Rare-earth doped single crystal (SC) yttrium aluminum garnet (YAG) fibers have great potential as high-power laser gain media. SC fibers combine the superior material properties of crystals with the advantages of a fiber geometry. Improving processing techniques, growth of low-loss YAG SC fibers have been reported. A low-cost technique that allows for the growth of optical quality Ho:YAG single crystal (SC) fibers with different dopant concentrations have been developed and discussed. This technique is a low-cost sol-gel based method which offers greater flexibility in terms of dopant concentration. Self-segregation of Nd ions in YAG SC fibers have been observed. Such a phenomenon can be utilized to fabricate monolithic SC fibers with graded index.
In this effort, we report on the preservation of the spatial mode quality as composite vortex beams propagate through a flashlamp pumped amplifier system. Because of the spatially asymmetric nature of the transient thermal lensing, a laser beam propagating through this type of amplifier will be distorted. This makes an ideal environment to assess the mode integrity of propagating composite vortex beams. We demonstrate that a 3-lobe composite vortex beam can propagate under extreme transient thermal lensing and maintain the mode structure through the amplification process. Even though the actual amplification wasn’t the main thrust of this effort, we demonstrate gain greater than a factor of 4 for two different seed energy levels. Since the flashlamp pumped system is an extreme case, this result shows the potential for using concentric vortex beams in high power amplifiers and could open up new applications in propagation and sensing.
0.5% Holmium (Ho) doped YAG single crystal fiber (SCF) was fabricated using the laser heated pedestal growth
(LHPG) method and amplification properties of the fabricated Ho:YAG SCF were studied. The relatively large lengthto-
diameter ratio provides guiding for both the pump and signal beams propagating in the SCF. The propagation and
gain of signals with different modes were studied. A numerical method based on finite difference (FD) beam
propagation method (BPM) combined with the rate equations was developed for theoretical simulation. The results are
encouraging to demonstrate the advantages of SCF for its fiber-like beam guiding property and solid state material gain
property. The simulation tool provides details about how the fiber shape and launched mode affect the gain and output
beam shape as well as predicts the amplification behavior of such unique specialty fibers.
High concentrations of the rare-earth elements erbium, holmium and thulium have been successfully doped into single crystal (SC) yttrium aluminum garnet (YAG, Y3Al5O12) fibers by use of the laser heated pedestal growth (LHPG) method. The spontaneous emission spectra and fluorescence were measured in the near-infrared (NIR). The results show progress towards forming a solid state laser able to produce a wavelength in the NIR, for high power applications.
3D Meta-Optics are optical components that are based on the engineering of the electromagnetic fields in 3D dielectric
structures. The results of which will provide a class of transformational optical components that can be integrated at all
levels throughout a High Energy Laser system. This paper will address a number of optical components based on 2D
and 3D micro and nano-scale structures and their performance when exposed to high power lasers. Specifically, results
will be presented for 1550 nm and 2000 nm spectral bands and power densities greater than100 kW/cm2.
This paper highlights recent developments in resonant optical devices for infrared (IR) and mid-infrared (mid- IR) lasers. Sub-wavelength grating based resonant optical filters are introduced and their application in 2 μm thulium fiber laser and amplifier systems has been discussed. The paper focuses on applying such filtering techniques to 2.8 μm mid-IR fiber laser systems. A narrowband mid-IR Guided-Mode Resonance Filter (GMRF) was designed and fabricated using Hafnium(IV) Oxide film/quartz wafer material system. The fabricated GMRF was then integrated into an Erbium (Er)-doped Zr-Ba-La-Al-Na (ZBLAN) fluoride glass fiber laser as a wavelength selective feedback element. The laser operated at 2782 nm with a linewidth less than 2 nm demonstrating the viability of GMRF’s for wavelength selection in the mid-IR. Furthermore, a GMRF of narrower linewidth based on Aluminum Oxide/quartz wafer material system is fabricated and tested in the same setup. The potentials and challenges with GMRFs will be discussed and summarized.