Grating-coupler assisted infrared spectroscopy on anisotropic multilayer systems: A comparative study

Wendler, L.; Finger, N.; Gornik, E.

doi:10.1016/j.infrared.2004.04.006

Cited by 6 publications

(4 citation statements)

References 61 publications

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“…v F = √ 2πN/m * is the Fermi velocity for 2DEG, where is the reduced Plank constant and N is the electron sheet density. For example, in the AlGaAs/GaAs heterostructure [8,15], with typical values of m * = 0.063m 0 (m 0 is the electron rest mass), N = 10 16 m −2 and k = 10 6 m −1 , the nonlocal parameter X = 0.16 at the magnetic field B = 1 T. At this condition, the local limit approximation (X 1) could be applied. For collisionless electrons (electron relaxation time τ → ∞), the dispersion of 2D magnetoplasmon-polaritons is [16]…”

Section: Introductionmentioning

confidence: 99%

“…Section 2 derives the general formula for the calculation of MPP complex frequencies and absorptions according to the structural and physical parameters in the heterostructure with grating couplers. Taking the AlGaN/GaN structure as a case study, we compute the real and imaginary parts of the MPP frequencies and the absorption spectrum at different wavevectors and magnetic field taking advantage of the slightly modified homemade program based on coupled wave method (CWM) [5,8,15] in section 3. Influences of nonlocal correction terms in the magnetoconductivity and contributions of phonons in polar semiconductors, polarization of the incident THz field and retardation effects are also discussed.…”

Section: Introductionmentioning

confidence: 99%

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Terahertz magnetoplasmon-polaritons with nonlocal corrections for lossy two dimensional electron gas in GaN-based heterostructures

Cao

et al. 2017

J. Phys.: Condens. Matter

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The high electron concentration in GaN-based heterostructures necessitate the consideration of nonlocal corrections in the magnetoconductivity for the study of magnetoplasmon-polaritons (MPPs) in the lossy two dimensional electron gas system with grating couplers. With the complete set of Maxwell equations, the complex dispersion frequency and absorption spectrum are calculated numerically at different magnetic field (B = 10 T) and plasmon wavevectors (k = 5 × 10 m). Taking the AlGaN/GaN structure as a representative case, we observe the cyclotron resonance and its high order harmonics, as well as the MPP modes. The effective aspect ratio of the grating is determined according to the absorption spectrum. Effects of the nonlocal corrections on the dispersion frequency and absorption spectrum are analyzed in detail. The contributions of LO phonons, electron collisions, THz wave polarizations and retardations are also discussed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Terahertz magnetoplasmon-polaritons with nonlocal corrections for lossy two dimensional electron gas in GaN-based heterostructures

Cao

et al. 2017

J. Phys.: Condens. Matter

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“…The nonlocal magnetoconductivity tensor in function of the frequency, wavevector and magnetic field was introduced firstly to represent the electromagnetic behaviour of the 2DEG layer under the influence of magnetic field. For a multilayer system with periodic grating on top, the coupled wave method (CWM) [20] was utilized to find the wavevector along z axis and the electromagnetic field in the interleaved grating/air layer along x axis. Finally, the absorption spectrum was obtained based on the transfer matrix method which associates the electric and magnetic field components in each layer.…”

Section: Methods To Calculate the Absorption Spectrummentioning

confidence: 99%

Comparative study on calculated terahertz absorption spectra of different heterostructure materials with external magnetic field

Cao

2018

J. Phys. Commun.

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Room temperature operation and frequency tunability are attractive advantages of terahertz (THz) detectors based on the two-dimensional electron gas (2DEG) in the heterostructure material with external magnetic field. This work compared absorption spectra of four typical heterostructure materials (AlGaN/GaN, InAlN/GaN, AlGaAs/GaAs and SiGe/Si) with the nonlocal magnetoconductivity model at ambient and cryogenic temperatures in the frequency range 0-5 THz. The GaN based materials have the highest absorption amplitude, while the AlGaAs/GaAs material owns the largest frequency shift as the magnetic field increases up to 10 tesla, although superconducting magnets at cryogenic temperature are usually employed to provide that high magnetic field. The numerical results showed that the absorption properties (amplitude and frequency) could be further optimized by other parameters, such as the period and filling factor of the grating coupler, and the barrier thickness.

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“…20,26 In this work, we demonstrate how coupling thin-film samples to a diffraction grating substrate can be used to yield information about film thickness simultaneously during IRRAS measurements. Although grating-coupler assisted infrared spectroscopy has been reported for investigation of the excitation spectrum of inorganic multilayers, [27][28][29] it has not previously been combined with IRRAS for film thickness measurements. In this work, film thickness information is obtained through an anomolous absorbance in the infrared spectrum that appears at grazing angles of incidence.…”

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confidence: 99%

Grating-Coupler Assisted Infrared Reflection Absorption Spectroscopy for the Characterization of Organic Thin Films

Singh

Hillier

2006

Anal. Chem.

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We demonstrate how grating-coupler assisted infrared reflection absorption spectroscopy can be used to simultaneously determine the chemical identity and relative thickness of organic thin films. With a grating substrate, a threshold anomaly associated with passing off of the -1 diffracted order occurs at grazing angles of incidence, resulting in a sharp absorbance in the infrared. The position of this peak is sensitive to the grating geometry as well as the dielectric environment near its surface. Thus, shifts in the peak position can be used to determine the relative thickness of adsorbed films or quantify molecular adsorption events. To illustrate the characteristics and sensitivity of this phenomenon, several samples were prepared and tested, including self-assembled alkanethiolate monolayers with 11-mercaptoundecanoic acid, 11mercapto-1-undecanol, decanethiol, and a covalently linked layer of bovine serum albumin on a commercial, goldcoated grating. For these samples, the position of the threshold absorbance peak shifted to lower wavenumbers as film thickness increased, which is consistent with calculated shifts based upon an increasing refractive index at the interface. The sensitivity of this shift was measured to be 3.7 cm -1 nm -1 . These results illustrate how a grating substrate can be exploited in a standard infrared reflectance measurement to provide additional information about the relative thickness of adsorbed surface films.

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Grating-coupler assisted infrared spectroscopy on anisotropic multilayer systems: A comparative study

Cited by 6 publications

References 61 publications

Terahertz magnetoplasmon-polaritons with nonlocal corrections for lossy two dimensional electron gas in GaN-based heterostructures

Terahertz magnetoplasmon-polaritons with nonlocal corrections for lossy two dimensional electron gas in GaN-based heterostructures

Comparative study on calculated terahertz absorption spectra of different heterostructure materials with external magnetic field

Grating-Coupler Assisted Infrared Reflection Absorption Spectroscopy for the Characterization of Organic Thin Films

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