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THz Time-Domain Characterization of ...

Shen, Yue.

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THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface./
作者:	Shen, Yue.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2023,
面頁冊數:	197 p.
附註:	Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
Contained By:	Dissertations Abstracts International84-12B.
標題:	Electrical engineering. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30524843
ISBN:	9798379620257

THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface.
Shen, Yue.

THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface. - Ann Arbor : ProQuest Dissertations & Theses, 2023 - 197 p.

Source: Dissertations Abstracts International, Volume: 84-12, Section: B.

Thesis (Ph.D.)--University of California, Los Angeles, 2023.

This item must not be sold to any third party vendors.

Terahertz (THz) quantum cascade lasers (QCLs) are compact electrically pumped unipolar semiconductor laser which can produce a continuous wave radiation of high output power in the range of 1.2 to 5.6 THz. The QC vertical-external-cavity surface-emitting-laser (QC-VECSEL) is an external cavity configuration that supports high-power operation with excellent beam quality and broadband tunability. The key component of the QC-VECSEL is an amplifying reflectarray metasurface, based on a subwavelength array of surface-radiating metal-metal waveguide antenna elements loaded with QC-laser gain material. Despite its importance, up to now the spectral properties of the QC-metasurface have been designed by simulations and have only been verified indirectly through observation of the QC-VECSEL lasing characteristics, or by passive FTIR reflectance measurements at room temperature. Furthermore, design takes place using simulations based upon simplified models for the material loss and the QC-gain, where uncertain Drude model parameters for material losses are used, and the detailed interaction of the intersubband transition with the metasurface is neglected. In the past decade, THz time domain spectroscopy (THz-TDS) has been widely used to investigate gain spectra and laser dynamics of THz QC-lasers based on various ridge waveguide geometries.During my doctoral studies, I designed and built up a reflection-mode THz-TDS system to study amplifying quantum-cascade (QC) metasurface samples as a function of injected current density. The first direct spectral measurements were performed on QC-metasurfaces using reflection-mode THz-TDS. Several different kinds of metasurface were designed that were suitable for study by the THz-TDS system. Extremely strong absorption features for QC-metasurfaces whose resonance frequency designed below 3 THz is measured at zero bias, which is associated with coupling between the metasurface resonance and an intersubband transition within the QC material. In one case, nearly perfect absorption is observed due to the transition from weak to strong light-matter coupling condition. Increase in reflectance are observed as the devices are biased, both due to reduction in intersubband loss and the presence of intersubband gain. Significant phase modulation associated with the metasurface resonance is observed via electrical control for some certain metasurfaces, which may be useful for electrical tuning of QC-VECSEL. These results provide insight into the interaction between the intersubband QC-gain material and the metasurface and modify the design rules for QC-VECSELs for both biased and unbiased regions.

ISBN: 9798379620257Subjects--Topical Terms:

649834
Electrical engineering.
Subjects--Index Terms:

Intersubband transition

THz Time-Domain Characterization of Amplifying Quantum-Cascade Metasurface.
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500 $a Source: Dissertations Abstracts International, Volume: 84-12, Section: B.
500 $a Advisor: Williams, Benjamin S.
502 $a Thesis (Ph.D.)--University of California, Los Angeles, 2023.
506 $a This item must not be sold to any third party vendors.
520 $a Terahertz (THz) quantum cascade lasers (QCLs) are compact electrically pumped unipolar semiconductor laser which can produce a continuous wave radiation of high output power in the range of 1.2 to 5.6 THz. The QC vertical-external-cavity surface-emitting-laser (QC-VECSEL) is an external cavity configuration that supports high-power operation with excellent beam quality and broadband tunability. The key component of the QC-VECSEL is an amplifying reflectarray metasurface, based on a subwavelength array of surface-radiating metal-metal waveguide antenna elements loaded with QC-laser gain material. Despite its importance, up to now the spectral properties of the QC-metasurface have been designed by simulations and have only been verified indirectly through observation of the QC-VECSEL lasing characteristics, or by passive FTIR reflectance measurements at room temperature. Furthermore, design takes place using simulations based upon simplified models for the material loss and the QC-gain, where uncertain Drude model parameters for material losses are used, and the detailed interaction of the intersubband transition with the metasurface is neglected. In the past decade, THz time domain spectroscopy (THz-TDS) has been widely used to investigate gain spectra and laser dynamics of THz QC-lasers based on various ridge waveguide geometries.During my doctoral studies, I designed and built up a reflection-mode THz-TDS system to study amplifying quantum-cascade (QC) metasurface samples as a function of injected current density. The first direct spectral measurements were performed on QC-metasurfaces using reflection-mode THz-TDS. Several different kinds of metasurface were designed that were suitable for study by the THz-TDS system. Extremely strong absorption features for QC-metasurfaces whose resonance frequency designed below 3 THz is measured at zero bias, which is associated with coupling between the metasurface resonance and an intersubband transition within the QC material. In one case, nearly perfect absorption is observed due to the transition from weak to strong light-matter coupling condition. Increase in reflectance are observed as the devices are biased, both due to reduction in intersubband loss and the presence of intersubband gain. Significant phase modulation associated with the metasurface resonance is observed via electrical control for some certain metasurfaces, which may be useful for electrical tuning of QC-VECSEL. These results provide insight into the interaction between the intersubband QC-gain material and the metasurface and modify the design rules for QC-VECSELs for both biased and unbiased regions.
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650 4 $a Computer engineering. $3 621879
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653 $a Intersubband transition
653 $a Light-matter coupling
653 $a Quantum cascade lasers
653 $a Terahertz
653 $a Time domain spectroscopy
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690 $a 0752
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710 2 $a University of California, Los Angeles. $b Electrical and Computer Engineering 0333. $3 3542511
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