由分子束外延生长的高速GaAs异质结双极光电晶体管

本文报导了一种新颖的异质结光电晶体管(HPT),它采用的是双基区结构,以便使发射极-基极耗尽区置于宽禁带材料中。在半绝缘衬底上制造出了小型的HPT,其最大电流增益β=300。用微微秒脉冲染色激光器已获得响应时间,其上升时间缩短到250ps。FWHM=320ps。     

高峰值功率皮秒超短脉冲抽运KTP晶体倍频研究

脉冲光纤激光器具有输出光束质量好、峰值功率高等优势,易于激发晶体内部的非线性效应。晶体非线性效应能够将光纤激光的近红外输出波段变换至深紫外或中红外等波段。利用实验室自主搭建的中心波长为1064nm,脉宽为650ps的脉冲光纤激光器抽运KTP(磷酸钛氧钾)晶体,实现了高功率超短脉冲对1064nm激光的单程倍频,输出532 nm激光。将脉冲宽度由650 ps压缩至1 ps后,抽运激光的峰值功率密度达到24.97GW/cm2,有效地将单程倍频转换效率从0.8%提高到8.4%。研究了不同平均功率、脉宽、光斑直径的超短脉冲下KTP晶体的倍频效率,验证了未来在振荡腔结构下实现KTP晶体高效倍频的可行性。     

基于光电-电光变换的高功率激光装置时标激光系统EI北大核心CSCD

提出了一种时标基准信号红外长程传输结合近程光电-电光转换的时标激光系统设计方案,该方案首先使用红外单模光纤完成时间基准信号的长程传输,然后使用光电探测器将红外时标基准信号转换为电信号驱动蓝光直调LD激光器,最终获得输出波长为450 nm,输出功率47 mW,脉冲宽度为120 ps的时标光信号。实验结果表明,所提方案可为激光驱动器提供窄脉宽,可长程传输的时标光信号用于甚多束紫外激光脉冲同步同发监测,同步监测精度可达10 ps。文中技术方案规避了敏感的固体激光放大与倍频过程,提高了时标光脉冲波形的稳定度与同步监测系统的可靠性。     

CaS:Eu,Sm薄膜的红外上转换发光效率

采用电子束蒸发和磁控溅射技术制备了具有红外上转换和光存储特性的电子俘获材料CaS:Eu,Sm薄膜,利用不同脉宽的超短红外激光测试了它们的红外上转换效率,指出CaS:Eu,Sm薄膜的红外上转换发光效率不仅与制备工艺及热退火工艺密切相关,而且存在"耗尽"现象.薄膜透过率及空间分辨率测试表明,尽管膜厚及热退火处理对薄膜的透过率及空间分辨率有影响,但它们可显著增加CaS:Eu,Sm薄膜的红外上转换发光效率.     

基于光电-电光变换的高功率激光装置时标激光系统

提出了一种时标基准信号红外长程传输结合近程光电-电光转换的时标激光系统设计方案，该方案首先使用红外单模光纤完成时间基准信号的长程传输，然后使用光电探测器将红外时标基准信号转换为电信号驱动蓝光直调LD激光器，最终获得输出波长为450 nm，输出功率47 mW，脉冲宽度为120 ps的时标光信号。实验结果表明，所提方案可为激光驱动器提供窄脉宽，可长程传输的时标光信号用于甚多束紫外激光脉冲同步同发监测，同步监测精度可达10 ps。文中技术方案规避了敏感的固体激光放大与倍频过程，提高了时标光脉冲波形的稳定度与同步监测系统的可靠性。     

被动调Q固体激光器上转换效应的数值模拟

在主动调Q固体激光器上转换效应(ETU)理论的基础上,给出了包含上转换效应项的被动调Q固体激光系统的耦合速率方程组。采用变步长龙格-库塔数值方法,针对Nd∶YAG激光晶体和Cr4 ∶YAG可饱和吸收体,对上转换效应对输出脉冲参数的影响进行了数值分析。在低抽运功率条件下,上转换效应对输出脉冲的能量和峰值功率影响较大;在高抽运功率条件下,上转换效应对平均输出功率影响较大。在抽运功率逐渐增加的过程中,上转换效应对输出脉冲能量和峰值功率的影响逐渐减弱,对输出激光的脉冲宽度(FWHM)和重复频率的影响则可以被忽略。数值计算结果与实验所得结果基本一致。     

高效快速的硅雪崩光电二极管

本文报导了高效,快速的保护环硅雪崩光电二极管(GAPD)和拉通型雪崩光电二极管(RAPD)。为使 GAPD 消除光电流中的扩散慢分量,在理论上分析和计算了零场区对它的影响。通过单晶片背面蚀洞减薄,并在背面作硼扩散构成内建场,以便在不增加工作电压的情况下,实现快速响应和高量子效率。并介绍了在中阻硅单晶片上,用离子注入制作高场区,用上述减薄方法制造了 RAPD。两种实验器件所获得的性能如下:GAPD—击穿电压为105～120V;对锁模 Nd:YAG 激光脉冲,输出脉冲半宽度τ=500ps,前沿为450ps,后沿为750ps,在λ=0.9μm 下,量子效率η≥30%。而 RAPD—击穿电压为120～180V,对锁模 Nd:YAG 激光脉冲,输出脉冲半宽度τ=450ps,前沿和后沿均为450ps,在λ=0.9μm 下,量子效率η≥60%。     

在中红外波段通过AgGaS_2降频变換产生可调微微秒脉冲

在差频情况下,一台Nd:YAG锁模激光器和一台行波染料激光器在AgGaS_2晶体里混频,生产微微秒脉冲。染料激光器在1200～1460nm之间是可调的。最后得到的参量脉冲可调波段为3.9～9.14μm。频谱带宽是相当窄的。测量值为△v=6.5cm~(-1),该值在整个测量范围内为一常数。百分之几的Nd:YAG激光光子转换为红外光子。21ps的泵浦脉冲产生8ps参量脉冲。     

CaS∶Eu,Sm薄膜的红外上转换发光效率

采用电子束蒸发和磁控溅射技术制备了具有红外上转换和光存储特性的电子俘获材料CaS∶Eu ,Sm薄膜 ,利用不同脉宽的超短红外激光测试了它们的红外上转换效率 ,指出CaS∶Eu ,Sm薄膜的红外上转换发光效率不仅与制备工艺及热退火工艺密切相关 ,而且存在“耗尽”现象。薄膜透过率及空间分辨率测试表明 ,尽管膜厚及热退火处理对薄膜的透过率及空间分辨率有影响 ,但它们可显著增加CaS∶Eu ,Sm薄膜的红外上转换发光效率。     

飞秒激光脉冲烧蚀涡轮叶片材料的仿真和实验

为研究飞秒激光脉冲对涡轮叶片材料的冲击打孔特性，使用双脉冲改写方程的激光光源项，并对涡轮叶片材料进行数值模拟，得到了镍基高温合金在飞秒激光双脉冲冲击打孔下的晶格和电子温度。通过对比单脉冲的模拟结果发现:双脉冲烧蚀情况下，材料电子和晶格出现2个峰值温度，且电子和晶格的平衡温度相比单脉冲提高345ｋ，平衡时间延长了5ps，用 美国Ray Crop生产的飞秒脉冲激光器，对镍基高温合金材料在不同的激光参数下:激光脉冲宽度、激光能量、激光频率、脉冲间隔对材料的烧蚀进行双脉冲打孔，得到孔的形貌特征，并与单脉冲打孔对比发现双脉冲打孔的质量和效率优于单脉冲。     

Picosecond optical pulse compression from gain-switched 1.3 ?m distributed-feedback laser diode through highly dispersive single-mode fibre

The first demonstration to compress the linearly chirped optical pulses from a gain-switched distributed-feedback laser diode (DFB-LD) is described at 1.3 ?m wavelength. By travelling through a highly dispersive single-mode fibre with 48 ps/nm normal dispersion, a 26 ps (FWHM) pulse having red-shift frequency chirping of 85 GHz (FWHM) is compressed to 8.3 ps with the time-bandwidth product of 0.71.     

四氯化碳的背向受激喇曼散射研究

用倍频Ｎｄ：ＹＡＧ锁模激光５３２ｎｍ泵浦ＣＣｌ４的背向受激喇曼散射，一阶斯托克斯谱线５４６ｎｍ的能量转移效率为１３％，脉宽（ＦＷＨＭ）为８ＰＳ，比泵浦激光５３２ｎｍ的脉宽４０ＰＳ明显变窄。     

Study of SBS slow light based on nano-material doped fiber

A novel optical fiber doped with nano material InP is manufactured by the modified chemical vapor deposition (MCVD). The slow light based on stimulated Brillouin scattering (SBS) in the optical fiber is studied. The results show that a time delay of ~738 ps is obtained when the input Stokes pulse is 900 ps(FWHM) and the SBS gain is ~15. It shows that a considerable time delay and an amplification of the input light can be achieved by this novel optical fiber.     

Optical pulse compression in 1.5 μm wavelength region usinglarge-positive-dispersion fibre and grating pair

Optical pulse compression at 1.5 μm has been conducted. 20 ps (FWHM) optical pulses from a Tl:KCl-colour-centre laser were compressed into pedestal-free 1.2 ps pulses using a large-positive-dispersion fibre and a grating pair. In addition, 280 fs pulses were obtained from the resultant 1.2 ps through the soliton compression effect in a negative-dispersion fibre     

High-speed pulse generation using a sinusoidally driven Ti:LiNbO3 directional coupler travelling-wave optical modulator

We report the generation of 47 ps (FWHM) optical pulses at a 5 Gbit/s repetition rate using a sinusoidally driven Ti-LiNbO3 directional coupler modulator with travelling-wave electrodes By selective DC bias of the switch, these pulses are obtained without overdriving and without velocity matching of the electrical and optical waves.     

Real-time oscilloscope observation of an ultrafast photodiode response to mode-locked laser pulses

Pulses of 100 ps full width at half maximum (FWHM) have been displayed on a direct current to 5-GHz real-time oscilloscope. The 100-ps duration includes contributions from the oscilloscope, the photodetector, and the laser pulse,Maximum current in the linear regime of the photodiode is ≈3 amperes so that electric pulses of ≈70 ps FWHM and ≈150 volts can be obtained with the laser-detector combination. Results of a simple optical method for determining the exposure time of high-speed electronic cameras are also briefly given.     

Epitaxial n+ layer GaAs mesa-finger interdigital surfacephotodetectors

Several varieties of interdigital surface photodetectors have been fabricated on semi-insulating GaAs using mesa-etched n⁺ epitaxial layers as the carrier collection electrodes. This structure provides a significant responsivity improvement over conventional metal-semiconductor-metal (MSM) photodiodes by eliminating the surface reflection of the metal fingers and by providing increased photoconductive gain. High-speed testing using 100-ps doubled Nd:YAG pulses gave FWHM (full width at half maximum) responses of less than 500 ps for a 4-μm finger width and spacing and showed minimal degradation from standard MSM detectors of the same surface geometry. By introducing no additional process steps, the mesa-finger detectors are also monolithically compatible with mesa-etched GaAs MESFET technology     

电子俘获材料的红外最小可激发阈值

在对撞脉冲锁模ＮｄＹＡＧ激光器产生的１．０６４μｍ超短红外脉冲激光激励下,采用参考光和测量光同时入射的测量方案,利用一台可见光条纹相机进行了电子俘获材料ＣａＳＥｕ,Ｓｍ的红外最小可激发阈值的研究,结果表明：在可见光条纹相机最小可探测能量密度Ｊｍｉｎ＝８．３×１０－１０Ｊ／ｍｍ２的条件下,测得电子俘获材料ＣａＳＥｕ,Ｓｍ的红外最小可激发阈值优于４．８×１０－９Ｊ／ｍｍ２。     

Reduction of laser chirp in 1.5 ?m DFB lasers by modulation pulse shaping

The dynamic linewidth of 1.5 ?m ridge waveguide DFB lasers is shown to be reduced by shaping the pulse of the laser modulating waveform. Pulse shaping is performed by a second-order network designed to cancel the small-signal laser resonance. Results demonstrate a dynamic linewidth reduction from 1.4 ? to 0.55 ? FWHM for a 500 ps pulse.