Coherent light generators – Particular temperature control – Heat sink
Reexamination Certificate
1998-07-09
2001-09-18
Leung, Quyen (Department: 2881)
Coherent light generators
Particular temperature control
Heat sink
C372S107000, C372S109000
Reexamination Certificate
active
06292499
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to optical systems and, more particularly, to a method and apparatus for mounting various optical components to an optical bench.
BACKGROUND OF THE INVENTION
In designing a typical optical system, the various optical components must be aligned to each other with positional tolerances on the order of sub-micrometers. Conventional systems use adjustable mounts that allow the position of the optical component to be adjusted after the component has been mounted to the optical bench. Unfortunately, such optical mounts are typically quite large and, due to their mechanical complexity, relatively expensive. Furthermore, once the optical component has been correctly located, it is typically difficult to lock the component into place, thereby preventing undesired component movement.
A variety of systems have been designed to precision align and bond optical components. For example, U.S. Pat. No. 4,749,842 discloses a method of mounting the lasant material in a laser ring resonator. As disclosed, the lasant material is first mounted to a thermally conductive block using an optical adhesive. The conductive block is soldered to the face of a heater, the heater bonded to a thermally insulative support structure. In order to optically align the lasant material, the heater raises the temperature of the solder to its softening point, allowing the position of the lasant material to be changed prior to the resolidification of the solder. The heater also can be used to maintain the lasant material at an elevated temperature, thus allowing the output wavelength of the laser to be thermally tuned.
U.S. Pat. No. 4,944,569 discloses a method of sequentially aligning optical fibers in a multi-fiber optoelectronic package. As disclosed, each fiber is individually mounted within a fiber block, the fiber blocks being soldered to a carrier platform. During alignment, the temperature of the carrier is sufficiently raised to cause the solder to soften. Once softened, the first fiber block and its captured fiber are optically aligned. After the first fiber block is aligned, the solder underlying the aligned fiber block is cooled past its solidification point with a thermoelectric cooler mounted underneath the carrier. By positioning thermoelectric coolers under each fiber block mounting location, the solder underlying each fiber block may be individually solidified, thus allowing the fibers to be selectively coupled and uncoupled from the carrier platform.
U.S. Pat. No. 5,170,409 discloses a low cost resonator assembly that is relatively easy to align and assemble. The system utilizes UV transparent mirror mounts. Mirrors are bonded to the mounts and the mounts are bonded to a support plate using a UV curable adhesive. Until the adhesive is subjected to UV radiation it remains viscous, thus allowing the mirrors as well as the mirror mounts to be continually adjusted until they are properly aligned. Once aligned, UV radiation is directed through the support plate to bond the mirror mounts and through the mirror mounts to bond the mirrors in place.
U.S. Pat. No. 5,329,539 discloses a compact solid state laser system that includes a laser diode pump, a laser gain medium, and various optical components. The diode pump and the laser gain medium each have individually controllable thermoelectric coolers that can be used to align and thermally tune the components. The optical platform that supports these components as well as the remaining laser system optical components is made of a thermally conductive, electrically non-conductive material that exhibits low thermal expansion. The bottom surface of the platform includes a plurality of individually controllable resistive heaters, the heaters being positioned immediately below solder pads on the top surface of the platform. The optical components of the laser system are positioned on the individual solder pads. Through the independent activation of the heater pads, individual components may be optically aligned and then soldered into place.
Although a variety of optical mounts have been designed, primarily for use with miniature optical components, an optical mount that can be used to easily and semi-permanently mount an optical component to an optical bench is desired.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for mounting components to an optical bench such that the components can be easily detached, realigned, and remounted. Components that can use the mount include, but are not limited to, mirrors, output couplers, windows, filters, lenses, optical fibers, nonlinear crystals, passive Q-switches, active Q-switches, piezoelectric elements, apertures, laser gain media, and detectors.
In one aspect of the invention, the optical component is mounted to an upright portion of the mount. The upright portion of the mount is preferably mounted to the base portion using solder although other coupling techniques can be used. The base portion includes a heater, such as a resistive heater, which can be used to solder the base plate to the optical bench. Alternately, the base plate can be bonded to the bench, the heater providing heat to cure the adhesive. Assuming the former approach, repositioning the mount is simply a matter of melting the solder with the base plate heater, repositioning the mount, and deactivating the heater. Deactivation of the heater causes the solder to solidify, thus re-coupling the mount to the bench.
In another aspect of the invention, both the base plate and the upright are fabricated from a ceramic material such as alumina. Due to the stiffness of such materials the mount has a high natural frequency, thus reducing the susceptibility of the mount to vibration. Additionally, if solder is used to couple the upright to the base and the base to the bench, the solder will quickly dampen any mount vibrations. Furthermore, due to the electrically insulating properties of the ceramic, the electrical connections to the heater are simplified. Lastly, the thermal properties of the ceramic base plate are used in the performance optimization of the heater.
In one embodiment of the invention, the upright is soldered to the base plate, the solder acting as part of the electrically conductive coupling between a pair of electrical connectors mounted on the upright and a pair of conductive pads attached to the resistive heater. The electrical connectors on the upright provide an easy means of applying a voltage to the resistive heater. Preferably the solder coupling the upright to the base plate has a higher melting point than the solder coupling the base plate to the optical bench. This allows the mount assembly to be completed prior to locating and soldering the mount to the bench. Additionally, the different melt temperatures allow the mount to be repositioned without causing the decoupling of the upright/base plate union.
In another aspect of the invention, a mounting tool is provided. The mounting tool grasps the mount with a pair of arms, the arms designed to hold the mount without blocking access to the optical component. Preferably the two arms of the mounting tool are electrically isolated from one another and are designed to contact the pair of electrical connectors on the upright. In use, the tool grasps the mount, applies sufficient voltage to the heater to melt the base plate mounting solder, positions the mount in the desired location, and deactivates the power source. After the solder has solidified thereby coupling the base to the mounting surface, the mounting tool can be released.
A further understanding of the nature and advantages of the present invention may be realized by reference to the remaining portions of the specification and the drawings.
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patent: 4079404 (1978-03-01), Comerford et al.
patent: 4635093 (1987-01-01), Ross
patent: 4731795 (1988-03-01), Clark et al.
patent: 4749842 (1988-06-01), Kane et al.
patent: 4752109 (1988-06-01), Gordon et al.
patent: 4807956 (1989-02-01), Tournereau et al.
patent: 4904036 (1990-02-01), B
Kulesa Larry B.
Pearson Leonard P.
Shannon David C.
Smith Diane E.
Aculight Corporation
Beck David G.
Leung Quyen
McCutchen Doyle Brown & Enersen LLP
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