Gain-saturation properties of a polarization-insensitive semiconductor amplifier and polarization-encoded wavelength conversion

Abstract

A semiconductor structure with both tensile and compressively (T/C) strained quantum wells (QWs) is a novel gain medium that has been used to demonstrate two-polarization lasers' and polarization-insensitive amplifiers.2 and it holds promise as a nonlinear optical element for polarization control. We have investigated the polarization dependence of the gain saturation in a polarization-insensitive traveling-wave amplifier (TWA) implemented with such a gain medium to determine whether the polarization insensitivity is retained as the amplifier saturates. We have used these devices to demonstrate polarization-encoded wavelength conversion. A modulation on a TM-polarized 1.319-μm control beam was transferred to a TE-polarized 1.316-μm signal beam with an unoptimized contrast ratio of 6 dB. In wavelength-division-multiplexing (WDM) applications such signal and control beams can be easily separated and redirected on the basis of polarization, thereby alleviating the problem of filtering two closely spaced optical frequencies.