University of California

Christopher D Marshall

Stephen Anthony Payne

William F Krupke

Howard T Powell

The invention provides an efficient, compact means of generating blue laser light at a wavelength near &tilde;493&plus;/&minus;3 nm, based on the use of a laser diode-pumped Yb-doped laser crystal emitting on its zero phonon line (ZPL) resonance transition at a wavelength near &tilde;986&plus;/&minus;6 nm, whose fundamental infrared output radiation is harmonically doubled into the blue spectral region. The invention is applied to the excitation of biofluorescent dyes (in the &tilde;490-496 nm spectral region) utilized in flow cytometry, immunoassay, DNA sequencing, and other biofluorescence instruments. The preferred host crystals have strong ZPL fluorecence (laser) transitions lying in the spectral range from &tilde;980 to &tilde;992 nm (so that when frequency-doubled, they produce output radiation in the spectral range from 490 to 496 nm). Alternate preferred Yb doped tungstate crystals, such as Yb:KY(WO,),, may be configured to lase on the resonant ZPL transition near 981 nm (in lieu of the normal 1025 nm transition). The laser light is then doubled in the blue at 490.5 nm.

Blue diode-pumped solid-state-laser based on ytterbium doped laser crystals operating on the resonance zero-phonon transition

In a master oscillator-power amplifier (MOPA) hybrid laser system, the master oscillator (MO) utilizes a Nd,-doped gain medium and the power amplifier (PA) utilizes a diode-pumped Yb,-doped material. The use of two different laser gain media in the hybrid MOPA system provides advantages that are otherwise not available. The Nd-doped gain medium preferably serves as the MO because such gain media offer the lowest threshold of operation and have already been engineered as practical systems. The Yb-doped gain medium preferably serves in the diode-pumped PA to store pump energy effectively and efficiently by virtue of the long emission lifetime, thereby reducing diode pump costs. One crucial constraint on the MO and PA gain media is that the Nd and Yb lasers must operate at nearly the same wavelength. The 1.047 &mgr;m Nd:YLF/Yb:S-FAP &lsqb;Nd:LiYF,/Yb:Sr,(PO,),F&rsqb; hybrid MOPA system is a preferred embodiment of the hybrid Nd/Yb MOPA.

Hybrid solid state laser system using a neodymium-based master oscillator and an ytterbium-based power amplifier

Ce.sup.3+ -doped LiSrAlF.sub.6 crystals are pumped by ultraviolet light which is polarized along the c axis of the crystals to effectively energize the laser system. In one embodiment, the polarized fourth harmonic light output from a conventional Nd:YAG laser operating at 266 nm is arranged to pump Ce:LiSrAlF.sub.6 with the pump light polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 crystal may be placed in a laser cavity for generating tunable coherent ultraviolet radiation in the range of 280-320 nm. Additionally, Ce-doped crystals possessing the LiSrAlF.sub.6 type of chemical formula, e.g. Ce-doped LiCaAlF.sub.6 and LiSrGaF.sub.6, can be used. Alternative pump sources include an ultraviolet-capable krypton or argon laser, or ultraviolet emitting flashlamps. The polarization of the pump light will impact operation. The laser system will operate efficiently when light in the 280-320 nm gain region is injected or recirculated in the system such that the beam is also polarized along the c axis of the crystal. The Ce:LiSrAlF.sub.6 laser system can be configured to generate ultrashort pulses, and it may be used to pump other devices, such as an optical parametric oscillator.

Growing community of inventors

Livermore, CA, United States of America

Christopher D Marshall