ANALYSIS AND ASSESSMENT OF THE GAIN OF OPTICALLY PUMPED SURFACE-NORMAL OPTICAL AMPLIFIERS

This paper analyzes and assesses the gain of optically pumped surface- normal MQW optical amplifiers. The proposed amplifiers have the advant age of polarization independence, high coupling efficiency to and from optical fibers, and flexibility of operating wavelength. We analyzed the gain characteristics of 100- to 200-period MQWs and verified the d ependence of gain on a strained lattice and selective doping. Theoreti cal analysis' of such MQWs shows a single-pass gain of 3 dB with broad operation bandwidth. A single-pass gain of 2.6 dB is obtained experim entally in an InGaAs/lnGaA1As MQW amplifier, which is compared with ca lculations. The use of a Fabry-Perot interferometer (FPI) structure in an optical amplifier is a useful way to increase the gain, but causes a problem of narrow operation bandwidth when the single-pass gain is low. Therefore, a single-pass gain above 2 to 3 dB is a prerequisite t o achieve both a high gain and moderate operation bandwidth in FPI-str uctured optical amplifiers. We have designed an FPI-structured surface -normal optical amplifier both with a high gain of 10.1 dB and broad o peration bandwidth of 4.6 nm, when a single-pass gain is 3 dB.