Microwave generation and transmission is possible using directly modulated laser diodes (LD) and optical fibres. The chirp of the LD together with the fibre dispersion influences the microwave spectrum significantly. We calculate the optical spectrum of the LD and the photocurrent spectrum before and after fibre transmission analytically, and compare them with experimental results. We also report on bit error rate measurements for various operating conditions and show that FM-AM conversion in the fibre counterbalances the attenuation when increasing the transmission length. Introduction Hybrid fibre rad0 (HFR) networks upgrade existing copper or optical fibre cables by wireless transmission channels, employing the microwave and mm-wave frequency range 20. . .70 GHz. HFR may be used for future micro and pico-cell broadband mobile communication systems, for wireless in-house connections, or for bridging inexpensively the 'last mile' to a subscriber having no access to a fibre or coax system. Three main technologies exist for transmitting and generating microwave signals by optical means, namely direct intensity modulation (IM) of a laser diode (LD), suppressed carrier modulation with an external Mach-Zehnder modulator , and heterodyne techniques in which optical waves of different frequencies are coherently mixed. We discuss the direct IM of a chirping LD with a sinusoidal subcarrier at fm = 1.95; 2.52; 3.52 and 3.716 GHz for producing at a remote location the lcth harmonic ( I C = 9; 7; 5 and 5) microwave signal at lcfm = 17.6 and 18.58 GHz. We calculate the optical and the photocurrent spectra for an m o d u l a t e d subcarrier at various LD modulation current amplitudes without and with transmission over a dispersive fibre, and compare these spectra to measurements. Decreased bit error rate (BER) power penalties for zncreaszng transmission lengths are explained by these results. I1 Rate equation approach The rate equations for the phase p of the power amplitude a of the electric field, for the photon number Np N la12, and for the carrier concentration n~ [l, Eq. (2.77, 74, 78)] [a, Eq. (3.89)] as a function of the injection current represent a highly nonlinear system of dfferential equations, from which the (optical) Fourier spectrum ii of the power amplitude a may be calculated only numerically. To gain more physical insight, we simplify the problem as follows. Simplified approach The optical output field of a LD is represented by an analytic signal a with amplitude A and total output power Pa leaving the resonator (time t , angular frequency wo = 2 ~ f 0 , vacuum speed of light c, vacuum wavelength XO, frequency fo = c/Xo, Planck's constant h, time constant T R from h t e resonator mirror reflectivities), Spectrum of chirping laser diode a ( t ) = Ao(t) eJwut , Ao(t) = /Ao(t)/eJ'PO(t), P,(t) = $ la(t)I2 = N p ( t ) h f o / ~ ~ . (1) Following the analysis of [3] (also cited in [I, Eq. (5.2)-(5.4)] [2, Eq. (3.222, 3.146)]), the instantaneous f
微波的产生和传输可以使用直接调制的激光二极管(LD)和光纤。LD的啁啾和光纤色散对微波频谱有显著影响。对光纤传输前后LD的光谱和光电流谱进行了解析计算，并与实验结果进行了比较。我们还报告了各种工作条件下的误码率测量，并表明光纤中的FM-AM转换在增加传输长度时抵消了衰减。混合光纤rad0 (HFR)网络通过无线传输通道升级现有的铜缆或光纤电缆，采用微波和毫米波频率范围20.70 GHz。HFR可用于未来的微蜂窝和微蜂窝宽带移动通信系统，用于无线内部连接，或用于廉价地桥接“最后一英里”到无法接入光纤或同轴电缆系统的用户。利用光学手段传输和产生微波信号的主要技术有三种，即激光二极管(LD)的直接强度调制(IM)、外部马赫-曾德尔调制器的抑制载流子调制和不同频率光波相干混合的外差技术。讨论了带正弦子载波的啁啾LD在调频= 1.95时的直接调频;2.52;3.52和3.716 GHz用于在远程位置产生lth谐波(I C = 9;7;5和5)lcfm = 17.6和18.58 GHz的微波信号。我们计算了在不同的LD调制电流幅值下，在无色散光纤传输和有色散光纤传输的情况下，一mod的光学和光电流谱，并将这些光谱与测量结果进行了比较。这些结果解释了增加传输长度所带来的误码率(BER)功率损失的降低。电场功率幅值a的相位p、光子数Np N la12和载流子浓度N ~ [1, Eq. (2.77, 74, 78)] [a, Eq.(3.89)]作为注入电流的函数的速率方程代表了一个高度非线性的微分方程系统，从中可以仅用数值方法计算功率幅值a的(光学)傅立叶谱ii。为了获得更多的物理洞察力，我们将问题简化如下。LD的简化方法光学输出字段由一个解析信号与振幅和总输出功率Pa离开谐振器(时间t,角频率我们f = 2 ~ 0,真空光速c,真空波长XO,频率fo = c / XO,普朗克常数h,时间常数t R从h t e谐振腔镜反射率),光谱的啁啾激光二极管(t) = Ao (t) eJwut Ao (t) = / Ao (t) / eJ 'PO (t) P (t)拉(t) I2 = = $ N o / P (t) h f ~ ~。(1)通过对[3]的分析(也引用于[1,Eq. (5.2)-(5.4)] [2, Eq.(3.222, 3.146)])，可以计算出瞬时频率偏差(频率啁啾)Afo(t)相对于平均频率fo。定义[2，式(3.106)]中的幅相耦合Henry因子为20，则绝热角频移w为2。对于aPa(t) = 2Pa(0)，其组分获得饱和参数EG，场约束因子r，光子寿命'rp，微分量子效率v d = t P / t r和谐振腔体积VK，我们写(忽略自发发射和任何空间非均匀性n ~) 3-4
{"title":"Microwave Generation And Transmission With Chirping Laser Diodes And Dispersive Fibres","authors":"W. Freude, R. Braun, G. Großkopf, F. Schmidt","doi":"10.1109/MWP.1997.740276","DOIUrl":"https://doi.org/10.1109/MWP.1997.740276","url":null,"abstract":"Microwave generation and transmission is possible using directly modulated laser diodes (LD) and optical fibres. The chirp of the LD together with the fibre dispersion influences the microwave spectrum significantly. We calculate the optical spectrum of the LD and the photocurrent spectrum before and after fibre transmission analytically, and compare them with experimental results. We also report on bit error rate measurements for various operating conditions and show that FM-AM conversion in the fibre counterbalances the attenuation when increasing the transmission length. Introduction Hybrid fibre rad0 (HFR) networks upgrade existing copper or optical fibre cables by wireless transmission channels, employing the microwave and mm-wave frequency range 20. . .70 GHz. HFR may be used for future micro and pico-cell broadband mobile communication systems, for wireless in-house connections, or for bridging inexpensively the 'last mile' to a subscriber having no access to a fibre or coax system. Three main technologies exist for transmitting and generating microwave signals by optical means, namely direct intensity modulation (IM) of a laser diode (LD), suppressed carrier modulation with an external Mach-Zehnder modulator , and heterodyne techniques in which optical waves of different frequencies are coherently mixed. We discuss the direct IM of a chirping LD with a sinusoidal subcarrier at fm = 1.95; 2.52; 3.52 and 3.716 GHz for producing at a remote location the lcth harmonic ( I C = 9; 7; 5 and 5) microwave signal at lcfm = 17.6 and 18.58 GHz. We calculate the optical and the photocurrent spectra for an m o d u l a t e d subcarrier at various LD modulation current amplitudes without and with transmission over a dispersive fibre, and compare these spectra to measurements. Decreased bit error rate (BER) power penalties for zncreaszng transmission lengths are explained by these results. I1 Rate equation approach The rate equations for the phase p of the power amplitude a of the electric field, for the photon number Np N la12, and for the carrier concentration n~ [l, Eq. (2.77, 74, 78)] [a, Eq. (3.89)] as a function of the injection current represent a highly nonlinear system of dfferential equations, from which the (optical) Fourier spectrum ii of the power amplitude a may be calculated only numerically. To gain more physical insight, we simplify the problem as follows. Simplified approach The optical output field of a LD is represented by an analytic signal a with amplitude A and total output power Pa leaving the resonator (time t , angular frequency wo = 2 ~ f 0 , vacuum speed of light c, vacuum wavelength XO, frequency fo = c/Xo, Planck's constant h, time constant T R from h t e resonator mirror reflectivities), Spectrum of chirping laser diode a ( t ) = Ao(t) eJwut , Ao(t) = /Ao(t)/eJ'PO(t), P,(t) = $ la(t)I2 = N p ( t ) h f o / ~ ~ . (1) Following the analysis of [3] (also cited in [I, Eq. (5.2)-(5.4)] [2, Eq. (3.222, 3.146)]), the instantaneous f","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"81 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131954062","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Introduction There is increased demand for high speed fiberoptic links operating in the millimeter wave range with good noise figure and high dynamic range [1,2]. These links are used in data communications, multimedia signal distribution, providing fiberoptic access to wireless communications, as well as radar and remote sensing. Most commonly used millimeter-wave subcarrier sources are actively or passively modelocked semiconductor lasers. They are small, compact but have undesirably high chirp and phase noise. Mode locked fiber lasers provide high performance, but are bulky. In this paper we describe a compact mode locked Nd: LiNb03 microchip laser incorporated into a microwave cavity. The significant novelty of this approach is that the same medium, the Nd: L imo3 crystal, serves the gain medium as well as the phase modulator, in microchip configuration. Experimental results include mode locking at 40GHz and a phase noise of -1 lOdBc/Hz at 1kJ& offset. The presentation will also include an analysis of the mode locking in this device.
对工作在毫米波范围内、具有良好噪声系数和高动态范围的高速光纤链路的需求不断增加[1,2]。这些链路用于数据通信、多媒体信号分发、为无线通信以及雷达和遥感提供光纤接入。最常用的毫米波副载波源是主动或被动锁模半导体激光器。它们体积小，结构紧凑，但具有不受欢迎的高啁啾和相位噪声。锁模光纤激光器提供高性能，但体积庞大。在本文中，我们描述了一个紧凑的锁模Nd: LiNb03微芯片激光器集成到一个微波腔。这种方法的重要新颖之处在于，在微芯片配置中，相同的介质Nd: L imo3晶体既可以作为增益介质，也可以作为相位调制器。实验结果包括在40GHz时的模式锁定和在1k &偏移时的相位噪声为-1 lOdBc/Hz。演示还将包括对该设备中的模式锁定的分析。
{"title":"Modelocked Microchip Laser With Millimeter Wave Subcarrier","authors":"P. Herczfeld, A. Vieira, V. Contarino","doi":"10.1109/MWP.1997.740227","DOIUrl":"https://doi.org/10.1109/MWP.1997.740227","url":null,"abstract":"Introduction There is increased demand for high speed fiberoptic links operating in the millimeter wave range with good noise figure and high dynamic range [1,2]. These links are used in data communications, multimedia signal distribution, providing fiberoptic access to wireless communications, as well as radar and remote sensing. Most commonly used millimeter-wave subcarrier sources are actively or passively modelocked semiconductor lasers. They are small, compact but have undesirably high chirp and phase noise. Mode locked fiber lasers provide high performance, but are bulky. In this paper we describe a compact mode locked Nd: LiNb03 microchip laser incorporated into a microwave cavity. The significant novelty of this approach is that the same medium, the Nd: L imo3 crystal, serves the gain medium as well as the phase modulator, in microchip configuration. Experimental results include mode locking at 40GHz and a phase noise of -1 lOdBc/Hz at 1kJ& offset. The presentation will also include an analysis of the mode locking in this device.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"299 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121151864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An optical radar receiver link for S-band (3 GHz) application has been evaluated theoretically and experimentally. The total radar link including preamplifier shows a noise figure (NF) of 3 dB and a spurious free dynamic range (SFDR) of 104 dBIH2”. The optical link itself has a maximum SFDR of 115 dBIH2” at 3 GHz.
{"title":"A High Performance Fiber Optical S-band Radar Link","authors":"J. Onnegren, A. Alping","doi":"10.1109/MWP.1997.740289","DOIUrl":"https://doi.org/10.1109/MWP.1997.740289","url":null,"abstract":"An optical radar receiver link for S-band (3 GHz) application has been evaluated theoretically and experimentally. The total radar link including preamplifier shows a noise figure (NF) of 3 dB and a spurious free dynamic range (SFDR) of 104 dBIH2”. The optical link itself has a maximum SFDR of 115 dBIH2” at 3 GHz.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127239598","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Optoelectronic processing of microwave signals' requires photodetectors with both high speed and high saturation level. The low optical saturation intensities of classical high-speed photodiodes limit the delivered microwave power to few tenths of microwatts" ', '. In order to increase the saturation level of microwave photodetectors, we have proposed an original application of the synchronous drift, in a photoconductor, of photogenerated carriers with a moving interference pattern', '. This traveling fringes photodetector (TFP) provides a large detection volume that could be suitable for efficient generation of microwave signals. In this paper, we discuss on the influence of contacts on the TFP performances. We also present experimental results obtained with an optimized forward bias p.i.n GaAs sample that shows a sensitivity of 1 A" at resonance.
微波信号的光电处理需要高速、高饱和的光电探测器。经典高速光电二极管的低光学饱和强度限制了微波功率的传输，只有十分之一微瓦。为了提高微波光电探测器的饱和水平，我们提出了一种在光导体中具有移动干涉图案的光生载流子的同步漂移的原始应用。这种行条纹光电探测器(TFP)提供了一个大的探测体积，可以适用于微波信号的高效产生。本文讨论了接触对TFP性能的影响。我们还介绍了用优化的正偏置p.i.n GaAs样品获得的实验结果，该样品在共振时显示出1 a ' '的灵敏度。
{"title":"The Traveling Fringes Photoconductor Principle And Optimization","authors":"T. Merlet, D. Dolfi, J. Huignard","doi":"10.1109/MWP.1997.740238","DOIUrl":"https://doi.org/10.1109/MWP.1997.740238","url":null,"abstract":"Optoelectronic processing of microwave signals' requires photodetectors with both high speed and high saturation level. The low optical saturation intensities of classical high-speed photodiodes limit the delivered microwave power to few tenths of microwatts\" ', '. In order to increase the saturation level of microwave photodetectors, we have proposed an original application of the synchronous drift, in a photoconductor, of photogenerated carriers with a moving interference pattern', '. This traveling fringes photodetector (TFP) provides a large detection volume that could be suitable for efficient generation of microwave signals. In this paper, we discuss on the influence of contacts on the TFP performances. We also present experimental results obtained with an optimized forward bias p.i.n GaAs sample that shows a sensitivity of 1 A\" at resonance.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125532551","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We propose and demonstrate a scheme for upconversion of [F subcarrier signals with a millimeter-wave carrier using nonlinear photodetection and remote carrier supply. In a preliminary experiment, the former is realized by using ,a commercially available photodiode under its saturation condition, and the latter is provided by a suibharmonically hybrid mode-locked semiconductor laser. It is demonstrated that a 66-GHz carrier generated from the mode-llocked laser and 400-MHz subcarriers of IF laser output are successfully mixed after transmission over a 30-km non-dispersionshifted optical fiber.
{"title":"Millimeter-wave Upconversion By Nonlinear-photodetection Using A Carrier Generated From A remote Mode-locked Semiconductor Laser","authors":"T. Hoshida, M. Tsuchiya, T. Kamiya","doi":"10.1109/MWP.1997.740261","DOIUrl":"https://doi.org/10.1109/MWP.1997.740261","url":null,"abstract":"We propose and demonstrate a scheme for upconversion of [F subcarrier signals with a millimeter-wave carrier using nonlinear photodetection and remote carrier supply. In a preliminary experiment, the former is realized by using ,a commercially available photodiode under its saturation condition, and the latter is provided by a suibharmonically hybrid mode-locked semiconductor laser. It is demonstrated that a 66-GHz carrier generated from the mode-llocked laser and 400-MHz subcarriers of IF laser output are successfully mixed after transmission over a 30-km non-dispersionshifted optical fiber.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131681486","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Zolomy, T. Berceli, Attila Hilt, G. Járó, C. Aitchison, A. Baranyi, J. Ladvansky, J.Y. Liang
A new approach is presented utilizing low-noise distributed amplification based on a hybrid integration technology. This way eight-octave bandwidth has been achieved with a responsivity characteristics flat from 40 MHz up to 10 GHz.
{"title":"Eight-octave Bandwidth Optical Receiver Using Distributed Amplification","authors":"A. Zolomy, T. Berceli, Attila Hilt, G. Járó, C. Aitchison, A. Baranyi, J. Ladvansky, J.Y. Liang","doi":"10.1109/MWP.1997.740248","DOIUrl":"https://doi.org/10.1109/MWP.1997.740248","url":null,"abstract":"A new approach is presented utilizing low-noise distributed amplification based on a hybrid integration technology. This way eight-octave bandwidth has been achieved with a responsivity characteristics flat from 40 MHz up to 10 GHz.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131119367","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Radar, missile guidance and communications systems typically have rigid spatial constraints. However, in conventional systems, large amplifiers and motors are requirtxl to transmit high power and scan the antenna main beam, respectively. Waveguide typically is used because it has low loss and high power capability, but is bulky and not easily routed. These obstacles have: led to continuing research in system and component designs to produce integrated and compact designs. One method that has shown promise in remedying some of these problems is the active antenna array, which integrates active components directly into the antenna platform. Research has shown that power can be combined quasi-optically in active antenna arrays [I]-[3]. Also, the main beam can be electronically scanned by controlling the phase between adjacent antenna elements [4]-[5]. Recently, an active phased array with optical input and beam-scanning capability was reported [6]. In [6], a microwave reference signal is prlovided through an optical fiber link, but array control signal are provided electronically. In this work, a novel method of controlling individual array elements for beam-scanning is accomplished by optically illuminating commercially available MESFET transistors.
{"title":"An Active Phased Array With Optical Control And Beam-scanning Capability","authors":"W. Deal, T. Itoh","doi":"10.1109/MWP.1997.740255","DOIUrl":"https://doi.org/10.1109/MWP.1997.740255","url":null,"abstract":"Radar, missile guidance and communications systems typically have rigid spatial constraints. However, in conventional systems, large amplifiers and motors are requirtxl to transmit high power and scan the antenna main beam, respectively. Waveguide typically is used because it has low loss and high power capability, but is bulky and not easily routed. These obstacles have: led to continuing research in system and component designs to produce integrated and compact designs. One method that has shown promise in remedying some of these problems is the active antenna array, which integrates active components directly into the antenna platform. Research has shown that power can be combined quasi-optically in active antenna arrays [I]-[3]. Also, the main beam can be electronically scanned by controlling the phase between adjacent antenna elements [4]-[5]. Recently, an active phased array with optical input and beam-scanning capability was reported [6]. In [6], a microwave reference signal is prlovided through an optical fiber link, but array control signal are provided electronically. In this work, a novel method of controlling individual array elements for beam-scanning is accomplished by optically illuminating commercially available MESFET transistors.","PeriodicalId":280865,"journal":{"name":"International Topical Meeting on Microwave Photonics (MWP1997)","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-09-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132034849","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Krause, S. Dankowski, P. Kiesel, S. Tautz, U. Keil, H. Seichter, G. Dohler
We report on carrier and field dynamics in low temperature grown GaAs (LT-GaAs) layers by differential transmission. LT-GaAs is grown by molecular beam epitaxy under standard growth conditions except a lower substrate temperature of 200°C to 300°C instead of the usual 600°C. This leads to an incorporatioln of up to 1.5% excess arstmic in the crystal, mainly as A h and Asi, accompanied by V G ~ . These defects cause some outstanding properties of the material, for instance an extremely short carrier lifetime. Subsequent annealing at temperatures between 450°C and 900°C results in high resistivity and raised breakdown fields. All properties of LT-GaAs depend strongly on both the growth and the annealing temperature. The combination of short carrier lifetimes and high breakdown fields makes LT-GaAs a very interesting material for ultrafast electro-optical modulators. In particular, they are suitable for switching high optical power due to low (dark currents and small photo currents, which result in low electrical energy dissipation. IDC measurements on metal-semiconductor-metal (MSM)-modulators on 1 pm thick LT-(A1)GaAs layers yield remarkalble transmission changes ofup to 1:1.8. In this paper we focus on the dynamics of electroabsorption. Lifetimes of photogenerated carriers in LT-GaAs are well investigated without electric fields. However, the behavior under the influence of an electric field is essential for the development of electronic devices of any kind. We performed pump and probe experiments on LT-GaAs MSIM-modulators with lOOfs optical pulses from a mode-locked Ti:sapphire laser with spectral width of 8 nm. Taking advantage of an epitaxial lift-off technique we separated the LT-GaAs layers from the substrates and attached them to a thin sheet of glass. The field is applied via interdigitated finger contacts (MSM-contacts). We detected the transmission changes of th~e probe beam which are induced by the pump beam as a function of the delay between the two pulses. Measurements with and without applied voltage are compared'.
本文报道了低温生长GaAs (LT-GaAs)层的载流子动力学和场动力学。LT-GaAs通过分子束外延在标准生长条件下生长，只是衬底温度较低，为200°C至300°C，而不是通常的600°C。这导致晶体中含有高达1.5%的过量砷，主要以A h和Asi的形式存在，并伴有V G ~。这些缺陷导致了材料的一些突出特性，例如极短的载流子寿命。随后在450°C和900°C之间的温度下退火导致高电阻率和升高的击穿场。LT-GaAs的所有性能都与生长温度和退火温度密切相关。短载流子寿命和高击穿场的结合使LT-GaAs成为一种非常有趣的超快电光调制器材料。特别是，由于低暗电流和小光电流，它们适合于切换高光功率，从而导致低电能损耗。在1pm厚的LT-(A1)GaAs层上的金属-半导体-金属(MSM)调制器上的IDC测量产生了高达1:8 .8的显著传输变化。本文主要研究电吸收动力学。在没有电场的情况下，研究了LT-GaAs中光生载流子的寿命。然而，在电场影响下的行为对于任何类型的电子设备的发展都是必不可少的。我们利用光谱宽度为8 nm的锁模Ti:蓝宝石激光器的lofs光脉冲对LT-GaAs msim调制器进行了泵浦和探针实验。利用外延提升技术，我们将LT-GaAs层从基板上分离出来，并将其附着在薄玻璃上。磁场通过指间触点(msm -触点)施加。我们检测了在泵浦光的作用下，探针束的传输变化随两个脉冲间延时的变化。对有电压和无电压的测量结果进行比较。
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