We report a preliminary experiment result of poling in a femtosecond-laser-treated LiNbO3 (LN) crystal. Because of the precision of the femtosecond laser machine, we can control the width and depth of snicks exactly. Then the high-voltage electric field was operated on +z side of the LN crystal. The visible poling pattern was observed by a microscope and machining parameter influences the electric field distribution in the crystal. This approach does not need expensive masks and the periods of PPLN can be adjusted flexibly. Although the mechanism of core formation is not very clear yet, we believe that it would provide a novel technique of making prototype PPLN and other periodically poled crystals.
We present an optically pumped vertical external cavity surface emitting laser using the semiconductor gain chip composed of quantum wells. With a semiconductor saturable absorber mirror (SESAM), we obtained a Q-switched-like pulse output. The output power reached more than 3 mW at a center wavelength of 1007nm whose repetition frequency was 100 kHz and time bandwidth was 500ns. We discussed the possible reasons that the output power was lower compared with the CW operation. We also investigated the relationship between the intra-cavity intensity and the output pulse width. By designing the gain chip more carefully and increasing the pump power, it should be possible to obtain entirely mode-locking operation.
A stable passively Q-switched Nd: YVO4 laser was demonstrated by use of a GaAs absorber grown at a low temperature (LT GaAs absorber) by the Metal Organic Chemical Vapor Deposition (MOCVD) technique, as well as an output coupler. The shortest pulse duration measured was about 12 ns with a single-pulse energy of 4.84 μJ, and the highest average output power is 1.16 W. The repetition rate is 360 KHz, which corresponds to the pump power of 2.8W.
Pico-second solid-state lasers with multi-watt average power and multi-kilowatt peak power are required for numerous applications such as UV generation and pumping of optical parametric oscillators for RGB laser TV display. In the past few years laser diode bars as pump source with continue output power of hundreds watts or more have become commercially available. LD side pumping YAG laser module can be used to generate high reputation mode locked output pulse with SESAM (Semiconductor Saturable Absorber Mirror) as an end cavity mirror. In this paper, we demonstrate an all solid-state mode-locked YAG laser with three-mirror folded cavity with a SESAM mirror, 80MHz pulse rate, about 10ps pulse width, and 2W 1064 nm output power. Thermal effect of laser rod, and polarization of intra-cavity beam are considered in laser cavity design. The enhancement of laser performance and decreasing Q switching effect are discussed. Further investigation is greatly needed.
We presented a diode end-pumped passively mode-locked Nd: YVO4 picosecond laser with a semiconductor saturable absorber mirror home made. Choosing a low-transmission output coupler and extending the cavity length suppressed the Q-switching mode-locked tendency in V-shaped cavity. We observed the pulse trains gone with a continuous background which was decreased with the decreasing of pulse repetition rate. The stable continuous mode-locked pulse was attained. The pulse repetition rate was 80.4MHz and the corresponding spectrum width was measured to be 0.15nm.
In this paper, optimized Gires-Tournois mirrors were designed. The mirror structure was composed of 38 alternating Ta2O5 and SiO2 layers and could be regarded as two sections: high-reflectivity section consisted of a series of quarter-wavelength optical thickness stack and negative-dispersion section consisted of only 13 layers. The designed mirrors exhibit the desired performance. These mirrors were fabricated by use of ion beam sputtering. By use of such Gires-Tournois mirrors, dispersion of mode-locked fetosecond Ti:sapphire laser was compensated and 32fs pulse was obtained.
Based on the incorporation of the structure and the distance of an amplitude grating, we put forward an equation to calculate the Fresnel diffractive field of the grating with an arbitrary opening ratio at any fractional Talbot distance. Because the transmissive function of a phase grating can be regarded as a linear combination of that of amplitude gratings, from above equation for calculating the Fresnel diffractive field of an amplitude grating, we present an analytical equation to calculate the Fresnel diffractive field of an arbitrary multiple phase grating. Using the analytical equation, we can conveniently study the fractional Talbot effect and its application of the arbitrary multiple phase grating. We give a new approach to analyze the Fresnel diffraction of a grating.
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