Abstract-Terahertz Generation by Optical Rectification in Sugar Crystal

 

Federico Sanjuan, Gwenaël Gaborit, Jean-Louis Coutaz,

https://link.springer.com/article/10.1007/s10762-021-00795-6

We report on THz pulse generation through optical rectification of femtosecond laser pulses in sugar crystals. The sugar crystals were grown from an aqueous solution of caster cane sugar bought in a local grocery. Sugar exhibits rather good nonlinear coefficients (d23≃56$d_{23}\simeq 56$ pm/V), but the optical-THz conversion efficiency remains quite weak because of the lack of phase-matching, when pumped by a laser beam of 0.8-μm central wavelength. Nevertheless, sugar availability at a low price makes it a relevant material for trial experiments.

Abstract-Terahertz wave generation from liquid nitrogen

Alexei V. Balakin, Jean-Louis Coutaz, Vladimir A. Makarov, Igor A. Kotelnikov, Yan Peng, Peter M. Solyankin, Yiming Zhu, and Alexander P. Shkurinov

Fig. 1. Experimental setup. M–dielectric mirror; MM–metallic mirror; BS–beam splitter; 𝜆/2$\lambda /2$–half-wave phase plate; L–lens; PM–off-axis parabolic mirror; BBO–β$\mathrm{\beta }$-barium borate crystal.

https://www.osapublishing.org/prj/abstract.cfm?uri=prj-7-6-678

We present the results of research carried out for the first time, to the best of our knowledge, on the generation of terahertz radiation under the action of “single-color” and “dual-color” high-power femtosecond laser pulses on liquefied gas–liquid nitrogen. Our experimental results supported by careful theoretical interpretation showed clearly that under femtosecond laser radiation, liquid and air emit terahertz waves in a very different way. We assumed that the mobility of ions and electrons in liquid can play an essential role, forming a quasi-static electric field by means of ambipolar diffusion mechanism.

© 2019 Chinese Laser Press

Abstract-Electrodynamic resonance of surface conduction and THz transmission through arrays of rectangular apertures in opaque metallic thin films

Christophe Minot, Christophe Dupuis, Edmond Cambril, Frédéric Garet, and Jean-Louis Coutaz, 

https://www.osapublishing.org/josaa/abstract.cfm?uri=josaa-36-6-964

A modal method is developed analytically to investigate the THz optical transmission and reflection of a metallic thin film perforated by a 2D array of rectangular apertures. For subwavelength apertures, this optical model is interpreted in terms of passive electrical circuits, with interface admittances accounting for the THz surface conduction properties of the metallic film. The reactive component of the admittance of the evanescent diffraction cloud is shown to exhibit resonant behavior governed by the shape factors of the array. Interaction of such an electrodynamic resonance with the Rayleigh diffraction orders may alter their standard Fano profiles. Experimental evidence of the resonance is obtained owing to lineshape analysis of transmittance measurements in the THz range on metallic thin films deposited on a dielectric substrate, both above and below the first Wood–Rayleigh anomaly.

© 2019 Optical Society of America

Abstract-Full electro-optic terahertz time-domain spectrometer for polarimetric studies

Federico Sanjuan, Gwenaël Gaborit, and Jean-Louis Coutaz

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-57-21-6055

We present a terahertz (THz) time-domain spectrometer dedicated to polarimetric studies. THz pulses are generated through optical rectification in a ⟨111⟩$⟨111⟩$-cut cubic crystal. The ⟨111⟩$⟨111⟩$ crystal cut produces a THz polarization state similar to that of the exciting laser beam. Detection of the THz pulses is performed by electro-optic sampling in a similar crystal, and a dual detection scheme allows us to measure simultaneously the two polarization components of the THz beam. We experimentally illustrate that the polarization of the THz beam can be adjusted by adjusting the laser polarization. This technique alleviates the need for a polarization controller at THz frequencies.

© 2018 Optical Society of America

Abstract-Comparative Study of Material Parameter Extraction Using Terahertz Time-Domain Spectroscopy in Transmission and in Reflection

Maxime Bernier, Frédéric Garet, Eiji Kato, Benjamin Blampey, Jean-Louis Coutaz,

https://link.springer.com/article/10.1007%2Fs10762-018-0463-9

As no terahertz signal is transmitted through opaque materials, reflection terahertz time-domain spectroscopy is obviously the dedicated setup. On the other hand, optical properties of transparent and thick samples are extracted more accurately with transmission terahertz time-domain spectroscopy. In this paper, we report the intrinsic frontier above or below which it is preferable to use either reflection or transmission setup for probing with the best accuracy possible a given sample.

NATO launches first scientific cooperation initiative with Algeria

For the first time, the NATO Science for Peace and Security (SPS) Programme is supporting a multi-year research project with Algeria. The new activity will develop an innovative detection system to help in the fight against terrorism while engaging key partners in practical cooperation.

https://www.nato.int/cps/en/natohq/news_148023.htm

Experts involved in the SPS project “Implementation of a Terahertz Imaging and Detection System” gathered at NATO Headquarters to kick off the innovative scientific project between NATO and Algeria

Kicked off at NATO Headquarters on 26 October 2017, the new project brings together the Université Savoie Mont Blanc (France), Ecole Militaire Polytechnique (Algeria) and KTH Royal Institute of Technology (Sweden) to work on the design and development of a terahertz (THz) imaging and detection system. This new system will be able to detect hazardous objects like concealed weapons or explosives and will help to secure vulnerable places from terrorist threats, such as airports, railway stations, critical infrastructure as well as government buildings.

“THz frequency range is a scientific field that has seen rapid technological advances and growth in interest for its potential application in a number of domains, ranging from security, imaging, detection, and product inspection to chemical spectroscopy, astronomy, telecommunication, material characterisation and medical applications,” said Professor Jean-Louis Coutaz from Université Savoie Mont Blanc, which is leading this research initiative.

The kick-off meeting marked the start of the project which will strengthen ties between NATO, France and two partner countries, Algeria and Sweden, through practical cooperation. By providing cutting-edge technological solutions in support of the fight against terrorism, this SPS project is also contributing to NATO’s wider efforts to project stability beyond Alliance borders. It also represents an important milestone in NATO’s engagement with partners in the south. “By building expert networks, north to south, this activity will help to develop scientific skills and technology to counter emerging threats,” said Professor Fredrik Laurell from Sweden.

The new system is to be installed at the Ecole Militaire Polytechnique of Bordj El Barhri, Algeria. In the long run, this experimental set-up will provide an important basis for further scientific research in this field in Algeria. “This SPS project, for the first time, will provide terahertz imaging capabilities for Algeria. This will enable scientific research in this field, fostering a generation of young scientists from Algeria,” said Dr Deniz Beten, Senior SPS and Partnership Cooperation Advisor. Dr Mohamed Lazoul, from Ecole Militaire Polytechniqueand SPS Project Co-Director, stated that “the system will improve the capability of our institution in this cutting-edge technology and will allow significant sharing of expertise and know-how in the field of terahertz imaging detection, that will be a key technology in support of the fight against terrorism in the years to come.”

NATO’s SPS Programme is supporting practical cooperation between the Alliance and partner countries in civil science, technology, innovation and knowledge exchange.

Abstract-Imaging of broadband terahertz beams using an array of antenna-coupled microbolometers operating at room temperature

http://www.opticsinfobase.org/oe/abstract.cfm?uri=oe-21-4-4817

Jonathan Oden, Jérome Meilhan, Jérémy Lalanne-Dera, Jean-François Roux, Frédéric Garet, Jean-Louis Coutaz, and François Simoens  »View Author Affiliations

We present results of 2D real-time imaging of terahertz (THz) beam generated by a photoconductive antenna driven by a femtosecond oscillator. The detector, operating at room temperature, is a 320 x 240 array of antenna-coupled microbolometers with integrated CMOS read-out electronics delivering 25 images per second. High quality images of broadband THz beams covering the 0.1-2 THz range are recorded while maintaining a signal-to-noise ratio of 10 for detected THz power as low as 25 nW. The compactness of the easy-to-use uncooled camera makes it very useful for the alignment of systems such as THz time-domain spectrometers and for the characterization of emitters, optics and other components.

Abstract-Diffractive paper lens for terahertz optics

Agnieszka Siemion, Andrzej Siemion, Michał Makowski, Jarosław Suszek, Jarosław Bomba, Adam Czerwiński, Frédéric Garet, Jean-Louis Coutaz, and Maciej Sypek

Abstract

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-37-20-4320

Passive terahertz (THz) setups require optical elements with large diameters for optimal harvesting of weak signals. High f -number implies sophisticated aspheric designs to ensure optimal resolution and good energetic efficiency. Trial and error testing of such optics is expensive and numerical modeling is time consuming; hence, we propose extremely cheap diffractive lenses for THz made of regular paper. They are easy to manufacture even with large diameters, and the optical function can be easily customized, which can be used for initial experimental testing of THz setups. Characterization of the proposed diffractive lenses with time-domain spectroscopy is presented and discussed