Improved 2nd harmonic rise-time in a thermal-lens-dominated extended-cavity micro-laser
Many commercially available compact, micro-cavity diode-pumped solid-state lasers achieve a stable resonator condition following the formation of an intra-cavity thermal lens. Typically, this thermal lens forms as a result of localized thermal expansion in the host material due to the very high optical power of the infrared pump beam. Additionally, most common DPSS host media, such as Nd:YAG and Nd:YVO4 exhibit high dn/dT, change in refractive index with temperature. Thermal lens formation time dominates stable resonator establishment and, thus, the rise-time of the intra-cavity-generated visible second-harmonic output light. Thermal lens formation time may range from 10's of microseconds to several milliseconds, depending on pump power, the host material dn/dT, and the volume and length of the host material. This paper describes a unique approach that improves the second-harmonic rise-time - and, thus, the modulation bandwidth - for high-power VECSELs by several orders of magnitude. This approach, while typically used in some laser systems for other purposes, allows direct modulation of high-power VECSELs to greater than 100 megahertz with second-harmonic rise-time of a few nanoseconds.
Solid-state blue laser technology
The optically pumped semiconductor (OPS) chip consists of two sections, both semiconductor alloys grown by MBE epitaxy. The top section is the gain medium and the bottom section is a high reflecting mirror that constitutes one of the ends of the cavity. The gain at 976 nm is provided by narrow layers of InGaAs quantum wells, the composition of the spacer layers is chosen such as to make them transparent to the laser wavelength, and strongly absorbent to the pump wavelength (around 800 nm).
Resonant Auger decay study of C1s -> pi* core-excited OCS
The present work aims at characterizing short-lived C1s((-1)) pi*((1)) core-excited states of the OCS molecule based on the analysis of the vibrational fine structure and lineshape profiles of the high-resolution resonant Auger decay spectra recorded at the excitation energies along the C1s -> pi* resonance in the binding energy region 15-19eV. Very different behavior in terms of lineshape and resonant enhancement is observed for the (A) over tilde, (B) over tilde and (C) over tilde final states. This is explained by (1) the variation in the C-O bond lengths for the states involved in the electronic relaxation and (2) different contributions in terms of Mulliken population to the molecular orbitals determining the electronic character of the corresponding states. Since the final-state geometries are known from a number of previous experiments and ab initio calculations, the geometry of the C1s((-1)) pi*((1)) intermediate states can be predicted in analogy with e.g. the N-2, CO2 and N2O molecules. (C) 2009 Elsevier B.V. All rights reserved. (Less)