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  Nonlinear optical crystal optimized for ytterbium laser host wavelenghtsUSPTO Application #: 20070211774Title: Nonlinear optical crystal optimized for ytterbium laser host wavelenghts Abstract: A material for harmonic generation has been made by substitutional changes to the crystal LaCa4 (BO3)3 also known as LaCOB in the form Re1xRe2yRe3zCa4(B03)3O where Re1 and Re2, (rare earth ion 1 and rare earth ion 2) are selected from the group consisting of Sc, Yttrium, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, and Lu; Re3 is Lanthanum; and x+y+z=1. (end of abstract)
Agent: Michael C. Staggs Assistant Laboratory Counsel - Livermore, CA, US Inventors: Christopher A. Ebbers, Kathleen I. Schaffers USPTO Applicaton #: 20070211774 - Class: 372022000 (USPTO) Related Patent Categories: Coherent Light Generators, Particular Beam Control Device, Nonlinear Device, Frequency Multiplying (e.g., Harmonic Generator) The Patent Description & Claims data below is from USPTO Patent Application 20070211774. Brief Patent Description - Full Patent Description - Patent Application Claims
RELATED APPLICATION [0001] This application is a Divisional of application Ser. No. 10/261,902 entitled "Nonlinear Optical Crystal Optimized for Ytterbium Laser Host Wavelengths," filed Oct. 1, 2002, the disclosure of which is herein incorporated by reference in its entirety. BACKGROUND OF THE INVENTION [0003] 1. Field of the Invention [0004] The present invention relates to solid-state laser materials, and specifically to noncritical phase matching laser materials capable of non-linear harmonic conversion of a specific wavelength. [0005] 2. State of Technology [0006] Ytterbium doped laser hosts emit in the wavelength range between 970 nm and 1047 nm. Some examples of these crystals are Ytterbium doped strontium fluoro-apatite (i.e., Yb:SFAP), Ytterbium doped yttrium aluminum garnet (Yb:YAG), Ytterbium aluminum garnet (YbAG), Yb doped glass (Yb:glass), Yb doped potassium gadolinium tungstate (Yb:KGd(WO4).sub.2), and Ytterbium doped fused silica (Yb:SiO.sub.2). Each host has specific application and utility. Collectively, these lasers emit in the range of 970-1045 nm. For example, Yb:SFAP emits at several specific wavelengths, such as 1047 and 985 nm. As another example, Yb:YAG has a tunable laser emission between 1020 and 1045 nm, with a peak emission occurring at 1030 nm. [0007] Frequency conversion of such lasers discussed above has been found to be useful for many applications. For example, frequency doubling of the 1029-nm emission of Yb:YAG leads to laser light at the wavelength of 514.5 nm. This specific wavelength is emitted by the Argon-ion laser and is a wavelength that has many beneficial and useful applications. For example, the 514.5-nm wavelength is useful in the biotechnology field for cell sorting of biological compounds. By utilizing frequency conversion, a solid-state frequency converted laser has the potential to replace the Ar-ion gas laser for this specific wavelength. [0008] Background information on improved frequency mixing crystals for harmonic generation of laser beams is contained in U.S. Pat. No. 5,123,022 entitled "Frequency Mixing Crystal," to Ebbers et al., patented Jun. 16, 1992 including the following: "The improvement of said means of harmonic generation comprising a crystal having the chemical formula X.sub.2Y(NO.sub.3)5.2nZ.sub.2O wherein X is selected from the group consisting of Li, Na, K, Rb, Cs, and Tl; Y is selected from the group consisting of Sc, Y, La, Ce, Nd, Pr, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, Lu, Al, and In; Z is selected from the group consisting of H and D; and n ranges from 0 to 4." [0009] Background information on frequency mixing crystals by congruently melted compositions including a lanthanide is contained in international application No. WO 96/26464 entitled "Non-linear Crystals And Uses Thereof," to Gerard et al., patented Feb. 16, 1996, including the following: "The crystals are prepared by crystallizing a congruent melting composition of general formula: M.sub.2LnO(BO.sub.3).sub.3, wherein M is Ca or Ca partially substituted by Sr or Ba, and Ln is a lanthanide from the group which includes Y, Gd, La and Lu. Said crystals are useful as frequency doublers and mixers, as an optical parametric oscillator or, when partially substituted by Nd.sup.3+, as a frequency doubling crystal. [0010] Accordingly, a need exists to improve solid-state frequency materials for specific wavelengths. An ideal crystal is not difficult to grow, has a high nonlinear optical coefficient, has a high optical damage threshold, and birefringence and contains dispersion properties that allow for noncritical phasematching at specific wavelengths. The present invention involves such a crystal. SUMMARY OF THE INVENTION [0011] Accordingly, the present invention provides a frequency conversion crystal which is noncritically phasematched having a general chemical formula [0012] Re1xRe2yRe3zCa.sub.4(B0.sub.3).sub.3O, wherein Re1 and Re2 are selected from the group consisting of Sc, Yttrium, La, Ce, Pr, Nd, Sm, Eu, Gd, Th, Dy, Ho, Er, Tm, Yb, and Lu; Re3 is Lanthanum; and x+y+z=1. [0013] Another aspect of the present invention provides a laser system having incorporated therein the frequency mixing crystal described herein. [0014] Accordingly, the present invention provides an external or intracavity frequency conversion crystal with an increased birefringence to make such a crystal suitable for noncritical phasematching or substantially noncritical phasematching of wavelengths between about 970 and about 1047 nm, wavelengths emitted by Ytterbium doped laser hosts. Such a crystal is useful for medical and biological applications wherein a specific wavelength can be applied in a single shot or variable repetition rate pulsed format. BRIEF DESCRIPTION OF THE DRAWINGS [0015] The accompanying drawings, which are incorporated into and form a part of the disclosure, illustrate an embodiment of the invention and, together with the description, serve to explain the principles of the invention. [0016] FIG. 1(a) illustrates the external morphology of a crystal produced by the present invention. [0017] FIG. 1(b) illustrates the relative orientation of crystallographic (X, Y, Z) axes with regard to crystallographic axes (a, b, c) of a monoclinic structure. [0018] FIG. 2 shows a plot of birefringence versus rare earth ion size to illustrate the sensitivity of the birefringence of a crystal, such as in the present invention, to the size of a trivalent cation. [0019] FIG. 3 is a basic schematic of an apparatus incorporating the crystal of the present invention in an intra-cavity configuration. [0020] FIG. 4 is a basic schematic of an apparatus incorporating the crystal of the present invention in an external cavity configuration. DETAILED DESCRIPTION OF THE INVENTION Continue reading... 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