Phase Retrieval in Terahertz Time-Domain Measurements: a “how to” Tutorial

Jepsen, Peter Uhd

doi:10.1007/s10762-019-00578-0

Cited by 72 publications

(35 citation statements)

References 29 publications

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“…Nevertheless, these delicate differences do not have a significant influence on our research goal of understanding the origin of molecular vibrations, which contribute to the major absorptions in the experiment. Note that the good agreement between experimental and theoretical vibrational spectra gives an interesting possibility for obtaining THz absorption spectra by simulations without time‐consuming experiments and data analysis, [ 42 ] particularly for organic crystals with many complex absorption peaks involved. In addition, it may allow for a more clear understanding of the origin of the absorption peaks (not possible in the experiment), that is, the specific molecular vibrational motion of organic nonlinear optical salt crystals as discussed in the following section.…”

Section: Resultsmentioning

confidence: 99%

Solid‐State Molecular Motions in Organic THz Generators

Kim

Park

Seok

et al. 2020

Advanced Optical Materials

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Organic nonlinear optical salt crystals are widely used as efficient broadband THz generators. Although solid state molecular motions of organic crystals can greatly influence THz generation characteristics, their origin and effects on THz photonics are not clearly identified. In this work, the origin of solid‐state molecular motions of the state‐of‐the‐art nonlinear optical organic salt crystals and their effects on THz generation characteristics are theoretically investigated. A model crystal, HMQ‐TMS (2‐(4‐hydroxy‐3‐methoxystyryl)‐1‐methylquinolinium 2,4,6‐trimethylbenzenesulfonate) with large macroscopic optical nonlinearity, which is very attractive for intense broadband and narrowband THz wave generation, is chosen. The solid‐state molecular vibrations of HMQ‐TMS crystals can be classified in three frequency regions: phonon mode region, intramolecular motion region, and their mixing region. For the first time for ionic organic crystalline THz generators, the contributions of cationic chromophores and anionic matchmakers on each of vibrational modes are quantitatively separated. In addition, the influence of solid‐state molecular vibrations of HMQ‐TMS crystals on the generated THz spectra is investigated. These results provide an essential information for design of new organic nonlinear optical salt crystals for THz generators as well as detectors and for optimization of THz generation performance.

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Section: Resultsmentioning

confidence: 99%

Solid‐State Molecular Motions in Organic THz Generators

Kim

Park

Seok

et al. 2020

Advanced Optical Materials

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“…6) before the arrival of the first echo. Since the available time window is a central part of THz-TDS analysis [29], these echoes are important to consider when planning a given experiment. The available temporal window is 2nd/c, which for the 525-μm wafers used here equals 12 ps.…”

Section: Broadband Attenuation With Silicon Wafersmentioning

confidence: 99%

Attenuation of THz Beams: A “How to” Tutorial

Kaltenecker

Kelleher

Zhou

et al. 2019

J Infrared Milli Terahz Waves

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Attenuation of ultrashort THz pulses poses a significant technological challenge due to the broadband nature of such light pulses. Several methods exist for this purpose, including crossed wire grid polarizers, high refractive index, high resistivity silicon wafers, and ultrathin metal films. In this review, we discuss the operational principles of these methods, and highlight some of the advantages and potential pitfalls of the methods. We describe the limits of high-frequency operation of wire grid polarizers, relevant for contemporary ultra-broadband THz sources in air photonics. We discuss the effects of multiple reflections and interference in sequences of silicon wafers for attenuation, and finally discuss the potential of using ultrathin metallic films for broadband attenuation.

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“…A reference time-domain trace is recorded, followed (or preceded) by a measurement of the sample (Figure 2a).A Fourier transform is applied to the time-domain data, yielding spectral data (Figure 2b). THz transmission loss in the sample is evident in the difference between the reference and sample spectra.The THz optical parameters of the sample are calculated from the spectral data of reference and sample (Figure 2c) [11,12,13,14]. The refractive index is obtained from the phase data; whereas the absorption coefficient is derived from the amplitude data, taking into account the previously calculated refractive index.…”

Section: Instrumentationmentioning

confidence: 99%

“…The THz optical parameters of the sample are calculated from the spectral data of reference and sample (Figure 2c) [11,12,13,14]. The refractive index is obtained from the phase data; whereas the absorption coefficient is derived from the amplitude data, taking into account the previously calculated refractive index.…”

Section: Instrumentationmentioning

confidence: 99%