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).
High-power surface emitting semiconductor laser with extended vertical compound cavity
Novel, electrically pumped, vertical compound cavity InGaAs lasers emitting at 980 nm are described. These have generated 1 W continuous-wave multimode and 0.5 W continuous-wave in a fundamental TEM/sub 00/ mode and single frequency, with 90% coupling efficiency into a singlemode fibre.