间隔可调多波长光纤激光器的实验研究

半导体光放大器(SOA)的非均匀加宽特性对产生多波长激光非常有利。本文对两段式立奥-萨尼亚克(Lyot-Sagnac)滤波器进行了详细的理论分析,实现了一种基于半导体光放大器的新型多波长光纤激光器。它利用立奥-萨尼亚克滤波器的波长选择性,在室温下得到了约18个具有30 dB信噪比的多波长激光输出。波长范围1556~1577 nm。通过调节立奥-萨尼亚克环内的偏振控制器,多波长激光的波长间隔可在两种国际电信联盟(ITU)标准波长间隔(0.4 nm和0.8 nm)间选择。这种构型的光纤激光器具有稳定性好、波长间隔可控、信噪比高等优点。     

光纤复合环形腔单模激光器的研究

单模光纤激光器在光通讯和光传感中具有广阔的应用前景。分析了复合腔光纤激光器的构成及单模的实现特点,提出了一种新颖的光纤复合环形腔激光器结构,并对其进行了实验研究。该激光器使用了波长为980nm的半导体激光器作为泵浦源。三个腔长均为2m,彼此之间的腔长差为1～2mm的光纤环形滤波器与主谐振腔构成复合腔。此激光器在波长为1562nm处得到了线宽小于0.1nm的单模激光输出,输出的光功率可达到1mW。该激光器的阈值为5mW,斜率效率为4%。     

Dual-wavelength S-band erbium-doped fiber double-ring laser

We propose and demonstrate an S-band CW dual-wavelength erbium-doped fiber (EDF) dual-ring laser using a compound-ring filter (CRF) with various coupling losses inside the gain cavity. Employing a ring filter combined within the cavity, the fiber laser can lase a dual wavelength without any filter inside the ring loop. The dual-wavelength output exhibits a good performance having optical side-mode suppression ratios (SMSRs) of 31.6 and 31.8 dB and output powers of ?9.6 and ?9.3 dBm at 1505.58 and 1506.43 nm, respectively, when the coupling loss is 30% inside the cavity. In addition, the output stabilities of the dual-wavelength laser have also been analyzed.     

Quasi-monolithic ring resonator for efficient frequency doubling of an external cavity diode laser

A quasi-monolithic second-harmonic-generation ring resonator assembled with miniaturized components is presented. The ring contains a 10-mm-long bulk periodically poled lithium niobate crystal for second-harmonic generation, four plane mirrors and two gradient-index lenses. All parts are mounted on a glass substrate with an overall size of 19.5 mm×8.5 mm×4 mm. As pump source a broad-area laser diode operated in an external resonator with Littrow arrangement is utilized. This external cavity diode laser provides near diffraction limited, narrow-bandwidth emission with an optical output power of 450 mW at a wavelength of 976 nm. Locking of the diode laser emission to the resonance frequency of the ring cavity was achieved by an optical self-injection locking technique. With this setup more than 126 mW of diffraction-limited blue light at 488 nm could be generated. The opto–optical conversion efficiency was 28% and a wall plug efficiency better than 5.5% could be achieved.     

Broadly Tunable SOA-Based Active Mode-Locked Fibre Ring aser by Forward Injection Optical Pulse

We present a broadly tunable active mode-locked fibre ring laser based on a semiconductor optical amplifier （SOA）, with forward injection optical pulses. The laser can generate pulse sequence with pulsewidth about 12ps and high output power up to 8.56 dBm at 2.5 GHz stably. Incorporated with a wavelength-tunable optical bandpass filter, the pulse laser can operate with a broad wavelength tunable span up to 37nm with almost constant pulsewidth. A detailed experimental analysis is also carried out to investigate the relationship between the power of the internal cavity and the pulsewidth of the output pulse sequence. The experimental configuration of the pulse laser is very simple and easy to setup with no polarization-sensitive components.     

Multiwavelength fiber ring lasing by use of a semiconductor optical amplifier

A multiwavelength fiber ring laser obtained by use of a semiconductor optical amplifier (SOA) with a simple laser cavity configuration is reported. A Fabry-Perot filter was used in the fiber laser ring cavity to achieve more than 50 simultaneous wavelength lasing oscillations with a frequency separation of 50 GHz. The resulting stable broadband multiwavelength lasing operation was attributed to broadband and flat gain of the SOA, which has a gain flatness of 0.8 dB for more than 20 nm. The laser has a total output power of -3 dBm and a signal-to-spontaneous-noise ratio of 30 dB.     

Wavelength-tunable erbium fiber ring laser in single-frequency operation utilizing Fabry-Perot laser with Sagnac cavity

We propose and demonstrate experimentally a stabilized and wavelength-selective erbium-doped fiber ring laser in single-longitudinal-mode operation with Fabry-Perot laser diode (FP-LD) and using a tunable bandpass filter (TBF) inside and outside a Sagnac ring cavity. The side-mode suppression ratios of 21 dB and 36.5 dB and the output power of -3.6 dB m and -8.7 dB m in the wavelengths of 1524.45-1562.35 nm and 1531.07-1562.35 nm with the tuning step of 1.4 nm can be achieved when the TBF outside and inside Sagnac loop, respectively. The output wavelength variation of zero and the output power fluctuation of <0.1 dB are also obtained. Moreover, the transmission efficiency of the ring laser has also been performed experimentally under a 1.25, 2.5 and 10 Gb/s external modulation, respectively.     

SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train

An actively mode-locked fiber ring laser based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) is demonstrated to operate stably with a simple configuration. By forward injecting an easily-generated external pulse train, the mode-locked fiber laser can generate an optical-pulse sequence with pulsewidth about 6 ps and average output power about 7.9 mW. The output pulses show an ultra-low RMS jitter about 70.7 fs measured by a RF spectrum analyzer. The use of the proposed forward-injection configuration can realize the repetition-rate tunability from 1 to 15 GHz for the generated optical-pulse sequences. By employing a wavelength-tunable optical band-pass filter in the laser cavity, the operation wavelength of the designed SOA-based actively mode-locked fiber laser can be tuned continuously in a wide span between 1528 and 1565 nm. The parameters of external-injection optical pulses are studied experimentally to optimize the mode-locked fiber laser.     

基于半导体光放大器的可调谐多波长光纤激光器

报道了一种新型环形腔可调谐多波长光纤激光器,腔内以半导体光放大器为增益介质,利用高双折射光纤构成的高双折射环形镜的滤波特性,在室温下,获得了基本符合ITU-T标准100GHz的17个波长以上的稳定多波长输出.各信道峰值功率差小于6 dB,线宽小于0.102 nm,信噪比大于25 dB.通过调节高双折射环形镜内的偏振控制器状态实现了这一组波长整体在50GHz范围内连续可调谐.并利用实验方法,对该光纤激光器应用于掺铒光纤放大器对多信道放大性能测试的可行性进行了初步探讨.     

双光纤光栅外腔半导体激光器相干失效研究

根据双光纤Bragg光栅(FBG)外腔半导体激光器相干失效的物理过程, 运用速率方程和双FBG耦合模理论, 分析了双FBG外腔半导体激光器相干失效产生和控制的条件, 提出了实现和控制双FBG外腔半导体激光器相干失效多模稳定工作的方法. 双FBG外腔半导体激光器在相干失效下具有多模的稳定工作状态, 相干失效长度缩短, 相干失效长度内光谱稳定. 实验测量结果表明, 外腔反射率为3%时, 从非相干失效状态到相干失效状态, 半峰值全宽度从0.5 nm突然展宽到0.9 nm. 在相干失效状态下, 功率稳定, 边模抑制比大于45 dB, 在0℃–70℃工作温度范围内峰值波长漂移小于0.5 nm, 最小相干失效长度小于0.5 m. 双FBG外腔半导体激光器相干失效的应用对提高光纤放大器和光纤激光器的性能具有重要意义. 关键词： 非线性 半导体激光器 双光纤Bragg光栅 相干失效     

Quasi-common-path microchip laser feedback interferometry with a high stability and accuracy

We report on an improved scheme of quasi-common-path microchip laser feedback interferometry, which demonstrates a high stability and accuracy. An additional beam splitter is used to divide the external cavity into a measuring feedback cavity and a reference feedback cavity. With this scheme, the optical path lengths of the measuring and reference feedback light can be made nearly the same, thus greatly reducing the long-period phase fluctuation caused by the laser frequency drift. The final system performances are evaluated as followed: the short-term displacement resolution is better than 2 nm, the output fluctuation is less than 10 nm within a 40-min-long stability test, and the maximum error within the 100-μm range is 25 nm when calibrated with the Agilent 5529A dual-frequency laser interferometer.     

An Enhanced Bismuth-Based Brillouin/Erbium Fiber Laser with Linear Cavity Configuration

A multi-wavelength Brillouin/erbium-doped fiber laser (BEFL) which operates in 1594 nm region is demonstrated using a 215 cm long Bismuth-based EDF and SMF. Two optical circulators were used at the output ends of the system to form a linear cavity to produce a cascaded Brillouin Stokes and anti-Stokes. A stable output laser comb of more than 20 lines was obtained with a spacing of approximately 0.089 nm at a Brillouin pump power of 4 dBm and two 1,480-nm pumps at powers of 100 mW. The number of lines is relatively higher compared with the ring cavity BEFL.     

Wavelength-spacing continuously tunable multi-wavelength SOA-fiber ring laser based on Mach–Zehnder interferometer

A Mach–Zehnder interferometer (MZI) which is used as a wavelength-spacing tunable comb filter in a fiber ring laser is built by employing an optical variable delay line (OVDL). Stable multi-wavelength semiconductor optical amplifier (SOA)-fiber ring laser based on an SOA and the MZI comb filter is achieved. Wavelength spacing can be continuously tuned by adjusting the OVDL and, as an example, multi-wavelength lasing with the wavelength spacing of 0.4, 0.8, or 1.6 nm is demonstrated. The output of the proposed multi-wavelength SOA-fiber ring laser is quite stable at room temperature and the output spectrum can be adjusted by controlling the bias current of the SOA.     

基于无源三环复合子腔的2050 nm波段单纵模掺铥光纤激光器EI北大核心CSCD

提出了一种在2050 nm波段的基于新型无源三环复合子腔的单纵模掺铥光纤激光器。对所提出的新型复合三环子腔滤波器进行了详细的理论分析,可以通过调整其有效自由光谱范围和透射带宽实现超窄带滤波,从而确保激光器的单纵模运行。所搭建激光器的输出波长为2048.48 nm,光信噪比为70 dB,100 min内的波长和功率波动分别小于0.02 nm和0.453 dB。实验结果表明,激光器可以工作在稳定的单纵模输出状态。该激光器有望用于自由空间光通信或用作多普勒激光雷达的高功率光纤激光器的种子源。     

Injection-locked single-frequency laser with an output power of?220?W

A solid-state laser system for the next generation of gravitational wave detectors with an output power of 220?W at the wavelength of 1064?nm is presented. Single-frequency operation of the laser was achieved by injection-locking of a high-power ring oscillator to an amplified non-planar ring oscillator (NPRO) following the Pound?CDrever?CHall scheme. The high-power stage which features four longitudinally pumped Nd:YAG laser crystals as active media in a ring resonator configuration was designed for reliable long term operation. Using a non-confocal ring cavity to filter the output beam, a pure TEM₀₀ mode with 168 W output power was obtained.     

A compact high efficient diode-double-passing-pumped mid-IR Tm:YLF laser at room temperature

A new compact high efficient diode-double-passing-pumped Tm:YLF laser at room temperature is presented. Using a crystal of 3 mm × 3 mm × 12 mm 4% doping Tm:YLF and double-end-double-passing pumping cavity structure without complex optical splitter pumping system, 5.6 W CW 1907.6 nm laser is obtained at 26.2 W 792 nm pumping laser. The slope efficiency is as high as 37.8% and the spectrum width is 2 nm. The relationship between cavity length and output laser is also analyzed. Experiments verify that the highest energy and convertion efficiency can be reached by optimizing the oscillator cavity length. Finally, we used this Tm:YLF laser to pump Ho:YAG crystal at room temperature and achieved 1.65 W 2.1 μm output laser with slope efficiency 67%.     

A Single Mode Fibre Laser by Applying Self-Injection Locking with a DFB Structure

We report a novel single-frequency fibre ring laser using self-injection locking with a distributed-feedback （DFB） fibre laser at 1550nm. The operating wavelength is controlled by a saturable absorber and a DFB fibre laser in the ring cavity, the saturable absorber acts as a narrow band-pass filter. In the primary experiment, the laser output exceeds 100mW with the linewidth less than 2kHz. The laser is stable, and no mode-hopping is observed within eight hours. Compared with other cavity designs using spatial hole-burning, our laser shows high controllability.     

Switchable single-longitudinal-mode dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier

We propose and demonstrate a novel single-longitudinal-mode (SLM) dual-wavelength erbium-doped fiber ring laser incorporating a semiconductor optical amplifier. The SOA biased in its low-gain regime greatly reduces the gain competition of the two wavelengths. The stable SLM operation is guaranteed by a passive triple-ring cavity and a fiber Fabry-Perot filter. The dual-wavelength output with a 40 GHz wavelength spacing is switchable in the range of 1533-1565.4 nm.     

Multiwavelength erbium-doped fiber ring laser using a LiNbO<Subscript>3</Subscript> multifunction chip for fiber gyroscope

We present a novel configuration of multiwavelength erbium-doped fiber ring laser (MW-EDFL) using a LiNbO₃ multifunction chip for fiber gyros at room temperature. The polarizer incorporating a piece of high-birefringence fiber in the input port of the Y-type chip forms the Lyot periodic filter at intervals of 0.5 nm wavelength. One of two modulators inserted in the ring cavity has been used as frequency shifter by applying a sawtoothed signal, while the output port of the other is used as the output port of the laser. Simultaneous multiwavelength lasing is experimentally demonstrated by applying a sawtoothed signal with the order of 10 kHz to the phase modulator to prevent single-wavelength oscillation. The MW-EDFL output is linearly polarization light that meets the requirement of external modulation for wavelength-division-multiplexing applications.     

Efficient second-harmonic generation of continuous-wave Yb fiber lasers coupled with an external resonant cavity

Efficient second-harmonic generation of continuous-wave Yb fiber lasers is reported. A simple bow-tie external resonant cavity incorporating a type I LBO nonlinear optical crystal was employed for second harmonic frequency conversion of a multi-longitudinal-mode Yb fiber laser. It is shown that strong coupling was formed between the Yb fiber laser and the external cavity and, as a result, the laser produced 9.1 W of green output at 535 nm for 43?W of absorbed diode pump power at 975 nm corresponding to an optical conversion efficiency of 21?% with respect to absorbed diode pump power. The prospects for further improvement are discussed.