<title>Multisection traveling-wave semiconductor laser amplifiers: analysis and optimization</title>

Abstract

Semiconductor laser amplifiers have been the object of increasing interest in recent years. Such an interest is due to the possibility of low noise direct amplification of optical signals in future high speed and coherent optical transmission systems. The travelling wave amplifier (TWA) is a Fabry-Perot amplifier (FPA) with anti-reflection coated end facets. TWAs present the disadvantage of a higher spontaneous emission noise level, which in FPAs is reduced by the wavelength selective cavity effect. On the other hand, the spectral characteristics of FPAs also mean a reduced signal bandwidth and the possibility of undesirable amplified signal reflections. With respect to homogeneously pumped laser amplifiers, multi-section structures for TWAs (MS-TWAs) seem to be attractive from the point of view of both the adjustable parameters (electrical pumping of each section) and the device performances in terms of gain saturation characteristics and four-wave mixing. In this paper we consider the possibility of optimizing 1.55 micrometers MS-TWAs with respect to the length and the electrical injection level of each homogeneously pumped region and to the input signal wavelength. The optimization is accomplished by taking into account the continuous-wave (cw) gain-output power characteristics and the thermal effects within the device. The analysis of the transient behavior shows that optical input pulses can undergo considerable amplitude distortion, if the amplifier is not properly designed.© (1992) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.