Stable and widely tunable dual-wavelength continuous-wave operation of a semiconductor laser in a novel Fabry-Perot grating-lens external cavity

We propose and experimentally demonstrate an external-cavity configuration for a 1.5-/spl mu/m InGaAsP semiconductor laser to generate tunable dual-wavelength optical output over a wavelength range of 60.8 nm. The Fabry-Perot (FP) grating-lens external cavity consists of a FP filter, a diffraction grating, a converging lens, and a totally reflecting mirror. The dual wavelength CW output has a spectral separation of 0.9 nm and a side-mode-suppression ratio of over 25 dB throughout the tuning range. The relative intensity variation between the two lasing wavelengths is smaller than 1.2 dB without any observable mode hopping.