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Ultrafast dynamics in semiconductor devices

Zhang, Botao (2011) Ultrafast dynamics in semiconductor devices. Doctoral Dissertation, University of Pittsburgh.

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    Abstract

    This research focuses on three types of GaAs-based semiconductor devices, namely oxide confined vertical-cavity surface-emitting lasers (VCSEL), GaAs/AlGaAs quantum dots and GaAs microdisk lasers. An individual transverse mode distribution in a VCSEL has been resolved by a scanning confocal microscope in connection with an optical spectrum analyzer. With resonant femtosecond pulse injection, we directly perturb the cavity field of a VCSEL. After the injection, the lasing and nonlasing mode dynamics are measured. Spatio-temporal resolution of the VCSEL's modes helps us to understand how to lock transverse modes and work toward a new type of mode-locked pulse laser. By injecting cross-polarized laser pulses into a VCSEL cavity, we also studied the ultrafast polarization effects of a single-mode VCSEL. Based on time-resolved microscopic photoluminescence (μPL) from single self-assembled GaAs/AlGaAs quantum dots, we unambiguously identify one of the emission lines as arising from positive trions (two holes and one electron) in these nominally undoped quantum dots. The trion is formed via tunneling of one electron out of the dot after optical excitation of a biexciton. The rise time of the trion emission line matches the decay time of the biexciton due to electron tunneling. Time-resolved whispering-gallery modes (WGMs) of GaAs microdisk lasers show a redshift in time. After the fs laser pulse pump, there is a turn-on delay of the microdisk laser lasing emission. With the increasing pump power, the WGMs shift to shorter wavelength.


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    Item Type: University of Pittsburgh ETD
    ETD Committee:
    ETD Committee TypeCommittee MemberEmail
    Committee ChairSnoke, David Wsnoke@pitt.edu
    Committee MemberLevy, Jeremyjlevy@pitt.edu
    Committee MemberChen, Kevin Ppec9@pitt.edu
    Committee MemberCoalson, Robrob@mercury.chem.pitt.edu
    Committee MemberSavinov, Vladimirvladimirsavinov@gmail.com
    Title: Ultrafast dynamics in semiconductor devices
    Status: Unpublished
    Abstract: This research focuses on three types of GaAs-based semiconductor devices, namely oxide confined vertical-cavity surface-emitting lasers (VCSEL), GaAs/AlGaAs quantum dots and GaAs microdisk lasers. An individual transverse mode distribution in a VCSEL has been resolved by a scanning confocal microscope in connection with an optical spectrum analyzer. With resonant femtosecond pulse injection, we directly perturb the cavity field of a VCSEL. After the injection, the lasing and nonlasing mode dynamics are measured. Spatio-temporal resolution of the VCSEL's modes helps us to understand how to lock transverse modes and work toward a new type of mode-locked pulse laser. By injecting cross-polarized laser pulses into a VCSEL cavity, we also studied the ultrafast polarization effects of a single-mode VCSEL. Based on time-resolved microscopic photoluminescence (μPL) from single self-assembled GaAs/AlGaAs quantum dots, we unambiguously identify one of the emission lines as arising from positive trions (two holes and one electron) in these nominally undoped quantum dots. The trion is formed via tunneling of one electron out of the dot after optical excitation of a biexciton. The rise time of the trion emission line matches the decay time of the biexciton due to electron tunneling. Time-resolved whispering-gallery modes (WGMs) of GaAs microdisk lasers show a redshift in time. After the fs laser pulse pump, there is a turn-on delay of the microdisk laser lasing emission. With the increasing pump power, the WGMs shift to shorter wavelength.
    Date: 31 January 2011
    Date Type: Completion
    Defense Date: 02 September 2010
    Approval Date: 31 January 2011
    Submission Date: 22 November 2010
    Access Restriction: 5 year -- Restrict access to University of Pittsburgh for a period of 5 years.
    Patent pending: No
    Institution: University of Pittsburgh
    Thesis Type: Doctoral Dissertation
    Refereed: Yes
    Degree: PhD - Doctor of Philosophy
    URN: etd-11222010-005112
    Uncontrolled Keywords: Ultrafast optoelectronics; quantum dots; semicondutor lasers; VCSEL
    Schools and Programs: Dietrich School of Arts and Sciences > Physics
    Date Deposited: 10 Nov 2011 15:05
    Last Modified: 14 May 2012 12:26
    Other ID: http://etd.library.pitt.edu/ETD/available/etd-11222010-005112/, etd-11222010-005112

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