Search results for "Rating"
showing 10 items of 2021 documents
Q-switching of an all-fiber laser by acousto-optic modulation of a fiber Bragg grating.
2009
We report active Q-switching of an all-fiber laser using a Bragg grating based acousto-optic modulator. Q-switching is performed by modulating a fiber Bragg grating with an extensional acoustic wave. The acoustic wave modulates periodically the effective index profile of the FBG and changes its reflection features. This allows controlling the Q-factor of the cavity. Using 1 m of 300 ppm erbium-doped fiber and a maximum pump power of 180 mW, Q-switch pulses of 10 W of peak power and 82 ns wide were generated. The pulse repetition rate of the laser can be continuously varied from few Hz up to 62.5 kHz.
Fiber laser with combined feedback of core and cladding modes assisted by an intracavity long-period grating
2011
We present a fiber laser made in a single piece of conventional doped-core fiber that operates by combined feedback of the fundamental core mode LP((0,1)) and the high-order cladding mode LP((0,10)). The laser is an all-fiber structure that uses two fiber Bragg gratings and a long-period grating to select the modes circulating in the cavity; the laser emits at the coupling wavelength between the core mode LP((0,1)) and the counterpropagating cladding mode LP((0,10)) in the Bragg gratings. This work demonstrates the feasibility of high-order mode fiber lasers assisted by long-period gratings.
Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating
2009
We report an actively Q-switched all-fiber laser based on magnetostriction modulation of a Bragg grating. The laser employs a pair of Bragg gratings as reflective mirrors, one of which is bonded to a magnetostrictive element. Lengthening of the magnetostrictive element when a magnetic field is applied shifts the Bragg wavelength of the grating, allowing control of the Q-factor of the cavity and, thus, performing active Q-switching. The magnetostrictive modulator is small, compact and requires less than 300 mW electrical drive power. Using erbium-doped fiber and a maximum pump power of 120 mW, Q-switch pulses of more than 1 W peak power were obtained, with a pulse repetition rate that can be…
Tunable chirp in Bragg gratings written in tapered core fibers
2002
In this paper we present a technique to control the chirp of a fiber grating capable to produce positive or negative chirp in a single grating. The device is based on a uniform period grating written in a tapered core fiber, this grating has a positive chirp that can be reduced and removed by subjecting the fiber to mechanical stress, after some stress level the grating chirps to negative values. A chirp range of ±4 nm with respect to a central wavelength of 1546 nm has been experimentally achieved.
<title>Tunable chirp in Bragg gratings written in tapered core fibers</title>
2001
In this paper we present a technique to control the chirp of a fiber grating capable to produce positive or negative chirp in a single grating. The device is based ona uniform period grating written in a tapered core fiber, this grating has a positive chirp that can be reduced and removed by subjecting the fiber to mechanical stress, after some stress level the grating chirps to negative values. A chirp range of +/- 4 nm with respect to a central wavelength of 1546 nm has been experimentally achieved.
<title>Amorphous As-S-Se films for holographic recording</title>
2003
The amorphous As40S15Se45 films as recording media for optical holography were studied. The results on research of transmission and Bragg grating holographic recording and readout conditions are presented. The recording of transmission holographic gratings was performed by He-Ne (0.6328 μm) or Kr+ (0.6764 μm) laser beam, while the readout of the diffraction efficiency was made at Bragg angle using He-Ne (0.6328 and 1.15 μm) or diode (0.805 μm) laser lines. It is shown that self-enhancement of Bragg grating reflectors is possible. The influence of thin film interference conditions on holographic recording parameters is demonstrated.© (2003) COPYRIGHT SPIE--The International Society for Optic…
Effective length of short Fabry-Perot cavity formed by uniform fiber Bragg gratings
2009
In this paper, we describe the properties of Fabry-Perot fiber cavity formed by two fiber Bragg gratings in terms of the grating effective length. We show that the grating effective length is determined by the group delay of the grating, which depends on its diffraction efficiency and physical length. We present a simple analytical formula for calculation of the effective length of the uniform fiber Bragg grating and the frequency separation between consecutive resonances of a Fabry-Perot cavity. Experimental results on the cavity transmission spectra for different values of the gratings' reflectivity support the presented theory.
Tunable Dispersion Compensator Based on a Fiber Bragg Grating Written in a Tapered Fiber
2004
We report a novel dispersion tunable device for first-order dispersion compensation. It is based on a fiber Bragg grating written in a tapered fiber with a specific profile. The taper profile allows tuning the dispersion of the grating by stretching the fiber while the linearity of the group delay is preserved. A device with 0.8 nm of useful bandwidth and dispersion value tunable over more than 400 ps/nm is reported.
In-fiber Fabry-Perot refractometer assisted by a long-period grating
2010
We present an optical fiber refractometer based on a Fabry-Perot interferometer defined by two fiber Bragg gratings and an intracavity long-period grating that makes the light confined in the resonator interact with the surrounding medium. The external refractive index is monitored by the resonant frequencies of the Fabry-Perot interferometer, which can be measured either in transmission or in reflection. In this first experiment, wavelength shifts measured with a resolution of 0.1 pm have allowed one to establish a refractive index detection limit of 2.1x10(-5).
Radiation hardening of FBG in harsh environments
2014
International audience; The difficulties encountered in the implementation of a temperature or strain sensor based on Fiber Bragg Grating in a harsh radiative environment are introduced. We present the choices made to select both a radiation-resistant fiber in terms of transmission and also the grating inscription conditions necessary to write radiation tolerant FBGs in such fibers with a femto-second laser. The response of different classes of gratings was also studied under radiation at high doses (>1MGy). The comparison between F- and Ge-doped fibers was highlighted.