Gain recovery of bulk semiconductor optical amplifiers

The gain recovery time of 1.55-μm bulk semiconductor optical amplifiers (SOA's) with lengths from 500 to 1500 μm has been measured with a continuous-wave (CW) probe in the time domain. It is shown to decrease with increasing length down to 60 ps for the longest SOA. This behavior is theoretically explained. A lower limit for the recovery time is observed and explained     

半导体光放大器的增益特性和偏振特性

介绍了半导体光放大器的两个重要特性:增益特性和偏振特性。增益特性中,描述了放大器中增益调制现象和增益饱和现象,并介绍了提高半导体光放大器增益的方法。偏振特性中,分析了半导体光放大器增益偏振敏感产生的原因,并列举了低偏振敏感度放大器的实现方法。最后报道了近几年才被注意的半导体光放大器相位偏振敏感特性。     

Proposed scheme for polarization insensitive GaInNAs-based semiconductor optical amplifiers

A novel scheme for polarization insensitive GaInNAs-based semiconductor optical amplifiers is proposed in which TE and TM polarization gain is almost equal for GaInNAs quantum wells with GaInAs barriers. The proposed scheme involves the growth of GaInAs metamorphic layers on GaAs. Based on a k /spl middot/ p Hamiltonian that accounts for the N-induced modifications of the bandstructure, we calculate the optical properties of GaInNAs-GaInAs quantum wells and explore the effect of GaInAs barriers on the valence band mixing effects. The TE and TM amplifier gain of GaInNAs-based semiconductor optical amplifiers with GaInAs barriers is then analyzed.     

量子阱半导体光放大器的增益偏振相关性研究

应用能带计算理论,研究了张应变量大小、量子阱厚度对量子阱半导体光放大器(SOA)中的增益偏振相关性的影响.采用张应变量子阱为有源区,设计了增益偏振无关的1.55 μm的SOA,它可以在较宽的载流子浓度范围、较宽的光波长范围内满足增益对偏振的不灵敏要求.另外,还采用混合应变量子阱为有源区,设计了增益偏振无关的1.31μm的SOA.     

Influence of residual facet reflectivity on nonlinearities in semiconductor optical amplifiers

A dynamic model for multichannel amplification by semiconductor optical amplifiers is used to predict the influence of the residual facet reflectivities on intermodulation distortion. For 25 dB of singlepass gain a reflectivity of 5*10/sup -4/ will result in 3 dB excess distortion.<>     

Intraband gain dynamics in bulk semiconductor optical amplifiers:measurements and simulations

We investigate experimentally and numerically the gain recovery time and gain compression resulting from intraband effects induced by sub-picosecond optical pulses in bulk semiconductor optical amplifiers. With the help of data produced by pump-probe measurements, the dependence of the intraband gain dynamics on pulse energy, device bias current, and length is discussed. The simulation results show a good agreement with the experimental data     

A novel method for polarization insensitive four-wave mixing in semiconductor optical amplifiers

A new method for obtaining polarization insensitive four-wave mixing with phase inversion in a semiconductor optical amplifier is proposed. The method uses the simplest configuration with co-propagating pump and signal waves. The possibility of polarization insensitive four-wave mixing is shown for a tensile quantum well. Polarization insensitivity can be obtained by the right detuning of the pump wavelength from the gain peak.     

Modeling broad-area semiconductor optical amplifiers

The authors report on the wave optics modeling of broad-area semiconductor amplifiers used in a double-pass reflective configuration. The results show excellent agreement with recent reports of 2.5 and 12 W of nearly diffraction-limited output from such systems. Several design issues that must be considered in a practical laser communication system based on this class of amplifier are discussed     

基于保持光注入的半导体光放大器自偏振旋转性能的改善

研究了基于“保持光”（holding beam）注入（HBI）改善半导体光放大器（SOA）自偏振旋转（SPR）性能的方法。HBI虽然降低了SOA的偏振模式增益,但是缩短了对TE和TM模式的增益恢复时间,从而加速了SOA器SPR特性对超快信号的响应。以基于SOA的SPR特性的光功率均衡为例,我们发现,HBI可以明显抑制和...     

Multiwavelength lasers based on semiconductor optical amplifiers

Stable multiwavelength lasing is demonstrated with a novel laser, in which a semiconductor optical amplifier offers optical gain and cascaded sampled fiber gratings serve as a comb filter. Five lasing lines are obtained with a fixed wavelength spacing of 0.8 nm. Optical power fluctuations among the lasing lines are improved by adjusting the reflectivity profile through the cascade of two sampled gratings     

Long wavelength vertical-cavity semiconductor optical amplifiers

This paper overviews the properties and possible applications of long wavelength vertical-cavity semiconductor optical amplifiers (VCSOAs). A VCSOA operating in the 1.3-μm wavelength region is presented. The device was fabricated using wafer bonding; it was optically pumped and operated in reflection mode. The reflectivity of the VCSOA top mirror was varied in the characterization of the device. Results are presented for 13 and 12 top mirror periods. By reducing the top mirror reflectivity, the amplifier gain, optical bandwidth, and saturation output power were simultaneously improved. For the case of 12 top mirror periods, rye demonstrate 13-dB fiber-to-fiber gain, 0.6 nm (100 GHz) optical bandwidth, a saturation output power of -3.5 dBm and a noise figure of 8.3 dB. The switching properties of the VCSOA are also briefly investigated. By modulating the pump laser, we have obtained a 46-dB extinction ratio in the output power, with the maximum output power corresponding to 7-dB fiber-to-fiber gain. All results are for continuous wave operation at room temperature     

Cross-polarization modulation in semiconductor optical amplifiers

The polarization sensitivity of semiconductor optical amplifiers can be assessed in terms of gain or in terms of induced phase shift. Although the former aspect has received a lot of attention, the latter is rarely mentioned in the literature. Nevertheless, this birefringence leading to a rotation of the lightwave polarization at the output of the device may give rise to some interesting or unwanted effects. An optical control of the birefringence can be applied to wavelength conversion, signal regeneration, all-optical switching or gating. In this letter, the variation of the birefringence with input polarization and input power is measured     

Sampling pulses with semiconductor optical amplifiers

We demonstrate three techniques to measure the instantaneous frequency and intensity of optical pulses using semiconductor optical amplifiers (SOAs). Four-wave mixing, gain-saturation, and interferometric switching through a nonlinear optical loop mirror are three mechanisms by which sampling is done. We have experimentally measured the intensity and chirp profiles of pulses with energies as low as 10 fJ. Since the nonlinearity in the SOA is relatively slow, these measurement techniques are most appropriate for picosecond pulses often found in telecommunication applications. The temporal resolution of these methods are limited by timing jitter, which was ≈0.5 ps for the mode-locked laser diodes we used in our experiments, and by the width of the switching window     

Wavelength conversion using semiconductor optical amplifiers

This paper reports a detailed theoretical study of the dynamics of wavelength conversion using cross-gain and cross-phase modulation in semiconductor optical amplifiers (SOA's) involving a large signal, multisection rate equation model. Using this model, recently reported experimental results have been correctly predicted and the effects of electrical and optical pumping on the conversion speed, modulation index, and phase variation of the converted signal have been considered. The model predicts, in agreement with experimental data, that recovery rates as low as 12 ps are possible if signal and pump powers in excess of 14 dBm are used. It also indicates that conversion speeds up to 40 Gb/s may be achieved with less than 3 dB dynamic penalty. The employment of cross-phase modulation increases the speed allowing, for example, an improvement to 60 Gb/s with an excess loss penalty less than 1 dB     

All-optical signal processing based on semiconductor optical amplifiers

In this paper,we review the recent progress in the optical signal processing based on the nonlinearity of semiconductor optical amplifiers (SOAs).The four important optical signal processing functional blocks in optical switching are presented,i.e.,optical wavelength conversion,optical regeneration,optical logic,and optical format conversion.We present a brief overview of optical wavelength conversion,and focus on various schemes to suppress the slow gain recovery of the SOA and improve the operating speed of the SOA-based optical switches.Optical regeneration including re-amplification,re-shaping and re-timing is also presented.Optical clock recovery that is essential for optical regeneration is reviewed.We also report the recent advances in optical logic and optical format conversion,respectively.After reviewing the four important optical signal processing functional blocks,the review concludes with the future research directions and photonic integration.     

Noise figure of vertical-cavity semiconductor optical amplifiers

The noise figure of vertical-cavity semiconductor optical amplifiers (VCSOAs) is investigated theoretically and experimentally. Limitations on the noise figure set by the reflectivity of the mirrors are studied. Highly reflective mirrors lead to increased output noise as well as lasing at moderate carrier densities, which imposes a limit on the obtainable population inversion. Expressions for the excess noise coefficient, which governs signal-spontaneous beat noise enhancement due to finite mirror reflectivity, are presented for transmission and reflection-mode operation. Experimental results from a VCSOA operating in the reflection mode at 1.3 μm are presented. The results, from optical as well as electrical measurement techniques, are analyzed and compared to theoretical values     

Theoretical study of GaInNAs-GaAs-based semiconductor optical amplifiers

We have calculated the basic properties of multiple-quantum-well semiconductor optical amplifiers (SOAs) with active regions based on the newly proposed material GaInNAs. The band structure is modeled using k/spl middot/p theory and accounting for strain effects and the material gain in the context of free-carrier theory. The performance of structures with different nitrogen composition that emit at the same wavelength is modeled using a multisection approach accounting for spontaneous emission. The trends in the SOA performance related parameters are identified and explained.     

垂直腔半导体光放大器带宽特性研究

为了研究垂直腔半导体光放大器(vertical cavity semiconductor optical amplifiers,VCSOA)中抽运光功率、分布布喇格反射镜(distributed Bragger reflector,DBR)周期数以及输入信号强度对其带宽特性的影响,采用传输矩阵法进行了数值模拟。计算模型中考虑了载流子和光强沿纵向的分布,以及腔内介质折射率的不均匀性对光波传输的影响。得到的结果与文献中的结论符合较好。结果表明,提高VCSOAs的抽运水平可以增大其峰值增益,同时会缩小其增益带宽;减小DBR周期数可以获得更大的增益带宽积。另外,输入光信号强度对VCSOA带宽的大小也有较大的影响。     

1.5 mu m band travelling-wave semiconductor optical amplifiers with window facet structure

1.5 mu m band travelling-wave semiconductor optical amplifiers (TWAs), characterised by their window facet structure and symmetrised active waveguide, have been developed. 1.5 dB spectral gain ripple and 1.3 dB TE-TM mode gain difference at 22 dB signal gain were achieved simultaneously. An average facet reflectivity as low as 0.06% was estimated.<>     

Influence of probe depletion and cross-gain modulation on four-wavemixing of picosecond optical pulses in semiconductor optical amplifiers

The influence of probe depletion (PD) and cross-gain modulation (XGM) on four-wave mixing (FWM) of picosecond optical pulses in semiconductor optical amplifiers has been investigated numerically. The effects of PD and XGM become more significant for shorter input pulsewidth, higher pulse energy and smaller pump-probe frequency detuning. Results indicate that if the effects of PD and XGM are neglected the FWM efficiency can be seriously overestimated