Polarization imaging of imperfect <i>m</i>-plane GaN surfaces

Sakai, Yuji; Kawayama, Iwao; Nakanishi, Hachiro; Tonouchi, Masayoshi

doi:10.1063/1.4979511

Cited by 29 publications

(14 citation statements)

References 18 publications

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“…Unlike other methods, the resolution in LTEM is not limited by the THz wavelength but by that of the optical source, allowing THz-emission spectroscopy and -emission imaging of various samples of sub-micrometer scale achievable. [22][23][24][25] In the recently developed system, a nonlinear optical crystal (NLOC) is employed as a 2D THz emitter, and THz waves are locally generated in the process of optical rectification at the irradiation spots of femtosecond (fs) laser beams. 26 Since the fs laser beams are focused at the output surface of the NLOC, the beam diameter of the generated THz waves is approximately the same size as that of the focused beam spot which overcomes the diffraction limit of THz waves.…”

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confidence: 99%

Invited Article: Terahertz microfluidic chips sensitivity-enhanced with a few arrays of meta-atoms

et al. 2018

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We present a nonlinear optical crystal (NLOC)-based terahertz (THz) microfluidic chip with a few arrays of split ring resonators (SRRs) for ultra-trace and quantitative measurements of liquid solutions. The proposed chip operates on the basis of near-field coupling between the SRRs and a local emission of point like THz source that is generated in the process of optical rectification in NLOCs on a sub-wavelength scale. The liquid solutions flowing inside the microchannel modify the resonance frequency and peak attenuation in the THz transmission spectra. In contrast to conventional bio-sensing with far/near-field THz waves, our technique can be expected to compactify the chip design as well as realize high sensitive near-field measurement of liquid solutions without any high-power optical/THz source, near-field probes, and prisms. Using this chip, we have succeeded in observing the 31.8 fmol of ion concentration in actual amount of 318 pl water solutions from the shift of the resonance frequency. The technique opens the door to microanalysis of biological samples with THz waves and accelerates development of THz lab-on-chip devices.

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Invited Article: Terahertz microfluidic chips sensitivity-enhanced with a few arrays of meta-atoms

et al. 2018

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“…The dynamics-related information provided is different from that provided by typical photoluminescence, electroluminescence, and laser-induced photocurrent characterization methods [6]. We have reported several examples in which defect analysis [7], noncontact surface potential estimation [8,9], and nondestructive evaluation of solar cells [10] are demonstrated and shown that TES and LTEM are practical tools for semiconductor research and development. In the present study, we employ TES and LTEM to study local ultrafast photocarrier dynamics in β-Ga 2 O 3 , which has an ultrawide bandgap of approximately 4.7-4.9 eV [3,[11][12][13].…”

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confidence: 95%

Terahertz Emission Spectroscopy and Microscopy on Ultrawide Bandgap Semiconductor β-Ga2O3

et al. 2020

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Although gallium oxide Ga2O3 is attracting much attention as a next-generation ultrawide bandgap semiconductor for various applications, it needs further optical characterization to support its use in higher-performance devices. In the present study, terahertz (THz) emission spectroscopy (TES) and laser THz emission microscopy (LTEM) are applied to Sn-doped, unintentionally doped, and Fe-doped β-Ga2O3 wafers. Femtosecond (fs) laser illumination generated THz waves based on the time derivative of the photocurrent. TES probes the motion of ultrafast photocarriers that are excited into a conduction band, and LTEM visualizes their local spatiotemporal movement at a spatial and temporal resolution of laser beam diameter and a few hundred fs. In contrast, one observes neither photoluminescence nor distinguishable optical absorption for a band-to-band transition for Ga2O3. TES/LTEM thus provides complementary information on, for example, the local mobility, surface potential, defects, band bending, and anisotropic photo-response in a noncontact, nondestructive manner. The results indicated that the band bends downward at the surface of an Fe-doped wafer, unlike with an n-type wafer, and the THz emission intensity is qualitatively proportional to the product of local electron mobility and diffusion potential, and is inversely proportional to penetration depth, all of which have a strong correlation with the quality of the materials and defects/impurities in them.

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“…2020, 8,1900892 mentation of THz emission spectroscopy to 2D systems is a viable and credible approach to realizing such ultrafast optical control. [128][129][130][131][132][133][134][135][136][137][138][139][140][141] In the specific area of active metamaterials research, combining the electronic and magnetic control with the optical THz functionality of metamaterials promises several new possibilities for the technological utility of THz light-matter interaction. [136,137] Thus, material research by and for THz technology is one of the most exciting research fields where we can study the intrinsic nature of materials and devices.…”

Section: Wwwadvopticalmatdementioning

confidence: 99%

“…[136,137] Thus, material research by and for THz technology is one of the most exciting research fields where we can study the intrinsic nature of materials and devices. [128][129][130][131][132][133][134][135][136][137][138][139][140][141] In the specific area of active metamaterials research, combining the electronic and magnetic control with the optical THz functionality of metamaterials promises several new possibilities for the technological utility of THz light-matter interaction. [142] Figure 23.…”

Section: Wwwadvopticalmatdementioning

confidence: 99%

Terahertz Emission Functionality of High‐Temperature Superconductors and Similar Complex Systems

Rana

Tonouchi

2019

Advanced Optical Materials

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During the past two decades, terahertz (THz) science and technology have rapidly expanded in all fundamental and applied aspects of physical, chemical, and biological sciences. In physical sciences, these developments have been twofolds: i) the use of THz technology in understanding the complexities of materials and ii) the exploration of new THz functionalities of emerging materials for further advancement of THz technology. Here, the THz emission spectroscopy and the ultrafast functionality of three pillars of electronic and magnetic condensed matter systems that emerged in the following order: high-temperature superconductors, colossal magnetoresistive manganites, and magnetoelectric multiferroics are reviewed. Emission functionality refers to the emitted THz radiation that carries the information of the underlying functional property of the material such that the overall effect evolves as the THz decoding of the information in a noninvasive manner and on an ultrafast timescale.The HTSC is one of the most attractive perovskite oxides in terms of fundamental science and future applications such as in quantum information and THz devices. Superconductivity

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Polarization imaging of imperfect m-plane GaN surfaces

Cited by 29 publications

References 18 publications

Invited Article: Terahertz microfluidic chips sensitivity-enhanced with a few arrays of meta-atoms

Invited Article: Terahertz microfluidic chips sensitivity-enhanced with a few arrays of meta-atoms

Terahertz Emission Spectroscopy and Microscopy on Ultrawide Bandgap Semiconductor β-Ga2O3

Terahertz Emission Functionality of High‐Temperature Superconductors and Similar Complex Systems

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