External cavity multiline semiconductor laser for WDM applications

Abstract

A novel technical approach to build a multiwavelength laser source for DWDM applications is described. The basic idea of this system is to maintain simultaneous lasing operation in a gain medium at different wavelengths without mode competition. The system uses a novel dispersive cavity. By designing this cavity structure appropriately, the system creates its own microcavities-channels each lasing independently at different wavelengths across the complete gain spectrum of the laser active material. Multifrequency lasing on the basis of a single diode laser chip was analyzed theoretically and demonstrated experimentally. A simultaneous generation across ~80% of the FWHM of the luminescence bandwidth of the GaAlAs active medium (657-667 nm) in multifrequency regime with a special pre-assigned spectral composition (8 independent lines were obtained and up to tens of lines possible) was realized. The minimum spectral separation between lines was 6.2 GHz . The linewidth of each oscillation line was less than 2 GHz and the total output power of the laser was about 50mW. It was demonstrated that the output radiation could be collimated to laser beam with a divergence less than 5 mrad. For DWDM applications a version of this superbroadband semiconductor laser operating in one of the telecommunication wavelength bands around 1.3 or 1.5 µm is proposed.