An exposure apparatus has a laser device that is small, easy to maintain, and
capable of producing an output that is unlikely to be affected by optical surges
occurring in the beginning of operation. A single-wavelength laser oscillator (11)
supplies a laser beam (LB1) to a fiber optic amplifier (13) through
an optical modulator (12). The amplified laser beam is split by splitters
(14, 16-1 to 16-m), amplified by optical amplifier
units (18-1 to 18-n) and supplied through a fiber bundle
(19) to a wavelength converter (20), which in turn converts the split
beams into ultraviolet laser radiation (LB5) for use as exposure light.
The optical modulator (12) outputs light pulses during the generation of
ultraviolet light. The optical modulator (12) also produces laser radiation
during the absence of ultraviolet light, but the laser radiation has substantially
the same average output and a considerably low peak compared with that during the
generation of ultraviolet light.
