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123 results on '"Ropagnol, X."'

1. Near-optimal intense and powerful terahertz source by optical rectification in lithium niobate crystal

Author

Guiramand, L., Nkeck, J. E., Ropagnol, X., Ozaki, T., and Blanchard, F.

Subjects
Physics - Optics
Abstract

Using an affordable ytterbium laser with sub-mJ of energy combined with a novel pulse compression technique, we demonstrate an extremely competitive state-of-the-art terahertz (THz) source with 53 mW of average power and 310 kV/cm at focus from the tilted-pulse front pumping scheme in lithium niobate at room temperature. Key points of this demonstration include the use of a pump pulse duration of 280 fs in combination with an echelon mirror. Our results present unmatched combined characteristics and are highly competitive with the existing THz sources pumped at the mJ range. This demonstration is a step towards the democratization of access to intense and powerful THz pulses., Comment: 6 pages, 5 figures, 1 table

Published
2021

2. Terahertz phase imaging of large-aperture liquid crystal modulator with ITO interdigitated electrode.

Author

Le Bourlout, A, Pusenkova, A, Lafrenière-Greig, J, Ropagnol, X, Galstian, T, and Blanchard, F

Subjects
TERAHERTZ time-domain spectroscopy, LIQUID crystal states, LAMB waves, PHASE modulation, LIQUID crystals
Abstract

We have fabricated and characterized a large-aperture electrooptic phase modulation device operating in the terahertz (THz) frequency range. The device consists of a 1.6 mm thick nematic liquid crystal placed between glass plates with a novel interdigitated electrode design. Using THz time-domain spectroscopy (THz-TDS) coupled with raster scanning imaging, we evaluated phase modulation across a 25 mm diameter LC device and mapped the spatial uniformity of phase shift. Our results confirm the functionality of the LC cell as a controllable quarter-wave plate at 0.26 THz and half-wave plate at 0.52 THz. This work contributes to the development of large-aperture and transmissive LC devices as low-cost phase plates for THz waves and paves the way for future applications in THz modulators. [ABSTRACT FROM AUTHOR]

Published
2024
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3. Aligned copper nanorod arrays for highly efficient generation of intense ultra-broadband THz pulses

Author

Mondal, S., Wei, Q., Ding, W. J., Hafez, H. A., Fareed, M. A., Laramée, A., Ropagnol, X., Zhang, G., Sun, S., Sheng, Z. M., Zhang, J., and Ozaki, T.

Subjects
Physics - Plasma Physics
Abstract

We demonstrate an intense broadband terahertz (THz) source based on the interaction of relativistic-intensity femtosecond lasers with aligned copper nanorod array targets. For copper nanorod targets with length 5 \mu m, a maximum 13.8 times enhancement in the THz pulse energy (in $\leq$ 20 THz spectral range) is measured as compared to that with a thick plane copper target under the same laser conditions. A further increase in the nanorod length leads to a decrease in the THz pulse energy at medium frequencies ($\leq$ 20THz) and increase of the electromagnetic pulse energy in the high-frequency range (from 20 - 200 THz). For the latter, we measure a maximum energy enhancement of 28 times for the nanorod targets of length 60 \mu m . Particle-in-cell simulations reveal that THz pulses are mostly generated by coherent transition radiation of laser produced hot electrons, which are efficiently enhanced with the use of nanorod targets. Good agreement is found between the simulation and experimental results., Comment: 14 pages, 5 figure

Published
2016

4. Aligned copper nanorod arrays for highly efficient generation of intense ultra-broadband THz pulses.

Author

Mondal, S, Wei, Q, Ding, WJ, Hafez, HA, Fareed, MA, Laramée, A, Ropagnol, X, Zhang, G, Sun, S, Sheng, ZM, Zhang, J, and Ozaki, T

Subjects
physics.plasm-ph, Biochemistry and Cell Biology, Other Physical Sciences
Abstract

We demonstrate an intense broadband terahertz (THz) source based on the interaction of relativistic-intensity femtosecond lasers with aligned copper nanorod array targets. For copper nanorod targets with a length of 5 μm, a maximum 13.8 times enhancement in the THz pulse energy (in ≤20 THz spectral range) is measured as compared to that with a thick plane copper target under the same laser conditions. A further increase in the nanorod length leads to a decrease in the THz pulse energy at medium frequencies (≤20 THz) and increase of the electromagnetic pulse energy in the high-frequency range (from 20-200 THz). For the latter, we measure a maximum energy enhancement of 28 times for the nanorod targets with a length of 60 μm. Particle-in-cell simulations reveal that THz pulses are mostly generated by coherent transition radiation of laser produced hot electrons, which are efficiently enhanced with the use of nanorod targets. Good agreement is found between the simulation and experimental results.

Published
2017

5. Terahertz emission enhancement of GaAs-based photoconductive antennas via the nanodecoration of their surface by means of pulsed-laser-deposition of gold nanoparticles.

Author

Isgandarov, E., Pichon, L., Ropagnol, X., El Khakani, M. A., and Ozaki, T.

Subjects
GOLD nanoparticles, ANTENNAS (Electronics), PULSED laser deposition, FIELD emission, LASER pulses, SURFACE plasmons, SURFACE plasmon resonance
Abstract

We report a systematic study of free-space terahertz (THz) emission from photoconductive antennas (PCAs) nanodecorated with gold nanoparticles (Au-NPs) deposited by using the pulsed laser deposition (PLD) technique. H-shaped dipole micro-structured PCAs fabricated on semi-insulating GaAs substrates were decorated under various PLD conditions. Thus, by increasing the number of laser ablation pulses (NLP) of the Au target, both the average size of Au-NPs and the surface loading of PCAs increase. Compared with non-decorated PCAs, those decorated with Au-NPs exhibit significant enhancement in the radiated THz pulse amplitude. A maximum enhancement of ∼2.3 was achieved at NLP = 1250. Under this optimal NLP condition, not only is the average Au-NP size (of ∼15 nm) favorable for light absorption via localized surface plasmons, but also the inter-distance between NPs, the light reflectance, and facilitated transport of photocarriers, all combine to yield a stronger THz field emission. For higher NLP (≥2000), NPs coalesce and tend to form continuous film NPs, which not only significantly limits the light scattering toward the GaAs underlying substrate, but also electrically shorts the PCA. Finally, the Au-NP decoration of GaAs PCAs was also found to improve their overall thermal conductivity, making them much more thermally stable than their non-decorated counterparts. [ABSTRACT FROM AUTHOR]

Published
2023
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6. Broadband heterodyne electro-optic sampling using a lithium niobate ridge-waveguide

Author

Mine, S., Gandubert, G., Nkeck, J. E., Ropagnol, X., Murate, K., Blanchard, F., Mine, S., Gandubert, G., Nkeck, J. E., Ropagnol, X., Murate, K., and Blanchard, F.

Abstract

We demonstrated the bandwidth broadening of terahertz waves detected by heterodyne electro-optical sampling by implementing a ridge waveguide structure in a lithium niobate (LiNbO3) crystal. Such an approach effectively reduces absorption loss, eases the phase matching condition and enhances the nonlinear interaction length through the optical confinement effect. As a result, we have more than doubled the bandwidth and improved the signal-to-noise ratio compared with an equivalent approach in a bulk LiNbO3 crystal. Heterodyne electro-optic sampling in a ridged-waveguide structure is only marginally dependent on the probe beam wavelength, suggesting its potential as a versatile method for broadband terahertz detection.

Published
2024

12. Strong-field optoelectronics in solids

Author

Vampa, G., Hammond, T. J., Taucer, M., Ding, Xiaoyan, Ropagnol, X., Ozaki, T., Delprat, S., Chaker, M., Thiré, N., Schmidt, B. E., Légaré, F., Klug, D. D., Naumov, A. Yu., Villeneuve, D. M., Staudte, A., and Corkum, P. B.

Published
2018
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26. Mass-production of terahertz devices

Author

Zhuldybina, M., primary, Beliveau, L.-P., additional, Mansourian, M., additional, Ropagnol, X., additional, Trinh, N. D., additional, Bois, C., additional, and Blanchard, F., additional

Published
2021
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39. Improvement in thermal barriers to intense terahertz generation from photoconductive antennas.

Author

Ropagnol, X., Bouvier, Marcel, Reid, M., and Ozaki, T.

Subjects
*PHOTOCONDUCTIVE cells, *ELECTRIC fields, *RECTIFICATION (Electricity), *FEMTOSECOND pulses, *CONDUCTION bands
Abstract

We study the generation of free-space terahertz (THz) pulses at low THz frequencies using 6H-SiC and 4H-SiC photoconductive antennas. We investigate the dependence of the THz electric field radiated from the biased SiC emitters on the applied bias field and on the incident optical fluence. In this work, bias fields as high as 32 kV/cm, and optical fluences up to 2.5 mJ/cm² (for the 400 nm laser), and 7.5 mJ/cm² (for the 800 nm laser) were used. THz generation with back- and front-side illumination of the antennas is also examined. It is found that the SiC antenna, when illuminated from the backside, generates higher THz electric fields. The performance of 6H-SiC and ZnSe photoconductive antennas are compared. We show that, taking advantage of the superior thermal properties of SiC compare with ZnSe, the THz output power generated with the 6H-SiC photoconductive antenna under optimum conditions is 2.3 times larger that with a ZnSe photoconductive antenna. [ABSTRACT FROM AUTHOR]

Published
2014
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45. Sub-cycle THz nonlinear optics

Author

Chai, X., primary, Ropagnol, X., additional, Raeis-Zadeh, S. M., additional, Reid, M., additional, Safavi-Naeini, S., additional, and Ozaki, T., additional

Published
2018
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