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Virgina Tech, Blacksburg VA
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Recent Events

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Recent EVENTS

Photonics West


22 - 27 January 2011
The Moscone Center
San Francisco, California, USA


  • M. T. Crowley, N. B. Patel, D. Murrell, M. Breivik, C.-Y. Lin, Yan Li, L. F. Lester, "Modeling the impact of temperature on the performance of monolithic passively mode-locked quantum dot lasers", Presented in 2011 SPIE Photonics West Annual Meeting, San Francisco, CA.

  • N. G. Usechak, M. Grupen, V. I. Kovanis; N. A. Naderi, Yan Li, L. F. Lester, "Modulation effects in multi-section semiconductor lasers", Presented in 2011 SPIE Photonics West Annual Meeting, San Francisco, CA.

  • Michael C. Pochet, Nader A. Naderi, Vassilios I. Kovanis, Luke F. Lester, "Optical injection of quantum-dash semiconductor lasers at 1550 nm for tunable photonic oscillators",  Presented in 2011 SPIE Photonics West Annual Meeting, San Francisco, CA.

LEOS 2010


The 23rd Annual Meeting of the IEEE Photonics Society


 Denver, Colorado | 7 - 11 November 2010


  • Yan. Li, M. Breivik, C. Feng, C.-Y. Lin, N. Patel,W. Zortman, M. Crowley and L. F. Lester, "A Low Repetition Rate All-Active Monolithic passively Mode-locked Quantum Dot Laser"

  • N. G. Usechak, M. Grupen, V. Kovanis, N. A. Naderi, Yan. Li, and L. F. Lester, "Cavity-Enhanced Modulation in Gain-Lever Semiconductor Lasers"

  • F. Grillot, N. A. Naderi, C.-Y. Lin, K. Yang, A. Gin, A. Shirkhorshidian and L. F. Lester,"Two-Color Quantum-Dot DFB Laser for
    Terahertz Applications".

  • N. A. Naderi, M. C. Pochet, F. Grillot, A. Shirkhorshidian, V. Kovanis, and L. F. Lester, "Manipulation of the Linewidth Enhancement Factor in an Injection-Locked Quantum-Dash Fabry-Perot Laser at 1550nm".

  • C.-Y. Lin, F. Grillot, Yan Li, R. Raghunathan and L. F. Lester, "Characterization of Timing Jitter in a Quantum Dot Passively Mode-Locked Laser at Low Offset Frequency".

  • J. Kim, C.-Y. Lin, Yan. Li, Albuquerque, N. A. Naderi, C. G. Christodoulou, L. F. Lester, "Beam Steering of a Linearly Tapered Slot Antenna Array Integrated with Quantum Dot Mode-Locked Lasers".

CLEO ConferenceThe Conference on Lasers and Electro-Optics (CLEO)

The International Quantum Electronics Conference (IQEC)


 May 16-May 21, 2010; San Jose, CA


  • Luke F. Lester, Chang-Yi Lin, Yan Li, Junghoon Kim, Christos G. Christodoulou

    "Reconfigurable, Multi-Section Quantum Dot Mode-Locked Lasers" ( Invited paper)

    Abstract: The optical characterization and applications of quantum dot mode-locked lasers constructed using a reconfigurable, unit-cell approach are discussed including diverse waveform generation, optical to RF signal conversion, and optimal laser layout design.

    Session: CMII1
    Date/time: 
    Monday, May 17, 2010, 3:45 PM


  • Chang-Yi Lin, Frederic Grillot, Nader A. Naderi, Yan Li, Luke F. Lester

    "Ultra-Low RF Linewidth in a Quantum Dot Mode-Locked Laser Under External Optical Feedback Stabilization"

    Abstract: The effect of external optical feedback on quantum dot two-section passively mode-locked lasers is investigated. The RF linewidth narrows down from 8 KHz in the free-running situation to a very low value of 350 Hz.

    Session: CMII6
    Date/time: 
    Monday, May 17, 2010, 5:15 PM


  • M. Pochet, N. A. Naderi, Kovanis, and L. F. Lester

    "Optically Injected Quantum Dash Lasers at 1550nm Employed as Highly Tunable Photonic Oscillators"

    Abstract: Experimental investigation of an optically-injected quantum dash laserí»s operational map shows large regions
    of period-one operation. The enhanced and undamped relaxation oscillations of the period-one state are discussed as a building block for tunable photonic oscillators.

    Session: CTuZ6
    Date/time: 
    Tuesday, May 18, 2010, 3:45 PM

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Photonics West

           2010 SPIE Photonics West

           23 - 28 January 2010
           The Moscone Center
           San Francisco, California, USA

           

  • Luke F. Lester, Daniel J. Kane, Nicholas G. Usechak, Chang-Yi Lin, Yan Li, Yong-Chun Xin, Vassilios I. Kovanis ,"Pulse Characteristics of passively mode-locked quantum dot lasers" ( Invited paper)

          Session: OPTO: Novel In-Plane Semiconductor Lasers IX
          Pres. number: 
7616-6
          Date/time: 
Monday, January 25, 2010, 10:50 AM

  • Yan Li, Furqan L. Chiragh, Chang-Yi Lin, Yong-Chun Xin, Luke F. Lester, "Double-interval harmonic mode-locking technique for diverse waveform generation"

          Session: OPTO: Novel In-Plane Semiconductor Lasers IX
          Pres. number: 
7616-13
          Date/time: 
Monday, January 25, 2010, 2:20 PM          

  • Nader A. Naderi, Michael C. Pochet, Vassilios Kovanis, Luke F. Lester, "Bandwidth Improvement by manipulating the high-frquency roll-off of an injection-locked QD laser operating at 1310nm"

          Session: LASE: Physics  and Simulation of Optoelectronic Devices XVIII
          Pres. number: 
7567-47
          Date/time: 
Wednesday, January 27, 2010, 3:10 PM

  • Michael C. Pochet, Nader A. Naderi, Nathan B. Terry, Vassilios Kovanis, Luke F. Lester, "Linewidth Enhancement factor and Dynamical Response of an Injection-Locked Quantum-Dot Fabry-Perot Laser at 1310nm"

          Session:  OPTO: Novel In-Plane Semiconductor Lasers IX
          Pres. number: 
7616-15
          Date/time: 
Monday, January 25, 2010, 3:10 PM

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frontiers Optics

           2009 MRS Fall Meeting

           November 30 - December 4
           Boston, MA

           

  • Kai Yang, Mohamed A. El-Emawy, Ting-yi Gu, Andreas Stintz, Luke F. Lester, "GaAs Based InAs/InGaAs Quantum Dots-in-a-Well Solar Cells and Their Concentration Applications."

          Pres. number:  R3.2
          Date/time: 
Monday, November 30, 2009, 8:00 AM
          Location: 
Exhibit Hall D (Hynes) 

  • Ting-yi Gu, Kai Yang, Mohamed A. El-Emawy, Andreas Stintz, Luke F. Lester, "Suppression of Edge Recombination in InAs/InGaAs DWELL Solar Cells"

          Pres. number:  Q2.7
          Date/time: 
Monday, November 30, 2009, 3:45 PM
          Location: 
Exhibit Hall D (Hynes) 

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frontiers Optics     

               OSA Frontiers in Optics 2009
               October 11-15, 2009
               San Jose, CA  

  • Kai Yang, Mohamed A. El-Emawy, Ting-yi Gu, Andreas Stintz, Luke F. Lester, "GaAs-Based InAs/InGaAs Quantum Dot Solar Cells for Concentration Applications"

          Session: FMBOptics for Renewable Energy
          Pres. number: 
FMB4
          Date/time: 
Monday, October 12, 2009, 3:00 PM
          Location: 
Gold  

  • Michael C. Pochet, Nader A. Nader, Nathan B. Terry, Vassilios Kovanis, Luke F. Lester, "Operational Behavior of an Injection-Locked Quantum-Dash Fabry-Perot Laser at Zero-Detuning"

          Session: LSTuA -  General Laser Science
          Pres. number:  LSTuA7
         
Date/time:  Tuesday, October 13, 2009, 9:30 AM
          Location: Sacramento 

  • Chang-Yi Lin, Yong-Chun Xin, Yan Li, Furqan L. Chiragh, Luke F. Lester, "Cavity Design of Monolithic Long-Wavelength InAs/InP Quantum Dash Passively Mode-Locked lasers"

          Session: FThK -  Optoelectronics
          Pres. number: 
FThK1
         
Date/time:  Thursday, October 15, 2009, 10:30 AM
          Location: 
Glen Ellen 

  • Tingyi Gu, Kai Yang, Mohamed A. El-Emawy, Andreas Stintz, Luke F. Lester, "Resistance to Edge Recombination in InAs/InGaAs Quantum Dot Solar Cells"

          Session: FMB -  Optics for Renewable Energy
          Pres. number:  FMB5
         
Date/time:  Monday, October 12, 2009, 3:15 PM
          Location: Gold

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CLEO ConferenceThe Conference on Lasers and Electro-Optics (CLEO)

The International Quantum Electronics Conference (IQEC)


 May 31-June 5, 2009; Baltimore, Maryland


  • F. Grillot, N. A. Naderi, M.  Pochet, C.-Y Lin, and L. F. Lester
    "Influence of the Linewidth Enhancement Factor on the Critical Feedback Level in a Quantum Dash Laser"

    Abstract: Contributions of both the ground and excited states (GS/ES) in the degradation of the coherence collapse threshold in a quantum dash (QDash) laser are analyzed. The excited states are found to strongly alter the device's feedback sensitivity


  • F. Grillot, C.-Y. Lin, N. A. Naderi, M.  Pochet, and L. F. Lester
    "Effects of Optical Feedback in InAs/GaAs Monolithic Quantum Dot Passively Mode-Locked Lasers"

    Abstract: The results experimentally show that mode-locking conditions are significantly affected when the feedback rate is strong enough to bring the laser within the coherence collapse regime


  • M. Pochet, N. A. Naderi, F. Grillot, N. Terry, V. Kovanis, and L. F. Lester
    "Methods for Improved 3-dB bandwidth in an Injection-Locked QDash Fabry-Perot Laser at 1550-nm"

    Abstract: The alpha parameterĺs impact on an injection-locked Fabry-Perot QDash laserĺs bandwidth is analyzed. A large α is a primary approach to suppress the sagin the response and increase the bandwidth underpositive frequency detuning.


  • C.-Y. Lin, N. A. Naderi, F. Chiragh, J. H. Kim, Y.-C. Xin, C. G. Christodoulou, and L. F. Lester
    "31% DC to RF Differential Efficiency Using Monolithic Quantum Dot Passively Mode-Locked Lasers"

    Abstract:

    • 31% DC to RF differential efficiency is reported for the conversion of a quantum dot mode-locked laserí»s (QDMLL) optical output to RF

    • 50% external quantum efficiency in the saturable absorber (SA) is reported

    • The method of deriving the conversion efficiency of the QDMLL is investigated

    • The RF signal characterization and the operating regime of stable mode locking (ML) is analyzed


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IPRM2009   

           2009 International Conference on Indium Phosphide and Related Materials
           Newport Beach, CA 10-14 May 2009


  • N. A. Naderi, M. Pochet, F. Grillot, C.-Y. Lin, and L. F. Lester
    "Temperature Effects on the Modulation Response of an Injection-Locked InAs/InP Quantum-Dash laser"

    Abstract: Injection-locking of semiconductor lasers is known to provide several improvements to directly modulated lasers, including enhanced Modulation Bandwidth. Extracting the relevant operating parameters from measured data is highly beneficial in order to aid in future simulations. This work is focused on extracting the operating parameters from a coupled system using an InAs/InP Quantum-Dash Fabry-Perot laser as the slave. Using the conventional rate equations describing an injection-locked system, a novel modulation response function is derived which implicitly incorporates non-linear gain through the free-running relaxation oscillation frequency and damping rate of the slave laser. A major challenge that has been identified for injection-locked lasers is to eliminate the undesirable dip in the modulation response at low frequency under strong injection. Quantum-Dash semiconductor lasers have been shown to possess characteristics that are well-suited for solving this problem. In this work the impact of the slave laser linewidth enhancement factor, a, on the modulation response and bandwidth of an injection-locked Quantum-Dash laser is analyzed.

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Photonics West     SPIE Photonics West
     San Jose, CA     24-29 January 2009



  • F. Grillot, N. A. Naderi, M. C. Pochet, C.-Y. Lin and L. F. Lester
    "Systematic investigation of the alpha parameter influence on the critical feedback level in QD lasers"

    Abstract: The dramatic variation in the linewidth enhancement factor (alpha parameter) that has been reported for quantum dot lasers makes them an interesting subject for optical feedback studies. A low alpha parameter combined with a high damping factor is especially interesting because it should increase the tolerance to optical feedback in these devices and may offer potential advantages for direct modulation. It will be presented that under specific conditions, i.e., in the case of a strong enhancement in the alpha parameter, the feedback sensitivity of the laser can vary by as much as 10 dB within the same device.


  • M. C. Pochet, N. A. Naderi, F. Grillot, N. B. Terry, V. I. Kovanis and L. F. Lester
    "Analysis of the modulation response of an injection locked quantum-dash Fabry-Perot laser at 1.55 Ám"

    Abstract: A modulation response function based on the fundamental rate equations describing injection-locked laser systems is shown to accurately model experimental data collected on an injection-locked system using a quantum dash fabry-perot semiconductor laser. The modulation response model incorporates non-linear gain, along with a factor relating the deviation of the steady state field magnitude of the locked slave laser from its free running value at high injection ratios and negative frequency detuning. By first performing a thorough characterization of the free running slave laser, the number of unknown parameters in the modulation response function for the coupled laser system is reduced, and the remaining unknown parameters can be determined by performing a least-square fit to experimental data. The extracted operating parameters include the injection strength, linewidth enhancement factor, coupled phase between the master and slave, and field ratio characterizing the deviation of the locked slave laser from its free running value. These parameters can be used to calculate a detuning frequency that can be compared to the experimentally observed value, allowing the validity of the model to be evaluated. A method to more accurately calculate the injection strength based on the experimental setup and operating conditions is discussed in order to bridge the gap between experiment and simulation and determine the injection strength necessary to maximize the modulation bandwidth.

    Keywords: Injection-locked laser, quantum-dash, modulation response.


  • F. Grillot, K. Veselinov, M. Gioannini, J. Even, S. Loualiche and I. Montrosset
    "Theoretical analysis of 1.55 Ám InAs/InP (311B) quantum dot lasers based on a Multi-population rate equation model"

    Abstract: In this paper, a theoretical model is used to investigate the lasing spectrum properties of InAs/InP(113)B quantum dot (QD) lasers emitting at 1.55 Ám. The numerical model used is based on a multi-population rate equation (MPRE) analysis. It takes into account the effect of the competition between the inhomogeneous broadening (due to the QD size dispersion) and the homogeneous broadening as well as a nonlinear gain variation associated to a multi-mode laser emission. The double laser emission and the temperature dependence of lasing spectra of self-assembled InAs/InP quantum dot lasers is studied both experimentally and theoretically.


  • C.-Y. Lin, Y.-C. Xin and L. F. Lester
    "Monolithic 1.58 micron InAs/InP quantum dash passively mode-locked lasers"

    Abstract: Monolithic InAs quantum dash 1.58-micron passively mode-locked lasers grown on an InP substrate are reported. A repetition rate of up to 18.5 GHz has been realized. The dashes-in-a-well (DWELL) active region consists of 5 stacks of InAs quantum dashes embedded in compressively strained Al0.20Ga0.16In0.64As quantum wells separated by 30-nm undoped tensile-strained Al0.28Ga0.22In0.50As spacers on both sides of the DWELL. 4 micron-wide ridge waveguides with cavity lengths in the range 2-3 mm were fabricated with equal-length, electrically-isolated anode contacts, each 0.5 mm in length. The modal gain and loss spectra of the InAs active region were then measured through the improved segmented contact method, and the characteristics that make InAs quantum dash materials system desirable for semiconductor mode-locked lasers were identified. The segmented waveguides were then reconfigured into mode-locked lasers by wire bonding the segments together to form separate gain and absorber regions that use the same DWELL active region. A highly reflective coating (95%) was applied to the mirror facet next to the absorber while the other facet was cleaved. To assist in the cavity design and determine the relative length of the absorber and gain sections, a model for the cavity geometry of two-section passively mode-locked lasers was studied that is based on a microwave photonics perspective. The new set of theoretical equations was used to find the optimal device layout using the measured modal gain and loss characteristics as input data.

    Keywords: Quantum Dash, Mode-locked Lasers, Semiconductor lasers

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Leos     The 21st Annual Meeting of The IEEE LASERS & Electro-Optics Society
     Newport Beach, CA     9-13 November 2008


  • N. A. Naderi, M. Pochet, F. Grillot, N. Terry, V. Kovanis, L. F. Lester
    "Extraction of Operating Parameters from an Injection-Locked Quantum-Dash Fabry-Perot Laser at 1.55 Ám"

    Abstract: Using a series of modulation response curves for an injection-locked quantum dash laser, characteristic parameters of the system were extracted by means of a theoretical model that incorporates non-linear gain.


  • F. Grillot, A. Martinez, K. Merghem, J.G. Provost, F. Alexandre, R. Piron, O. Dehaese, S. Loualiche, L. F. Lester and A. Ramdane
    "Stable Above-Threshold Linewidth Enhancement Factor in a 1.52 Ám InAs/InP (311B) Quantum Dot Laser"

    Abstract: The αH-factor behavior with current is investigated in a 1.52 Ám InAs/InP (311B) QD laser. It is shown that due to low gain compression effects, no divergence of the αH-factor occurs unlike 1.3 Ám InAs/GaAs QD lasers.


  • F. Grillot, N. A. Naderi, M. Pochet, C. Yi. Lin and L. F. Lester
    "Variation of the Critical Feedback Level in a 1550 nm Quantum-Dash Fabry-Perot Semiconductor Laser"

    Abstract: Dynamic properties of a 1550 nm quantum dash laser are investigated. Due to an increase in the linewidth enhancement factor (αH-factor) with bias current, a collapse in the feedback sensitivity as high as 20dB is reported.


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