We have developed innovative high power polarized 1064nm pulsed fiber laser for efficient nonlinear frequency
conversion and by frequency doubling its output generated 30W of average power with 68% conversion efficiency at
532nm. This new 1064nm pulsed fiber laser operates at 1.8MHz repetition rate with 1.3ns pulse duration and close to
bandwidth-limited spectral linewidth. The developed laser delivers 46W average power at 1064nm in the linearly
polarized output beam with a polarization extinction ratio 20dB. This laser has a truly solid-state design required for
deployment into the industrial environment and can be used for nonlinear frequency conversion to generate high power
emission in the visible and UV parts of optical spectrum as well as for other applications. The overall 16% efficiency
demonstrated in generating 532nm is believed to be the highest wall plug efficiency achieved by any solid-state or fiber
lasers with visible output. We expect that over 20% total efficiency for the fiber laser with tens of watts output in the
green spectral range will be available.
We have developed pulsed fiber laser with computer controlled pulse duration and multi-kilowatt output peak power in a diffraction-limited beam. The diode laser as a master oscillator and Yb-based fiber amplifiers were used in a MOPFA configuration. The output pulse duration can be arbitrary selected in the range from 4ns to over 200ns with 1ns resolution. Pulse duration does not depend on the repetition rate and remains the same for all operational frequencies in the range from 10kHz to over 140kHz. The short length of the large mode area Yb-doped fiber was used to amplify the generated pulses to over 40kW peak power and several watt of the average power. The output pulse-to-pulse energy instability was less than 1% for all operational frequencies. Due to the single mode design of the delivery fiber, the measured output beam quality M2 was found to be smaller than 1.05. The developed laser presents a solid-state design to be used in the industrial environment for applications where primary requirements are the beam quality, high repetition rate, small pulse-to-pulse energy instability and reliable laser operation on the real factory floor.
We have developed all fiber format pulsed lasers with bandwidth-limited emission and over 12kW peak power for the 1064nm and 1550nm wavelength ranges. The master oscillator followed by power fiber amplifier configurations were employed with operational frequencies from 100kHz to over 2MHz range and 2ns pulse duration. The pulse duration remains the same for all repetition rates. The designs of the low NA core fibers deployed ensure stable single spatial mode emission with 12μm and 14μm mode field diameter (MFD) for 1064nm and 1550nm correspondingly. The output emission bandwidth was below 0.1nm and pulse-to-pulse energy stability better than 1% were measured for all operational frequencies and output powers. Single mode fiber design of the fiber amplifiers ensured diffraction-limited output beam quality with M2 less than 1.1. New lasers can be used for nonlinear frequency conversion to generate emission in the visible and UV parts of optical spectrum as well as in other applications.
We have developed a compact laser system capable of amplifying nanosecond-scale pulses form a few picojoules to 20J. The system has a 40-mm clear aperture and a 37-mm working aperture for high-energy output. We measured less than 1 wave phase distortion over full 37-mm aperture for a pulse with 18-J output energy at a shot repetition rate of one shot every 10 min. In experiments with a 30-mm diam beam, a flat-top spatial profile with 4 percent rms over the entire beam diameter was demonstrated for a 1-ns pulse with 20_j output energy. The amplifier has a net gain up to 1013 and fits easily on a 5-ft X 14-ft optical table.
The dual-tripler scheme for enhancing the bandwidth of third-harmonic generation, proposed by Eimerl et al., has been experimentally demonstrated for the conversion of 1054- nm radiation to 351 nm. The results are in excellent agreement with theory and show that the spacing between the triplers must be carefully controlled. Designs are given for the addition of a second tripler to OMEGA and the NIF. An approximately threefold increase in bandwidth is predicted for both laser systems.
We present the requirements, design, and experimental results for a negative feedback-controlled Nd:YLF regenerative amplifier for the OMEGA laser system. This externally synchronizable region boosts the energy of temporally shaped optical pulses from the subnanojoule to the submillijoule energy level with a measured long-term output energy stability of 0.2 percent rms. To our knowledge this represents the highest energy stability ever demonstrated for a millijoule-level laser system, either flashlamp pumped or diode pumped. In addition to the excellent stability and reproducibility, the regen output is very insensitive to the injected pulse energy and the temporal distortions due to the negative feedback are immeasurable. Four regenerative amplifiers equipped with this negative feedback system have operated flawlessly on OMEGA over the past two year period.
We have modeled the output of a feedback stabilized regenerative amplifier (regen). We solve the rate equations including upper- and lower-laser-level lifetimes explicitly. The complete regen dynamics including the losses due to the feedback stabilizer are modeled. We provide a prescription for determining the injection-pulse shape required to produce a given output-pulse shape from this region. The model shows excellent agreement to measured regen output. This model of the regen along with our code RAINBOW, completely describes the temporal dynamics of the OMEGA laser system allowing OMEGA users to specify on-target pulse shapes in advance.
We present the design and preliminary experimental data for the multicolor fiducial laser to be used as a primary timing reference for UV and x-ray streak cameras on the 40-kJ UV OMEGA laser system.
The optical pulse-shaping system for the 60-beam 30-kJ (UV) OMEGA fusion laser is capable of producing complex temporally shaped optical pulses for amplification and delivery to fusion targets. The pulse-shaping system consists of optical modulators driven by an optically activated electrical waveform generator. The electrical waveform generator consists of Si photoconductive switches, and variable impedance microstrip lines. Complex optical pulse shapes with 50 to 100 ps structure have been produced.
An optical pulse-shaping system will be implemented on the OMEGA laser that is capable of producing complex optical pulse shapes. The pulse-shaping system relies on photoconductive switches that are activated with a pulse compressed by the stimulated Brillouin scattering (SBS) process. The SBS activation pulse provides overall system bandwidth and eliminates laser prepulse noise. The SBS process is modeled in detail to understand the performance and limitations of the OMEGA pulse-shaping system. Experimental results and numerical simulations are presented in the SBS pulse-steepening and pulse-compression regimes. Good qualitative agreement is obtained between theory and experiments.
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