A Step-by-Step Tunable Compound External Cavity Semiconductor Laser with Two-Side Feedback Coupling

A kind of compound external cavity semiconductor lasers (CECSL) is presented, by which laser with a discretely tunable wavelength can be obtained to meet the potential demands of the wavelength division multiplexing system. By the introduction of two-side feedback coupling in the CECSL, the CECSL can operate more efficiently, and its side-mode suppression ratio is high up to 50 dB.