Economic single mode lasers for WDM

Development of a cheap and simple laser which has narrow linewidth, suppressed sidemodes, is insensitive to temperature change and which can be easily fabricated at a range of wavelengths from a single wafer is one of the most sought after goals of optical communications for Wavelength Division Multiplexing. Toward such a device we have produced edge-emitting Fabry-Perot cavity lasers that have waveguide perturbations that modulate the output cavity mode spectra. The suppression of the cavity modes is a function of the geometry and positioning of the perturbations, therefore emission wavelength is insensitive to device temperature. Single mode operation is easily achieved with only three perturbations defined by standard optical lithography. Arrays of devices from a single chip display ranges of emission wavelengths, suggesting possible future applications to optical communications. Modelling using an optical field transfer matrix model indicates that this is not a reflectivity-controlled process, as for DBR structures, but rather a loss process that suppresses unwanted cavity modes. Fourier transforms of emission spectra display features corresponding to the waveguide perturbations and are being utilised as a design tool to select peak emission wavelength.