Search results for "Toe"
showing 10 items of 3824 documents
Q-switched all-fibre laser using a fibre-optic resonant acousto-optic modulator
2007
Abstract We report an actively Q-switched all-fibre laser using a fibre-optic resonant acousto-optic modulator as Q-switching element. The modulator consists of a short-length fibre Bragg grating modulated by a standing longitudinal elastic wave, being the grating length much shorter than the acoustic wavelength. Q-switch pulses were successfully obtained from an Er3+-doped fibre laser at repetition rates of 18 and 37 kHz.
Generation of Bound States of Three Ultrashort Pulses With a Passively Mode-Locked High-Power Yb-Doped Double-Clad Fiber Laser
2004
We report the generation of high-power ultrashort bound states of three pulses in an ytterbium-doped double-clad fiber laser. The laser is mode-locked through nonlinear polarization rotation technique in a unidirectional cavity configuration. A pair of diffraction grating is incorporated in the cavity to compensate for the normal dispersion of the fiber. The laser generates chirped bound states of three pulses with either equal or different time separations, with more than 500-pJ energy per pulse. These pulses are subsequently compressed to 100 fs with a compression factor of more than 40.
Actively Q-switched DFB fiber laser for Brillouin sensor applications
2009
Q-switching of distributed feedback (DFB) fiber lasers permits to achieve high peak powers, preserving an ultra narrow linewidth [1,2]. The development of a new in-line acousto-optic modulator based on a magnetostrictive actuator, instead of a piezoelectric-based device, permits an efficient excitation of elastic pulses propagating along the optical fiber and an easy access to both emission outputs of the laser. The repetition rate can be continuously adjusted, as well as the amplitude of the elastic pulses. The interaction of these elastic pulses with a fiber Bragg grating written in an erbium-doped fiber permits an actively Q-switched operation of the DFB fiber laser [3]. The birefringenc…
Single- to three-wavelength switchable ytterbium-doped fiber laser based on intracavity induced loss by a long-period holey fiber grating
2011
In this paper, we propose and demonstrate a versatile and simple single-, dual- and three-wavelength switchable ytterbium-doped fiber laser using the intracavity induced-loss generated by a mechanically induced long-period grating (MLPFG) in a holey fiber. The laser net gain in the cavity is reshaped through the MLPFG by adjusting the twist rate and the pressure of the holey fiber in the long-period grating. In this way, the twist response of the MLPFG enables the laser to switch between the single-, dual-, and three-wavelength operations and the tuning of the simultaneous two- and three-wavelengths. These results are of great interest in the design of flexible multiwavelength sources with …
Smart Q-switching for single-pulse generation in an erbium-doped fiber laser
2012
In this paper, we report an active Q-switching of an erbium-doped fiber laser with special modulation functions and novel laser geometry. We experimentally demonstrate that using such a smart Q-switch approach, Q-switch ripple-free pulses with Gaussian-like shape and 17.3 ns width can be easily obtained. The idea behind the smart Q-switch is to suppress one of two laser waves contra-propagating along the fiber cavity, which arises after Q-cell opening, and to eliminate the minor sub-pulses.
Active Q-switched distributed feedback erbium-doped fiber lasers
2005
This letter presents a distributed feedback fiber laser that operates in an actively controlled Q-switched regime. The laser is based on a Bragg grating made in an erbium-doped fiber. The grating has a defect induced by a magnetostrictive transducer that configures the distributed feedback laser structure. The phase shift generated by the defect can be dynamically modified by an electric current, permitting active Q-switching of the laser. The laser generates pulses of 75 ns duration and the repetition rate can be continuously adjusted from 0 to 10 kHz.
4W continuous-wave narrow-linewidth tunable solid-state laser source at 546nm by externally frequency doubling a ytterbium-doped single-mode fiber la…
2009
A high-power continuous-wave coherent light source at 545.5nm is described. We use 8.3W from a solid-state ytterbium-doped single-mode fiber oscillator/amplifier system as input into an external frequency doubling stage. This system produces up to 4.1 W of stable green single-frequency laser radiation. We characterize the light source by performing absorption spectroscopy on iodine across the full tuning range of the fiber laser and saturation spectroscopy on one strong iodine line of the doppler-broadened spectrum.
Time‐resolved absorption and luminescence following electron‐hole pair creation in ZnO
2008
We report transient absorption induced by electron-hole excitation in undoped ZnO. A laser pump/continuum probe method covers 2–300 ps, and an electron pulse with lamp transmission covers 8–300 ns. The broad absorption spectrum increases monotonically with wavelength from 900 to 1600 nm. Following a reasonable hypothesis that the free-carrier-like induced infrared absorption is proportional to the total number of free carriers, excitons, and shallow-trapped carriers in the sample, these data allow setting an upper limit on the quantum efficiency of a specified lifetime component of luminescence. For the undoped commercial ZnO studied in this report, the quantum efficiency of room temperatur…
Direct Methane Oxidation on La1-xSrxCr1-yFeyO3-δ perovskite-type oxides as Potential Anode for Intermediate Temperature Solid Oxide Fuel Cells
2016
Abstract La1−xSrxCr1−yFeyO3−δ (x = 0, 0.1, 0.15, 0.2; y = 0, 0.3, 0.5) perovskite-type oxide powders were synthesized by solution combustion synthesis and characterized by X-ray diffraction, X-ray photoelectron spectroscopy and H2-temperature programmed reduction. Selected compositions were studied by CH4-temperature programmed reduction in the absence and in the presence of H2S. Temperature programmed oxidation and structural characterizations were performed in order to discriminate the nature of residual deposits on the catalyst surface. The study about reduction in different methane-based mixture revealed that total and partial methane oxidation occurred in the range ∼450–1000 °C indepen…