Vertical-cavity semiconductor discriminator for amplified spontaneous emission

In communications, optical amplification introduces noise in the system through amplified spontaneous emission (ASE), which degrades the system performance. The non-linear transmission characteristics of semiconductor absorbers can be adjusted to substantially improve the extinction ratio of an optical data sequence and remove low intensity noise over a wide spectral range. By combining an optical amplifier with a non-linear gate based on a semiconductor saturable absorber one can make a compact device with excellent characteristics. we report on a monolithic all-optical discriminator that operates in the 1.55-μm spectral range in the reflection mode. The performance of the discriminator/gate was tested in two-stage amplifier system. Efficient ASE suppression is demonstrated by applying a closely optimized MQW structure.