Coherent, Inc.

Coherent Optics Europe Limited

Dennis G Fischer

David Trost

Philip Baumeister

Bruce E Perilloux

Arnold L Bloom

J Michael Yarborough

Thomas F Johnston, Jr

Gerald M Mitchell

Mark H Lange

A Neil Boucher

Charles K Langhorn

Larry Giammona

An optical filter uses a multi-layer, stack of alternating dielectric layers () of different refractive indices, a dielectric spacer layer () and metal layer (), to achieve a narrow overall absorption bandwidth, with high reflectance upon either side. A tunable (optical) filter variant uses a dielectric stack and spacer coating of spatially-varying thickness, that is a coating of depth varying, say linearly and/or circularly, according to position across an absorbent layer or substrate, whereby, at different positions on the surface, a different wavelength is absorbed. A tunable laser () uses opposed tunable filters () bounding a lasing medium (), such as COgas, for selective variable stimulated emission of radiation ().

Induced absorption filter (IAF)

A filter system for reflectively blocking laser radiation in the visible spectrum includes a multilayer interference structure arranged for reflectively blocking a continuous band of wavelengths including the laser radiation and transmitting other wavelengths in the visible spectrum. The filter system is arranged to control transmission of the other wavelengths of the visible spectrum such that the filter system has an essentially neutral transmission color and maximum photopic transmission consistent with the band of wavelengths reflectively blocked.

Laser blocking filter with neutral transmission color

A waveguide including a folded, coated reflector highly reflective of radiation having two different wavelengths over a wide range of incidence angles, including grazing incidence angles. The waveguide can be employed for guiding laser radiation useful for medical or other applications, such as a combined HeNe and CO.sub.2 laser beam. In some embodiments, the invention is a hollow waveguide formed by folding a flat, coated substrate into a polygonal shape. Because the coated substrate is folded, rather than rolled into a cylindrical tube, the bending stress on the coating is concentrated at the corners of the polygonal waveguide rather than distributed over the waveguide's entire surface. Although the coating may crack at the corners of the waveguide's polygonal cross-section, the flat surfaces between the waveguide edges will be intact, and the cracks in the corners will have an insignificant effect on waveguide performance.

Optical coating for reflecting visible and longer wavelength radiation

A dichroic optical filter including a substrate that is substantially transparent to visible radiation, and an oxide semiconductor layer on the substrate for reflecting an infrared wavelength (such as an infrared treatment beam wavelength). An example of a suitable oxide semiconductor for reflecting a treatment beam from a CO.sub.2 layer is indium tin oxide. Preferably, the filter includes a specially designed multilayer coating on the oxide semiconductor layer to enhance the reflection of infrared and longer wavelength radiation. This multilayer coating includes alternating quarter-wave layers of high and low refractive index materials, each having an optical thickness substantially equal to a quarter-wavelength of infrared radiation to be reflected. Preferably also, the multilayer coating includes a thin multilayer coating between each pair of adjacent quarter-wave layers, with these thin multilayer coatings being designed to enhance the filter's transmission of visible radiation, while not significantly affecting the filter's reflection of infrared wavelengths. Also preferably, the multilayer coating includes a second multilayer coating which reflects a narrow band of visible radiation (such as visible radiation from a HeNe laser aiming beam), while transmitting most visible wavelengths.

Dichroic optical filter

A coated reflector reflective of radiation having two different wavelengths over a wide range of incidence angles, including grazing incidence angles. The coated reflector can be employed in a waveguide for laser radiation useful for medical or other applications, such as a combined HeNe and CO.sub.2 laser beam. Preferably, the coated reflector includes a metal substrate and a multi-layer stack thereon, the multi-layer stack consists of alternating dielectric layers of high and low refractive index material, each pair of adjacent high and low index layers of the stack has a combined matched optical thickness substantially equal to an incident short (e.g., visible) wavelength multiplied by a factor M/2, and the total matched optical thickness of the stack is substantially equal to (2N-1).lambda..sub.L /8, where M and N are positive integers and .lambda..sub.L is an incident long wavelength (such as the wavelength of a CO.sub.2 laser beam). Preferably, the substrate is silver, the high index dielectric is zinc sulfide, and the low index dielectric is yttrium fluoride or cerium fluoride. In other embodiments, the invention is a coated substrate having substantially parallel indentations along which it can be folded into a polygonal shape for use a waveguide.

A wedge mirror is disclosed for suppressing the high gain wavelengths in a laser. The mirror is provided with a pair of opposed surfaces lying in nonparallel planes. Each of the surfaces is provided with a wavelength selective coating. The coating on the surface of the mirror facing the gain medium is highly reflective of the high gain wavelength and highly transmissive of the low gain wavelength. This surface is oriented so that the light from the high gain wavelength is reflected out of the cavity. The outer surface of the mirror is highly transmissive of the high gain wavelength and highly reflective of the low gain wavelength. The combination of the wavelength selective coatings and the wedge configuration allows the high gain wavelength to be suppressed while the low gain wavelength oscillates. The subject mirror is particularly suited for suppressing the 1.06 and 1.33 micron wavelengths in Nd:YAG while allowing the 1.44 micron wavelength to lase.

Cavity mirror for suppressing high gain laser wavelengths

A laser 10 is disclosed in which there are incorporated one or more diffractive optical elements (DOE's) 20. The DOE's can be used in place of conventional optics to save costs and allow design of resonators not heretofore possible. The ability to vary the reflectivity of the surface of a DOE in any desired pattern allows unprecedented control of both the intracavity mode as well as the mode of the output beam.

Laser resonators employing diffractive optical elements

A polarization preserving reflector for reflecting an incident beam of monochromatic radiation, said beam having a polarization configuration and an angle of incidence. The polarization preserving reflector comprises a substrate; a highly reflective layer positioned adjacent to said substrate; and at least two thin film optical layers one of which being positioned adjacent to the highly reflective layer, one of the thin film optical layers having a high refractive index and another having a low refractive index, for maintaining the incident polarization configuration while producing a high reflectance upon reflection of the beam therefrom in a wide range of the angle of incidence from approximately zero degrees to 75 degrees.

Polarization preserving reflector and method

A broad band phase shifting system, having a fixed angle of phase retardation, has at least one broad band reflecting means in the system. The broad band reflecting means also has an angle of phase retardation, with the angle of phase retardation of the reflecting means less than the fixed angle of phase retardation of the system.

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Auburn, CA, United States of America

Dennis G Fischer