Coherent light generators – Particular active media – Gas
Reexamination Certificate
2001-05-04
2003-11-04
Ip, Paul (Department: 2828)
Coherent light generators
Particular active media
Gas
C372S045013, C372S093000, C372S094000
Reexamination Certificate
active
06643313
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to laser devices, and more particularly to compact lasers suitable for portable applications.
BACKGROUND OF THE INVENTION
One area of science that offers significant size advantages, while overcoming the limitations of reducing the number and size of conventional parts is microelectromechanical systems (MEMS). MEMS, or the closely related field of microoptoelectromechanical systems (MOEMS), refers to systems that combine electrical and mechanical components, including optical components in the case of MOEMS, into a package that is physically very small. These systems are generally fabricated using integrated circuit fabrication techniques or similar techniques such as surface micromachining, bulk micromachining and reactive ion etching (RIE). For example, using MEMS/MOEMS, various transducers, resonators, and mirrors have been built that occupy sizes that are generally measured in terms of microns or millimeters. The degree of complexity of a given MEMS/MOEMS article depends on the number of movable levels or planes that the fabrication technique provides. MEMS/MOEMS techniques have not been applied to gas laser fabrication.
Conventional carbon dioxide lasers are large, cumbersome, and are difficult to package, particularly for portable applications. Even folded waveguide designs, such as the laser device disclosed in U.S. Pat. No. 5,610,936 to Cantoni, is too large to be useful for virtually all portable applications, being at least approximately 15-20 centimeters in length.
Accordingly, it would be desirable to provide a more compact laser device which can still deliver reasonably high output power. A MOEMS laser could allow construction of a laser device occupying a fraction of the size required for existing lasers. If a method could be devised for fabricating a MOEMS laser, such a laser would offer substantially reduced size and weight. Moreover, such a device would be more precise and cost effective due to advantageous manufacturing processes similar to those used for fabrication of microelectronics. Moreover, a MOEMS laser device could provide increased reliability and lower cost due to the ability to fabricate a highly compact waveguide substrate having a plurality of narrow folded waveguide paths, or preferably be used to fabricate a monolithic highly compact laser system on a single die of a bulk substrate material.
SUMMARY OF THE INVENTION
A laser device includes a waveguide substrate having a plurality of intersecting folded waveguide paths, the plurality of folded waveguide paths having widths of no more than approximately 1 mm, the folded waveguide paths having a surface area to volume ratio of at least 4 mm
−1
. The folded waveguide paths can have widths of no more than approximately 0.5 mm, or from approximately 10&mgr; to 0.5 mm.
The laser device can further include a re-entrant cavity adapted for substantially surrounding and sealing the sides and bottom of the waveguide substrate, and at least one plate layer disposed on the waveguide substrate. The laser can further include an electrode array disposed on the at least one plate layer, the electrode array including a plurality of conductive traces adapted for alignment with the plurality of folded waveguide paths. At least one plate layer can be formed from a material selected from the group consisting of Al
2
O
3
and BeO.
The laser device can further include a bulk substrate material having a plurality of die, the waveguide structures are formed on the bulk substrate material. The bulk substrate material can be used to form the waveguide substrate. The laser can further include a RF oscillator, wherein the RF oscillator is formed on the die, the RF oscillator adapted for electrically pumping the laser. The laser can further include at least one lasing material selected from the group of gases consisting of CO
2
, CO and N
2
O. Preferably, the lasing material is CO
2
.
The bulk substrate material can be selected from the group consisting of Al
2
O
3
, BeO and Si. The laser can further include a pair of mirrors attached to substantially opposing ends of the waveguide substrate.
A method for forming a laser device includes the steps of providing a waveguide substrate, forming a folded waveguide structure from a plurality of intersecting folded waveguide paths formed in the waveguide substrate, the folded waveguide paths having widths of no more than approximately 1 mm, the folded waveguide paths having a surface area to volume ratio of at least 4 mm
−1
. The folded waveguide paths can have widths of no more than approximately 0.5 mm, or from approximately 10&mgr; to 0.5 mm.
The method for forming a laser device can further include the steps of providing a re-entrant cavity, placing the waveguide substrate into the re-entrant cavity, providing at least one plate layer, and sealing at least one plate layer on top of the plurality of folded waveguide paths. At least one plate layer can include an electrode array thereon, the electrode array having conductive traces aligned to substantially match the plurality of folded waveguide paths. The method can further include the step of providing a bulk substrate material having a plurality of die, wherein a plurality of the folded waveguide structures are formed on the bulk substrate material. The bulk substrate material can be used as the waveguide substrate. The bulk substrate material can be selected from the group consisting of Al
2
O
3
, BeO and Si.
The method can be made monolithic by including the steps of coating the plurality of die with at least one coating layer onto the walls of the folded waveguide paths to reduce intracavity waveguide path losses, forming at least one plate layer on the plurality of die, the at least one plate layer positioned on top of the plurality of folded waveguide paths, and forming mirrors on the plurality of die, the mirrors positioned on substantially opposite ends of the laser. The method can further include the step of forming a conductive electrode array having a plurality of conductive traces on the plurality of die, the electrode array positioned on at least one of the plate layers, the plurality of conductive traces substantially aligned with the folded waveguide paths. The method can further include the step of forming an RF power supply on the plurality of die.
The laser can be used for many applications, but is particularly useful for portable applications due to its small size. For example, the laser can processing electromagnetic signals including, but not limited to, LIDAR, communication systems, chemical detection and military target designators.
REFERENCES:
patent: 3361987 (1968-01-01), De Maria
patent: 4815094 (1989-03-01), Cantoni
patent: 4870654 (1989-09-01), Cantoni et al.
patent: 5031190 (1991-07-01), Behfar-Rad
patent: 5097479 (1992-03-01), Opower
patent: 5132983 (1992-07-01), Behfar-Rad
patent: 5231642 (1993-07-01), Scifres et al.
patent: 5241555 (1993-08-01), Spitzer
patent: 5271031 (1993-12-01), Baer
patent: 5610936 (1997-03-01), Cantoni
patent: 5746513 (1998-05-01), Renken
patent: 6038076 (2000-03-01), Bouzid et al.
patent: 6155490 (2000-12-01), Ackley
Akerman & Senterfitt
Ip Paul
Nguyen Tuan
UT Battelee, LLC
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