Research

The Ménard’s lab focuses on the development of terahertz (THz) photonics techniques to investigate dynamical condensed matter systems.

The far-infrared region of the electromagnetic spectrum of light corresponding to optical wavelengths between 10 µm and 1000 µm, and known as the terahertz (THz) band, is one of the richest areas of research and development. Located between the near-infrared (NIR) and microwave regions, THz radiation covers an ideal photon-energy window to access many elementary excitations in materials such as phonons, plasmons, excitons, and molecular vibrations. THz unique properties can also be used to achieve high-speed wireless communication or image objects embedded in plastics, ceramics textiles, and many other materials considered as opaque. However, the generation, control, and detection of THz radiation remain technically challenging to this day. There is therefore a dire need for innovation in this field to improve state-of-the-art technologies and demonstrate new applications.

Our work can be decomposed into 4 axes of research:

THz slow-motion camera: single-pulse THz spectroscopy of real-time phenomena with µs resolution.

In one project, we design a system able to rapidly acquire successive THz waveforms to enable real-time monitoring of fast and non-reproducible phenomena [1,2]. In this configuration, each THz waveform is encoded on a chirped supercontinuum resembling a stretched rainbow (see picture). The detection is then ultimately determined by the repetition rate of the laser generating both the THz pulse and the supercontinuum. Although this rate can be well into the MHz range, in practice the technique is limited by the response time of the optical sensors and read-out time of components. Here we overcome this obstacle by using dispersive Fourier transform spectroscopy of the NIR pulse inside a km-long fiber. We achieve time-resolved THz spectroscopy with a table-top setup at record rates of 1 MHz. This innovative work lays the foundation towards resolving fast irreversible physical and chemical processes with time resolution approaching 1 µs.

THz quantum photonics: single-THz-photon detection

In another project, we explore new techniques to detect THz radiation with unprecedented high sensitivity and fast response time [3]. Our configuration combines the advantages of a near-infrared single-photon counter with electro-optic sampling, a commonly used technique to time resolve a THz waveform. This detection technique relies on a nonlinear optical process. Here, we use this process to transfer all information carried by the THz wave to near-infrared photons that can be easily detected by commercial detectors. The use of a single-photon counter allows us to push our detection limit to the single photon. We believe this technology will contribute to address future needs in wireless communication systems to enable short-range data-hungry applications, like virtual reality or ultra-fast wireless data exchange between devices. Considering that the ultimate sensitivity of our configuration can approach the single-THz-photon resolution, interesting quantum THz experiments might soon be within reach.

Quantum molecular materials via light-matter hybridization.

[4]

Nonlinear phenomena at low energies driven by high-field THz

Finally, are also interested in developing new experimental geometry to achieve and explore the regime of high-field THz [4]. Recently we demonstrated a unique high-field THz source with a spectral peak centered at 2.6 THz. The setup relies on optical rectification of intense near-infrared pulses inside a GaP nonlinear crystal to generate THz peak fields up to 300 kV/cm. Our technique takes advantage of a phase grating directly etched at the surface of GaP, which enables a tilted-pulse-front configuration that optimizes phase-matching conditions. This high-field THz source will be used to drive coherent phenomena and explore nonlinear effects in the region between 2 and 4 THz.

[1] N. Couture et al. Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a rate of 50 kHz. Nature Communications 14, 2595 (2023)

[2] N. Couture et al. Performance analysis of table-top single-pulse terahertz detection up to 1.1 MHz. arXiv.2309.09803 (2023)

[3] D. J. Jubgang Fandio et al. Sub-zeptojoule detection of terahertz pulses by parametric frequency upconversion. arXiv.2310.08452 (2023)

[4] A. Jaber et al. Hybrid THz architectures for molecular polaritonics. arXiv:2304.03654 (2023)

[5] W. Cui et al. High-field THz source centered at 2.6 THz. Opt. Express 31, 32468 (2023)