On the amplified spontaneous emission noise modeling of semiconductor optical amplifiers

We perform a theoretical investigation of two modeling approaches for the amplified spontaneous emission (ASE) noise of a semiconductor optical amplifier (SOA), namely a stochastic time-domain and a deterministic frequency-domain approach. The theoretical results are compared to one another having as reference experimental measurements obtained from a commercial device. Special emphasis is placed on the modeling of the material gain as it is a key parameter in determining the ASE spectral characteristics. A comprehensive set of equations for both modeling approaches is developed and their numerical solution is analyzed in detail.     

Suppression of amplified spontaneous emission in a femtosecond chirped-pulse amplifier

The suppression of amplified spontaneous emission (ASE) that arises during the femtosecond chirped-pulse amplification is presented. On the basis of the distinct differences in the spatial, temporal and spectral region between ASE and the amplified laser signal, the noise arising from ASE was effectively filtered out. The ratio between the amplified femtosecond pulse and the ASE peak power was higher than 10⁷. Pulses as short as 38 fs were amplified to peak power of 1.4 TW.     

Suppression of the amplified spontaneous emission in ultraintense and ultrashort lasers by a highly efficient saturable absorber

For ultraintense and ultrashort laser facilities, there are few efficient and reliable methods for suppressing the amplified spontaneous emission (ASE) generated in the last several amplifiers. In the paper, we applied a highly efficient saturable absorber to suppress the ASE. Experiments were carried out to study the absorption property of the saturable absorber and the enhancement of temporal contrast with it in the front-end system of the SILEX-I laser facility with a central wavelength of 800 nm. We also analyzed the effects of the saturable absorber on other laser parameters, such as the spectrum, the spatial beam profile, and energy stability. The results show that the saturable absorber is highly efficient and the transmissivity is as high as 90%. The temporal contrast is improved by more than one order of magnitude. Meanwhile, the saturable absorber has little impact on other parameters. With these advantages, the saturable absorber is an efficient, appropriate and convenient solution to suppressing the ASE generated in the front-end system and also in the last several amplification stages for ultraintense and ultrashort lasers.     

掺钛蓝宝石激光放大器中放大自发辐射效应研究

 给出了描述掺钛蓝宝石激光放大器的速率方程组，通过对放大介质内反转粒子数密度和放大自发辐射的时间和空间特性的数值计算与分析，提出可通过控制泵浦光脉冲和信号光之间的时间延迟来有效地抑制放大自发辐射对放大器增益的影响。     

Amplified spontaneous emission from nitrogen laser pumped dye lasers

The nitrogen laser pumped dye laser output has been studied with emphasis on the behaviour of amplified spontaneous emission (ASE) with respect to the tuning wavelength, pump energy, dyes and their concentration and solvents. Spectral spread of ASE is narrower than fluorescence and its maximum is shifted towards the red side. However, lasing occurs beyond the ASE region. ASE is small at high gain wavelength and increases at the edges of the gain curve. Laser energy is highest at the ASE peak with minimum ASE present in the output. ASE is reduced with increased laser energy in the energy transfer dye lasers.     

高功率激光片状放大器中自发辐射放大研究

 采用理论模拟和实验研究相结合的方法，研究了高功率激光片状放大器中的自发辐射放大(ASE)效应。建立了一套较完整的包含空间和时间的3维ASE模型，分析了不同电压、不同储能分布和不同泵浦时刻、不同增益长度积条件下ASE效应对放大器储能效率和小信号增益系数的影响。对4×2×3组合式放大器的计算结果表明：随着泵浦电压升高，ASE效应明显加强；23kV泵浦电压下，ASE效应造成的平均储能下降210%，小信号增益系数损耗为16.62%，增益不均匀性为7.44%；增益长度积可以作为判断ASE效应的依据，其值越大，ASE效应越强。     

金原子的放大自发辐射脉冲的弛豫振荡

首次报道了由金原子发出的波长627.8nm的放大自发辐射脉冲具有弛豫振荡.得出其在时间域和频率域的规律.这种振荡可能是高增益脉冲辐射系统的一种普遍现象.     

High-power supercontinuum generation in highly nonlinear, dispersion-shifted fibers by use of a continuous-wave Raman fiber laser

High-power supercontinua are demonstrated in highly nonlinear, dispersion-shifted fibers with a continuous-wave Raman fiber laser. Supercontinuum growth is experimentally studied under different combinations of fiber length and launch power to show output powers as high as 3.2 W and bandwidths greater than 544 nm. Modulation instability (MI) is observed to seed spectral broadening at low launch powers, and the interplay between MI and stimulated Raman scattering plays an important role in the growth of the continuum at high launch powers. The effect on continuum generation of parametric four-wave mixing coupled with the higher-order dispersion properties of the fiber is investigated.     

The generation of amplified spontaneous emission in high‐power CPA laser systems

An analytical model is presented describing the temporal intensity contrast determined by amplified spontaneous emission in high‐intensity laser systems which are based on the principle of chirped pulse amplification. The model describes both the generation and the amplification of the amplified spontaneous emission for each type of laser amplifier. This model is applied to different solid state laser materials which can support the amplification of pulse durations . The results are compared to intensity and fluence thresholds, e.g. determined by damage thresholds of a certain target material to be used in high‐intensity applications. This allows determining if additional means for contrast improvement, e.g. plasma mirrors, are required for a certain type of laser system and application. Using this model, the requirements for an optimized high‐contrast front‐end design are derived regarding the necessary contrast improvement and the amplified “clean” output energy for a desired focussed peak intensity. Finally, the model is compared to measurements at three different high‐intensity laser systems based on Ti:Sapphire and Yb:glass. These measurements show an excellent agreement with the model.

     

飞秒激光脉冲在高非线性光子晶体光纤中产生超连续谱的实验研究

使用钛宝石激光器抽运一根长1m的高非线性光子晶体光纤,获得的超连续谱波长覆盖范围为420—1700nm,输出功率为170mW,转换效率在20%以上;对实验结果给出了详细的分析,并与理论模拟结果相比较,认为超连续谱产生的主要原因是高阶孤子的分裂和四波混频效应.同时研究了不同抽运功率和不同抽运波长下超连续谱产生的情况,发现对同一根光纤,抽运功率由小到大变化时,可将输出的光谱分为初始展宽,剧烈展宽和饱和展宽三个阶段,当输出的光谱处于初始展宽和饱和展宽阶段时,都会存在一定的抽运残留,当输出的光谱处于剧烈展宽时,转 关键词： 光子晶体光纤 超连续谱 高阶孤子 反常色散区     

飞秒激光脉冲在高非线性光子晶体光纤中产生超连续谱的实验研究

使用钛宝石激光器抽运一根长1m的高非线性光子晶体光纤，获得的超连续谱波长覆盖范围为420—1700nm，输出功率为170mW，转换效率在20%以上；对实验结果给出了详细的分析，并与理论模拟结果相比较，认为超连续谱产生的主要原因是高阶孤子的分裂和四波混频效应.同时研究了不同抽运功率和不同抽运波长下超连续谱产生的情况，发现对同一根光纤，抽运功率由小到大变化时，可将输出的光谱分为初始展宽，剧烈展宽和饱和展宽三个阶段，当输出的光谱处于初始展宽和饱和展宽阶段时，都会存在一定的抽运残留，当输出的光谱处于剧烈展宽时，转     

Characteristic comparison of single-pumped L-band erbium-doped fiber amplified spontaneous emission sources

We experimentally investigate the single-pumped L-band (1570–1610 nm) erbium-doped fiber amplified spontaneous emission (ASE) source in four configurations with single-pass forward, single-pass backward, double-pass forward (DPF), and double-pass backward structures. The characteristics are examined and compared in terms of the output power, mean wavelength, spectral linewidth, and pumping conversion efficiency. Among them, only DPF configuration is satisfied, and other configurations are intrinsically hard to be an L-band ASE source for applications. Such results are significantly different as compared with their corresponding C-band counterparts.     

高功率光纤激光器中ASE噪声的测量方法（英）

高峰值功率脉冲光纤激光器在激光雷达系统中有着广泛的应用。然而,光纤激光器中放大自发辐射噪声（ASE）严重影响了系统的探测性能。提出一种测量高峰值功率脉冲光纤激光器中ASE噪声的方法。在该方法中,首先对高峰值功率的激光脉冲衰减,然后在时域分别测量和计算ASE噪声和激光脉冲的相对能量。给出了光纤激光器在驱动电流分别为6 A,7 A和8 A时衰减后的ASE噪声廓线以及ASE噪声占激光脉冲能量的比例。     

天光一号预放大器中的放大自发辐射效应

 在三维放大自发辐射（ASE）的模拟计算中，计入了侧壁反射效应以及KrF自发辐射的谱线形状（高斯型、洛伦兹型及平顶型）的影响，并对空间网点的影响进行了考察。经过综合分析，给出了ASE对预放大器放大特性影响的上、下限范围。当计入平顶型频谱分布，壁反射系数为 0 .2时，与不计入ASE的情形对比，天光一号预放大器的提取效率下降为35%。     

Effect of different metal-backed waveguides on amplified spontaneous emission

We investigate the effect of a metallic electrode on the ability for poly[2-methoxy-5-(2’-ethylhexyloxy)-1,4phenylene vinylene](MEH-PPV) film to undergo amplified spontaneous emission(ASE).The threshold of the device with Ag cladding is about 10 times greater than that of a metal-free device,but metal such as Al completely shuts off ASE.The ASE recurs when a thin spacer layer,such as a few nanometers of SiO 2,is introduced between the MEH-PPV film and the Al cladding.Compared with the Cu or Al electrode,the Ag cladding is most suited to serve as an electrode with its low optical loss due to its high work-function and reflectivity.     

铋基掺铒光纤放大器中放大自发辐射处理研究

分别设计了一个带光隔离器和一个带光环形器的复合型宽带铋基掺铒光纤放大器(Bi-EDFA),理论上研究了Bi-EDFA中对于后向传输放大自发辐射(ASE)的处理对放大器性能的影响。研究表明,在C+L波段多波长信号同时输入情形下,通过在铋基掺铒光纤中插入一个光隔离器抑制后向传输的ASE,可以提高放大器各波长信号增益,降低噪声系数。利用一个光环形器引导后向传输的ASE去泵浦一段未抽运的低掺杂铋基掺铒光纤,可以显著地提高放大器长波段信号增益,而噪声系数只是略有增加,理论研究与报道的实验结果达到了比较好的一致。研究结果对于新型宽带Bi-EDFA的设计和应用具有一定实际指导意义。     

120-nm,10-GHz supercontinuum generation in a dispersion-shifted fiber pumped by a three-stage compressed gain-switched DFB laser

The supercontinuum (SC) generation in conventional dispersion-shifted fiber (DSF) at the repetition rate of 10 GHz with a three-stage compressed gain-switched distributed feedback (DFB) laser as pump source was demonstrated. A novel SC pulse source with a bandwidth up to 120 nm was obtained. At the same time, the stable, narrow pulses with pulsewidth of 9.2 ps and time-bandwidth product of 0.46 were filtered out across the whole SC bandwidth.     

Initial dynamics of supercontinuum generation in highly nonlinear photonic crystal fiber

We present a theoretical and experimental analysis of supercontinuum generation in very short lengths of high-nonlinearity photonic crystal fibers. The Raman response function for Schott SF6 glass is presented for what is believed to be the first time and used for numerical modeling of pulse propagation. Simulation and experiments are in excellent agreement and demonstrate the rapid transition to regimes of spectral complexity due to higher-order nonlinear effects.     

The amplified spontaneous emission in TE CO2 laser with a half-cavity

The new structure with a half-cavity in TE CO₂ laser is described. In this device, a total of nearly 50 lines from transitions in P and R branches of the 9.6 and 10.6 μm bands is observed. The energy, the spot pattern and pulse width of those lines are tested.     

Optimization of highly nonlinear dispersion-flattened photonic crystal fiber for supercontinuum generation

A simple type of photonic crystal fiber (PCF) for supercontinuum generation is proposed for the first time. The proposed PCF is composed of a solid silica core and a cladding with square lattice uniform elliptical air holes, which offers not only a large nonlinear coefficient but also a high birefringence and low leakage losses. The PCF with nonlinear coefficient as large as 46 W 1 · km-1 at the wavelength of 1.55 μm and a total dispersion as low as ±2.5 ps · nm-1 · km-1 over an ultra-broad waveband range of the S-C-L band (wavelength from 1.46 μm to 1.625 μm) is optimized by adjusting its structure parameter, such as the lattice constant Λ , the air-filling fraction f , and the air-hole ellipticity η. The novel PCF with ultra-flattened dispersion, highly nonlinear coefficient, and nearly zero negative dispersion slope will offer a possibility of efficient super-continuum generation in telecommunication windows using a few ps pulses.