The United States of America As Represented by the United States

United States Enrichment Corporation

Other

Jim J Chang

Bruce E Warner

Ernest P Dragon

Terry W Alger

Luis E Zapata

Isaac Louis Bass

A method and apparatus for micromachining and microdrilling which results in a machined part of superior surface quality is provided. The system uses a near diffraction limited, high repetition rate, short pulse length, visible wavelength laser. The laser is combined with a high speed precision tilting mirror and suitable beam shaping optics, thus allowing a large amount of energy to be accurately positioned and scanned on the workpiece. As a result of this system, complicated, high resolution machining patterns can be achieved. A cover plate may be temporarily attached to the workpiece. Then as the workpiece material is vaporized during the machining process, the vapors condense on the cover plate rather than the surface of the workpiece. In order to eliminate cutting rate variations as the cutting direction is varied, a randomly polarized laser beam is utilized. A rotating half-wave plate is used to achieve the random polarization. In order to correctly locate the focus at the desired location within the workpiece, the position of the focus is first determined by monitoring the speckle size while varying the distance between the workpiece and the focussing optics. When the speckle size reaches a maximum, the focus is located at the first surface of the workpiece. After the location of the focus has been determined, it is repositioned to the desired location within the workpiece, thus optimizing the quality of the machined area.

Method and apparatus for precision laser micromachining

A new, compact, side-pumped laser pump cavity design which uses non-conventional optics for injection of laser-diode light into a laser pump chamber includes a plurality of elongated light concentration channels. In one embodiment, the light concentration channels are compound parabolic concentrators (CPC) which have very small exit apertures so that light will not escape from the pumping chamber and will be multiply reflected through the laser rod. This new design effectively traps the pump radiation inside the pump chamber that encloses the laser rod. It enables more uniform laser pumping and highly effective recycle of pump radiation, leading to significantly improved laser performance. This new design also effectively widens the acceptable radiation wavelength of the diodes, resulting in a more reliable laser performance with lower cost.

Compact and highly efficient laser pump cavity

A new material processing apparatus using a short-pulsed, high-repetition-rate visible laser for precision micromachining utilizes a near diffraction limited laser, a high-speed precision two-axis tilt-mirror for steering the laser beam, an optical system for either focusing or imaging the laser beam on the part, and a part holder that may consist of a cover plate and a back plate. The system is generally useful for precision drilling, cutting, milling and polishing of metals and ceramics, and has broad application in manufacturing precision components. Precision machining has been demonstrated through percussion drilling and trepanning using this system. With a 30 W copper vapor laser running at multi-kHz pulse repetition frequency, straight parallel holes with size varying from 500 microns to less than 25 microns and with aspect ratios up to 1:40 have been consistently drilled with good surface finish on a variety of metals. Micromilling and microdrilling on ceramics using a 250 W copper vapor laser have also been demonstrated with good results. Materialogroaphic sections of machined parts show little (submicron scale) recast layer and heat affected zone.

Apparatus for precision micromachining with lasers

Several different cold cathode configurations for a gas discharge device each having a plurality of grooves of selected spacing, depth and width to improve the emission of electrons in a gas discharge device. Each of the cold cathode configurations can be machined from a single piece of a selected material. Several of the configurations can be assembled with individual elements which is easily seen from the various figures.

Hollow - cathode electrode for high-power, high-pressure discharge

A new injection-controlled laser resonator incorporates self-filtering and self-imaging characteristics with an efficient injection scheme. A low-divergence laser signal is injected into the resonator, which enables the injection signal to be converted to the desired resonator modes before the main laser pulse starts. This injection technique and resonator design enable the laser cavity to improve the quality of the injection signal through self-filtering before the main laser pulse starts. The self-imaging property of the present resonator reduces the cavity induced diffraction effects and, in turn, improves the laser beam quality.

Growing community of inventors

Dublin, CA, United States of America

Jim J Chang