K.D. Choquette

University of Illinois, Urbana-Champaign, Urbana, Illinois, United States

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Publications (485)515.38 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate 2-dimentional coherently coupled bottom-emitting VCSEL arrays. In-phase operation has been obtained from 3-element triangular arrays, while out-of-phase operation has been obtained from 2x2, 3x3, and 4x4 arrays.
    CLEO: Science and Innovations; 06/2014
  • SPIE Photonics Europe; 05/2014
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    ABSTRACT: We report on an optically pumped vertical-external-cavity surface-emitting laser array exhibiting coherent coupling. Imaging of the far field shows interference consistent with in-phase coherent coupling, and a majority of total power is present in the central on-axis lobe. The physical mechanism of operation is attributed to diffractive coupling, wherein a small portion of the light emitting from each emitter is shared with adjacent emitters of the array.
    IEEE Photonics Technology Letters 03/2014; 26(5):430-432. · 2.04 Impact Factor
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    ABSTRACT: Electrically-injected vertical external cavity surface emitting laser (VECSEL) arrays are an attractive source for lowcost, high-brightness applications. Optical pumping can be used to investigate the emission properties of such devices without undergoing complex device fabrication. The design of such arrays is based on a single VECSEL chip, a 2D lens array, and a flat output coupling dichroic mirror. In this work, we report on the demonstration of an optically pumped, coherently-coupled VECSEL array. The array achieves a maximum total output power of >60 mW and lasing spectrum indicates single-mode operation. Near-field characterization reveals 37 individual lasing elements in a hexagonal array. Far-field measurements show an interference pattern which is consistent with inphase coherent coupling, with >60% of the total output power present in the on-axis central lobe. The physical origin of coherent coupling is attributed to diffractive coupling. The simplicity of the optical cavity design suggests scalability to much larger arrays, making the result of particular interest to the development of low-cost, highbrightness diode sources.
    02/2014;
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    ABSTRACT: Microcavity laser design and performance optimization requires a quantitative knowledge of the cavity optical losses. A generalized method using sub-threshold spectral measurements matched to model calculations is demonstrated to determine optical loss in microcavity lasers. Cold-cavity spectral characteristics are used to extract the size-dependent optical loss for small diameter oxide-confined vertical-cavity surface emitting lasers. For oxide aperture diameters less than 4 μm, the oxide scattering loss can be greater than 10 cm−1, similar to the typical values of free carrier absorption loss.
    Applied Physics Letters 01/2014; 104(10):101103-101103-3. · 3.52 Impact Factor
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    ABSTRACT: We carry out a detailed characterization of continuous wave threshold behavior of coupled-cavity vertical-cavity surface-emitting lasers with various radii of the ion-implantation and oxide apertures. We obtainmodal threshold current maps and wavelength at threshold and identify three groups of lasers with qualitatively different behavior, i.e. 1) lasing only on the short, 2) on both short and long and 3) only on the long wavelength fundamental mode. All lasers show profound impact of the current induced self-heating. In order to elucidate this impact, we improve the existing rate equation model by considering nonuniform longitudinal temperature distribution and adding the gain and refractive index temperature dependencies. We are able to reproduce the experimentally observed switchings between different longitudinal modes, as well as all the three different types of modal behavior.
    Journal of Lightwave Technology 12/2013; 31(23):3726-3734. · 2.56 Impact Factor
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    ABSTRACT: We demonstrate the first clearly in-phase emission and first continuous-wave operation from a bottom-emitting, coherent VCSEL array. A 2x1 array with an antiguided index profile was used, representing a critical step towards coherent, high-brightness arrays.
    CLEO: Science and Innovations; 06/2013
  • CLEO: Science and Innovations; 06/2013
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    ABSTRACT: Previously reported simulations have suggested that depositing thin layers of metal over the surface of a single-mode, etched air hole photonic crystal (PhC) vertical-cavity surface-emitting laser (VCSEL) could potentially improve the laser's side-mode suppression ratio by introducing additional losses to the higher-order modes. This work demonstrates the concept by presenting the results of a 30 nm thin film of Cr deposited on the surface of an implant-confined PhC VCSEL. Both experimental measurements and simulation results are in agreement showing that the single-mode operation is improved at the same injection current ratio relative to threshold.
    Optics Letters 06/2013; 38(11):1936-8. · 3.39 Impact Factor
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    ABSTRACT: In-phase emission from a bottom-emitting, coherently coupled, vertical cavity surface-emitting laser array is demonstrated for the first time. Various array geometries are examined. An antiguided index profile is used to obtain the preferred on-axis far-field peak from a 2 × 1 array up to 0.9 mW, representing a critical step towards coherent, high-brightness two-dimensional laser arrays.
    Electronics Letters 01/2013; 49(14):897-898. · 1.04 Impact Factor
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    ABSTRACT: With the separation of optical and current apertures, photonic crystal vertical-cavity surface-emitting lasers can reach a 3-dB small-signal modulation bandwidth of > 18 GHz while lasing in the fundamental mode. Because of reduced chromatic dispersion, such devices enable error-free transmission over 1-km OM4 multimode fiber at a data rate of 25 Gb/s and operating at a current density of 5.4 kA/cm2. This can potentially lead to a laser source that is useful for rack-to-rack transmissions in large data centers and potentially long device lifetime.
    IEEE Photonics Technology Letters 01/2013; 25(18):1823-1825. · 2.04 Impact Factor
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    ABSTRACT: Planar index-guided proton-implanted photonic crystal vertical-cavity surface-emitting lasers are fabricated and characterized. Index guiding from the photonic crystal improves the performance of the lasers by creating a stable light output versus current response, reducing the threshold current, and enhancing the differential quantum efficiency. Examination of the etch depth dependence of laser efficiency reveals various mechanisms that affect the laser performance and modal properties such as optical loss, Joule heating, and spectral gain-resonance alignment. Photonic crystal designs can be chosen which result in lasing operation only in the fundamental transverse mode from threshold to maximum power, even for the condition of blue-shifted gain spectrum relative to the cavity resonance. Suitable photonic crystal designs are shown to be manufacturable due to the planar device topology, the use of optical lithography in all processing steps, and compatibility with virtually any vertical-cavity surface-emitting laser epitaxial designs.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19(4):4900107-4900107. · 4.08 Impact Factor
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    ABSTRACT: We demonstrate electronic beam steering using phased vertical cavity laser arrays at record high speed (1.4·108 deg/s) and sensitivity to current (1.2 deg/100 μA). The relative phase and coherence between the array elements are extracted with a Fraunhoffer propagation method. The spatially resolved spectrum and beam steering dynamics are also analyzed. The thermo-optic effect is found to dominate the phase-shifting mechanism at lower speed steering, while the electronic variation in index dominates at higher speeds (≥10 MHz).
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19(4):1701006-1701006. · 4.08 Impact Factor
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    ABSTRACT: A photonic crystal vertical-cavity surface-emitting laser with a spectral width of 0.16 nm and a 3dB small signal modulation bandwidth of 16.2 GHz is demonstrated. Separation of optical and current apertures enables a narrow spectral width and an extremely low operating current density of ~ 1 kA/cm2 simultaneously. It can potentially be used as a high-reliability laser source that enables error-free transmission over long multimode fibre links at high data rate.
    Electronics Letters 01/2013; 49(9):612-613. · 1.04 Impact Factor
  • J.D. Sulkin, P.M. Ferreira, K.D. Choquette
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    ABSTRACT: We report nanoscale patterning of concentric ring-shaped metal corrugations around a subwavelength aperture in Ag deposited on the top facet of a vertical cavity surface-emitting laser. The presence of the patterned rings results in more than doubling the collected far-field power and a significant reduction in far-field angular width. These plasmonic aperture lasers thus have the unique property of both a small near-field spot and a relatively low beam divergence. Finite-difference time-domain simulations are consistent with the experimental results and show that the far-field pattern is highly sensitive to misalignment of the aperture and to the presence of multiple transverse laser modes.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19(3):4601504-4601504. · 4.08 Impact Factor
  • M.T. Johnson, D.F. Siriani, K.D. Choquette
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    ABSTRACT: Beam steering with optical phased arrays is accomplished by introducing a relative phase shift between array elements (McManamon et al., 2009). This is typically achieved by altering the refractive index difference between elements, which alters the optical path length of incident radiation traveling through the elements. Beam steering with VCSEL arrays has also been shown to rely on such a refractive index variation (Johnson et al.) which is implemented by adjusting the current injection to the elements. However, if we view the VCSEL array as a waveguide from the active region through the distributed Bragg Reflectors, it can be shown that the index-induced phase shift between elements would only account for less than 1/100th of the observed phase shift. It is thus evident that phased VCSEL arrays rely on a fundamentally different phase-shifting mechanism. To investigate this, we turn to coupled mode theory, which has previously been applied to the dynamics of coupled edge emitting laser arrays and phase tuning in injection-locked VCSELs.
    Photonics Conference (IPC), 2013 IEEE; 01/2013
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    ABSTRACT: The work has demonstrated both top and bottom emitting coherently coupled VCSEL arrays operating in the preferred in-phase supermode. Moreover, it was shown that phase tuning between the array elements is possible with varying injection current to the array elements. With the bottom emitting arrays, these would be able to scale up the array size, maximum power, and beam steering properties.
    Photonics Society Summer Topical Meeting Series, 2013 IEEE; 01/2013
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    ABSTRACT: Coherently coupled vertical-cavity surface-emitting laser arrays offer unique advantages for nonmechanical beam steering applications. We have applied dynamic coupled mode theory to show that the observed temporal phase shift between vertical-cavity surface-emitting array elements is caused by the detuning of their resonant wavelengths. Hence, a complete theoretical connection between the differential current injection into array elements and the beam steering direction has been established. It is found to be a fundamentally unique beam-steering mechanism with distinct advantages in efficiency, compactness, speed, and phase-sensitivity to current.
    Applied Physics Letters 01/2013; 103(20):201115-201115-4. · 3.52 Impact Factor
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    ABSTRACT: We present a detailed comparison of experimental and simulated optical spectra obtained from a 980-nm photonic-crystal (PhC) VCSEL. We demonstrate good qualitative agreement of the experimental spectra with the calculated emitted wavelengths for number of VCSEL structures with different PhC designs. We show the statistical analysis which reveals that strong confinement introduced by the photonic crystal contributes to the conformity between experiment and theory. For shallow etching of the photonic crystal holes, narrow optical aperture, and large diameter air-holes, we observe that diffraction and mode leakage through the PhC holes becomes the dominating phenomena, and then any fabrication imperfection may contribute to discrepancy between theory and experiment.
    IEEE Journal of Selected Topics in Quantum Electronics 01/2013; 19:1701908. · 4.08 Impact Factor
  • Hyejin Jeong, K.D. Choquette
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    ABSTRACT: Vertical cavity surface emitting lasers (VCSELs) are an important light source for applications in communication and appliances consumer use. However, the types of III-V semiconductor materials that can be used to manufacture monolithic VCSELs are limited to only few choices. Moreover, limitations of the device materials will also limit the functionality of VCSELs incorporated into microsystems. Various heterogeneous integration approaches have been developed to overcome this limits [1, 2]. We previously demonstrated a bonding approach onto foreign substrates which incorporates fully fabricated VCSEL arrays which do not require additional processing after bonding and optical characteristics are maintained after the bonding process [3]. In this work we report VCSEL thermal modeling using COMSOL simulations to investigate the relation between laser performance and temperature. Good agreement is obtained between simulation and experiments for VCSEL lasing wavelength with varying oxide aperture and mesa size under operation near maximum output power. Using this model, the thermal rollover at peak output power of VCSELs on different substrates is discussed.
    Photonics Conference (IPC), 2013 IEEE; 01/2013

Publication Stats

4k Citations
515.38 Total Impact Points

Institutions

  • 2000–2014
    • University of Illinois, Urbana-Champaign
      • • Department of Materials Science and Engineering
      • • Department of Electrical and Computer Engineering
      Urbana, Illinois, United States
  • 1993–2012
    • Sandia National Laboratories
      • Semiconductor Material and Device Sciences Department
      Albuquerque, New Mexico, United States
  • 2011
    • University of Illinois at Chicago
      • Department of Chemistry
      Chicago, IL, United States
  • 2010–2011
    • McGill University
      • Department of Electrical & Computer Engineering
      Montréal, Quebec, Canada
  • 2009
    • Mission College
      Santa Clara, California, United States
  • 2007
    • The Optical Society
      Society Hill, New Jersey, United States
    • nLIGHT
      Vancouver, British Columbia, Canada
  • 2006
    • Chung-Ang University
      • School of Electrical and Electronics Engineering
      Sŏul, Seoul, South Korea
  • 2003
    • Tampere University of Technology
      • Optoelektroniikan tutkimuskeskus
      Tampere, Western Finland, Finland
  • 1999–2000
    • Cornell University
      Ithaca, New York, United States
    • EMCORE Corporation
      Albuquerque, New Mexico, United States
  • 1997–2000
    • Colorado State University
      • Electrical & Computer Engineering
      Fort Collins, CO, United States
    • Honeywell
      Morristown, New Jersey, United States
    • University of Connecticut
      • Department of Physics
      Storrs, CT, United States
  • 1998–1999
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
    • University College Cork
      • Department of Physics
      Cork, M, Ireland
  • 1995
    • Palo Alto Research Center
      Palo Alto, California, United States
  • 1994–1995
    • Air Force Institute of Technology
      • Department of Electrical & Computer Engineering
      Wright-Patterson AFB, OH, United States
    • University of Wisconsin–Madison
      • Department of Electrical and Computer Engineering
      Madison, Wisconsin, United States
  • 1991–1993
    • AT&T Labs
      Austin, Texas, United States