Quasi-CW UV laser with low peak pulse-power
AssigneeCoherent, Inc.
InventorsLuis A. Spinelli, Sergei V. Govorkov, R. Russel Austin
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Abstract
Laser apparatus is disclosed in which fundamental-wavelength optical pulses delivered from a mode-locked laser resonator at a pulse-repetition frequency (PRF) are converted to harmonic-wavelength pulses in an optical delay loop. One example is disclosed in which the harmonic-wavelength pulses are delivered directly from the delay loop. Another example is disclosed in which the harmonic-wavelength pulses are divided by the delay loop into a number of temporally spaced-apart replicas thereof, and the delay loop delivers bursts of replicas of different one of the harmonic wavelength pulses at a burst-repetition frequency equal to or a multiple of the PRF of the resonator.
Claims15
Laser apparatus comprising:
- a laser-resonator arranged to deliver fundamental-wavelength optical pulses having a pulse-duration, the fundamental-wavelength optical pulses being temporally equispaced by a pulse-repetition period τ and delivered at a pulse-repetition frequency (PRF) equal to 1/τ;
- and
- an optical delay loop including one or more optically nonlinear crystals and arranged to receive the fundamental-wavelength optical pulses, the optical delay loop being configured and arranged such that each fundamental-wavelength pulse is converted within the optical delay loop into a harmonic-wavelength pulse and further arranged to convert each of the harmonic-wavelength into a plurality of replicas thereof, with the replicas of each harmonic-wavelength pulse being temporally spaced apart by about τ/N where N is an integer equal to or greater than 2.
An optical delay loop for receiving pulses of laser light at a first wavelength comprising:
- a plurality of mirrors, wherein a first of said mirrors is partially transmissive to said first wavelength and arranged to receive the pulses of light, said mirrors being positioned to circulate the light pulses about a loop;
- and
- at least one non-linear crystal within the loop for converting the first wavelength of light to a second wavelength and wherein either said first mirror or a second mirror is partially transmissive to the second wavelength whereby the pulses of second wavelength laser light are divided into a plurality of pulse replicas exiting the loop through said mirror which is partially transmissive to said second wavelength.
A method of converting the wavelength of light of pulses in a train of pulses of laser light having a first wavelength and a first repetition rate and reducing the peak power of the converted pulses while substantially maintaining the average power of the train of converted pulses, said method comprising the steps of:
- directing the train of pulses into a delay loop, said delay loop having at least one non-linear crystal therein, said crystal for converting the first wavelength light into second wavelength light;
- and
- generating a plurality of replica pulses of second wavelength light which exit the delay loop in a train having a higher pulse repetition rate than the first repetition rate and wherein the pulses have a lower peak power than the initial pulses in the train.
A method as recited in 10, wherein the pulse replicas exit the delay loop along a common path.
Dependencies are inferred from the claim text.