Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells
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| Language: | English |
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University of Cincinnati / OhioLINK
2014
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396453493 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-ucin1396453493 |
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oai_dc |
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NDLTD |
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English |
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Physics phase coherent photorefractive effect four wave mixing exciton lifetime electron grating lifetime electron grating buildup and decay optical coherence imaging through turbid media |
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Physics phase coherent photorefractive effect four wave mixing exciton lifetime electron grating lifetime electron grating buildup and decay optical coherence imaging through turbid media Dongol, Amit Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells |
| author |
Dongol, Amit |
| author_facet |
Dongol, Amit |
| author_sort |
Dongol, Amit |
| title |
Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells |
| title_short |
Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells |
| title_full |
Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells |
| title_fullStr |
Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells |
| title_full_unstemmed |
Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells |
| title_sort |
carrier dynamics and application of the phase coherent photorefractive effect in znse quantum wells |
| publisher |
University of Cincinnati / OhioLINK |
| publishDate |
2014 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396453493 |
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AT dongolamit carrierdynamicsandapplicationofthephasecoherentphotorefractiveeffectinznsequantumwells |
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1719436078743552000 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-ucin13964534932021-08-03T06:23:19Z Carrier Dynamics and Application of the Phase Coherent Photorefractive Effect in ZnSe Quantum Wells Dongol, Amit Physics phase coherent photorefractive effect four wave mixing exciton lifetime electron grating lifetime electron grating buildup and decay optical coherence imaging through turbid media <p>The intensity dependent diffraction efficiency of a phase coherent photorefractive (PCP) ZnSe quantum well (QW) is investigated at 80 K in a two-beam four-wave mixing (FWM) configuration using 100 fs laser pulses with a repetition rate of 80 MHz. The observed diffraction efficiencies of the first- and second-order diffracted beam are on the order of 10<sup>-3</sup> and 10<sup>-5</sup>, respectively, revealing nearly no intensity dependence. The first-order diffraction is caused by the PCP effect where the probe-pulse is diffracted due to a long-living incoherent electron density grating in the QW. The second-order diffraction is created by a combination of diffraction processes. For negative probe-pulse delay, the exciton polarization is diffracted at the electron grating twice by a cascade effect. For positive delay, the diffracted signal is modified by the destructive interference with a <i>χ</i><sup>(5)</sup> generated signal due to a dynamical screening effect. Model calculations of the signal traces based on the optical Bloch equations considering inhomogeneous broadening of exciton energies are in good agreement with the experimental data.</p><p>To study the carrier dynamics responsible for the occurrence of the PCP effect, three-beam FWM experiments are carried out. The non-collinear wave-vectors <b>k</b><sub>1</sub>, <b>k</b><sub>2</sub> and <b>k</b><sub>3</sub> at central wavelength of 441 nm (~2.81 eV) were resonantly tuned to the heavy-hole exciton transition energy at 20 K. In the FWM experiment the time coincident strong pump pulses <b>k</b><sub>1</sub> and <b>k</b><sub>2</sub> create both an exciton density grating in the QW and an electron-hole pair grating in the GaAs while the delayed weak pulse <b>k</b><sub>3</sub> simultaneously probes the exciton lifetime as well as the electron grating capture time. The model calculations are in good agreement with the experimental results also providing information about the transfer delay of electrons arriving from the substrate to the QW. For negative probe-pulse delay we still observe a diffracted signal due to the long living electron density grating in the QW. The electron grating build-up and decay times are also studied with the modified three-beam FWM set-up. Using an optical shutter for pump pulses <b>k</b><sub>1</sub> and <b>k</b><sub>2</sub> , the dynamics of the electron grating formation and its decay is continuously probed by a delayed pulse <b>k</b><sub>3</sub>. The obtained build-up and decay times are found to depend nearly linearly on the intensity of incident pulses <b>k</b><sub>1</sub> and <b>k</b><sub>2</sub> being on the order of several microseconds at low pump intensities.</p><p>The PCP effect in ZnSe QW possesses a time-gating capability which can be used for real-time holographic imaging. In this work we demonstrate contrast enhanced real time holographic imaging (CEHI) of floating glass beads and of living unicellular animals (Paramecium and Euglena cells) in aqueous solution. We also demonstrate CEHI of a ~100 µm thick wire concealed behind a layer of chicken skin. The results demonstrate the potential of PCP QWs for real-time and depth-resolved imaging of moving micrometer sized biological objects in transparent media or of obscured objects in turbid media.</p> 2014-10-23 English text University of Cincinnati / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396453493 http://rave.ohiolink.edu/etdc/view?acc_num=ucin1396453493 unrestricted This thesis or dissertation is protected by copyright: some rights reserved. It is licensed for use under a Creative Commons license. Specific terms and permissions are available from this document's record in the OhioLINK ETD Center. |