Efficient 2-Micron Laser Driver for Laser Acceleration
- Aqwest LLC
Laser acceleration of nuclear particles is an emerging technology aimed to supplant the traditional radio-frequency (RF) accelerators while offering several orders of magnitude reduction in size and cost. Although laser acceleration has been demonstrated in 1990's and it is now pursued worldwide, production of particle currents comparable to RF accelerators is impeded by the lack of a powerful, efficient, and economical laser acceleration driver (LAD). Today’s LADs operate only at few hertz (Hz) pulse repetition frequency (PRF) because of the waste heat deposited into the laser gain material (LGM). To attain pulse frequencies in the targeted kilohertz or even megahertz range Hz, the ultrafast lasers (UFL) for LAD require new LGM supporting longer (>1 µm) wavelengths for improved plasma coupling, broad bandwidth (BW) for amplification of femtosecond (fs)-class pulses, and wall-plug efficiencies >20%. The objective of this project was to investigate a new thulium (Tm) -based LAD. In particular, we fabricated, tested, and further developed a novel Tm-doped lutetium sesquioxide (Tm:Lu2O3) ceramic LGM lasing at 2 µm. In Phase II we used the initial Tm:Lu2O3 ceramic fabricated in Phase I to demonstrate efficient lasing and continuous wavelength tuning over 230 nm range. Aqwest worked with world's leading manufacturer of laser ceramics to fabricate and deliver (largest ever) ceramic Tm:Lu2O3 formed as (first ever) cosintered composites suitable for high-average power. The benefits of the ceramic Tm:Lu2O3 LGM include: 1) 2-µm wavelength for ponderomotive force of 4x that of 1-µm and 6x that of 0.8-µm lasers, 2) Output pulse energies and PRF scalable to Type I, II, III, and IV laser drivers, 3) BW of 230 nm offers >10% tunability and pulse compression to <50 fs, 4) "2 exited states for 1 pump photon” architecture enables >20% wall-plug efficiency, 5) Thermal conductivity >12 W/m-ºK for near-ambient temperature operation and low thermo-optic effect, and 6) Highest gain and stored energy density among leading Tm-doped materials. In Phase IIA, we further validated the ceramic Tm:Lu2O3 LGM. In particular, we 1) Used the mechanically robust Tm:Lu2O3 cosintered composites from Phase II to fabricate and test LGM (Figure 1-1) in the edge-pumped disk laser (EPDL) gain module for multi-pass amplifier (MPA), 2) Test-validated the EPDL gain tailoring concept, 3) Upgraded the wavelength-tunable seed laser constructed in Phase II to a q-switched operation for generation of nanosecond pulses relevant to LAD, 4) Fabricated Tm:Lu2O3 ceramic with improved quality, 5) Identified a concept for a liquid-cooled large-aperture final amplifier for Type IV LAD, and 6) Updated our concept designs for Type II, III, and IV LAD. The Tm:LLu2O3 laser technology and knowhow developed in this project has paved a way to 3 other projects: 1) The development of Tm:Lu2O3-based amplifier for Type III LAD as a part of DE-SC0019921, 2) Adoption of Tm:Lu2O3 by the US Navy for an airborne blue laser sensor (via frequency quadrupling) (N6833519C0491 contract award to Aqwest), 3) Adoption of Tm:Lu2O3 by NASA for space-based blue laser sensor (negotiations in December 2019). Furthermore, the design of the MPA structures was adopted by DE-SC0015834 where it will be used as a preamplifier with Yb:YAG LGM for 1 µm wavelength. Continued funding of the ceramic Tm:Lu2O3 laser technology will greatly advance the maturity of the laser acceleration and its transition into the hands of the user community while also being highly beneficial for novel laser fusion approaches and for commercial laser material processing.
- Research Organization:
- Aqwest LLC
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP)
- DOE Contract Number:
- SC0013762
- OSTI ID:
- 1576180
- Type / Phase:
- SBIR (Phase IIA)
- Report Number(s):
- REP1911290
- Country of Publication:
- United States
- Language:
- English
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