In-band noise suppression using novel monolithically integrated semiconductor optical amplifier-based ultra-compact interferometers

Novel all-optical noise suppressors based on the nonlinear transfer function properties of monolithically integrated active waveguide interferometers are proposed and demonstrated. Through a power map imbalance between the two arms of the interferometers, each of which contains multi-contact semiconductor optical amplifiers, a nonlinear transfer function is created, which can then be exploited to achieve in-band noise suppression. The authors demonstrate the use of such a mechanism in ultra-compact Mach-Zehnder and Michelson interferometers (MIs). Experimental work demonstrates a 5.0-dB optical signal-to-noise ratio improvement for the Mach-Zehnder and an 8.4-dB improvement for the MIs, respectively. It is shown that for input data the Mach-Zehnder is capable of providing a Q factor improvement of 4.1 dB. To the authors knowledge, these devices constitute the smallest integrated interferometer structures reported to date demonstrating in-band noise suppression.