Lucent Technologies Inc.

At&t Bell Laboratories

Arthur Mike Sergent

Alfred Yi Cho

Deborah Lee Sivco

Claire F Gmachl

Federico Capasso

Albert Lee Hutchinson

Alessandro Tredicucci

James Nelson Baillargeon

Raffaele Colombelli

Milton L Peabody

Joseph Michael Freund

Young-Kai Chen

George John Przybylek

Won-Tien Tsang

Dennis Mark Romero

Oskar Jon Painter

Gerald Nykolak

Laura Ellen Adams

Sung-Nee George Chu

Donald M Tennant

Michael C Wanke

Tawee Tanbun-Ek

Clyde George Bethea

Jenn-Ming Kuo

Roosevelt People

Ming-Chiang Wu

Harold Yoonsung Hwang

Alexey Belyanin

Mariano Troccoli

Wei-Chiao William Fang

Maurice A Chin

Roberto Paiella

Kartik Srinivasan

Alexander Soibel

Oana Malis

George Sung-Nee Chu

Julie S Eng

An optoelectronic transducer comprises a unipolar, intraband active region and a micro-cavity resonator. The resonator includes a 2D array of essentially equally spaced regions that exhibits resonant modes. Each of the spaced regions has a depth that extends through the active region and has an average refractive index that is different from that of the active region. The refractive index contrast, the spacing of the spaced regions, and the dimensions of the spaced regions are mutually adapted so that the array acts as a micro-cavity resonator and so that at least one frequency of the resonant modes of the array falls within the spectrum of an optoelectronic parameter of the active region (i.e., the gain spectrum where the transducer is a laser; the absorption spectrum where the transducer is a photodetector). In a first embodiment, the transducer is an ISB laser, whereas in a second embodiment it is a unipolar, intraband photodetector. In other embodiments, the laser is a surface-emitting ISB laser and the photodetector is a vertically-illuminated detector. In another embodiment, a nonlinear optical material is optically coupled to the micro-cavity resonator, which in one case allows an ISB laser to exhibit bistable operation.

Unipolar, intraband optoelectronic transducers with micro-cavity resonators

A broadband CLE capable of operation simultaneously at multiple wavelengths comprises: a core region including a multiplicity or cascade of stages, each stage including a radiative transition region. A first group of stages emits radiation at a first wavelength and at a first aggregate intensity per group, and a second group of stages emits radiation at a second wavelength and at a second aggregate intensity per group lower than the first intensity. The invention is characterized in that the second group has more stages than said first group, and the per-stage intensity of the first group is greater than that of the second group. This design reduces the difference between said first and second aggregate intensities. In one embodiment, groups that are located at or near to the ends of the cascade have more stages than groups that are centrally located within the cascade regardless of their wavelength. Our invention significantly reduces variations in modal gain across the desired broadband spectrum and produces sufficiently flat gain without requiring elaborate redesign of the stages. These features enable cw operation of a broadband intersubband laser.

Broadband cascade light emitters

An optical device comprises a cavity resonator and an intracavity ridge waveguide. The ridge waveguide includes a monolithically integrated intersubband core region and a nonlinear mixing region (NMR). In response to external pumping energy the core region generates laser light at a first frequency and in a first transverse mode. In response to the laser light the NMR generates parametric light at a second frequency and in a second transverse mode. For phase matching the effective-refractive-index-versus-ridge-width characteristics of the modes of the laser and the parametric light intersect one another at a phase matching width and so that, at greater widths, the effective refractive index of the mode of the higher frequency light is less than that of the lower frequency light. For true phase matching the width of the ridge is made to be essentially equal to the phase matching width.

Phase matched parametric light generation in monolithically integrated intersubband optical devices

The measurement of intersubband electroluminescence (ISB-EL) in unipolar quantum cascade lasers is achieved by forming a longitudinal cleave through the active region and waveguide of the QC laser device, exposing a complete side face of the device, including the active region. The conventional laser facets at the entrance and exit of the active region are coated with a highly reflective material and the emission from the exposed side face is measured. In theory, the sideface emission would comprise only the ISB-EL spontaneous emission, but some additional laser emission (due to scattering in the imperfect waveguide structure) also exits along this sideface. Spatial filtering and/or polarization monitoring can be used to differentiate the laser emission from the ISB-EL spontaneous emission.

Technique for measuring intersubband electroluminescence in a quantum cascade laser

The RT regions of an ISB light emitter comprise pre-biased SLs and a multiplicity of split quantum wells (SPQWs). A SPQW is a quantum well that is divided into a multiplicity of sub-wells by a first barrier layer sufficiently thin that the upper and lower energy states are split beyond their natural broadening and contribute to different minibands in each RT region. In contrast, adjacent SPQWs are coupled to one another by second barrier layers. The thicknesses of the latter layers are chosen so that minibands are created across each RT region. In one embodiment, the emitter includes an I/R region between adjacent RT regions, and in another embodiment the I/R regions are omitted.

Flat minibands with spatially symmetric wavefunctions in intersubband superlattice light emitters

In a mesa geometry semiconductor laser, a patterned dielectric coating used to define the stripe geometry contact on the top the mesa and to provide significant waveguiding comprises a chalcogenide glass. Applications to intersubband (e.g., quantum cascade) lasers are specifically described.

Mesa geometry semiconductor light emitter having chalcogenide dielectric coating

A mounting technology that increases the cw operating temperature of intersubband lasers, without increasing the risk of hot spots near the facets and short circuits near the perimeter of the laser chip, is described. In accordance with one embodiment of our invention, a method of fabricating a intersubband semiconductor laser comprises the steps of providing a single crystal semiconductor substrate, forming on the substrate an epitaxial region that includes a core region and an intersubband active region in the core region, forming front and back facets that define an optical cavity resonator, forming a metal electrode on the epitaxial region so as to provide an electrical connection to said active region, and mounting said laser on a heat sink, characterized in that the mounting step includes the steps of (i) soldering the electrode to the heat sink so that the front facet overhangs an edge of the heat sink and (ii) cleaving off the overhanging portion of the laser so as to form a new front facet that is essentially flush with the edge of said heat sink. In accordance with another embodiment, our invention is further characterized in that metal electrode to the epitaxial region is recessed from the edges of the laser chip. In accordance with yet another embodiment, our invention is further characterized in that the back facet of the laser is coated so that any solder that might tend to creep onto the back facet contacts the coating and not semiconductor material (in particular the ends of the active region).

Mounting technology for intersubband light emitters

A method for testing semiconductor laser devices is described. The method includes testing a monolithically integrated semiconductor laser device via electrical contact testing and/or far field testing. These tests will provide the total performance of the entire device. Further, the method includes accurate cleaving off of a portion of the laser device and re-testing to determine the relative performance of the remainder of the device. Through comparison of the test and re-test results, it is possible to reduce the design cycle for monolithically integrated semiconductor laser devices by detecting design flaws and imperfections or by ascertaining a more advantageous design.

Method for design and development of a semiconductor laser device

A tunable semiconductor laser comprises a gain section having an MQW active region, a uniform pitch grating DFB region, and first waveguide. A composite reflector, including a second MQW region and a second waveguide, forms a cavity resonator with the DFB region. A voltage applied to the composite reflector induces a quantum confined stark effect, thereby allowing the wavelength to be altered. In one embodiment, the current drive to the active region and the shape of the first waveguide (e.g., a raised-sine function) are mutually adapted so that N longitudinal modes have essentially the same threshold gain and so that the DFB region spanned by the first waveguide is segmented into N zones, each zone providing optical feedback at a different wavelength corresponding to a different longitudinal mode.

Broadband tunable semiconductor laser source

A GaAs-based self-aligned laser with emission wavelength in the approximate wavelength regime 0.87-1.1 .mu.m is disclosed. The laser is a strained layer QW laser and is readily manufacturable. Preferred embodiments of the inventive laser do not comprise Al-containing semiconductor alloy. Lasers according to the invention can for instance be used advantageously as 0.98 .mu.m pump sources for Er-doped fiber amplifiers.

Article comprising a strained layer quantum well laser

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New Providence, NJ, United States of America

Arthur Mike Sergent