Design of nondispersion optical feedback system using diffraction grating for semiconductor laser multiple longitudinal modes control

The external optical feedback system with a diffraction grating and mirrors is designed as a light source system in wavelength division multiplexing transmission. This system can select not only oscillation center wavelength but also spectral range in semiconductor lasers by using an identical grating twice. Experimental results demonstrate selected oscillations of single and double longitudinal modes in a multimode semiconductor laser.