Questek, Inc.

Gary K Klauminzer

Steven N Bittenson

George F Caudle

S Spencer Merz

James D Campbell

An excimer laser including a discharge chamber containing a mixture of halogen, rare gas and buffer gas uses two gas sources to replenish the halogen in the discharge chamber while maintaining the concentrations of all the gases at the optimum levels. One of the gas sources, source A, contains a mixture of the rare gas and the buffer gas in optimum concentrations. The other gas source, source B, contains both the rare gas and the buffer gas, in optimum relative concentrations, and also the halogen, in a concentration which is greater than optimum. As the laser operates and the gain of the laser decreases due to halogen depletion, gas from source B is injected into the discharge chamber to raise the halogen concentration. Gas is then released from the chamber to reduce the chamber pressure to the original level. When halogen replenishment does not suffice to restore the laser gain, due to the build-up of contaminants in the chamber, a portion of chamber gas is released and it is replenished with fresh gas from both sources in proportions adequate to provide optimum concentrations of the various gases.

Excimer laser output control device

A laser unit, including an optical power measuring device, measures, as the beam sample, a portion of the laser beam that is reflected out of the laser beam path by a wedge shaped front mirror, that is, an optical wedge. The front mirror has two surfaces, a partially reflective surface which reflects a portion of the beam back into the laser cavity and a nominally non-reflecting surface which permits a portion of the beam to exit the laser. The non-reflecting surface does in fact reflect some energy and, because of the wedge shape of the mirror, this energy is directed away from the laser beam path. The intensity of this off-path reflection is measured to determine the laser output power.

Laser output power measuring method and apparatus

In a pulsed laser which is periodically energized so that it emits a pulse of radiation following each periodic energization, a feedback loop control system is provided for controlling energization of the laser so that the laser output radiation pulses are substantially constant over a relatively long period of operation, the feedback loop including a detector for detecting the laser pulses and producing an electrical signal representative of each pulse and a comparing circuit responsive to those electrical signals and a reference signal that represents the constant laser output level desired, for comparing the electric signals and the reference signals producing a control signal for controlling the energy of the periodic energization.

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Lexington, MA, United States of America

Gary K Klauminzer