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。     

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。     

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。     

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.     

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.     

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。     

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 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.     

Experimental investigation of supercontinuum generation in highly nonlinear dispersion-shifted fiber pumped by spectrum-sliced amplified spontaneous emission

Spectral broadening of spectrum-sliced amplified spontaneous emission (SS-ASE) in highly nonlinear, dispersion-shifted fiber in different dispersion regimes is investigated experimentally. We find that, the spectral noise of the amplified SS-ASE pump from Er³⁺-doped fiber amplifier seeds the spectral broadening via four-wave mixing or modulation instability. Stimulated Raman scattering, red-shifted Raman solitons, and blue-shifted dispersion waves all enhance the broadening of the spectrum. The effect of the polarization state of pump on supercontinuum generation is also investigated, and it is found that, linear polarization is more efficient than random polarization for pumping supercontinuum. Supercontinuum with −10 dB bandwidth of 200 nm is generated by launching linearly polarized pump with 33.5 dB m power into anomalous dispersion regime near to zero dispersion wavelength of fiber.     

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。     

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%。     

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.     

放大自发辐射对激光冲击处理7050铝合金的影响

利用高功率钕玻璃激光器对7050铝合金表面进行了冲击处理,保持泵浦功率不变,用压电传感器和示波器测试了激光冲击产生的压力波形,用X射线应力测量仪测量了激光冲击后铝合金表面的残余应力,并用非接触式光学轮廓仪分析了激光冲击后铝合金的表面形貌,研究了放大自发辐射强度对激光冲击处理7050铝合金冲击压力、残余应力和粗糙度影响的微观机理。研究结果表明:在泵浦功率不变前提下,放大自发辐射强度的增大降低了激光冲击波压力,铝合金表面残余压应力也随之降低,同时铝合金表面粗糙度增大。     

放大自发辐射对激光冲击处理7050铝合金的影响

 利用高功率钕玻璃激光器对7050铝合金表面进行了冲击处理,保持泵浦功率不变,用压电传感器和示波器测试了激光冲击产生的压力波形,用X射线应力测量仪测量了激光冲击后铝合金表面的残余应力,并用非接触式光学轮廓仪分析了激光冲击后铝合金的表面形貌,研究了放大自发辐射强度对激光冲击处理7050铝合金冲击压力、残余应力和粗糙度影响的微观机理。研究结果表明:在泵浦功率不变前提下,放大自发辐射强度的增大降低了激光冲击波压力,铝合金表面残余压应力也随之降低,同时铝合金表面粗糙度增大。     

Loss prediction of three-level amplified spontaneous emission sources in radiation environment

A model of three-level amplified spontaneous emission (ASE) sources, considering radiation effect, is proposed to predict radiation induced loss of output power in radiation environment. Radiation absorption parameters of ASE sources model are obtained by the fitting of color centers generation and recovery process of gain loss data at lower dose rate. Gain loss data at higher dose is applied for self-validating. This model takes both the influence of erbium ions absorption and photon bleaching effect into consideration, which makes the prediction of different dose and dose rate more accurate and flexible. The fitness value between ASE model and gain loss data is 99.98%, which also satisfies the extrapolation at the low dose rate. The method and model may serve as a valuable tool to predict ASE performance in harsh environment.     

Simultaneous brightness enhancement and wavelength conversion to the eye‐safe region in a high‐power diamond Raman laser

Brightness enhancement in an external cavity diamond Raman laser designed for high power conversion of a neodymium (1064 nm) laser to the eye‐safe spectral region is reported. Using a multimode input beam pulsed at 36 kHz pulse repetition frequency, 16.2 W with 40% overall conversion efficiency was obtained at the second Stokes wavelength of 1485 nm. The output beam had a quality factor of which is a factor of 2.7 times lower than that of the input beam, resulting in a higher overall brightness. The output power, brightness, and brightness enhancement obtained represent significant advances in performance for Raman lasers as well as other competing kHz‐pulsed eye‐safe technologies.     

Threshold reduction of a pulsed narrow-band β-Ba2BO4 optical parametric oscillator in a grazing–incidence configuration by injection of amplified spontaneous emission

Threshold reduction of a nanosecond, narrowband β-barium borate optical parametric oscillator by injection of amplified spontaneous emission (ASE) from a dye laser is described. The BBO-OPO uses a grazing–incidence–grating cavity and pumped at 355 nm by a single-mode Nd : YAG laser. A threshold reduction of 33% has been achieved over a tuning range of 20 nm using this technique.     

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。     

Classical and quantum self amplified spontaneous emission in a high gain free electron laser

We describe the quantum theory and the photon statistics of self amplified spontaneous emission (SASE) in a high gain free electron laser (FEL) using Glauber's quantum theory of coherence. We generalize a previous theory by taking into account many-mode effects and the initiation process resulting from classical shot noise, quantum noise, an injected coherent field and coherent bunching. In particular, we define the concept of quantum SASE which is appropriate when the initial quantum fluctuations dominate over the classical shot noise. We also discuss the conditions for the observation. Quantum SASE is a new quantum phenomenon in which the single electron uncertainty fluctuations of the conjugate variables position and momentum produce exponential amplification of the vacuum field.