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Madison, WI, United States

Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 149.88K | Year: 2011

The technical objectives of this proposal are: 1) the design of 3.8-4.2 micron-emitting, active-photonic-crystal (APC) quantum-cascade (QC) lasers by using passive phase-locking in a monolithic structure in order to achieve multiwatt-range, diffraction-limited powers; and 2) the development of the key crystal- growth processes for realizing the proposed APC QC laser: the growth and characterization of QC active- region materials (i.e., InGaAs/AlInAs strained-layer superlattices) on virtual substrates. Novel deep-well (DW) QC lasers will be designed to suppress carrier leakage out of active regions, resulting in electro-optic characteristics with low temperature sensitivity. For achieving high coherent power at the chip level, a novel type of APC-type structure is proposed whose elements are DW-QC lasers emitting in the 3.8-4.2 micron region. The design will be for APC devices of built-in index step an order of magnitude higher than for conventional APC-QC devices, as to achieve stable-beam operation in CW operation to high coherent powers. For 3.8-4.2 micron-emitting devices the design will be for usable CW powers larger than 7 W delivered in diffraction-limited beams. A plan for monolithically scaling coherent power to the 50-100 W range and the economical fabrication of the proposed APC devices with high production yield will be developed.


Grant
Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase II | Award Amount: 199.98K | Year: 2014

The technical objective of this proposal is to demonstrate a Quantum Cascade Laser (QCL) emitting in the 3.0-3.5 & #181;m wavelength region, which employs a metamorphic buffer layer (MBL). It is the goal of this program to develop a QCL single-stripe device which will operate in a single, diffraction-limited lobe under room temperature continuous-wave (CW) operation to moderately high (~ 0.5 W) output powers. The use of the MBL allows for a lower-strain QCL active-region design compared with conventional approaches which employ InP substrates. Advanced conduction-band-engineered QC lasers will be used, since they allow virtual suppression of carrier leakage out of the devices active regions, resulting in electro-optical characteristics much less temperature sensitive than for conventional QCL devices; and thus allowing for significant increases in average power and CW wallplug efficiency.


Grant
Agency: Department of Defense | Branch: Army | Program: STTR | Phase: Phase I | Award Amount: 100.00K | Year: 2010

The technical objectives of this proposal are: 1) the design of 8 micron-emitting active-photonic-crystal (APC) quantum-cascade (QC) lasers by using passive phase-locking in a monolithic structure in order to achieve multiwatt-range, diffraction-limited powers; and 2) the development of the key fabrication steps for realizing the proposed APC QC laser. Deep-well (DW) QC lasers will be used in the design since they suppress carrier leakage out of active regions, resulting in electro-optical characteristics much less temperature sensitive than for conventional QC devices; thus allowing for significant increases in average power and wallplug efficiency. At an emission wavelength of 8 microns the estimated increase in average power for a single QC laser is from 0.2 W to 0.5 W. For coherently scaling the power at the chip level, a novel type of APC-type structure is proposed whose elements are DW-QC lasers. The design will be for APC devices of built-in index step an order of magnitude higher than for conventional APC-QC devices, as to achieve stable-beam operation in quasi-CW or CW operation to high coherent powers with high wallplug efficiency. For 8 micron-emitting devices the design will be for usable average powers more than 3 W, delivered in diffraction-limited beams.


Kirch J.D.,University of Wisconsin - Madison | Shin J.C.,University of Wisconsin - Madison | Chang C.-C.,University of Wisconsin - Madison | Mawst L.J.,University of Wisconsin - Madison | And 2 more authors.
Electronics Letters | Year: 2012

A new deep-well quantum-cascade laser (QCL) design, for which the barrier layers in the active region are tapered such that their conduction band edges increase in energy from the injection barrier to the exit barrier, results in significant suppression of the carrier leakage in 4.8m-emitting devices. For heatsink temperatures in the 20-60°C range, the characteristic temperature coefficients for threshold, T 0, and slope efficiency, T 1, reach values as high as 231K and 797K, respectively. The T 1 values are more than a factor of two higher than the best reported values for high-performance, 4.6-4.9 μm-emitting QCLs of similar injector-doping level. At 20°C, the threshold-current density for uncoated, 30-period, 3mm-long devices is only ∼1.55kA/cm 2. © 2012 The Institution of Engineering and Technology. Source


Sigler C.,University of Wisconsin - Madison | Kirch J.D.,University of Wisconsin - Madison | Earles T.,Intraband LLC | Mawst L.J.,University of Wisconsin - Madison | And 2 more authors.
Applied Physics Letters | Year: 2014

Resonant coupling of the transverse-magnetic polarized (guided) optical mode of a quantum-cascade laser (QCL) to the antisymmetric surface-plasmon modes of 2nd-order distributed-feedback (DFB) metal/semiconductor gratings results in strong antisymmetric-mode absorption. In turn, lasing in the symmetric mode, that is, surface emission in a single-lobe far-field beam pattern, is strongly favored over controllable ranges in grating duty cycle and tooth height. By using core-region characteristics of a published 4.6μm-emitting QCL, grating-coupled surface-emitting (SE) QCLs are analyzed and optimized for highly efficient single-lobe operation. For infinite-length devices, it is found that when the antisymmetric mode is resonantly absorbed, the symmetric mode has negligible absorption loss (∼0.1cm-1) while still being efficiently outcoupled, through the substrate, by the DFB grating. For finite-length devices, 2nd-order distributed Bragg reflector (DBR) gratings are used on both sides of the DFB grating to prevent uncontrolled reflections from cleaved facets. Equations for the threshold-current density and the differential quantum efficiency of SE DFB/DBR QCLs are derived. For 7mm-long, 8.0μm-wide, 4.6μm-emitting devices, with an Ag/InP grating of ∼39% duty cycle, and ∼0.22μm tooth height, threshold currents as low as 0.45A are projected. Based on experimentally obtained internal efficiency values from high-performance QCLs, slope efficiencies as high as 3.4W/A are projected; thus, offering a solution for watt-range, single-lobe CW operation from SE, mid-infrared QCLs. © 2014 AIP Publishing LLC. Source

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