TECHNICAL FIELD

The present disclosure relates to lasers and, in particular, to quantum cascade laser and related methods.

BACKGROUND

Quantum cascade lasers (QCLs) differ from traditional semiconductor diode lasers in that they do not use a p-n junction for light emission. Multiple active regions are “cascaded” so that each injected electron can emit multiple photons and therefore enhance laser gain. Each active region includes a multi-layered semiconductor material structure. This multi-layered semiconductor material structure is designed to have an electronic band structure that gives the desired emission wavelength, and is manufactured with nanometer-level thickness control.

Most commercially available QCLs are of the “edge-emitting” variety. In these, linear ridges are created by etching vertically through the layered structure, which has been grown on a wafer substrate. These are cleaved so that the active region comprises a rectangular ridge several millimeters in length, which forms a waveguide. The laser radiation is amplified by passing back and forth along the axis of the ridge. Laser emission occurs on the end facets of these ridges.

SUMMARY

Generally speaking, a QCL may include a substrate and semiconductor layers adjacent the substrate and defining an active region. The active region may have a longitudinal axis canted at an oblique angle to the at least one emitting facet of the laser chip. The QCL may include an optical grating being adjacent the active region and configured to emit one of a continuous wave (CW) laser output or a pulsed laser output through the at least one emitting facet.

In some embodiments, the optical grating may define a plurality of ridges substantially parallel with the longitudinal axis of the active region. For example, the optical grating may comprise a Bragg grating. The active region may be configured to operate in a single lateral mode.

Additionally, the optical grating may comprise a shallow ridge configuration grating with etching stopped before reaching the active region and the QCL may include an electrical contact strip coupled to the semiconductor layers. The electrical contact strip may have a width configured to control an effective active region width.

Also, the active region may have a thickness less than or equal to 1.3 μm, and the active region may have a width greater than or equal to 20 μm. The active region may have an elongate shape extending laterally across the substrate.

Another aspect is directed to a QCL system. The QCL system may include at least one QCL comprising a substrate, at least one emitting facet, and semiconductor layers adjacent the substrate and defining an active region. The active region may have a longitudinal axis canted at an oblique angle to the at least one emitting face of the substrate. The at least one QCL may comprise an optical grating being adjacent the active region and configured to emit one of a CW laser output or a pulsed laser output through the at least one emitting facet. The QCL system may include a driver circuit coupled to the at least one QCL. In some embodiments, the at least one QCL may include an array thereof arranged in W-shape.

Another aspect is directed to a method for making a QCL. The method may include forming a substrate and at least one emitting facet, and forming a semiconductor layers adjacent the substrate and defining an active region. The active region may have a longitudinal axis canted at an oblique angle to the at least one emitting facet of the substrate. The method may comprise forming an optical grating being adjacent the active region and configured to emit one of a CW laser output or a pulsed laser output through the at least one emitting facet.

