G.A.J. Markillie

Effect of vaporization and melt ejection on laser machining of silica glass micro-optical components

A new regime for silica glass machining for micro-optical fabrication applications, which uses pulsed CO2 laser radiation in the 2.5-100-micros pulse width region that has been generated by an acousto-optic modulator, is investigated. A filamentary melt ejection process that generates fibers and significant melt displacement limits machining quality below 30-micros pulse width. Ablation and melt ejection thresholds are quantified relative to pulse width, and the region from 30 to 50 micros is identified for low-threshold, smooth machining without melt displacement and ejection effects.

Spatially resolved measurement of the electrical properties of the rf discharge in a fast-axial-flow laser with a rectangular cross section

A measurement procedure is reported for the power density, internal current density and plasma voltage along the flow direction of a discharge section of a fast-axial-flow laser. The rf discharge has a rectangular cross section and a narrow electrode gap for operation at high pressure. Both cw and time resolved pulsed measurements have been made.

Applications of new enhanced-pulse planar waveguide lasers in electronic substrate processing

Summary form only given. We have developed a new laser technology capable of peak/average power ratios of >35, and a /spl times/10 reduction in pulse duration, with no reduction in average power. This laser incorporates improved radiofrequency discharge stabilisation techniques permitting efficient pulsed electrical power transfer and the achievement of homogeneous laser-gain media at very high input power densities (/spl sim/800W/cm/sup -3/), corresponding to input peak power levels of 24 kW at elevated gas pressures (>200 Torr). We report the application of this new enhanced-pulse planar waveguide laser for the machining of electronic PCB substrate materials, including organic resins, metal foils, glasses and ceramic substrates.

High peak power CO2 planar waveguide lasers for direct high resolution machining

The peak power and gain available from the RF excited planar waveguide CO2 laser has been enhanced for pulses in the 10 to 100 ?s range at pulse repetition rates up to 4 kHz. The specific peak power output for unit electrode area has been enhanced to a value of240 kW.m-2 . Relative to cw, the small signal gain coefficient has been pulse enhanced by a factor of 7 to 2.5 m-1

Rapid prototyping of refractive micro-optics using slab waveguide CO/sub 2/ lasers

Summary form only given. This paper explores methods of improving the glass machining capabilities of sealed-off, pulsed RF, slab waveguide CO/sub 2/ lasers. Such devices offer a wide range of pulse durations (/spl tau//sub p/), pulse repetition frequencies (PRFs) and peak powers. In quartz and soda lime glass, the 10.6 /spl mu/m laser wavelength has an absorption depth of a few microns and a reflection coefficient of /spl sim/10%. This enables rapid prototyping of inexpensive refractive micro-optics with machining rates ranging from 10 to 50 /spl mu/m per shot. In a preliminary study, we successfully machined a cylindrical refractive micro-lens using a commercially available CO/sub 2/ slab waveguide laser.

Ultra super pulse CO/sub 2/ planar waveguide laser for direct micro-machining

Summary form only given. Planar waveguide CO/sub 2/ lasers have become the preferred technology for many material processing applications because of their practical advantages in terms of high average power levels, pulsed operation at high repetition rates, excellent beam quality, ultracompact, scaled device construction and ease of computer control. We describe the performance of a planar waveguide laser, which is designed to produce short duration, high energy pulses at high repetition rates.

Electrical properties of narrow-gap slab rf discharges in a high-pressure fast-axial-flow CO2 laser

High pressure operation of a fast-axial-flow CO2 laser, with a rectangular cross-section RF slab discharge is demonstrated in both cw and pulsed modes. Spatially resolved measurements of discharge power densities give good agrement with total input powers while calculated values of sheath thickness correspond with visual observations of the gas discharge. Variations in power density and sheath thickness along the gas flow axis are interpreted in terms of pressure gradients and gas flow choking within the discharge.