A simple method of broadband distributed Raman amplifier is presented based on Chirped Fiber Bragg Grating Filter. C+L band gain flattened distributed fiber Raman amplifier with bandwidth of 50nm (1520nm~1570nm) and 15 dB averaged gain and ± 0.6dB gain ripple using single pump has been demonstrated. Compared to design methods of other existing Raman amplifier, our method has a substantial improvement in simplifying system.
We study single-shot damage morphology of MgF2 irradiated under 800 nm laser using scanning electronic microscope (SEM). The dependence of damage threshold on laser pulse width is measured by the linear relationship between the area of damage spot and the logarithm of laser energy. The pulse duration ranges from 55 fs to 750 fs. We develop the multiple-equation model (Phys. Rev. Lett. Vol.92, pp.187401, 2004), in which two-photon absorption in the conduction band is considered. The experimental results agree well with our model.
The temporal pulse shaping was realized by using temporal-space transforming pulse-shaping system with the own-designed "Knife edge" apparatus, for the first time to our best knowledge, in a large energy laser facility with the output energy of 454.37J. A quasi-square laser pulse with the pulse width of 1.16ns, the rising time of 337ps, the falling time of 360ps, and the temporal filling factor of 81.2% was obtained. It is quite satisfied with the requirement of physical experiment. In addition, the further improvements of our system have been suggested in order to enhance the stability and the flexibility as well as the restoring ability of the temporal-space transforming process.
Comparative study of spectroscopic properties of Er3+/Tm3+-codoped and Er3+/Tm3+/Yb3+ codoped tellurite glasses under a single wavelength pumping at 980nm were investigated. In the Er3+/Tm3+-codoped tellurite glasses, we have found that there exists fluorescence emissions at both 1.53 and 1.74 μm, which correspond to the transitions of the Er3+:4I13/2→4I15/2 and Tm3+:3F4→3H6, respectively. Tm3+ act as an efficient co-dopant for depopulation of the Er3+:4I13/2 level, and thus reducing the optical amplification efficiency. Meanwhile, the addition of a small amount of Tm3+ to the Er3+ doped tellurite glass causes the quenching of the green up-conversion fluorescence around 524 and 546nm resulting in red visual. In the Er3+/Tm3+/Yb3+ codoped tellurite glasses, fluorescence emissions at both 1.53 and 1.63 μm communication windows were firstly observed. What’ more, The FWHM (fluorescence width at half maximum) at 1.53 and 1.63 μm are 55nm and 50nm, respectively. This novel three earth ions co-doping method could be applied to other low photon energy glasses, which would be possibly used for potential dual wavelength fiber-optic amplifiers to broaden the communication windows.
A diode pumped Nd:YLF regenerative amplifier is developed, which works at wavelength of 1053nm and repetition rates of 1Hz. It can produce laser pulses of 2mJ energy, 4ns width in the base transverse mode TEM00. Total gain of 1x107 is reached, and pulse-to-pulse energy fluctuation doesn't exceed ±4.7% Experimental setup and detailed results are presented.
A novel method is investigated for compensating deflection in a spatial-temporal transform pulse shaping system: using optical fiber instead of a second electrooptic deflector. By changing the width and shape of filter, pulse duration ranging from 740ps to 4.5ns is observed, and the mode quality of output beam is good. This novel method has relaxed requirements on electrooptic deflector and simplified the whole system.
An electro-optic deflector system is developed to re-shape the optical pulse from a Q-switched Nd:YLF oscillator. The shaped optical pulses are tunable in pulse width by scanning the slit and optical pulses of sub 500 ps are obtained. Except the slit width, its position on the scanning plane also determines the shaped pulse width and even causes pulse distortion if the slit is located close to the edge of the scanned beam. The shortest pulse width can be achieved by this system is determined by the transform limitation. This electro-optic deflector system is successfully used in the SG-II high power laser facility.
An erasable optical recording medium was made by vacuum deposition of copper tetra cyanoquino dimethane organometallic materials writable and erasable with an He-Ne laser. With He-Ne laser output power of 13 mW at 632 nm, the threshold pulse width was 0.2 - 2 microsecond(s) . The readout signal contrast was 29%. The write-erase cycles were observed under optimum condition.
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