CW SHG Research Articles

Watt-level SHG in undoped high step-index PPLN ridge waveguides

Nonlinear quadratic waveguides are key components to obtain efficient frequency conversion. In this paper we present the performances of highly multimode periodically poled lithium niobate (PPLN) ridge waveguides for high power CW SHG are presented. We report the generation of 1 W of second harmonic on the fundamental guided mode with a conversion efficiency of 56% at telecom wavelengths. A stable nonlinear process is obtained despite use of an undoped congruent LiNbO3 crystal. The input damage threshold of the ridge waveguide is found to set the maximum usable power.

Fluorescence properties of Phycocyanin and Phycocyanin-human serum albumin complex

In this work, the fluorescence properties of Phycocyanin (PC) and the corresponding quenching effects are investigated in attendance of human serum albumin (HSA). At first, PC is excited at 532nm using CW SHG Nd:YAG laser, then the emission wavelength, Stokes shift, quantum yield, extinction constant and self-quenching coefficient are obtained based on the modified Beer-Lambert equation. It is shown that a notable red shift appears in terms of PC concentration. According to the fluorescence spectra, the addition of HSA in PC solution leads to a significant reduction in the fluorescence signal via quenching events, however a lucid blue shift takes place in the same time. Stern-Volmer formalism is used to determine the quenching constant (KS), the number of binding sites (n) between PC and HSA as well as the association constant Ka for the purpose of facile transportation to the target in the context of drug delivery. Eventually, temperature dependent coefficients and corresponding spectral shifts are investigated over a wide range of temperatures at a couple of distinct PC concentrations to attest the dominant static quenching takes place. The rate of conjugate formations elevates at low temperatures leading to a certain blue shift. Furthermore, large KS is measured in the course of signal reduction, particularly at low PC populations. In fact, PC conjugation to HSA is essential interaction to enhance chemo drug transportation. Here, at the body temperature, the quenching coefficient decreases to facilitate the drug release. Moreover, the spectral shift of fluorescence emission can be useful for simultaneous monitoring and drug delivery treatment.

Tunable intra-cavity SHG of CW Ti:Sapphire lasers around 785 nm and 810 nm in BiBO-crystals

Phasematch curves as well as sensitivity to angular and wavelength misalignment for generation of second-harmonic of 785 nm and 810 nm in Bi(3)BO(6) crystal was calculated. Measurements were done for intra-cavity CW SHG in a Ti:Sapphire laser. The BiBO crystal was found to be excellent for this application. Temperature dependance was uncritical for both crystals, while power stability was good. Maximum blue output was 53 mW at 392 nm and 100 mW at 405 nm; corresponding to pump-to-blue optical conversion efficiencies of 0.96% and 1.82% respectively.

Efficient Green and Blue Light Generation Using SHG Devices with Periodically Poled Structures

We have developed efficient SHG devices for green and blue light generation with periodically poled structures in thick Z-cut MgO: LiNbO3 utilizing a multi-pulse poling method. Uniformly periodically domaininverted structures with a period of 6.95μm and 4.19μm were fabricated over 10-mm interaction length. We have demonstrated highly efficient green and blue light generation using bulk QPM-SHG devices with this structure. Using compact and high-power Nd: GdVO4 micro-laser, CW SHG of 1.03W at a wavelength of 531nm was generated with conversion efficiency of 16.5% by single-pass configuration at room temperature. Moreover, CW SHG of 167mW at a wavelength of 456nm was realized with a conversion efficiency of 8.3%.

Frequency Doubling of CW And Pulsed CO2 Lasers Using Diffusionbonded, Quasi-Phase-Matched Gaas Stacks

AbstractWe describe the fabrication, characterization and frequency doubling properties of first order stacks of diffusion bonded 2″ diameter GaAs wafers. Near IR imaging through the stacks indicated that excellent bonding was obtained over 40%–70% of the central area of the wafers. A power spectrum analysis of the spectral noise (due to interface reflections) appearing in the transmission data is shown to be a quantitative diagnostic tool useful for determining interface quality and for accurately estimating the thickness of the bonded layers in a stack. The conversion efficiency for a four layer stack at 10.6 microns was found to be 0.03% or 3 mJ for a 10 mJ pulse with a 100 nanosecond pulse length. The corresponding efficiency for cw SHG was found to be 0.0002%.

Simple, inexpensive autocorrelator for use with cw mode-locked lasers

An improved method of obtaining variable pulse spacing for use in a cw SHG autocorrelation interferometer is described.

LINEAR AND NONLINEAR OPTICAL PROPERTIES OF TRIGONAL SELENIUM

Measurement of the second-order nonlinear optical susceptibility of trigonal selenium yielded d11 = (9.7 ± 2.5) × 10−11 m/V. This value was obtained by cw SHG with a 10.6-μm CO2 laser at a phase-matching angle of 5.5° ± 0.3° to the optic axis. Factors affecting this measurement are discussed along with data on absorption, optical activity, and birefringence.