arXiv subjects

Angela Gamouras

Publications and source records attributed to Angela Gamouras.

7 recordsLinked to original sources

arXiv2026

Room-temperature THz photon detection via nonlinear upconversion with 2% full-system efficiency

Sensitive detection of terahertz (THz) radiation is fundamental to progress in spectroscopy, advanced wireless communication, and the realization of emerging quantum technologies. However, the intrinsically low photon energies in the THz range combined with thermal background radiation tend to constrain detector performance when operating at ambient temperatures. Here, we demonstrate efficient room-temperature THz detection based on nonlinear upconversion in the organic crystal N-benzyl-2-methyl-4-nitroaniline (BNA) to resolve frequencies from 1 to 7.5 THz. The system encompassing spectral filters and a single-photon counter achieves an overall detection efficiency of 2% for sum-frequency generated photons. This enables the detection of a train of 50 000 terahertz pulses carrying, on average, fewer than 0.04 photons per pulse, with a signal-to-noise ratio of unity. At a higher flux, when ~60 photons per pulse impinge on the BNA crystal, the per-pulse detection probability reaches 50%. After accounting for loss mechanisms in the setup, the nonlinear THz-to-near-infrared conversion efficiency in BNA exceeds 75%. These results demonstrate the feasibility of quantum experiments relying on single-photon-level THz detection via upconversion in nonlinear crystals in ambient conditions.

physics.optics↗

arXiv2026

Broadband THz spectroscopy system beyond 25 THz using BNA crystals and a tunable single-ring-fiber compressor

We present a terahertz time-domain spectroscopy (THz-TDS) system which accesses a broadband spectrum, efficiently covering the so-called "new THz gap" between 5 and 15 THz and extending beyond 25 THz. The system exploits nonlinear interactions within the organic crystal BNA (N-benzyl-2-methyl-4-nitroaniline) to generate and detect THz radiation upon excitation by a near-infrared (NIR) pulse centered at 1.03 $\mu$m. To enable broadband THz spectral monitoring, the NIR pulse from a Yb-based solid-state laser undergoes spectral broadening in a gas-filled single-ring hollow-core photonic crystal fiber, followed by a pulse compression to achieve durations as short as 31 fs. This approach paves the way for broadband spectroscopy in hard-to-access THz regions using widely available near-infrared ultrafast sources.

physics.optics↗

arXiv2025

Characterization of Terahertz Spectral Bands for Next Generation of Wireless Communications

The ever-increasing demand for high-speed data transmission continues to motivate research and development efforts towards the sixth generation (6G) of wireless communication technologies and beyond. The use of terahertz (THz) carrier frequencies is considered to achieve faster data transmission rates, with the potential to reach terabits per second. However, there is a necessity to study the impact of environmental factors affecting the signal transmission at these frequencies. One key challenge of THz signal propagation through air is water vapor absorption, which can severely limit the broadcast distance of THz wireless communications. In this work, we investigate the propagation distance of several THz channels under 35 % relative humidity atmospheric conditions using a table-top THz spectroscopy apparatus equipped with a sensitive THz detection system based on nonlinear parametric upconversion. Our results show seven transmission bands between 1 and 3 THz with negligible signal absorption at different propagation lengths with potential application in short-, mid- and long-range wireless communications.

physics.optics↗

arXiv2023

Sub-zeptojoule detection of terahertz pulses by parametric frequency upconversion

We combine parametric frequency upconversion with single-photon counting technology to achieve detection sensitivity down to the terahertz (THz) single-photon level. Our relatively simple detection scheme employs a near-infrared ultrafast source, a GaP nonlinear crystal, optical filters, and a single photon avalanche diode. This configuration is capable of detecting a weak THz signal with an energy of 590 zJ contained within a single pulse. Through averaging over 50k data points, the configuration can resolve a 0.5 zJ pulse energy, corresponding to an average of 0.5 photon per pulse. The corresponding noise-equivalent power and THz-to-NIR photon detection efficiency are $4.1 \times 10^{-17} W/\sqrt{Hz}$ and 0.19%, respectively. To test our scheme, we perform spectroscopy of water vapor between 1.0 and 3.7 THz and obtain results in agreement with to those acquired with a standard electro-optic sampling (EOS) method. Our technique provides a 0.2 THz spectral resolution offering a fast alternative to EOS THz detection for monitoring specific spectral components in THz spectroscopy, imaging and communications applications.

physics.optics↗

arXiv2023

Performance analysis of table-top single-pulse terahertz detection up to 1.1 MHz

Slow data acquisition in terahertz time-domain spectroscopy (THz-TDS) has hindered the technique's ability to resolve "fast" dynamics occurring on the microsecond timescale. This timescale, arguably too slow to be accessed via standard optical pump-probe techniques relying on ultrafast sources, hosts a range of phenomena that has been left unexplored due to a lack of proper real-time monitoring techniques. In this work, chirped-pulse spectral encoding, a photonic time-stretch technique, and high-speed electronics are used to demonstrate time-resolved THz detection at a rate up to 1.1 MHz. This configuration relies on a table-top source and a setup able to resolve every THz transient that it can generate. We investigate the performance of this system at different acquisition rates in terms of experimental noise, dynamic range, and signal-to-noise ratio. Our results pave the way towards single-pulse THz-TDS at arbitrarily fast rates to monitor complex dynamics in real-time.

physics.optics↗

arXiv2023

High-field THz source centered at 2.6 THz

We demonstrate a table-top high-field terahertz (THz) source based on optical rectification of a collimated near-infrared pulse in gallium phosphide (GaP) to produce peak fields exceeding 300 kV/cm with a spectrum centered at 2.6 THz. The experimental configuration, based on tilted-pulse-front phase matching, is implemented with a phase grating etched directly onto the front surface of the GaP crystal. Although the THz generation efficiency starts showing a saturation onset as the near-infrared pulse energy reaches 0.57 mJ, we can expect our configuration to yield THz peak fields up to 866 kV/cm when a 5 mJ generation NIR pulse is used. This work paves the way towards broadband, high-field THz sources able to access a new class of THz coherent control and nonlinear phenomena driven at frequencies above 2 THz.

physics.optics↗

arXiv2022

Single-pulse time-resolved terahertz spectroscopy of sub-millisecond time dynamics

Slow motion movies are not only fascinating to watch, they also allow us to see intricate details of the mechanical dynamics of complex phenomena. If the images in each frame are replaced by terahertz (THz) waves, such movies can monitor low-energy resonances and reveal fast structural or chemical transitions. Here, we combine THz spectroscopy as a non-invasive optical probe with a real-time monitoring technique to resolve non-reproducible phenomena at 50k frames per second. The concept, based on dispersive Fourier transform spectroscopy to achieve unprecedented acquisition speed of THz spectroscopy data, is demonstrated by monitoring sub-millisecond dynamics of hot carriers injected in silicon by successive resonant pulses as a saturation density is established. We anticipate that our experimental configuration will play a crucial role in revealing fast irreversible physical and chemical processes at THz frequencies with microsecond resolution to enable new applications in fundamental research as well as in industry, notably as a rapid supply chain monitoring system in high-volume manufacturing.

physics.optics↗