Mode-locked erbium-doped fiber ring laser using intracavity polarization-maintaining loop mirror

Erbium-doped fiber lasers at repetition rate of 40 and 80 GHz are demonstrated in an injection-locked and rational harmonic mode-locked ring cavity. The cavity has a polarization-maintaining loop mirror. The injection-locking pulse is generated at repetition rates of 20 and 40 GHz from another rational harmonic mode-locked fiber laser. When these pulses are injected into the second fiber laser, pulses at twice the repetition rates viz. 40 and 80 GHz are produced.     

Two contact, 1 cm long, monolithic extended cavity laser actively mode-locked at 4.4 GHz

A 1.0 cm long, two contact, monolithic extended-cavity laser has been fabricated and actively mode-locked at a repetition rate of 4.4 GHz to produce 9.0 ps optical pulses. Doubling of the optical pulse repetition rate of 8.8 GHz without changing the sinusoidal drive frequency is achieved by synchronously modulating two separate active regions.<>     

Repetition-frequency multiplication of mode-locked pulses usingfiber dispersion

In this paper, we describe a novel method for generating a highly repetitive optical pulse train using mode-locked pulses and the group-velocity dispersion (GVD) of optical fiber. An optical pulse train at a multiplied repetition frequency oscillation of an initial mode-locked pulse train is obtained by adjusting waveform fiber length in accordance with the mode-locking frequency and the fiber's GVD. A subterahertz optical pulse train (98-196 GHz) was successfully generated with low pulse intensity fluctuation     

Stable 80-GHz short pulse generation using the cascaded polarization-maintaining fiber loop mirrors

In this work, an optical short pulse generator is designed consisting of a pulse compressor and cascaded notch filter type repetition rate doublers. The performance characteristics such as pulsewidth and peak power as a function of design parameters are studied. The pulse compressor is optimized based on the simulation results. The 6-ps-wide pulses at 20-GHz repetition rate directly generated from mode-locked fiber laser are compressed to 1.25-ps-wide pulses. Using a set of polarization-maintaining fiber loop mirrors, the repetition rate is quadrupled and stable 1.45-ps-wide pulses at 80 GHz are achieved.     

A novel scheme for synchronous optical sampling based on multicast parametric process

We propose a novel scheme for synchronous optical sampling based on multicast parametric process. The linearly chirped and time-broadened pulses are utilized to replace the traditional mode-locked sampling pulses. An optical sampling rate of 80 Gbit/s is realized by using only one sampling source with repetition rate of 10 GHz.     

Picosecond pulses (2 ps) from hybrid mode-locked AlGaAs QW lasers with integrated active waveguide cavities

Single ultrashort optical pulses (2 ps with 17.6 GHz repetition rate) have been generated with hybrid mode-locked monolithic GaAs/AlGaAs lasers at lambda =856 nm. Instead of an external cavity, long active waveguides were used as resonators with a roundtrip frequency of 5.9 GHz. Increasing the pump current in the waveguide far above transparency led to 10 ps pulses with a high peak power of 110 mW.<>     

Higher order repetition rate multiplication for multiwavelength pulsed source

We demonstrate a polarization-insensitive all-fiber approach for higher order repetition rate multiplication of laser pulses using a birefringence loop mirror filter. Owing to the periodicity and wide bandwidth characteristic of the filter, simultaneous repetition rate multiplication of pulses at different wavelengths can be achieved. The repetition rates of a mode-locked fiber laser and an externally modulated multiwavelength laser source have been multiplied, respectively, by a factor of four. A 160-GHz total capacity, with four individual channels each operating at 40 GHz, has been experimentally demonstrated.     

Mode-locking at very high repetition rates more than terahertz inpassively mode-locked distributed-Bragg-reflector laser diodes

We propose a technique for achieving mode-locking at very high repetition rates more than terahertz with high output power using a distributed-Bragg-reflector (DBR) laser, including an intracavity saturable absorber. This method is based on harmonic passive mode-locking at high gain levels and the selectivity of harmonic numbers related to the spectrum-filtering property of the intracavity Bragg reflector. Transform-limited pulses at repetition rates from 500 GHz to 1.54 THz were generated with an output power exceeding 15 mW. We studied stability of harmonic pulses by using conventional self-consistent mode-locking equations. We also discuss the effect of the spectrum-filtering properties of the intracavity Bragg reflector to the characteristics of mode-locked pulses     

High-repetition-rate optical pulse generation using a rationalharmonic mode-locked fiber laser

Rational harmonic mode locking takes place in an actively mode-locked fiber laser when the modulation frequency f_m=(n+1/p)f_c, where n and p are both integers and f_c is the inverse of the cavity round-trip time, the 22nd order of rational harmonic mode locking has been observed when f_m ≈1 GHz. An optical pulse train with a repetition rate of 40 GHz has been obtained using a modulation frequency f_m=10 GHz. The theory of rational harmonic mode locking has also been developed. The stability of the mode-locked pulses is improved considerably when a semiconductor optical amplifier is incorporated into the fiber laser cavity. The supermode noise in the RF spectrum of a mode-locked laser is removed for a certain range of current in the semiconductor optical amplifier     

基于45°倾斜光栅的重复频率可切换被动谐波锁模光纤激光器

基于非线性偏振旋转（NPR）技术,搭建了一台重复频率可切换的被动谐波锁模掺铒光纤激光器。腔内45倾斜光纤光栅（45 TFG）作为一种理想的光纤型起偏器,与两侧偏振控制器（PC）一起实现非线性偏振旋转效应,实现激光器的稳定锁模输出。在673 mW恒定泵浦功率下,通过调节腔内的PC,观测到了从基频到37阶谐波等多种锁模状态。该激光器可产生稳定的最高重复频率脉冲为783 MHz,对应的谐波阶数是37阶,且具有41 dB的边模抑制比（SSR）。高重复频率且稳定性好的脉冲可用于特定的应用中,如现代光通信系统、光学传感等。     

基于微结构光纤的光纤环激光器

报道了一种基于微结构光纤(MF)的光纤环激光器.通过微调控制信号的频率,激光器实现了稳定的锁模状态,在C波段获得了重复频率为10 GHz、宽度小于8ps的相干光脉冲输出.在该激光器中,采用了掺Er光纤放大器(EDFA)作为腔内增益介质,并使用了25 m长、具有反常色散和高非线性的MF作为脉冲压缩介质.通过调整腔内的带通滤波器中心频率可以实现对工作波长的连续调谐,因此该激光器可作为波分复用(WDM)系统的可调谐光源.     

基于SOA的L波段多波长锁模光纤环形激光器

报道了一种基于半导体光放大器(SOA)的L波段多波长光纤环形激光器,采用自制的100GHz信道间隔的光纤Mach-Zehnder(M-Z)干涉仪作为梳状滤波器,电吸收调制器(EAM)实现主动锁模,在1593.6nm附近获得了11个波长的同步锁模脉冲序列,脉冲重复频率为10GHz,半高全宽约为24ps,不同波长间功率不平坦度小于1dB。激光器具有工作稳定、输出光谱较宽和不同波长间功率波动小的特性。     

Continuous-fiber modulator with high-bandwidth coplanar strip electrodes

Operation of a continuous-fiber modulator based on coupling from a fiber side-polished beyond cut-off to a multimode planar waveguide has been demonstrated for the first time at gigahertz frequencies. The bandwidth of the modulator electrode structure was /spl sim/4 GHz while the optical insertion loss was measured at <0.5 dB. The device was used to produce mode-locked pulse trains in an erbium fiber laser at repetition rates of /spl sim/3 GHz.     

主动锁模飞秒光纤激光器

报道了主动锁模飞秒脉冲掺Er3 光纤激光器的实验结果。在光纤环形腔中通过引入粗波分复用器(CWDM)作为宽带滤波器,实现了中心波长在1550 nm,重复频率为2.5 GHz,谱线3 dB带宽为10.2 nm(对应的脉冲宽度为247 fs)的激光脉冲输出。此时的抽运功率为186 mW,激光器输出平均功率为1.3 mW,从而获得了能够产生飞秒脉冲的高重复频率主动锁模掺Er3 光纤激光器。     

Coherent pulsed injection seeding of two gain-switchedsemiconductor lasers

High-power, narrow-spectrum, short pulses at a wavelength near 830 nm are needed for optical logic applications. The authors report the generation of two coherent trains of pulses by pulsed injection seeding of two gain-switched semiconductor lasers with one mode-locked master oscillator. The available power was doubled and both lasers emit in nearly identical spectral lines. Short pulses (30-50 ps) are generated at a repetition rate of 1.9 GHz. The spectrum is reduced to a single mode cluster and shows a 1.7 Å wide chirp suitable for pulse compression. The peak power is 0.1 W for each pulse train. The capability of this technique for coherent power combining is demonstrated     

Picosecond (<2.5 ps) wavelength-tunable ( approximately 20 nm) semiconductor laser pulses with repetition rates up to 12 GHz

A novel technique is used to produce picosecond wavelength-tunable optical pulses from gain-switched Fabry-Perot semiconductor lasers using fibre compression. Experiments are carried out with high power, large modulation-bandwidth lasers at 1.3 mu m. Pulses of 2.5 ps durations with repetition rates up to 12 GHz are obtained. Still shorter pulses ( approximately 1 ps) with higher repetition rates (18 GHz) are shown to be feasible.<>     

Gain Dependent Optimum Pulse Generation Rates of a Hybrid-Type Actively and Passively Mode-Locked Fiber Laser

We have experimentally observed and theoretically analyzed the gain dependent optimum repetition rates of a hybrid-type active and passive mode locked laser pulses in an erbium-doped fiber laser of the figure-of-eight geometry by utilizing a nonlinear amplifier loop mirror (NALM) as a saturable absorber and a directional-coupler type electro-optic modulator as an active mode locker. Transform-limited mode-locked pulses of about 10 ps width were obtained at repetition rates which correspond to harmonics of the cavity fundamental frequency and depend on the optical amplifier gain in the NALM.     

高次谐波锁模飞秒掺镱光纤激光器的噪声情况

高重复频率的飞秒激光在高速激光测距和三维成像等领域有着非常重要的作用。其中基于飞秒光纤激光器的高次谐波锁模是获得GHz量级以上高重复频率脉冲的重要手段之一。基于含腔内光栅对色散补偿的非线性偏振旋转（NPR）锁模的掺镱（Yb）光纤激光器,在180 mW泵浦光时获得了稳定的143 MHz基频锁模脉冲序列,当泵浦光功率升至1 W时获得了最高20次谐波（2.86 GHz）锁模脉冲序列输出。系统地对比研究了基频锁模与高次谐锁模状态下,脉冲重复频率精密锁定后的艾伦偏差和相位噪声,7次谐波锁模状态下重复频率锁定精度能够保持在10?13 Hz@1 s的稳定度,为高次谐波锁模飞秒激光脉冲序列用于精密测量提供了实验依据。     

Monolithic Mode-Locked Laser and Optical Amplifier for Regenerative Pulsed Optical Clock Recovery

We experimentally demonstrate optical clock recovery using a novel mode-locked laser (MLL) monolithically integrated with an output semiconductor optical amplifier. The laser's mirror placement is determined using lithography, allowing for mode locking and clock recovery at the exact frequency of the design (35.00 GHz), which is easily scalable to 40 GHz or higher. The design is compatible with other photonic integrated circuit components, enabling integrated signal processing with MLLs. The device generates pulses at 35.0-GHz repetition rate with 6-ps pulsewidth, over 12-dB extinction ratio (ER), and 8.3-dBm output power. Among other regenerative capabilities, the device performs optical clock recovery with 50% jitter reduction from a degraded input signal with low ER     

Generation of a 100-GHz optical pulse train by pulse repetition-rate multiplication using superimposed fiber Bragg gratings

We demonstrate the use of superimposed fiber Bragg gratings (FBGs) operating in reflection as amplitude and phase filtering stages for multiplying the repetition rate of a given optical pulse sequence. In particular, we use a 1-cm-long structure of two superimposed linearly chirped FBGs to generate a continuous optical pulse train with a repetition rate of 100 GHz (duty cycle /spl ap/50%) at a wavelength of 1.55 /spl mu/m from a 10-GHz mode-locked fiber laser.