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622 results on '"Ebrahim-Zadeh M"'

86. Dual frequency combs fourier transform spectroscopy based on optical parametric oscillators

Author

Jin, Y., Mandon, J., Bouillard, M., Cristescu, S.M., Harren, F.J.M., Ebrahim-Zadeh, M., Sorokina, I., Ebrahim-Zadeh, M., and Sorokina, I.

Subjects
Materials science, business.industry, Infrared spectroscopy, Pulse sequence, Astrophysics::Cosmology and Extragalactic Astrophysics, Fourier transform spectroscopy, symbols.namesake, Microsecond, Fourier transform, Optics, Dispersion (optics), symbols, Molecular and Laser Physics, Astrophysics::Earth and Planetary Astrophysics, Fourier transform infrared spectroscopy, business, Absorption (electromagnetic radiation), Astrophysics::Galaxy Astrophysics
Abstract

A dual frequency combs Fourier transform spectrometer, for real-time trace gas sensing, is demonstrated for the mid-infrared spectral region. Absorption and dispersion spectrum can be recorded between 2.7 and 4.7 µm in few microseconds.

Published
2013

87. Yb-fiber-laser-based, 1.8 W average power, picosecond ultraviolet source at 266 nm

Author

Chaitanya Kumar, S., Canals Casals, J., Sanchez Bautista, E., Devi, K., Ebrahim-Zadeh, M., and Universitat Politècnica de Catalunya. Institut de Ciències Fotòniques

Subjects
Nonlinear optics, Òptica no lineal
Abstract

We report a compact, stable, high-power, picosecond ultraviolet (UV) source at 266 nm based on simple single-pass two-step fourth-harmonic generation (FHG) of a mode-locked Yb-fiber laser at 79.5 MHz in LiB3O5 (LBO) and β-BaB2O4. Using a 30-mm-long LBO crystal for single-pass second-harmonic generation, we achieve up to 9.1 W of average green power at 532 nm for 16.8 W of Yb-fiber power at a conversion efficiency of 54% in 16.2 ps pulses with a TEM00 spatial profile and passive power stability better than 0.5% rms over 16 h. The generated green radiation is then used for single-pass FHG into the UV, providing as much as 1.8 W of average power at 266 nm under the optimum focusing condition in the presence of spatial walk-off, at an overall FHG conversion efficiency of ∼11%. The generated UV output exhibits passive power stability better than 4.6% rms over 1.5 h and beam pointing stability better than 84 μrad over 1 h. The UV output beam has a circularity of >80% in high beam quality with the TEM00 mode profile. To the best of our knowledge, this is the first report of picosecond UV generation at 266 nm at megahertz repetition rates.

Published
2015

88. High-Power, Widely Tunable, Room-Temperture, Picosecond Optical Parametric Oscillator Based on Cylindrical MgO:PPLN

Author

Chaitanya Kumar, S., Debray, Jérôme, Kemlin, Vincent, Boulanger, Benoit, Ishizuki, Hideki, Taira, Takunori, Ebrahim-Zadeh, M., Segonds, Patricia, Institut de Ciencies Fotoniques [Castelldefels] (ICFO), Cristaux Massifs (CrisMass), Institut Néel (NEEL), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Centre National de la Recherche Scientifique (CNRS)-Université Joseph Fourier - Grenoble 1 (UJF), Optique et Matériaux (OPTIMA), Laser Research Center for Molecular Science (LRCMS), Institute for Molecular Science, and Institució Catalana de Recerca i Estudis Avançats (ICREA)

Subjects
[SPI.OPTI] Engineering Sciences [physics]/Optics / Photonic, [SPI.OPTI]Engineering Sciences [physics]/Optics / Photonic, ComputingMilieux_MISCELLANEOUS
Abstract

International audience

Published
2015

91. Green-pumped optical parametric oscillator based on fan-out grating periodically-poled MgO-doped congruent LiTaO_3

Author

Sukeert, Chaitanya Kumar, S., and Ebrahim-Zadeh, M.

Abstract

We report a green-pumped optical parametric oscillator (OPO) based on periodically poled MgO-doped congruent lithium tantalate (MgO:cPPLT). Pumped at 532 nm by a frequency-doubled Q-switched Nd:YAG laser, and using a fan-out grating structure, the singly-resonant OPO provides continuous tuning across 689–1025 nm in the signal and 1106–2336 nm in the idler at room temperature by simple mechanical translation of the crystal. The tuning range can be further extended to 677 nm and 2479 nm in the signal and idler, respectively, by temperature tuning the crystal to 200°C. With a 29-mm-long crystal, the OPO generates 131 mW of average idler power at 1476.5 nm for an input pump power of 1.8 W at 25 kHz repetition rate, with a slope efficiency of 11.3%. Bulk damage in the MgO:cPPLT crystal has been observed for pump powers above ∼1.8  W, and at pump powers beyond ∼1.4  W under long-term operation. The passive power stability of the generated idler is 3.9% over 30 min, in a Gaussian spatial profile.

Published
2019

93. Enhancement of efficiency in femtosecond optical parametric oscillators using group-velocity-matching in long nonlinear crystals.

Author

O'Donnell, Callum F., Kumar, S. Chaitanya, and Ebrahim-Zadeh, M.

Subjects
OPTICAL parametric oscillators, CRYSTALS, QUANTUM efficiency
Abstract

The authors describe the exploitation of group-velocity-matching in femtosecond optical parametric oscillators (OPOs) for enhanced down-conversion efficiency into the mid-infrared (mid-IR). We demonstrate the concept in a femtosecond OPO based on a long MgO:PPLN crystal, for the first time, by utilizing group-velocity-matching between pump and idler pulses. Taking advantage of the wide phase-matching bandwidth when pumped near 1 µm enables the use of a 42-mm-long crystal, resulting in an oscillation threshold as low as 5 mW, pump depletion of 78%, and an idler quantum conversion efficiency up to 48% into the mid-IR. Using 80–100 fs pump pulses tunable across 997–1070 nm, we have generated idler radiation across 3132–4273 nm (2340–3193 cm−1) with spectral bandwidth of 140–180 nm, providing up to 65 mW of average power at 80 MHz repetition rate. The near-IR signal is tunable across 1392–1568 nm, with up to 76 mW of average power in transform-limited pulses of ∼400–600 fs duration without dispersion compensation. Preferential operation at group-velocity-matched wavelengths leads to intrinsically high passive power stability with <1% rms fluctuation over 1 h for both signal and idler. With the capability for rapid pump tuning in the mid-IR, this OPO represents a viable source for spectroscopic applications, which we demonstrate using CH4 gas. Extension to other quasi-phase-matched nonlinear crystals is also discussed. [ABSTRACT FROM AUTHOR]

Published
2019
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