USA As Represented by Secretary of the Navy

James R Lindle

Jerry R Meyer

Igor Vurgaftman

William W Bewley

Chadwick Lawrence Canedy

Mijin Kim

Chul-soo Kim

Filbert J Bartoli

Arthur W Snow

Chul Soo Kim

James S Shirk

Craig A Hoffman

Joseph F Pinto

Steven R Flom

Michael E Boyle

Richard G Pong

Chul-Soo Kim

An interband cascade gain medium is provided. The gain medium can include at least one thick separate confinement layer comprising Ga(InAlAs)Sb between the active gain region and the cladding and can further include an electron injector region having a reduced thickness, a hole injector region comprising two hole quantum wells having a total thickness greater than about 100 &#x212b;, an active gain quantum well region separated from the adjacent hole injector region by an electron barrier having a thickness sufficient to lower a square of a wavefunction overlap between a zone-center active electron quantum well and injector hole states, and a thick AlSb barrier separating the electron and hole injectors of at least one stage of the active region.

High-temperature interband cascade lasers

A gain medium and an interband cascade laser, having the gain medium are presented. The gain medium can have one or both of the following features: (1) the thicknesses of the one or more hole quantum wells in the hole injector region are reduced commensurate with the thickness of the active hole quantum well in the active quantum well region, so as to place the valence band maximum in the hole injector region at least about 100 meV lower than the valence band maximum in the active hole quantum well; and (2) the thickness of the last well of the electron injector region is between 85 and 110% of the thickness of the first active electron quantum well in the active gain region of the next stage of the medium. A laser incorporating a gain medium in accordance with the present invention can emit in the mid-IR range from about 2.5 to 8 &#x3bc;m at high temperatures with room-temperature continuous wave operation to wavelengths of at least 4.6 &#x3bc;m, threshold current density of about 400 A/cmand threshold power density of about 900 W/cm.

Interband cascade lasers

A gain medium and an interband cascade laser, an interband cascade amplifier, and an external cavity laser having the gain medium are presented. The gain medium can include any one or more of the following features: (1) the active quantum well region includes a thick and In-rich GaInSb hole well; (2) the hole injector includes two or more GaSb hole wells having thicknesses in a specified range; (3) the electron and hole injectors are separated by a thick AlSb barrier to suppress interband absorption; (4) a first electron barrier of the hole injector region separating the hole injector region from an adjacent active quantum well region has a thickness sufficient to lower a square of a wavefunction overlap between a zone-center active electron quantum well and injector hole states to not more than 5%; (5) the thickness of the first InAs electron well in the electron injector, as well as the total thickness of the electron injector, is reduced; (6) the number of cascaded stages is reduced; (7) transition regions are inserted at the interfaces between the various regions of the gain medium so as to smooth out abrupt shifts of the conduction-band minimum; (8) thick separate confinement layers comprising Ga(InAlAs)Sb are disposed between the active gain region and the cladding to confine the optical mode and increase its overlap with the active stages; and (9) the doping profile of the cladding layers is optimized to minimize the overlap of the optical mode with the most heavily-doped portion of the InAs/AlSb SL cladding layers. An interband cascade laser, an interband cascade amplifier, or an external cavity laser employing a gain medium having these features can emit at a wavelength of about 2.5 &#x3bc;m to about 8 &#x3bc;m at high temperatures.

An optical limiter structure which includes a limiter material preferably dissolved in a host. The limiter material is selected from substituted and unsubstituted phthalocyanines, naphthalocyanines, porphyrins, salts of these materials and mixtures thereof, whereas the host is selected from any material which can dissolve the limiter material to at least the extent of 0.1% by weight.

Optical limiter structure and method

A protective layer laser hardens an optical detector. The material for the rotective layer is Hg.sub.1-Y Cd.sub.Y Te, where Y is selected so that the band gap of the protective layer is higher than the expected energy level for photons impinging on the protective layer. Photons with energy levels lower than the band gap are transmitted by the protective layer while photons exceeding the band gap energy level are absorbed or reflected by the protective layer. A semiconductor junction can be formed on the opposite side of the substrate from a Hg.sub.X Cd.sub.X Te layer with a band gap lower than the expected energy level, so that photons transmitted through the substrate are absorbed in the Hg.sub.X Cd.sub.X Te layer and, therefore, detected at the junction. At sufficiently high intensities where detector damage could result, the protective layer switches so that the incident photons are either absorbed or reflected, thus protecting the detector from damage.

Laser hardened backside illuminated optical detector

Growing community of inventors

Bowie, MD, United States of America

James R Lindle