Multi-stage mopa with first-pulse suppression
a mopa system and multi-stage technology, applied in the direction of laser details, excitation process/apparatus, laser details, etc., can solve the problems of increasing the cost and complexity of the fast process shutter of such a mopa system, and achieve the effect of restoring stored energy and selecting the output power
Active Publication Date: 2015-03-12
COHERENT KAISERSLAUTERN
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Benefits of technology
The present invention is about an optical apparatus that generates a second train of pulses with a lower repetition frequency than the first train. The apparatus includes a mode-locked laser, a transient optical amplifier, and a multi-pass optical amplifier cooperative with an optical shutter. The apparatus can selectively transmit a plurality of pulses from the second train for further amplification. The diode-laser array power is set at a lower level to maintain constant thermal lensing in the amplifier during the first time period and at a higher level to restore stored energy in the amplifier before the arrival of the plurality of amplified pulses. The apparatus can generate CW radiation in response to the first-level pumping when amplified pulses are not being further amplified. The technical effect of this invention is to provide a more efficient and stable optical apparatus for generating high-quality pulses with controlled properties.
Problems solved by technology
The fast process shutter adds significant cost and complexity to such a MOPA system.
Method used
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[0015]Referring now to the drawings, wherein like components are designated by like reference numerals, FIG. 1 schematically illustrates a master oscillator and power amplifier (MOPA) 10 in accordance with the present invention. MOPA 10 includes a mode-locked master oscillator (seed-pulse laser) delivering a train of pulses at a first pulse-repetition frequency (PRF). The first PRF is determined by the resonator length of the seed-pulse laser and may be between about 10 and 200 MHz. A preferred seed-pulse laser is a mode-locked neodymium-doped yttrium vanadate (NdYVO4) laser providing seed-pulses of 10 picoseconds duration and pulse-energy of about 10 nanojoules (nj) at a PRF of 50 MHz. The seed-pulses are designated in FIG. 1 and other drawings by small non-barbed arrowheads.
[0016]The train of pulses from seed-laser 12 is directed by a front-surface polarizer (polarizing beam-splitter) 14 into a fast double-pass electro-optical (E-O) shutter 16. Shutter 16 is activated and deactiva...
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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.
Description
TECHNICAL FIELD OF THE INVENTION[0001]The present invention relates in general to first pulse suppression in solid-state laser systems. The invention relates in particular to first-pulse suppression and pulse-selection in solid-state, pulsed, master oscillator power amplifier (MOPA systems) using a mode-locked master oscillator.DISCUSSION OF BACKGROUND ART[0002]A high-power short pulse (a few picoseconds or less) solid-state MOPA system for material processing applications typically includes a mode-locked master oscillator which provides seed-pulses in a train at a pulse repetition rate (PRF) of several megahertz (MHz). A pulse-picker is provided for selecting single pulses or bursts of pulses from the seed-pulse train for further amplification at a lower PRF, for example, hundreds of kilohertz (kHz). The selected pulses are amplified by one or more solid-state amplifier stages. A fast process shutter, usually an electro-optic (EO) modulator is used to select from the amplified puls...
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IPC IPC(8): H01S5/04
CPCH01S3/11H01S3/091H01S3/08072H01S3/2308H01S3/10046H01S3/0813H01S3/09415H01S3/10015H01S3/1106H01S3/2316H01S3/2341H01S3/0085H01S5/041
Inventor KNAPPE, RALFSEIFERT, ALBERTWEIS, ALEXANDER
Owner COHERENT KAISERSLAUTERN