Claims
- 1. An article comprising a quantum cascade laser comprising a multilayer semiconductor structure disposed on a semiconductor substrate having lattice constant a.sub.0, wherein
- a) said multilayer semiconductor structure forms an optical waveguide that comprises a lower confinement region, a core region disposed on the lower confinement region, and an upper confinement region disposed on the core region;
- b) the core region comprises a multiplicity of nominally identical repeat units, with each repeat unit comprising an active region and a carrier injector region, with the active region having a layer structure comprising alternating layers of a first semiconductor material and a second semiconductor material, and selected to provide an upper and a lower carrier energy state, with a carrier transition from the upper to the lower carrier energy state resulting in emission of a photon of wavelength .lambda., and with the carrier injector region having a layer structure selected to facilitate carrier transport from the lower carrier energy state of the active region to the upper carrier energy state of the active region of an adjacent downstream repeat unit; and
- c) the quantum cascade laser comprises contacts selected to facilitate flowing an electric current through the multilayer semiconductor structure;
- CHARACTERIZED IN THAT
- d) the first semiconductor material is selected to have a lattice constant a.sub.1 >a.sub.0, and the second semiconductor material is selected to have a lattice constant a.sub.2 <a.sub.0, and furthermore is selected such that a conduction band energy discontinuity .DELTA.E.sub.c between said first and second semiconductor material is greater than 520 meV in absolute value.
- 2. An article according to claim 1, wherein said first and second semiconductor materials and repeat unit layer thicknesses are selected such that .vertline.(.delta.a.sub.1 /a.sub.0).SIGMA.t.sub.1 +(.delta.a.sub.2 /a.sub.0).SIGMA.t.sub.2 .vertline. is less than 0.2 (.delta.a.sub.1 /a.sub.0).SIGMA.t.sub.1, where .delta.a.sub.1 =a.sub.1 -a.sub.0, .delta.a.sub.2 =a.sub.2 -a.sub.0, .SIGMA.t.sub.1 and .SIGMA.t.sub.2 are the sums of the respective thicknesses of the first and second semiconductor material layers of a given repeat unit, and the vertical bars signify the absolute value.
- 3. An article according to claim 2, wherein the first and second semiconductor materials and layer thicknesses are selected such that .vertline.(.delta.a.sub.1 /a.sub.0).SIGMA.t.sub.1 +(.delta.a.sub.2 /a.sub.0).SIGMA.t.sub.2 .vertline. is less than or equal to 0.1 (.delta.a.sub.1 /a.sub.0).SIGMA.t.sub.1.
- 4. An article according to claim 1, wherein the quantum cascade laser further comprises a distributed feedback feature.
- 5. An article according to claim 4, wherein the distributed feedback feature is a Bragg grating disposed in a confinement region.
- 6. Article according to claim 1, wherein the article is a measurement system for measuring absorption of infrared radiation by a measurement species, wherein the measurement system comprises a source of single mode infrared laser radiation comprising the quantum cascade laser of claim 1; and further comprising a detector for detecting the single mode infrared laser radiation after passage thereof through a quantity of said measurement species.
- 7. Measurement system according to claim 6, wherein said measurement species is a gas disposed in a measurement cell.
- 8. Measurement system according to claim 6, wherein said measurement species is an unconfined gas.
- 9. Article according to claim 1, further comprising a current source connected to said electrical contacts, said current source providing a laser-heating current to the laser such that the wavelength of the single mode laser radiation varies in accordance with the laser-heating current.
- 10. Article according to claim 9, wherein said laser-heating current comprises a current ramp.
- 11. Article according to claim 1, wherein said single mode laser radiation has wavelength in the range referred to as the first atmospheric window.
- 12. Article according to claim 1, wherein said single mode laser radiation has wavelength in the approximate range 3-5 .mu.m.
GOVERNMENT CONTRACT
This invention was made with Government support under Contract No. DAA H0496C0026. The Government has certain rights in this invention.
US Referenced Citations (7)
Foreign Referenced Citations (1)
Number |
Date |
Country |
63-182550 |
Jul 1988 |
JPX |