Self-collimating multiwavelength lasers

Abstract

The present invention provides self-collimating multiwavelength lasers (MWL) including a planar gain medium with a resonance cavity defined by superimposed gratings. These laser devices are characterized by lasing wavelengths with multiple peaks in their reflectance spectra defined by the superimposed gratings. The gratings also limit beam divergence, producing self-collimated multiwavelength output, with the potential for high power. These devices can be implemented in any planar gain medium in which multi-peak gratings can be produced, including but not limited to semiconductors and doped glasses. The self-collimated MWL's disclosed herein have applications in areas such as DWDM (dense wavelength division multiplexing) communications systems, free-space uses such as interconnects, range-finding, and inter-satellite infrared communication. In one aspect the device is a multiwavelength ring cavity laser including a planar gain medium with two orthogonal pairs of supergratings (SG) A and B, which emulate the superposition of M and N single-pitch gratings respectively. SG-A has a set of M diffraction wavelengths that depends on the incident angle &thgr;; a similar dependence on &phgr;=&thgr;−90° exists for the set of N diffraction wavelengths of SG-B. Wavelength-angle pairs common to both SG-A and SG-B will be resonant within the cavity as a whole. When combined with optical gain, the result is lasing at M by N wavelengths, collimated at a well-defined output angle.