In this work, the laser-induced periodical surface structure (LIPSS) on silicon is generated by 532nm nanosecond laser with pulse duration of 10ns and repetition frequency of 10Hz. The formation of LIPSS is observed under laser fluence of 260mJ/cm2 and pulse number of 600 shots with p- and s-polarized laser. For p- polarized laser, when the incident angle is 10°, 20°, 30°, 45°, and 60°, the LIPSS period is 400nm, 743nm, 902nm, 1148nm and 2525nm correspondingly. Besides, the orientation of LIPSS is always perpendicular to the polarization direction of the incident laser. For s- polarized laser, the LIPSS is perpendicular to the polarization direction and the period increases with the incident angle when it is less than 42°. The period is 457nm, 515nm, 549nm and 610nm at incident angle of 10°, 20°, 35°, and 41° correspondingly. when the incident angle exceeds 42°, a set of crossed LIPSSs emerge which are symmetric about the polarization direction. Meanwhile, the period reduces a lot which is around 400nm.
The thermodynamic properties of silicon plasma generated by picosecond laser in vacuum were studied by using spatiotemporally resolved emission spectroscopy technique. Temporal and spatial evolution behavior about plasma has been analyzed. Meanwhile, the temporal and spatial dependence of silicon ions with different charges were examined. Finally, the validity of assuming a local thermodynamic equilibrium (LTE) in the silicon plasma expansion was checked, and the deviation degree of LTE was measured. The results indicate that the assumption was valid only at longer (< 180 ns) delay times in the area z < 4 mm away from the target surface. At the initial stage of plasma expansion, the plasma deviates from LTE due to the sharp decrease of plasma temperature and electron density.
Ring or conical light beams show great potential in many applications. We report on achievement of multi-ring-shaped conical beams through degenerated optical parametric generation (OPG) with tightly focused Gaussian pump beam in periodic polarized lithium niobate (PPLN) crystal. We observed continuous beam spatial pattern variation from multi to single ring and normal non-hollow beams by crystal temperature tuning. We attributed the experimental results to the effective polarized period changing under tightly focusing. This unique feature would exist in any quasi-phase matching processes and may find applications in optical trapping, manipulation, and even quantum field.
Based on the polarization period of 22.67um magnesium-oxide-doped lithium niobate (MgO: PPLN) Crystal, a 4f midinfrared imaging system was constructed. The electronic enhanced charge-couple device (EMCCD) was used to receive the mid-infrared images to improve the sensitivity of the systerm. The resolution tablets of USAF 1951 were used to confirm the performance of the optical system. In this experiment, mid-infrared upconversion from 3412 nm to 3482 nm were achieved by changing the crystal temperature and the wavelength of the signal light. The upconversion imaging at 3482nm was attained by a silicon based CCD camera with the conversion efficiency of 3.8×10-6 and the resolution of 2.52/2 lp/mm.
Based on the polarization period of 11.73um magnesium-oxide-doped lithium niobate (MgO: PPLN) Crystal, frequency up-conversion of continuous-wave (CW) 1559.5nm signal light has been demonstrated. It is pumped with an actively Qswitched diode-pumped Nd: YAG laser at 1064nm in micro cavity scheme. When operating at the temperature of 110.3 °C, the wavelength of output light is 632.5nm, and the maximum energy conversion efficiency is 1.1×10-4. The change of the output light characteristic as the operating temperature varies is studied, and the beam quality of the output laser is also analyzed.
The upconversion of an orbital angular momentum (OAM) carried light in communication band is preferable for building OAM-based upconversion optical communication networks. Here we experimentally study the behavior of OAM of communication band light in sum frequency generation process. The wavelength of the pump beam with sub-nanosecond pumping fields is 1064 nm and the communication band light is 1560 nm. Both beams are imprinted with OAM using vortex phase plates.The topological charges of the upconversion pulses at 632.5 nm are observed by a self-referenced interferometric technique. The OAM conserves in coupled nonlinear optical conversions is confirmed by counting the fringes in the interference intensity profile.The sum frequency generation is performed by using a periodically poled MgO-doped lithium niobate (PPLN) crystal under quasi-phase-matching conditions. We also gave analytical expressions for the upconversion of two OAM-carrying beams. The experimental results are well matched with the theoretical simulations.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.