Patent ID: 6563852
Filing Date: 2003-05-13
Classification: B82Y,H01S

Abstract:
A quantum cascade (QC) laser comprising a multilayer optical structure, said structure comprisinga core region of relatively large effective refractive index disposed between top and bottom cladding layers of relatively small effective refractive index, the core region comprising a multiplicity of nominally identical repeat units, each repeat unit comprising an active region and a carrier injection region, the active region having a layer structure selected to provide an upper and a lower carrier energy state, such that a carrier transition from the upper to the lower energy state results in emission of a photon of wavelength &lgr;, the carrier injection region having a layer structure selected to facilitate carrier transport from the lower energy state of the active region of a given repeat unit to the upper energy state of the active region of an adjacent downstream repeat unit, the top and bottom cladding layers disposed on either side of said core region, wherein at least said top cladding layer and said core region form a mesa structure; an insulating layer covering exposed surfaces of said cladding layers and said core region; and electrical contacts attached to the top and bottom cladding layers for facilitating the flow of electric current through the laser characterized in that the quantum cascade laser is self-mode-locking, wherein the insulating layer comprises a relatively thin layer of less than a micron in depth and the quantum cascade laser further comprises optically lossy sidewalls disposed to cover said relatively thin insulating layer in at least the area of said active region to provide mode coupling between said optically lossy sidewalls and said active region, said quantum cascade laser further comprising a relatively long active region cavity having a length of at least 3.5 mm so as to be sufficient for propagation losses to be greater than mirror losses.