Weakly Index-Guided Interband Cascade Lasers with No Grown Top Cladding Layer or a Thin Top Cladding Layer

A weakly index-guided narrow ridge interband cascade laser (ICL) having no grown top cladding layer or a thin grown top cladding layer, comprising:

• a semiconductor chip comprising:
• a GaSb or InAs substrate;
• an active core comprising 3 to 15 ICL gain stages;
• a bottom optical cladding layer disposed between the substrate and the active core, the bottom optical cladding layer having a refractive index lower than a refractive index of the active core;
• a top optical cladding layer disposed on top of the active core, the top optical cladding layer having a thickness of 0-500 nm and having a refractive index lower than the refractive index of the active core;
• a thin heavily n-doped top contact layer disposed on the top optical cladding layer;
• and
• a top index-guiding layer disposed on the heavily n-doped top contact layer, the top index guiding layer having a refractive index higher than the refractive index of the active core;
• an inner ridge formed on a portion of the semiconductor chip,
• the inner ridge being defined by a patterned area on the semiconductor chip and by removal of the top index-guiding layer to expose the heavily n-doped contact layer in areas of the semiconductor chip outside the inner ridge;
• a dielectric layer deposited on top of the semiconductor chip and patterned such that the dielectric layer covers the sides only of the inner ridge such that the top of the inner ridge is exposed to air,
• the dielectric layer being patterned to form contact openings in the semiconductor chip on at least one side of the inner ridge;
• and
• a metal layer deposited on the patterned dielectric,
• the metal layer forming top electrical contacts to the top contact layer, the metal layer and the top contact layer forming an uninterrupted electrical connection between the top electrical contacts and the inner ridge;
• wherein the air comprises at least a part of a top cladding layer of the ICL;
• and
• wherein the ICL further includes an ion bombardment region along the semiconductor chip on both sides of the inner ridge, the ICL being ion-bombarded at an ion energy and dose sufficient to strongly suppress a vertical flow of current in the ion bombardment region, the ion bombardment region extending laterally on both sides of the inner ridge at least to a distance of current spreading in the bombarded material.