Modulational-instability sigma-resonator fiber laser

A modulational-instability laser with a resonator in a sigma configuration has been developed. The importance of a suitable intracavity filter for removing the autocorrelation background of the output signal is shown. A pulse train with a repetition rate of 107 GHz determined by the Fabry-Perot etalon used in the resonator was obtained at 1.56mum .     

全光纤多种子激光脉冲产生系统

报道一种可精确同步输出宽带啁啾脉冲、纳秒级整形脉冲以及窄带光参量啁啾放大抽运脉冲的全光纤多种子激光脉冲产生系统.采用掺镱光纤锁模激光器和掺镱单纵模光纤振荡器作为系统的光源,将掺镱光纤锁模激光器输出的超短脉冲分束啁啾展宽至0.9ns后,一路进行放大产生10μJ量级的宽带啁啾脉冲为高能拍瓦激光器系统提供种子光脉冲,另一路通过1.2nm滤波产生140ps的基元脉冲,通过光纤堆积器产生可编程整形的2.3ns脉冲,再经过放大达到10μJ量级,提供任意整形的压缩脉冲.同时,将部分掺镱光纤锁模激光器输出的超短脉冲进行光电转换并锁相后,产生与锁模超短脉冲高精度同步的电脉冲用于触发幅度调制器,将掺镱单纵模光纤振荡器输出的连续光削波放大,产生光参量啁啾放大抽运脉冲.该系统能够根据物理实验的需要,非常灵活地在输出各种脉冲之间做出选择.     

脉冲幅度均匀化的有理谐波锁模光纤激光器

提出并实现了一种脉冲幅度可均匀化的有理谐波锁模光纤激光器。该激光器采用主动有理谐波锁模机制,可获得重复频率为整数倍调制频率的锁模脉冲信号。通过在光纤激光器谐振腔中添加非线性光纤放大环镜,并利用其反射率对输入信号强度的开关特性,实现对锁模脉冲信号的整幅。在1 GHz的调制频率下,分别获得了4 GHz和5 GHz重复频率的锁模脉冲信号输出,并且在一定的980 nm抽运功率下,可通过调节电光调制器的直流偏置电压大小以及调制信号的调制深度,使得脉冲幅度具有较好的均匀性。     

基于色散不对称光纤环形镜的锁模光纤激光器

在理论上数值计算了各种常量对色散不对称非线性光纤环形镜透射特性的影响。并分析了它作为被动锁模器件用于光纤激光器压窄脉冲的物理机制。利用8字形主被动混合锁模的结构在调制频率为9．998748700 GHz，波长为1566．65nm处获得了11ps的稳定锁模脉冲输出．对应谱宽0．297nm．同时在重复频率为9．995792825 GHz和9．996778256 GHz时分别得到了振幅均匀的二阶和三阶谐波锁模输出。证明色散不对称非线性光纤环形镜可以有效消减脉冲的尾翼和噪声．得到脉幅稳定的脉冲序列。     

基于波长330nm激光激发多色激光导星回波光子数的数值计算与探讨

采用无模激光器发射波长为330 nm的激光激发多色激光导星,需要考虑脉冲激光重频率、激光带宽、激光初始光斑直径以及大气透过率对回波光子数的影响.通过数值模拟,计算了高斯光束的脉冲激光和连续激光激发多色激光导星在实际大气中后向辐射330 nm和2207 nm波长的回波光子数.数值计算结果表明,在垂直发射和接收的情况下,当到达大气中间层的激光能量为1 W时,连续激光能够获得更多的回波光子数,并且回波光子数几乎无起伏.对于脉冲激光,提高脉冲激光重频率达到50 kHz以上时,多色激光导星330 nm的回波光子数随脉冲重频率的增加趋于有限值;当大气能见度小于5 km且大气相干长度为12.8 cm时,大约需要34 W以上的激光发射能量,才能获得满足使用自然星全倾斜探测的330 nm回波光子数.对于连续激光,相同情况下,大约需要20 W以上的激光发射能量.     

Generation of 40 GHz and 60 GHz Optical Pulses by Repetition Rate Multiplying with Comb-like Filter

The comb-like filter characteristic of a Fabry-Perot etalon in frequency domain was deployed to filter out the discrete spectral lines of injected 10GHz optical pulse train. By changing the free spectral range and obtaining the spectral components spaced to 4 and 6 times of the repetition rate, the pulse trains with 40 GHz and 60 GHz were successfully obtained.     

Generation of 40 GHz and 60 GHz Optical Pulses by Repetition Rate Multiplying with Comb-like Filter

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外注入非制冷式FP半导体增益开关激光器产生低抖动光脉冲的实验研究

报道了低成本、非制冷法布里-玻罗腔半导体增益开光激光器稳定地产生超短脉冲的实验研究.通过使用外部连续光注入,增益开光激光器的脉冲抖动得到了有效的抑制.实验结果表,明当选择合适功率的连续光注入到非制冷半导体增益开关激光器腔内,可以稳定地产生脉宽26 ps、抖动低于400 fs、重复频率2.5 GHz的脉冲序列.     

有理数谐波主被动锁模掺铒光纤激光器

在理论上详细分析了利用非线性光学环形镜（NOLM）来减小输出脉冲幅度波动,消除噪声并对脉冲进行压缩整形的物理机制。在主动锁模掺铒光纤环形激光器中（AHML－EDFL）接入一个非线性光学环形镜,形成结构新颖的主被动锁模掺铒光纤激光器（APHML－EDFL）,利用非线性光学环形镜所具有的饱和吸收体功能,成功地制抑了4阶有理数谐波锁模（RHML）中较大的幅度噪声,在1GHz量级的调制频率下,由主被动锁模掺铒光纤激光器获产生重复频率为5．1GHz,幅度相当稳定的4阶有理数谐波锁模脉冲序列。     

Pulse-amplitude equalization by negative impulse modulation for rational harmonic mode locking

We propose a novel technique based on negative impulse modulation for pulse repetition rate multiplication by rational harmonic mode locking with pulse-amplitude-equalized pulses directly from the laser cavity. We have generated a pulse train of 15 GHz with more than 16 dB suppression of unwanted amplitude modulation spurs by using a 1 GHz RF signal. This is the highest suppression ratio for a repetition rate multiplication factor of 15 to our knowledge.     

Generation of low-timing-jitter femtosecond pulse trains with 2 GHz repetition rate via external repetition rate multiplication

Generation of low-timing-jitter 150 fs pulse trains at 1560 nm with 2 GHz repetition rate is demonstrated by locking a 200 MHz fundamental polarization additive-pulse mode-locked erbium fiber laser to high-finesse external Fabry-Perot cavities. The timing jitter and relative intensity noise of the repetition-rate multiplied pulse train are investigated.     

Self-mode-locked Nd:GdVO4 laser with multi-GHz oscillations: manifestation of third-order nonlinearity

The large third-order nonlinearity of GdVO₄ crystals is employed to realize the compact efficient continuous-wave self-mode locking in the range of several GHz in a Nd:GdVO₄ laser with a simple linear cavity without the need of any additional components. With a pump power of 2.5 W, the compact laser cavity produces average output powers greater than 0.7 W with a pulse width as short as 23 ps in the range of 2–6 GHz.     

Time- and wavelength-interleaved optical pulse train generation based on dispersion spreading and sectional compression

A method to generate time- and wavelength-interleaved optical pulse trains based on dispersion spreading and sectional compression is proposed and demonstrated. A 4×2 GHz time- and wavelength-interleaved pulse train is generated from an input 2 GHz mode-locked pulse train. The advantages of the proposed scheme are its simplicity and robustness, since no microwave component or multiwavelength laser source is required. In addition, we demonstrate supercontinuum generation of an ultraflat 18 nm bandwidth spectrum with less than 0.5 dB fluctuation over the 3.2 nm central bandwidth.     

Ultrashort optical pulse monitoring using asynchronous optical sampling technique in highly nonlinear fiber

An asynchronous optical sampling scheme based on four-wave mixing （FWM） in highly nonlinear fiber （HNLF） is experimentally demonstrated. Based on this scheme, 10-GHz input pulse train with 1.8-ps pulse width is successfully sampled in 100-m HNLF. A single pulse at 10 GHz with 2.3-ps pulse width is rebuilt by using a 50-MHz frequency tunable free-running fiber laser as the sampling pulse source （SPS）. 40-GHz pulse train is used as the input signal. The rebuilt waveforms, together with the low-jitter eye diagram, are also presented.     

High Repetition Rate Optical Pulse Generation Using a Rational Harmonic Mode-Locking Technique in a Fiber Ring Laser

By applying a small frequency detuning to the RF modulation frequency, pulse trains with repetition rates of integer multiples of the RF modulation frequency have been obtained in an actively mode-locking fiber ring laser. Optical pulse trains with repetition rates of 20 GHz, 30 GHz and 40 GHz were generated respectively here. Furthermore, an interesting phenomenon of generation of pulse train with repetition rate half the modulation frequency was observed.     

Diode-pumped passively mode-locked Nd:GdVO<Subscript>4</Subscript> laser with a GaAs saturable absorber mirror

We report on a diode end-pumped passively mode-locked Nd:GdVO₄ laser. By using a GaAs wafer simultaneously as the saturable absorber and the output coupler, stable continuous-wave mode locking was achieved. The pulse width was measured to be 18.9 picoseconds at a repetition rate of 370 MHz. The most remarkable property of the laser is that its repetition rate can be changed from 370 MHz to 3.348 GHz by simply changing the cavity length. An average output power of 3.46 W at a 3.348 GHz repetition rate was obtained with a 14 W pump power. To our knowledge, this is the first demonstration of a passively mode-locked Nd:GdVO₄ laser using a GaAs wafer as the saturable absorber. PACS 42.55.Rz; 42.60.Fc; 42.55.Xi.     

High Repetition Rate Optical Pulse Generation Using a Rational Harmonic Mode Locking Technique in a Fiber Ring Laser

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High speed ultra short pulse fiber ring laser using photonic crystal fiber nonlinear optical loop mirror

A scheme to generate high speed optical pulse train with ultra short pulse width is proposed and experimentally studied. Two-step compression is used in the scheme: 20 GHz and 40 GHz pulse trains generated from a rational harmonic actively mode-locked fiber ring laser is compressed to a full width at half-maximum (FWHM) of ~ 1.5 ps using adiabatic soliton compression with dispersion shifted fibers (DSF). The pulse trains then undergo a pedestal removal process by transmission through a cascaded two photonic crystal fiber (PCF)-nonlinear optical loop mirrors (NOLM) realized using a double-ring structure. The shortest output pulse width obtained was ~ 610 fs for 20 GHz pulse train and ~ 570 fs for 40 GHz pulse train. The signal to noise ratio of the RF spectrum of the output pulse train is larger than 30 dB. Theoretical simulation of the NOLM transmission is conducted using split-step Fourier method. The results show that two cascaded NOLMs can improve the compression result compared to that for a single NOLM transmission.     

Spontaneous subpicosecond pulse formation with pulse repetition rate of 80 GHz in a diode-pumped Nd:SrGdGa3O7 disordered crystal laser

We explore the operation of spontaneous mode locking in a diode-pumped Nd:SrGdGa3O7 disordered crystal laser. The first- and second-order autocorrelations are simultaneously performed to evaluate the temporal characteristics. An 80 GHz pulse train with a pulse duration as short as 616 fs is observed. The maximum output power is 415 mW at a pump power of 6.1 W.     

10 GHz, 2.4 ps pulse generation using a single-stage dual-drive Mach-Zehnder modulator

This Letter reports on picosecond pulse generation at a repetition of 10 GHz by using a single-stage electro-optic LiNbO(3) Mach-Zehnder modulator, stressing the simplicity of its setup. It is analytically and experimentally proved that dual-arm modulation with in-phase sinusoidal signals having slightly different amplitudes generated a highly coherent optical comb with a great spectral flatness and a parabolic phase relationship in its spectrum. The generated comb was Fourier synthesized and shaped into an ultrashort pulse train with an optical bandpass filter and a dispersive fiber. The pulse source was highly stable, exhibiting an ultralow timing jitter of less than 130 fs.