Generation and detection of tunable ultrashort infrared and far-infrared radiation pulses of high intensity

We report on generation and detection of intense pulsed radiation with frequency tunability in the infrared and far-infrared spectral regions. Infrared radiation is generated with a transversally electrically excited high pressure CO₂ laser. A laser pulse of a total duration of about 300 ns consisted, due to self mode locking, of a series of single pulses, some with pulse durations of less than 450 ps and peak powers larger than 20 MW. Using these pulses for optical with durations less than 400 ps were obtained. For detection a new ultrafast superconducting detector was used.     

Generation and amplification of ultrashort optical pulses

During the last two years since the 1966 Iternational Quantum Electronics Conference further progress toward obtaining high-power light pulses has taken place. An effective method of ultrashort light pulse generation (mode locking) has been developed, further development of the method of coherent amplification of light pulses has been recorded, and new prospective ideas have been put forward. The present paper briefly reports on the data obtained by us in these directions.     

Generation of ultrashort electrical pulses in semiconductor waveguides

We report a novel device capable of generating ultrashort electrical pulses on a coplanar waveguide (CPW) by means of optical rectification. The device consists of a completely passive GaAs-based optical waveguide, which is velocity matched to a CPW line. Optical pulses are injected into the device and electrical pulses are collected at the output. Experimental results obtained in the laboratory show the potential of this device for high speed optical-to-electrical conversion.     

用LBO晶体产生紫外超短脉冲

将激光波长自由转换并加以利用是物理工作者追求的目标。为此人们正在不断开发波长转换用的各种非线性光学晶体。 三硼酸锂晶体(简称LBO)是首先由福建物构所开发成功的新型非线性光学晶体。除了有适中的有效倍频系数、损伤阈值高等特点外,最突出的特点是紫外透光区域可短至160nm,适     

Generation of high-average-power ultrabroad-band infrared pulses

This paper summarizes the results of analytical and numerical studies on a novel technique that is capable of providing high average power ultra broadband radiation that extends from approximately 2 to 16 μm. Such a spectrum has several potential applications, including telecommunications and remote sensing. Additional attractive features of the new source are its anticipated compact size, light weight, ruggedness, and affordable cost. The technique is based on the interaction of a beat wave with a nonlinear medium. The beat wave is formed from the mixing of two CO₂ laser beams with closely spaced wavelengths, such as 9.5 and 9.6 μm. The discrete ultrabroad-band spectrum is generated in a nonlinear optical medium by the self-phase modulation process, a third-order nonlinearity. The long-wavelength portion of the spectrum, i.e., from 5 to 16 μm is produced directly from the interaction of the beat wave with a GaAs crystal. The short-wavelength portion of the spectrum is produced from the interaction of a frequency-doubled beat wave with a GaAs crystal following the chirping of the pulse by a different GaAs crystal and its subsequent optimal compression by a thin sapphire slab     

Generation of ultrashort pulses from a neodymium glass laser system

A neodymium glass laser system capable of generating high-energy, ultrashort pulses at a convenient repetition rate is described. The effect of nonlinear frequency pulling on active mode locking is discussed. By minimizing the nonlinear frequency pulling, it is possible to routinely generate stable ~10-ps pulses at a 100-MHz repetition rate from the actively mode-locked oscillator. The regenerator amplifier increases the oscillator pulse energy to over 30 μJ at a 370-Hz repetition rate. Using intracavity self-phase modulation, the regenerative amplifier also broadens the pulse bandwidth to ~35 Å. By subsequent pulse compression while maintaining high energy, it is possible to produce 0.55-ps pulses with >10 μJ. An optical fiber pulse compressor further shortens the pulses to 30 fs (30 nJ), the shortest pulses ever generated at 1.054 μm from a neodymium laser system     

可调谐双波长低抖动增益开关光脉冲的产生

提出了一种产生可调谐双波长低抖动超短光脉冲的新方法。采用外光注入法来降低增益开关F-P激光脉冲的时间抖动,实现了脉冲光谱的双波长可调谐输出。实验中利用两个多量子阱DFB激光器作为外部种子光源,通过温度控制和偏振态调节使外部种子光有效地耦合到增益开关F-P激光器中,输出的光脉冲时间抖动(均方根)从2.57ps降低至1.06ps,双波长的边模抑制比可达25dB。通过改变DFB激光器和F-P激光器的工作温度,可实现波长从1540nm到1560nm的可调谐输出。     

Low power low noise high speed tunable CMOS radiation detection system

This paper presents a design of low power and low noise, high speed readout front-end system for semiconductor detectors. The architecture comprises a folded cascode charge sensitive amplifier with gain enhancement, a pole-zero cancellation circuit and a complex shaper circuit with Gm-C topology. A local feedback amplifier based on a wide swing gain boosting scheme with dc level shifting has been used. The system has been fabricated in a 0.13-µm CMOS technology with a single 1.2-V supply voltage. Experimental results show the flexibility of the system where the key parameters, such as decay time, charge gain and peaking time can be tuned. For a nominal peaking time of 150 ns the power consumption of the entire channel is less than 5 mW. A power consumption-low noise tradeoff will be considered to match a detector capacitance of 5 pF. The output pulse has a peak amplitude of 200 mV for a charge of 10 fC from the detector and achieves a linearity better than 1% up to an input charge range of 12 fC.     

Generation and radiation of high-power ultrawideband nanosecond pulses

The results of investigation of the generation and radiation of high-power ultrawideband electromagnetic pulses are presented. The possibility of obtaining wave beams of radiation with orthogonal polarizations of the electric field is shown. The radiating system is a 16-element antenna array that can be separated into two subarrays operating in orthogonal polarizations and excited by pulses separated in time. Two design versions of orthogonal subarrays are studied.     

产生单模可调谐ps单脉冲的串联超短腔染料激光器

报道了亚nsN_2激光脉冲泵浦的两级超短腔串联和一级放大组成的染料激光器,产生单模、波长可连续调谐、脉宽可达17ps的单脉冲.讨论了放大级获得最佳增益及抑制ASE等有关问题.     

Influence of ultrashort pulses of electromagnetic radiation on parameters of metal-insulator-semiconductor structures

The effect of pulsed electromagnetic radiation with a leading-edge duration of 1.4×10^?9 s and a total pulse duration of ～11.5×10^?9 s, a repetition rate of 10 kHz, and various pulse energies (?2.4×10^?4 J) on Al/SiO₂/Si structures is studied. Capacitance-voltage characteristics of such structures were measured before, during, and after exposure to ultrashort pulses. Changes dependent on the pulse energy caused by insulator polarization and a transformation of the nonequilibrium defect structure of the interface with the semiconductor as a result of the irradiation were found, as well as irreversible changes associated with a breakdown observed after the radiation was switched off.     

强激光超短脉冲在非线性介质中传输引起的超加宽

利用以三阶非线性系数为基础的平面波理论,通过直接解非线性波动方程,研究强场(～10~(14)W/cm~2)作用下,超短脉冲(80fs)在非线性介质中传播所引起的光谱超加宽现象。在忽略色散效应的情况下,得到输出脉冲Stokes和反Stokes展宽的不对称性,并定量地解释了R.L.Fork等人的实验。     

Stretched ultrashort pulses for high repetition rate swept-wavelength Raman pumping

We demonstrate a novel, high repetition rate, swept-wavelength Raman pump source. The pump is based on stretched femtosecond pulses, initially generated in a passively modelocked, erbium-doped, fiber laser, and wavelength shifted in highly nonlinear, dispersion shifted fiber. The pump wavelength has a linear sweep in time, with a repetition rate of 69 MHz. The pump has a center wavelength of 1470 nm, a full-width at half-maximum (FWHM) of 31 nm, and an average power of 350 mW. We characterize the pump by performing pump propagation experiments and electrical spectrum measurements of signal lasers amplified with the swept-wavelength pump.     

同步泵浦染料激光器产生高功率可调谐微微秒激光脉冲

本文介绍一种用Nd:YAG双锁模的倍频脉冲序列,同步泵浦以曲率半径R=2m的凹面光栅所组成的染料激光器,实现了高功率可调谐的微微秒染料激光输出。用条纹照相机对同步泵浦锁模激光系统中各部分的输出特性进行了实验研究和测试。     

Generation of sequences of ultrashort pulses in erbium doped fibre single ring lasers

Active and passive mode locking has been observed in an erbium doped fibre single ring laser. Pulse durations as short as 100 fs at a repetition rate of 300 GHz have been measured from an erbium doped fibre amplification stage placed at the output of the fibre ring. The ultrafast regime depends critically on the dynamical evolution of the light polarisation along the cavity.<>     

超短激光脉冲研究——产生和测量,选择和放大

关于被动锁模钕玻璃激光器产生超短脉冲的研究,在国外已做了大量的工作。我们对超短脉冲的研究也已有多年的历史了。本工作一方面是为了产生微微秒脉冲和亚毫微秒脉冲,以供某些物理实验应用;另一方面,进一步摸索锁模规律,考察饱和吸收体锁模机理,研究各种参数对锁模的影响以及超短脉冲的性质等等。     

Generation and radiation of high-power ultrawideband pulses with controlled spectrum

A pulsed source of the ultrawideband radiation based on a nonlinear line and a single combined antenna is proposed. The frequency that corresponds to the maximum radiation spectrum can be tuned in the interval 0.5–1.3 GHz. The effective radiation potential of the source is 95–310 kV.     

高强度红外光医疗系统的设计

本文根据几何光学原理,设计了一种高强度红外光治疗系统,该系统可经红外光纤输出0．3～3．5胂波长的红外光,经过聚焦后光斑能量密度可达17KW／cm^2,焦点光斑直径为0．3mm,该系统可实现在多种医疗上的应用。