Search results for "Physics::Optics"
showing 10 items of 1958 documents
Optical and photonic material hardness for energetic environments
2009
We studied the effects of dielectric change in the chemical composition and in the realization procedures under radiation exposure. We have compared the radiation effects on Ge-doped and F-doped fibers and preforms: the first play a crucial role in the photosensitivity property, the second improves the dielectric radiation hardness even at low concentrations. The use of different spectroscopic techniques (RIA, OA, EPR) allow the identification of the point defect formation mechanisms at the origin of the optical degradation properties.
Mode locking of an all-fiber laser by acousto-optic superlattice modulation
2009
Active mode locking of an erbium-doped all-fiber laser with a Bragg-grating-based acousto-optic modulator is demonstrated. The fiber Bragg grating was acoustically modulated by a standing longitudinal elastic wave, which periodically modulates the sidebands at twice the acoustic frequency. The laser has a Fabry-Perot configuration in which cavity loss modulation is achieved by tuning the output fiber Bragg grating to one of the acoustically induced sidebands. Optical pulses at 9 MHz repetition rate, 120 mW peak power, and 780 ps temporal width were obtained. The output results to be stable and has a timing jitter below 40 ps. The measured linewidth, 2.8 pm, demonstrates that these pulses ar…
Very low instability threshold in a three-level laser model with incoherent optical pumping
1997
Abstract The stability properties of a laser model based on a closed three-level atomic scheme with incoherent optical pumping are studied. Unexpectedly, the instability threshold can be very low approaching the lasing threshold for large unsaturated gain values.
Broadband Tuning of Four-Wave Mixing Bands Using Photonic Crystal Fibers
2016
We present an experimental study of the shift with temperature of widely-spaced FWM parametric bands generated in an ethanol-inflltrated photonic crystal fiber. We report broadband tuning of 175 nm and over 500 nm for the signal and idler bands, respectively, achieved through the thermo-optic effect. Numerical calculations were carried out and show good agreement with experimental data.
Interferometric Z-scan method for thermo-optical effect studies
2021
We demonstrated a new approach to measuring third-order nonlinear optical effects using an experimental setup incorporating both Z-scan and Mach-Zehnder interferometer methods. This method could be especially purposive for thermo-optical effect studies as it can simultaneously probe thermal gradient profile as well as absolute temperature changes induced by an optical beam. The experimental setup was tested using chloroform. Experimental measurements were carried out using 1064 nm Nd:YAG laser with 8 ns pulse width and 40 kHz pulse repetition rate. The measured nonlinear refractive index of chloroform was mainly induced by the thermo-optical effect. As thermo-optical response depends on bea…
Comprehensive formulation of temperature-dependent dispersion of optical materials: illustration with case of temperature tuning of a mid-IR HgGa_2S_…
2009
The temperature dependence of refractive indices of optical materials is characterized in this work by what we call their normalized thermo-optic coefficients. These are determined experimentally through interferometric measurements of thermal expansion and of changes in optical thickness at a few laser wavelengths as function of temperature. A suitable vectorial formalism applied to these data allows predicting the thermal evolution of the refractive index all over the useful range of transparency. The validity and reliability of our methodology is demonstrated through temperature tuning of a mid-IR HgGa2S4 optical parametric oscillator (OPO) pumped at 1.0642 μm by a Nd:YAG laser. Measured…
High-harmonic km-long self-pulsed Raman fiber laser
2011
Raman all-fiber lasers have attracted considerable interest during the past two decades due to their convenient use and extended wavelength coverage when compared to rare-earth-doped fiber lasers. Still, little is known about their potential as pulsed laser sources. Mode locked Raman fiber lasers have been demonstrated quite recently [1,2], as well as harmonic mode-locking with a record of 500,000 intra-cavity pulses in a dissipative four-wave mixing configuration using a fiber Bragg grating [3].
Wide wavelength-tunable passive mode-locked Erbium-doped fiber laser with a SESAM
2021
Abstract In this work we present a simple polarization-maintaining wavelength-tunable passive mode-locked Erbium-doped fiber laser with a semiconductor saturable absorber mirror (SESAM) as a mode locker. The cavity includes a Sagnac interferometer-based fiber optical loop mirror (FOLM) as a wide wavelength-tunable filter. Tunable mode-locking was experimentally achieved in the range of 1543.2 nm to 1569.5 nm by thermally adjustment of FOLM wavelength reflection. The output pulses have a repetition rate of 11.16 MHz with pulse duration about 0.9 ps. The experimental results were confirmed by numerical simulations.
Synthesis of optical pulses by use of similaritons.
2009
We propose and demonstrate experimentally a novel method for synthesizing chirp-free pulses of any desired temporal shape by means of chirp compensation and spectral filtering of optical Raman similaritons. The synthesized pulse shape is independent of the waveform, wavelength and energy of the initial pulses that are used for the similariton generation. Pulses are fully characterized by means of different techniques including cross-correlation and spectrum measurements, and the PICASO technique.
Multi-gigahertz repetition-rate-selectable passive harmonic mode locking of a fiber laser
2013
We demonstrate a passive harmonically mode-locked erbium-doped fiber laser that operates at selectable harmonics spanning from the 6th to the 928th, which corresponds to repetition rates ranging from 153 MHz to 22.2 GHz. The noteworthy laser output stability is attested by supermode suppression levels as large as 41 dB. The influence of a continuous wave background on harmonics stability is tested.