MULTI-STAGE MOPA WITH FIRST-PULSE SUPPRESSION

摘要

A solid-state MOPA includes a mode-locked laser delivering a train of pulses. The pulses are input to a fast E-O shutter, including polarization-rotating elements, polarizing beam-splitters, and a Pockels cell that can be driven alternatively by high voltage (HV) pulses of fixed long and short durations. A multi-pass amplifier follows the E-O shutter. The E-O shutter selects every Nth pulse from the input train and delivers the selected pulses to the multi-pass amplifier. The multi-pass amplifier returns amplified seed-pulses to the E-O shutter. The shutter rejects or transmits the amplified pulses depending on whether the HV-pulse duration is respectively short or long. Transmitted amplified pulses are delivered to a transient amplifier configured for separately suppressing first-pulse over-amplification and residual pulse leakage.

主权项

1. Optical apparatus comprising:
a mode-locked laser delivering a first train of pulses at a first pulse-repetition frequency (PRF); at least one transient optical amplifier having a solid-state gain-element optically pumped by radiation output from a diode-laser array for energizing the gain-element, the diode laser array having selectively variable output power; a multi-pass optical amplifier; an optical shutter arranged to select pulses from the first train thereof to provide a second train of pulses at a second PRF less than the first PRF, provide the selected pulses to the multi-pass amplifier to be amplified, receive a corresponding train of amplified pulses from the multi-pass amplifier and selectively transmit a plurality of pulses from the train of amplified pulses to the transient optical amplifier for further amplification, with pulses in the plurality thereof having about equal amplitude; wherein the diode-laser array power is set at a first level when amplified pulses are not being received to maintain about constant thermal lensing in the gain-element, set at a second level lower than the first level for a predetermined first time period in response to the plurality of pulses being selected for depleting stored energy in the gain-element, and set to a third level higher than the first level for a second time period prior to the arrival of the plurality of amplified pulses from the optical shutter to restore stored energy in the gain-element, with the first and second time periods being selected such that, when further amplified, all further-amplified pulses in the plurality thereof have about equal amplitude; and wherein the transient amplifier has a laser resonator including the gain-element, the laser-resonator generating CW radiation in response to the first-level pumping when amplified pulses are not being further amplified.