City of Industry, CA, United States
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Liu P.Q.,Princeton University | Hoffman A.J.,Princeton University | Escarra M.D.,Princeton University | Franz K.J.,Princeton University | And 5 more authors.
Nature Photonics | Year: 2010

Quantum cascade lasers are promising mid-infrared semiconductor light sources for molecular detection in applications such as environmental sensing or medical diagnostics. For such applications, researchers have been striving to improve device performance. Recently, improvements in wall plug efficiency have been pursued with a view to realizing compact, portable, power-efficient and high-power quantum cascade laser systems. However, advances have largely been incremental, and the basic quantum design has remained unchanged for many years, with the wall plug efficiency yet to reach above 35%. A crucial factor in quantum cascade laser performance is the efficient transport of electrons into the laser active regions. We recently theoretically described this transport process as limited by the interface-roughness-induced detuning of resonant tunnelling. Here, we report that an ultrastrong coupling design strategy overcomes this limiting factor and leads to the experimental realization of quantum cascade lasers with 40-50% wall plug efficiency when operated in pulsed mode at temperatures of 160K or lower. © 2010 Macmillan Publishers Limited. All rights reserved.

Yao Y.,Princeton University | Wang X.,AdTech Optics Inc. | Fan J.-Y.,AdTech Optics Inc. | Gmachl C.F.,Princeton University
Applied Physics Letters | Year: 2010

A quantum cascade laser structure is demonstrated that provides a broadband gain spectrum of 430 cm-1 with a peak emission wavelength around 4.8 μm. The laser active region is based on multiple transitions from strongly coupled upper states to lower laser states. In spite of the broad gain spectrum, high laser performance was demonstrated with low threshold current density (as low as 1.6 kA/ cm2), large slope efficiency (over 5 W/A) and high wall plug efficiency (up to 23%) in pulsed mode operation at 295 K. © 2010 American Institute of Physics.

Liu P.Q.,Princeton University | Wang X.,AdTech Optics Inc. | Gmachl C.F.,Princeton University
Applied Physics Letters | Year: 2012

We employ properly designed asymmetric Mach-Zehnder interferometer structures as effective wavelength filters and monolithically integrate them in conventional Fabry-Perot cavities to facilitate single-mode operation of the lasers. With such asymmetric Mach-Zehnder interferometer type laser cavities, continuously tunable single-mode operation of quantum cascade (QC) lasers is achieved in pulsed mode from 80 K up to room temperature and in continuous-wave mode with side-mode suppression ratio up to ∼35 dB. These devices are fabricated with the same process as simple ridge lasers, therefore providing a promising solution to achieving more cost-effective single-mode QC lasers. © 2012 American Institute of Physics.

Liu P.Q.,Princeton University | Wang X.,AdTech Optics Inc. | Fan J.-Y.,AdTech Optics Inc. | Gmachl C.F.,Princeton University
Applied Physics Letters | Year: 2011

We demonstrate single-mode quantum cascade lasers employing a folded Fabry-Perot cavity consisting of two straight sections connected by a semicircular section in a "hairpin" shape. These folded cavity lasers emitting at ∼4.5 μm are fabricated with identical processes as those for plain Fabry-Perot ridge lasers, and show a strong suppression of the comb of Fabry-Perot cavity modes, leading to tunable single-mode emission with up to 27 dB side mode suppression ratio and a single-mode operating current range of up to 60% above the threshold current when operated in pulsed mode; single-mode emission is achieved from 80 to ∼240 K. © 2011 American Institute of Physics.

Troccoli M.,AdTech Optics Inc. | Wang X.,AdTech Optics Inc. | Fan J.,AdTech Optics Inc.
Optical Engineering | Year: 2010

We present an overview of our recent results on the growth, fabrication, and characterization of high-power long-wave infrared quantum cascade lasers with multimode and single-mode waveguides. Powers of up to 1.2 W at wavelengths of λ=6.1μm are obtained with InGaAsInAlAs buried heterostructure lasers grown lattice matched on InP substrates. For longer wavelengths, up to λ=9μm, powers of P 800 mW are delivered from room-temperature-operated devices. Distributed-feedback waveguides have been fabricated with buried grating geometry, leading to single-mode emission of more than P 150 mW output at λ=7.74μm when the device is operated at room temperature in continuous mode. © 2010 Society of Photo-Optical Instrumentation Engineers.

Troccoli M.,AdTech Optics Inc.
Optics InfoBase Conference Papers | Year: 2014

We present our state-of-the-art results on distributed feedback and high power quantum cascade (QC) lasers. Application issues and perspectives of single mode and high power QCLs will also be discussed. © 2014 OSA.

Troccoli M.,AdTech Optics Inc.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2015

In this paper, we review and expand on our results dealing with high-power quantum cascade (QC) lasers and single-mode devices in the mid- and long-wave infrared (IR) regions of the spectrum (4-12 μm). The specifications and characteristics of state-of-The-art QC lasers fabricated by the metal-organic chemical vapor deposition technology are illustrated, along with their key application requirements and potential issues for future improvements. Single emitter QC lasers in the Watt-class range and narrow-linewidth low power DFBs spanning the whole mid-IR region are presented and analyzed. © 1995-2012 IEEE.

Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase I | Award Amount: 99.60K | Year: 2010

In Phase I we propose to demonstrate a room temperature continuous wave QC laser at 4.5µm with high power (P>0.5W) and wall plug efficiency (η>5%). The data will be used to design a high performance QC laser with projected wall plug efficiency exceeding 15% in continuous mode operation at room temperature. Our goal is to fabricate, characterize and package the high efficiency lasers in Phase II of the proposed project, and use beam combining methods to increase powers to above 3.5 W by combining six 1W single emitters with an estimated coupling efficiency of 65%. Preliminary sensing experiments, laser frequency modulation studies, and modeling of beam combining will also be carried out in Phase I with currently available lower efficiency lasers. The high efficiency devices will be designed at various possible emission wavelengths, ranging from the MWIR (3-5µm) to the LWIR (8-12µm). Modeling will take care of the three main aspects of efficiency improvement: heat management optimization, optical loss minimization, and electrical power reduction. The final phase I results will lead to a feasibility evaluation for a high power packaged laser with multiple high efficiency emitters combined in one rugged and portable package with estimates of its remote sensing and modulation capabilities.

Agency: Department of Defense | Branch: Missile Defense Agency | Program: SBIR | Phase: Phase II | Award Amount: 997.60K | Year: 2012

The proposed application for phase II deals with the prototyping and demonstration of a blackbody laser source of high brightness capable of simulating targets of varying temperature. This will enable a flexible and powerful missile plume simulator that can be used in airborne laser systems for targeting and seeker tests. Quantum cascade lasers are ideal for simulating light sources in the mid- and long-wave infrared, because their high spectral energy density is equivalent to that of a very bright blackbody source. When the QC material is electrically pumped, energy is directly converted into infrared light with an electro-optical conversion efficiency in the spectral range of interest of about 5-10%, which is orders of magnitude higher than the efficiency of a thermal source, whose emission is spread over a very broad spectral range and not directional. This high brightness sources can be very versatile and can be designed to target specific emission characteristics according to the application requirements. The QC laser based approach to simulating a black body can be achieved using current technology. The approach is versatile and scalable. Our proposal will deliver a QCL based prototype version of a blackbody element for simulation tests at different blackbody temperatures.

Jung S.,University of Texas at Austin | Jiang A.,University of Texas at Austin | Jiang Y.,University of Texas at Austin | Vijayraghavan K.,University of Texas at Austin | And 3 more authors.
Nature Communications | Year: 2014

Electrically pumped room-temperature semiconductor sources of tunable terahertz radiation in 1-5â €‰THz spectral range are highly desired to enable compact instrumentation for THz sensing and spectroscopy. Quantum cascade lasers with intra-cavity difference-frequency generation are currently the only room-temperature electrically pumped semiconductor sources that can operate in the entire 1-5â €‰THz spectral range. Here we demonstrate that this technology is suitable to implementing monolithic room-temperature terahertz tuners with broadband electrical control of the emission frequency. Experimentally, we demonstrate ridge waveguide devices electrically tunable between 3.44 and 4.02â €‰THz. © 2014 Macmillan Publishers Limited. All rights reserved.

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