillator consisted of Tm:YLF crystal end-pumped by a fiber coupled diode laser and active Q-switch with tunability option. About 7 W with near 35% slope efficiency was demonstrated in a free-running mode. The divergence angle was about 4.3 mrad and estimated parameter M² < 1.3. Continuous tuning by means of Lyot’s filter, consisted of 2 quartz plates in the range of 1879.0–1939.4 nm with less than 1-nm linewidth, was achieved. For the best case (10-ms pump pulse duration, 42-A pump current corresponding to 266 mJ of pump energy), the Q-switched energy was 10.5 mJ with pulse duration of 22 ns corresponding to near 0.5 MW peak power. The 2.5 W of average power with 12.6-kW peak power and 2000-Hz repetition rate was demonstrated for cw pumping regime.     

High repetition rate actively mode-locked Er:fiber laser with tunable pulse duration

An actively mode-locked fiber laser with controllable pulse repetition rate and tunable pulse duration is presented, in which an optical delay line(ODL) is used to adjust the cavity length precisely for regulating the repetition rate, and a semiconductor optical amplifier(SOA) is introduced for enabling the pulse duration control. Experimentally, continuous tuning of the repetition rate from 2 GHz to 6 GHz is realized, which is limited by the availability of an even higher repetition rate radiof...     

Passively mode-locked fiber laser with kilohertz magnitude repetition rate and tunable pulse width

We propose and demonstrate a strictly all-fiber, erbium doped passively mode-locked figure-eight fiber laser (EDFL). In the laser structure, we use the nonlinear optical loop mirror combination with a variable ratio coupler (VRC-NOLM) to achieve mode-locking. Due to the nonlinear effect in the nonlinear fiber, stable self-starting pulse is obtained. In order to reduce the repetition of pulse, a segment of nonlinear fiber (NLF) has been incorporated into the VRC-NOLM. The laser generates stable rectangular pulses with a low repetition rate (kilohertz magnitude) by extending the length of the cavity. Furthermore, the output pulse width of the fiber laser can be varied by changing the coupler ratio of the variable ratio coupler.     

Subpicosecond,widely tunable distributed feedback dye laser

A simple, achromatic, widely tunable distributed feedback dye laser arrangement is described. It makes use of a microscope objective, which images a transmission grating into the active medium. With this arrangement subpicosecond operation and broad tunability (400–760 nm) is reported.     

Stable and widely tunable all-fiber Pr(3+)-doped cw laser system using fiber Bragg gratings

A simple and strictly all-fiber 1300-nm cw laser is presented. It is tunable over 16 nm with 0.5-nm linewidth and several milliwatts of output power in the whole tuning range from 1292 to 1308 nm. The setup uses a fiber Bragg grating as a combined tuning element and narrow-band output mirror. The simplicity and stability of this system are due to the following two characteristics: First, polarization control is not necessary anywhere in the system, and second, a wavelength-selective system and a narrow-band mirror are combined into one novel fiber-optic element.     

CW,single-mode,tunable GaAs laser system with good frequency stability

A cryostat has been designed for the refrigeration of a semiconductor diode laser (presently GaAs), using a flow of helium gas with controlled temperature. The possibility of independent adjustment of the injection current and of the temperature of the GaAs laser support allows cw emission over a wide wavelength range (～100 Å for a given diode) while maintaining single-mode operation. A long-term frequency stability of ±30 MHz of the free-running single-mode laser has been obtained. By varying the dc injection current, it was possible to achieve linear scanning of the mode frequency, step by step or continuously, over at least 20 GHz without hopping. Possible applications in optical pumping and high-resolution spectroscopy are discussed.     

72-kW high-peak-power linearly-polarized single-mode pulsed fiber laser with 80 kHz repetition rate and 4.5 ns duration

We reported a 26 W linearly polarized single-mode Yb-doped photonic crystal fiber amplifier, working at 80 kHz repetition rate with 4.5 ns duration, corresponding 72 kW peak power. Using a acousto-optic Q-switched Nd:YVO₄ laser as the seed source, the 26 W average power of 1064 nm laser was obtained at a repetition rate of 80 kHz from a Yb-doped photonic crystal fiber amplifier, with 4.5 ns duration, polarization extinction ratio 11 dB and M ² < 1.2.     

Ytterbium-doped fiber amplifier with tunable repetition rate and pulse duration

A pulsed master-oscillator power fiber amplifier (MOPFA) system based on Yb³⁺-doped large mode area (LMA) double-clad optical fiber was developed. The system generated pulses of changeable duration ranging from about 8.5 to 250.0 ns at the repetition rate of up to 500 kHz. The laser system emitted up to 22 W of average output power at the wavelength of 1064 nm.     

Narrow-linewidth widely tunable hybrid Q-switched double-clad fiber laser

A laser-diode-pumped Yb-doped double-clad fiber laser operating in a hybrid Q-switched regime has been demonstrated. With pulsed pump light and stimulated Brillouin scattering of the gain fiber as the Q-switching mechanisms, the laser generated nanosecond pulses with a stable repetition rate. A single-pulse energy of as much as 143.1 microJ with a peak power of 28.6 kW was obtained. Use of an external-cavity diffraction grating in the Littman configuration permitted tuning of the laser wavelength over a 15.7-THz range from 1080 to 1140 nm, and a linewidth of 0.04 nm over the whole tuning range was achieved.     

Generation of high-energy dual-wavelength domain wall pulse with low repetition rate in an HNLF-based fiber ring laser

The generation of high-energy dual-wavelength domain wall pulse with a low repetition rate is demonstrated in a highly nonlinear fiber （HNLF）-based fiber ring laser. By introducing the intracavity birefringence-induced spectral filtering effect, the dual-wavelength lasing operation can be achieved. In order to enhance the cross coupling effect between the two lasing beams for domain wall pulse formation, a 215-m HNLF is incorporated into the laser cavity. Experimentally, it is found that the dual-wavelength domain wall pulse with a repetition rate of 77.67 kHz could be efficiently obtained through simply rotating the polarization controller （PC）. At a maximum pump power of 322 mW, the 655-nJ single pulse energy in cavity is obtained. The proposed configuration provides a simpler and more efficient way to generate high energy pulse with a low repetition rate.     

Highly efficient widely tunable subpicosecond double mode-locked laser

A high average power (≈150 mW) subpicosecond (0.5 ps) passively double mode-locked dye laser is described. Two synchronized cw pulse trains are generated which are independently tunable over broad wavelength ranges (≈600 Å).     

Continuously tunable, high-power, single-mode radiation from a short-pulse free-electron laser

This paper gives the first demonstration of high-power, continuously tunable, narrowband radiation that is produced by means of a free-electron laser (FEL) in the far-infrared region of the electromagnetic spectrum. A Fox-Smith intracavity étalon was used to induce phase coherence between the 40 optical micropulses that were circulating in the laser cavity. The corresponding phase-locked spectrum consisted of a comb of discrete frequencies separated by 1 GHz. A pair of external Fabry-Pérot étalons was used to filter out a single line from this spectrum. The power in the selected narrow line at 69 microm wavelength was equal to 250 mW during the macropulse of the laser. The spectral width of the selected line is as small as that of a single cavity mode, i.e., a fraction of 25 MHz, in single macropulses of the laser. The average bandwidth of 25 MHz is determined by mode hopping of the phase-locked FEL. The selected frequency hops over 25 MHz between the extrema of this band. The influence of partially coherent spontaneous emission and mode hopping on the final linewidth was studied. The narrow-linewidth radiation was scanned in frequency over 1 GHz. We show that the possibilities to scan over smaller or larger frequency intervals are unlimited.     

A Titanium-doped-sapphire laser source with tunable frequency,single-mode emission,and adjustable pulse duration

We present a laser source with several desirable characteristics, such as tunable wavelength in the near infrared, single-longitudinal-mode emission and variable pulse temporal duration in the nanosecond regime. The laser is based on an injection-seeded Titanium-doped-sapphire ring cavity. Our experiments show how the pulse duration can be varied in a controllable fashion either by changing the cavity length or by changing the pump energy. We present a theoretical model which successfully reproduces the experimental results by treating the operation of this type of laser as a gain-switching technique. As far as the stabilization of the laser cavity, we also present a novel solution involving the use of an avalanche photodiode.     

Design of a widely tunable laser with a chirped ladder filter

We theoretically investigated a digitally tunable laser with a chirped ladder filter and a ring resonator to obtain a wide wavelength tuning range covering the whole C- or L- band. The clear relation between the tuning range and laser structure, especially the ladder filter, is described analytically. The introduction of a chirped structure into a ladder filter is effective in achieving both wide tunability and a stable lasing mode. A numerical simulation based on multimode rate equations shows that a tuning range of over 40 nm and a mode suppression ratio over 40 dB can be achieved by introducing a chirped ladder filter.     

High repetition rate, compact micro-pulse all-solid-state laser

A high repetition rate, compact micro-pulse all-solid-state laser is designed. The diffusion bonded crystal of YAG, Nd:YAG, and Cr4+:YAG is taken as a monolithic cavity. The optimized initial transmission,output coupling, and pumping size of Cr4+:YAG are calculated. The experimental results show that the laser satisfies the requirement of a spaceborne laser range finder.