Laser Power Corporation

Melles Griot Limited

Sven E Nelte

David E Hargis

An efficient frequency-converted solid state laser that outputs a single beam utilizing an angled reflector situated within the laser cavity. The laser comprises an optical cavity including a first reflector and a second reflector. A gain medium situated within the optical cavity is energized by a pump source to excite a laser emission at a fundamental wavelength. A nonlinear material is arranged within the optical cavity to convert the laser emission to a second wavelength. The angled reflector, which is reflective of the second wavelength and transmissive of the first wavelength, is situated within the optical cavity between the first reflector and the nonlinear material. In operation, the forward-propagating converted beam is reflected from the second reflector, and then combines with the reverse-propagating converted beam. The angled reflector reflects the combined beam so that it exits from the optical cavity at a nonzero exit angle. Typically, the angled reflector and the exit angle are selected so that the angled reflector reflects substantially all polarizations of the combined beam. In some embodiments, the angled reflector is formed on the nonlinear material. In other embodiments, the gain medium is coupled to a surface that comprises the angled reflector, such as an optically transparent heatsink. Some embodiments include means for reflecting the first converted beam from the second reflector so that the reflected first converted beam is approximately in phase with the second converted beam within the nonlinear material.

Efficient frequency-converted laser with single beam output

An optically-pumped laser comprises a laser cavity, a solid-state gain medium and an optically transparent heat sink (OTH) situated within the laser cavity. The gain medium and OTH are thermally coupled and at least one of the solid-state gain medium and the OTH has an etalon structure thereby improving laser efficiency. The OTH advantageously provides effective heat transfer and permits higher average power operation, particularly for thin solid-state laser materials. A metallic heat sink may be thermally coupled to the OTH to improve heat transfer. In some embodiments, the laser is end-pumped with optical pump radiation through the OTH. A second intracavity OTH may be thermally coupled to the gain medium opposite the first OTH to provide longitudinal heat transfer in both directions. A frequency-converted laser may be provided by using a nonlinear material longitudinally cooled on each end by intracavity OTHs, at least one of which comprises an etalon structure. In some frequency-converted laser embodiments, first and second converted beams are output from the laser cavity along separate optical paths in a manner that advantageously prevents intracavity interference between the two converted beams.

Solid state laser with longitudinal cooling

A longitudinally-cooled laser element assembly comprises an optically transparent heat sink (OTH) coupled to a laser element and a heat sink. An etalon structure including a first flat surface and a second, substantially parallel flat surface is formed in the laser element and/or the OTH. In some embodiments, a balanced etalon is provided by forming a reflector on the second flat surface of the etalon that has a reflectivity approximately equal to the Fresnel loss at the interface between the OTH and the laser element. In some embodiments the laser element assembly includes a second OTH coupled to the laser element at a second interface, thereby defining a second Fresnel loss. Preferably, the second OTH has an index of refraction substantially equal to the index of refraction of the first OTH, so that said first and second Fresnel losses are approximately equal and a balanced etalon is formed. In some embodiments the laser element comprises a solid-state gain medium. In other embodiments the laser element comprises a nonlinear frequency conversion crystal. An intracavity frequency-converted laser is described in which OTHs are used to cool both the gain medium and the nonlinear material.

Optically transparent heat sink for longitudinally cooling an element in

An intracavity frequency-converted laser having an intracavity reflector situated to reflect converted radiation at a nonzero angle with respect to the optical axis. The laser includes an optical cavity that defines an optical axis, a gain medium for providing a fundamental laser emission, a pump source for pumping the gain medium, and a nonlinear material for frequency converting the fundamental laser emission to provide first and second converted beams that propagate in opposite directions within the optical cavity. An angled reflector that reflects optical radiation at the converted wavelength, but is transmissive at the fundamental wavelength is situated within the optical cavity to reflect one of the converted beams along a path angled with respect to the optical axis. Advantageously, reflecting the converted radiation before it propagates through the gain medium avoids absorption losses. Furthermore, interference between the reflected beam and other converted beam is avoided due to the angle of reflection. In one embodiment, the gain medium comprises an Nd.sup.3+ doped material, the laser is designed to lase on the .sup.4 F.sub.3/2 .fwdarw..sup.4 I.sub.9/2 transition at about 870-960 nm, and a nonlinear crystal is situated to frequency-double the emission of the gain medium to produce blue light at about 435-480 nm.

Efficient frequency-converted laser

A monolithic diode pumped solid-state laser (11) comprising as the laser host neodymium-doped yttrium orthovanadate (Nd:YVO.sub.4) (12, 52) or neodymium-doped gadolinium orthovanadate (Nd:GdVO.sub.4) (57, 67) operating on the .sup.4 F.sub.3/2 .fwdarw..sup.4 I.sub.9/2 (.about.914 nm or .about.912 nm respectively) transition, to which a suitable nonlinear optic material (16), such as potassium niobate (KNbO.sub.3) or beta barium borate (BBO), is bonded. The nonlinear crystal gives rise to intracavity frequency doubling to .about.457 or .about.456 nm. The microlaser is a composite cavity formed from a gain medium crystal and a nonlinear frequency doubling material which together have four spaced parallel dielectrically coated faces (14, 17, 18, 15) and which is positioned in close proximity to a diode laser pump source (13) for phase-matched harmonic generation of blue light along an axis of propagation which lies substantially perpendicular to the two faces of the composite cavity. By employing specific doping concentration-lengths products of lasant material and pumping the gain medium which has a specific crystalline orientation the desired efficient blue microlaser is achieved. Alternative embodiments combine the Nd:YVO.sub.4 and Nd:GdVO.sub.4 elements to enhance certain output characteristics of the laser.

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Carlsbad, CA, United States of America

Sven E Nelte