Harvard College

The University of Texas System

Massachusetts Institute of Technology

The State University of New York

The Texas A&M University System

Anasys Instruments Corporation

Maxion Technologies, Inc.

Transwave Photonics, Llc.

Mikhail A Belkin

Federico Capasso

Laurent Diehl

Benjamin G Lee

Seungyong Jung

Craig Prater

Robert W Adams

Kevin Kjoller

Serge Luryi

Antonio Sanchez-Rubio

Gregory L Belenky

John D Bruno

Andrea Alu

Richard L Tober

Mikhail V Kisin

Markus B Raschke

Anish K Goyal

Christian Pfluegl

Sergey Suchalkin

Leon Shterengas

Alexey Belyanin

Christian Pflugl

Karun Vijayraghavan

Jongwon Lee

Mykhailo Tymchenko

Feng Lu

Vladislav V Yakolev

Markus Christian Amann

Ross M Audet

Augustinas Vizbaras

James B MacArthur

Christian Pflügl

A photonic integrated circuit device includes a passive waveguide section formed over a substrate, a quantum cascade laser (QCL) gain section formed over the substrate and adjacent to the passive waveguide section, and a taper section disposed between and in contact with each of the passive waveguide section and the QCL gain section. In some embodiments, the passive waveguide section includes a passive waveguide core layer disposed between a first cladding layer and a second cladding layer. In some examples, the QCL gain section includes a QCL active region disposed between a first confinement layer and a second confinement layer, where the QCL active region has a lower index of refraction than each of the first and second confinement layers. In some embodiments, the taper section is configured to optically couple the QCL gain section to the passive waveguide section.

Quantum cascade laser with monolithically integrated passive waveguide

A nonlinear metasurface structure including a multi-quantum-well layer designed for a nonlinear response for a desired nonlinear optical process and an array of nanoantennas coupled to the intersubband transitions of the multi-quantum-well layer. Each nanoantenna in the array is designed to have electromagnetic resonances at or close to all input and output frequencies of a given nonlinear optical process. Nanoantennas allow efficient coupling of any incident and outgoing light polarizations to intersubband transitions. Nanoantennas may further provide significant field enhancement in the multi-quantum-well layer. As a result, the nonlinear metasurface structure can be designed to produce a highly nonlinear response for any polarization and angle of incidence of incoming and outgoing waves in a nonlinear optical process. Due to their very larger nonlinear response, efficient frequency conversion can be produced in these metasurfaces without the stringent phase-matching constraints of bulk nonlinear crystals.

Nonlinear metasurfaces based on plasmonic resonators coupled to intersubband transitions

A terahertz source implementing a {hacek over (C)}erenkov difference-frequency generation scheme in a quantum cascade laser. The laser includes an undoped or semi-insulating InP substrate with an exit facet that is polished at an angle between 10&#xb0; to 40&#xb0;. The laser further includes a first waveguide cladding layer(s) in contact with an active layer (arranged as a multiple quantum well structure) and a current extraction layer on top of the substrate. Furthermore, the laser includes a second waveguide cladding layer(s) on top of the active layer, where the first and second waveguide cladding layers are disposed to form a waveguide structure by which terahertz radiation generated in the active layer is guided inside the laser. The terahertz radiation is emitted into the substrate at a {hacek over (C)}erenkov angle relative to a direction of the nonlinear polarization wave in the active layer, and once in the substrate, propagates towards the exit facet.

Terahertz quantum cascade laser implementing a {hacek over (C)}erenkov difference-frequency generation scheme

Methods and systems include generating one or more mid-infrared frequencies based at least upon electron transitions in one or more quantum cascade heterostructures. The quantum cascade heterostructures are concurrently configured with a significant second-order nonlinear susceptibility, a significant third-order nonlinear susceptibility, and an insignificant group velocity dispersion. A set of mid-infrared frequencies (that may include a frequency comb) is generated in the quantum cascade heterostructures based at least upon a four-wave mixing of the one or more mid-infrared frequencies. The four-wave mixing arises at least from the significant third-order nonlinear susceptibility and the insignificant group velocity dispersion. A set of terahertz frequencies (that may include a frequency comb) is generated in the quantum cascade heterostructures based at least upon a difference frequency generation from mid-infrared frequency pairs selected from the set of mid-infrared frequencies. The difference frequency generation arises at least from the significant second-order nonlinear susceptibility.

Generating terahertz frequency combs from quantum cascade lasers using nonlinear frequency mixing

A laser source based on a quantum cascade laser array (QCL), wherein the outputs of at least two elements in the array are collimated and overlapped in the far field using an external diffraction grating and a transform lens.

Wavelength beam combining of quantum cascade laser arrays

An AFM based technique has been demonstrated for performing highly localized IR spectroscopy on a sample surface by using the AFM probe to detect wavelength dependent IR radiation interaction, typically absorption with the sample in the region of the tip. The tip may be configured to produce electric field enhancement when illuminated by a radiation source. This enhancement allows for significantly reduced illumination power levels resulting in improved spatial resolution by confining the sample-radiation interaction to the region of field enhancement which is highly localized to the tip.

High frequency deflection measurement of IR absorption

The present invention provides a QCL device with an electrically controlled refractive index through the Stark effect. By changing the electric field in the active area, the energy spacing between the lasing energy levels may be changed and, hence, the effective refractive index in the spectral region near the laser wavelength may be controlled.

Quantum cascade lasers with electrically tunable emission wavelengths

Methods and apparatus for improved single-mode selection in a quantum cascade laser. In one example, a distributed feedback grating incorporates both index-coupling and loss-coupling components. The loss-coupling component facilitates selection of one mode from two possible emission modes by periodically incorporating a thin layer of 'lossy' semiconductor material on top of the active region to introduce a sufficiently large loss difference between the two modes. The lossy layer is doped to a level sufficient to induce considerable free-carrier absorption losses for one of the two modes while allowing sufficient gain for the other of the two modes. In alternative implementations, the highly-doped layer may be replaced by other low-dimensional structures such as quantum wells, quantum wires, and quantum dots with significant engineered intraband absorption to selectively increase the free-carrier absorption losses for one of multiple possible modes so as to facilitate single-mode operation.

Methods and apparatus for single-mode selection in quantum cascade lasers

Apparatus and methods for generating radiation via difference frequency generation (DFG). In one exemplary implementation, a quantum cascade laser (QCL) has a significant second-order nonlinear susceptibility (&#x3c7;) integrated in an active region of the QCL. The QCL is configured to generate first radiation at a first frequency &#x3c9;, second radiation at a second frequency &#x3c9;, and third radiation at a third frequency &#x3c9;=&#x3c9;&#x2212;&#x3c9;based on difference frequency generation (DFG) arising from the non-linear susceptibility. In one aspect, the QCL may be configured to generate appreciable THz radiation at room temperature.

Methods and apparatus for generating terahertz radiation

A broadly tunable single-mode infrared laser source based on semiconductor lasers. The laser source has two parts: an array of closely-spaced DFB QCLs (or other semiconductor lasers) and a controller that can switch each of the individual lasers in the array on and off, set current for each of the lasers and, and control the temperature of the lasers in the array. The device can be used in portable broadband sensors to simultaneously detect a large number of compounds including chemical and biological agents. A microelectronic controller is combined with an array of individually-addressed DFB QCLs with slightly different DFB grating periods fabricated on the same broadband (or multiple wavelengths) QCL material. This allows building a compact source providing narrow-line broadly-tunable coherent radiation in the Infrared or Terahertz spectral range (as well as in the Ultraviolet and Visible spectral ranges, using semiconductor lasers with different active region design). The performance (tuning range, line width, power level) is comparable to that of external grating tunable semiconductor lasers, but the proposed design is much smaller and much easier to manufacture.

Broadly tunable single-mode quantum cascade laser sources and sensors

Growing community of inventors

Austin, TX, United States of America

Mikhail A Belkin