Low noise laser-based T-ray spectroscopy of liquids using double-modulated differential time-domain spectroscopy
Open accessAbstract
Liquid transmission studies at terahertz frequencies (0.1–10 THz) are valuable for understanding solvation dynamics of salts, exploring long-range structure in mixtures and probing biomolecules in suspension. T-ray (or THz) time-domain spectroscopy, based on terahertz pulse generation from ultrafast lasers, is a sensitive technique for measuring material parameters in this frequency range. This paper proposes and demonstrates a novel technique for increasing the sensitivity and repeatability of liquid studies with T-ray time-domain spectroscopy (TDS), reducing relative parameter measurement errors below 0.0001. The proposed technique combines dual-thickness liquid measurement with rapid modulation (double-modulated differential TDS) to reduce the effect of both thickness-measurement errors and T-ray noise errors below 0.0001. The possible reduction in error is calculated and a liquid differential TDS (DTDS) prototype is demonstrated, incorporating amplitude and mean detection for near-simultaneous measurement of two T-ray waveforms.
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Measurement errors in the optical constants obtained from THz-TDS have not been systematically analyzed.
“Nevertheless, measurement errors in the optical constants, so far, have not been systematically analyzed.”
From Uncertainty in terahertz time-domain spectroscopy measurement (2008) · cites this paper as [13]
Section 2.2 (page unavailable) derives how phase, amplitude, and thickness errors affect the measured refractive index and extinction coefficient. Section 4.2 (page unavailable) tests those uncertainty estimates against repeated TDS measurements. Rather than saying measurement errors have not been systematically analyzed, this paper performs such an analysis for liquid measurements. (LLM, conf=0.86)
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Experimental — accuracy not yet measuredPrevious literature on uncertainty models for optical constants in THz-TDS considers only signal noise and/or does not extend the model into the time domain, and developed linear models are rarely verified by nonlinear numerical simulation.
“In those cases the work only considers the influence of signal noise and/or does not extend the model into the time domain. Furthermore, the developed linear models are rarely verified by a nonlinear numerical simulation.”
From Uncertainty in terahertz time-domain spectroscopy measurement (2008) · cites this paper as [13]
Section 2.2 models uncertainty in refractive index and extinction coefficient from spectral phase, amplitude, and thickness errors; its equations do not extend the uncertainty model into the time domain. It therefore does not consider only signal noise. Section 4.2 validates the equations against experimental measurements, but the paper does not establish the broader claim that linear models are rarely checked by nonlinear numerical simulation. (LLM, conf=0.82)
Experimental — accuracy not yet measuredReported sources of randomness affecting a THz-TDS signal include laser intensity fluctuation, optical and electronic noise, delay line stage jitter, and registration noise.
“These sources include laser intensity fluctuation [9-11], optical and electronic noise [12,13], delay line stage jitter [14], registration noise [15], and so on.”
From Uncertainty in terahertz time-domain spectroscopy measurement (2008) · cites this paper as [13]
Citation [14] is attached specifically to “delay line stage jitter.” Section 2.2 discusses errors in measuring the liquid-thickness change, and Section 3.1 describes the scanning delay line, but neither identifies delay-line jitter as a source of THz-TDS signal noise. Searches for “delay line stage jitter,” “delay line timing positioning errors noise,” and “jitter” found no passage addressing that point. (LLM, conf=0.72)
Experimental — accuracy not yet measured
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References 34 · Cited by 36
- Authors
- Mickan, S. P., Shvartsman, R., Munch, J., Zhang, X.-C., & Abbott, D.
- Affiliations
- The University of Adelaide (AU)
- Rensselaer Polytechnic Institute (US)
- Corresponding author
- Zhang, Xi-Cheng
- Venue
- Journal of Optics B: Quantum and Semiclassical Optics
- Publisher
- IOP Publishing
- Published
- 2004-07-28
- Volume
- 6
- Issue
- 8
- Pages
- S786-S795
- ISSN
- 1464-4266 (ISSN-L)
- 1741-3575
- OpenAlex
- W2098478441
- Semantic Scholar
- 8ba0669b0734466599b73bce32d0aecc35e33a8e
- Cited by
- 36
- References
- 34
- Citations by year
- 2026: 1 · 2020: 1 · 2019: 2 · 2018: 1 · 2017: 4 · 2015: 2 · 2014: 1 · 2012: 3
- FWCI
- 3.26
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Journal of Optics B Quantum and Semiclassical Optics (publishedVersion)
- Adelaide Research & Scholarship (AR&S) (University of Adelaide) (submittedVersion)
- Funders
- National Science Foundation
- US-UK Fulbright Commission
- Clough
- Office of Science
- Army Research Office
- Topics
- Physical Sciences › Engineering › Electrical and Electronic Engineering › Terahertz technology and applications
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Laser-Matter Interactions and Applications
- Physical Sciences › Chemistry › Spectroscopy › Spectroscopy and Laser Applications
- Keywords
- terahertz time-domain spectroscopy, measurement error reduction, low-noise laser, solvation dynamics, liquid mixtures
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