Measurement of laser frequency response through heterodyne technique using optical modulation

Abstract

An optical modulation technique for measuring the parasitic-free frequency response of high frequency semiconductor lasers is demonstrated. In this technique, we heterodyne light from two continuously tunable external cavity travelling wave ring lasers to produce RF beat signal. The optical signal is injected into the active region of a probed semiconductor laser in order to optically modulate the laser. The modulated light output from the probed semiconductor laser is then analyzed through a HP Noise Figure Measurement System being used as a spectrum analyzer. The Noise Figure Measurement System is controlled by a micro-computer and can measure down to a noise level of-174 dBm. This technique has a very high sensitivity and the applicablity of this technique is not limited to any particular wavelength or to any special laser structure.