Abstract: A continuously variable beam combiner combines multiple input beams of different wavelengths into a single output beam in which the power of each input beam may be varied continuously.

Abstract: An optical communications transceiver comprises a transmitter for transming a communications signal having at least two wavelengths and a receiver for concurrently detecting the communications signal on each wavelength. The receiver compares the data content of the communications signal received on each wavelength and detects errors in the received data. A display displays valid received data.

Abstract: A wavelength independent optical probe comprises an optical waveguide, a arizing beamsplitter, an optical detector, a quarter-wave plate, a focusing mirror, and a probe enclosure.

Abstract: An optical probe for illuminating a location outside or inside a medical ient with a range of optical wavelengths appropriate to both diagnostic and surgical procedures comprises a polarization-preserving optical waveguide to conduct a polarized light beam to a polarizing beamsplitter, an optical detector to detect light deflected by the beamsplitter, a quarter-wave plate to couple the light between a non-refractive focusing element and a target, and a probe enclosure.

Abstract: A laser diode power combiner comprises a dye laser operably coupled to an array of laser diodes for combining optical power from the laser diodes into a single, coherent laser beam.

Abstract: A tunable laser produces laser emission at at least two wavelengths simuleously. The tunable laser includes at least two gain elements, where each gain element generates a different wavelength. Means for optically exciting each laser gain element is appropriately disposed for either end pumping or side pumping to produce a laser emission within a preselected range of wavelengths. A wavelength dispersing element such as a prism is disposed in the laser resonator cavity for dispersing the wavelengths operating simultaneously within the laser resonator cavity and to create separate regions for each laser gain element. Laser gain elements may be tunable laser gain elements or discrete emitting laser gain elements. Arbitrarily large wavelength separations between the wavelengths operating simultaneously may be achieved in this manner producing stable cw or pulsed output, Q-switched or line narrowed depending on the means disposed within the laser resonator cavity.

Abstract: A laser comprises an upconversion laser gain element made of a crystalline xide host doped with activator ions for emitting output radiation at an output wavelength. The gain element is pumped by pumping radiation at a pumping wavelength that is longer than the output wavelength. A laser resonator comprising a reflective element and an output coupler is arranged with the gain element to resonate the output radiation. The reflective element is spaced from the output coupler by a distance approaching the radius of curvature of the reflective element or the output coupler. The pumping radiation has a waist that is substantially coincident with the waist of the output radiation within the active region of the gain element.

Abstract: A laser produces laser emission at two or more wavelengths simultaneously. he laser includes at least two gain elements, and each gain element generates a different wavelength. A single optical pumping source is used for optically exciting all laser gain elements contained within the laser resonator cavity. A wavelength dispersing element such as a prism is disposed in the laser resonator cavity for dispersing the wavelengths operating simultaneously within the laser resonator cavity and to create separate regions for each laser gain element. Laser gain elements may be tunable laser gain elements or discretely emitting laser gain elements. Arbitrarily large wavelength separations between the wavelengths operating simultaneously may be achieved in this manner to produce stable cw or pulsed output, which may be Q-switched or line narrowed. Intracavity sum frequency generation can be produced efficiently by using a non-linear sum frequency generating crystal disposed at a laser resonator cavity waist.

Abstract: A method and apparatus for producing stimulated emission from a laser gain element containing an organic dye are described in which optical pumping is produced by visible laser diodes. Low threshold pump power and high optical conversion efficiency are achieved by producing a laser resonator mode waist at or near the laser gain element and spatially superimposing a pump mode waist at or near the laser resonator mode waist. Using low power visible AlGaInP laser diodes and the dyes rhodamine 700, oxazine 750, DOTCI or oxazine 1 in the laser gain element, incident pump threshold powers as low as 5.4 mW, optical conversion efficiencies of 49% and tunable emission between 700 nm and 800 nm were achieved. This laser was scaled to higher cw output power by using a DCM-based pump dye laser. In a preferred embodiment the laser resonator has two reflective elements in a nearly hemispherical configuration. Angular multiplexing of laser diodes to scale to higher laser diode pump power is described.

Abstract: A laser is end pumped by laser diodes and is repetitively Q-switched using an intracavity variable speed moving aperture. The aperture apparatus includes a precision motor which drives a pair of matched aperture blades and produces efficient Q-switched operation over a wide range of output powers and repetition rates. Each aperture blade may contain an identical number of transmissive and opaque regions, and two aperture blades may be mounted onto the motor in a manner that allows continuous adjustment of the aperture width. In a preferred embodiment the aperture blades are shaped as circular discs. The laser resonator mode is nearly hemispherical, and the aperture blade is located at or near the laser resonator mode waist. When pumped with the optimum pump flux, efficient repetitively Q-switched operation is obtained as long as the Q-switch opening time is shorter than the pulse build-up time.

Abstract: A tunable laser produces laser emission at at least two wavelengths simuleously. The tunable laser includes at least two gain elements, where each gain element generates a different wavelength. Means for optically exciting each laser gain element is appropriately disposed for either end pumping or side pumping to produce a laser emission within a preselected range of wavelengths. A wavelength dispersing element such as a prism is disposed in the laser resonator cavity for dispersing the wavelengths operating simultaneously within the laser resonator cavity and to create separate regions for each laser gain element. Laser gain elements may be tunable laser gain elements or discrete emitting laser gain elements. Arbitrarily large wavelength separations between the wavelengths operating simultaneously may be achieved in this manner producing stable cw or pulsed output, Q-switched or line narrowed depending on the means disposed within the laser resonator cavity.

Abstract: A frequency agile laser illuminates a scene with floods of emissions of different wavelengths. As the wavelengths, or laser color changes, certain objects will stand out with respect to their background so that detection and recognition is enhanced to permit appropriate action. This technique has application in the location of underwater objects.

Abstract: An apparatus for producing rapidly modulated coherent optical emission is described in which a doubly resonant cavity produces amplitude modulated sum frequency generation. The configuration of the resonator provides a region where both fundamental wavelengths are overlapped and another region where both fundamental wavelengths are spatially distinct. The resonator further contains a laser gain element in the other region where the wavelengths are spatially distinct to produce one of the two fundamental resonant wavelengths. A laser source injects a signal into the resonator at the other resonant wavelength. The injected wavelength is at or near a wavelength for which the laser gain element can be optically pumped. In one embodiment, one laser both injects a signal into the resonator and simultaneously pumps the laser gain element contained within the resonator cavity. The resonator further contains a nonlinear crystal for intracavity sum frequency generation of the two fundamental wavelengths.

Abstract: A means for intracavity sum frequency generation is described in which a er operates simultaneously, cw, at two wavelengths where the net gain at one wavelength is substantially lower than that at the other. The optical alignment of the resonator provides a region where both fundamental wavelengths are overlapped, and another region where both feedback paths are spatially distinct. An active feedback mirror is located in the path of the lower net gain laser transition to provide optical amplification at that wavelength. The laser resonator further contains a sum frequency generating crystal for intracavity sum frequency generation of the two fundamental wavelengths. The sum frequency generating crystal is placed near a laser resonator cavity mode waist in the region where both wavelengths are spatially superimposed, producing the sum frequency of the two wavelengths.

Abstract: A means for intracavity sum frequency generation is described in which a laser operates simultaneously at two wavelengths. The laser resonator further contains a sum frequency generating nonlinear crystal which is oriented for efficient sum frequency generation of the two fundamental wavelengths. The optical alignment of the resonator provides a region where both fundamental wavelengths are overlapped and are focused. The nonlinear sum frequency generating crystal is placed near this focus in the region where both wavelengths are spatially superimposed, producing the sum frequency of the two wavelengths. Line narrowing of the individual two fundamental wavelengths produces a line narrowed sum frequency generated output. Mirror coatings on all reflective elements are highly reflective for both fundamental wavelengths to produce a high intracavity fluence at both of these frequencies.

Abstract: A tunable laser is described in which the gain element is fabricated to produce wavelength dispersion within the laser resonator cavity. Specifically, the laser gain element has Brewster angled entrance and exit faces which allow it to operate as a wavelength dispersive element while simultaneously performing the functions of an optical gain element within a laser cavity. Wavelength tuning is effected by angular rotation of one of the end reflective elements in the cavity. By using suitable dispersive materials for the laser gain element no additional tuning elements are required providing high efficiency, low threshold laser operation for a variety of optical excitation methods. The laser gain element replaces other discrete intracavity laser tuning means required for tunable lasers, including prisms, diffraction gratings, and birefringent filter elements.

Abstract: Efficient, low threshold laser emission from a laser crystal doped with chromium and neodymium ions is obtained when pumped by visible laser diodes in the range of 610 nm to 680 nm. A typical laser Cr,Nd:GSGG crystal having an extraordinarily broad absorption bandwidth allows high pump efficiencies when using visible laser diodes, particularly in comparison to the Nd:YAG laser. The broad absorption bandwidth tolerance of the Cr,Nd:GSGG crystal to the pumping wavelengths allows visible diode pumping of the neodymium transition without regard to the wavelength of the visible diodes. Longitudinal or end-pumping to take advantage of the emission properties of the visible laser diodes, a nearly hemispherical laser resonator configuration and other co-doped Cr,Nd laser host materials are disclosed. Consequently, costs are reduced for the semiconductor pump as well as producing a compact, efficient, lightweight and reliable laser previously unachievable with other types of laser or lamp pumping.

Abstract: A tunable solid state laser produces a laser emission at one or more wavelengths simultaneously. The tunable solid state laser includes a laser resonator defined by an output coupler reflective element, two fold mirrors, and one or more high reflectivity end elements to form a reflective path in a laser resonator cavity therebetween with a laser crystal disposed in the laser resonator cavity. A means for optically exciting the laser crystal is appropriately disposed for end pumping the laser crystal to produce a laser emission in a predetermined range of wavelengths. A wavelength dispersing element such as a prism is disposed in the laser resonator cavity between one of the fold mirrors and the high reflectivity end elements for tuning the laser emission at one or more of the desired wavelengths in the predetermined range of wavelengths, the dispersing element being transparent to the laser emission over the predetermined range of wavelengths.

Abstract: An internally folded scalable laser has a gain medium with an internal face nd an external face and at least one internal-fold face subtending an angle which may be about 90.degree.. An output coupler that is partially reflective of the resonator mode is oriented to receive and reflect resonator mode in a direction normal to the internal face to avoid resonator mode astigmatism and to define a folded hemispherically-shaped resonator cavity extending from the output coupler and through an active volume in the gain medium to the external face. A pumping mode source disposed adjacent to the external face is oriented to focus a first pumping mode in a direction normal to the external face in a boom waist at or inside the external face in the folded resonator cavity to define an active volume in the gain medium and to avoid pumping mode astigmatism.

Abstract: A laser having a Cr.sup.3+ doped Colquiriite mineral host gain element, such as Cr:LiCAF, Cr:LiSAF or Cr:LiSGAF, is pumped by the pumping beam from at least one visible laser diode to provide tunable laser emission. TheSTATEMENT OF GOVERNMENT INTERESTThe invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.