Development of rare earth doped polycrystalline alumina (RE:Al2O3) for short pulsed, high powered lasers (UCSD)
Abstract
or the study of light-matterinteractions, directed energy (DE) applications,communications/tracking systems, etc. We propose to developthe first pulsed lasers based on a rare earth (RE) dopedpolycrystalline aluminaa ceramic that is not typicallythought of as a viable gain media. The advantages of alumina(Al2O3) over state-of-the-art gain materials such as yttriumaluminum garnet (Y3Al5O12, YAG) and laser glasses aresignificant; it has higher thermal conductivess, all attributesthat could lead to more stable, more powerful lasers in mobileapplications important to ONR, DoD and the DE community.We propose to dope the ceramics with a variety of rare earths,providing emission at various wavelengths particularly inregions where pulsed, high power laser choices are limited.Despite promising attributes, producing RE doped aluminaceramics for lasers has steep synthesis/processing challenges.They cannot be made using traditional equilibrium methodssuch as Czochralski single crystal growth or traditionalsintering because the equilibrium solubility limits of REs in the Al2O3 is on the order of 10-3 to 10 -4 at%, not high enough to produce lasing (~1 to 10-1 at%). Recently however we have produced Nd-doped alumina (Nd:Al2O3) with transmission and dopant concentrations high enough toproduce population insertion and gain (Figure 1 and see preliminary results) an achievement that will produce the first Nd:Al2O3 laser emitting at ~1064 nm. We have demonstrated that this new gain material has broader wavelength bandwidth than RE doped glasses (needed to produce ultrashortpulses) and higher thermal conductivity than RE doped YAG (needed achieve high pulse repetition rates i. e. high average power) [1]. Here we plan to significantly extend the usability by producing the first RE:Al2O3, pulsed lasers. The result will be gain materials/lasers that can be pumped harder than RE:YAG crystals while delivering shorter pulses at higher repetition ratesthan RE:Glasses.The work will be divided into three Research Directions powder with various RE dopants (Nd, Er, Yb, Tm) at concentrations between 0.1 and 1 at%). The powders will be densified, producing laser quality ceramic disks which can be cut into bars, slabs or used as disks in laser cavities. Development of rare earth doped polycrystalline alumina (RE:Al2O3) for short pulsed, high powered lasers. RD2) Characterize optical properties and material microstructure. We will extensively characterize the ceramic nano/microstructure (grain size, RE dopant concentration and distribution) to provide feedback for improving optical performance of ceramics. We will measure absorption cross section, emission cross-sections, emission lifetimes. Measurements will be doneat room and cryogenic temperatures to better understand absorption and emission physics (we have down to capabilities down to 8K). We will also perform single pass gain and damage threshold experiments to provide design parameters for laser designs. RD3) Design and construct pulsed lasers from RE:Al2O3 ceramics. We will use similar pulseamplification, Q-switching, and mode-locking schemes that have been developed for RE:YAG,RE:Glass and RE:YLF. For example, we will use a electro-optic Q-switching with lithium niobateor KDP Pockels cell. Another design possibility is a passively mode-locked cavity using Fabry-Perot saturable absorbers (FPSA). Semiconductor based FPSAs can be obtained commercially fora variety of wavelengths. These initial deigns will be optimized according to the opticalperformance of the RE:Al2O3 ceramics. We propose to concentrate on Nd, Er and Tm as dopantsto deliver 1 - 2 m pulsed lasers.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 20, 2020
- Source ID
- N000142012724
Entities
People
- Javier E Garay
Organizations
- Office of Naval Research
- United States Navy
- University of California, San Diego