Rare-earth doped single-crystal (SC) Yttrium Aluminum Garnet (YAG) fibers are excellent candidates for high power lasers. These SC fiber optics combine the favorable low Stimulated Brillouin Scattering (SBS) gain coefficient and excellent thermal properties to make them an attractive alternative to glass fiber lasers and amplifiers. Various rare-earth doped SC fibers have been grown using the laser heated pedestal growth (LHPG) technique. Several cladding methods, including in-situ and post-growth cladding techniques, are discussed in this paper. A rod-in-tube approach has been used by to grow a fiber with an Erbium doped SC YAG fiber core inserted in a SC YAG tube. The result is a radial gradient in the distribution of rare-earth ions. Post cladding methods include sol-gel deposited polycrystalline.
The ability to image through a scattering or diffusive medium such as tissue or hazy atmosphere is a goal which has
garnered extensive attention from the scientific community. Existing imaging methods in this field make use of phase
conjugation, time of flight, iterative wave-front shaping or statistical averaging approaches, which tend to be either time
consuming or complicated to implement. We introduce a novel and practical way of statistical averaging which makes
use of a rotating ground glass diffuser to nullify the adverse effects caused by speckle introduced by a first static diffuser
/ aberrator. This is a Fourier transform-based, holographic approach which demonstrates the ability to recover detailed
images and shows promise for further remarkable improvement. The present experiments were performed with 2D flat
images, but this method could be easily adapted for recovery of 3D extended object information. The simplicity of the
approach makes it fast, reliable, and potentially scalable as a portable technology. Since imaging through a diffuser has
direct applications in biomedicine and defense technologies this method may augment advanced imaging capabilities in
Single crystal (SC) yttrium aluminum garnet (YAG, Y3Al5O12) as a host material has the ability to be doped with high
concentrations of Er3+ ions. We utilize this ability to grow a 50% Er3+ doped YAG SC fiber, which was inserted into
a SC YAG tube. This rod-in-tube was used as a preform in our laser-heated pedestal growth (LHPG) apparatus to
grow a fiber with a radial distribution of Er3+ ions. The work shows that there is a distribution of Er3+ ions from their
fluorescence and two different techniques were used to measure the index of refraction.
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.
A new method is analyzed for 3-D cooling of solids based on near-resonant, stimulated Raman scattering on a
narrowband transition together with optical pumping on a broadband transition. Estimates of achievable cooling rates
indicate that Raman cooling offers significant improvement over anti-Stkes fluorescence cooling at cryogenic
temperatures and should enable the attainment of sub-Kelvin termperatures, starting from ambient conditions in bulk
samples. Also the method is not restricted to ions with small Stokes shifts, and should therefore lead to diversification of
the material platforms used for optical refrigeration.
In recent years there has been a significant evolution in the development of high purity growth methods for nanoparticles in the 10 nm size range. Concurrently, new processing methods have led to the emergence of laser quality transparent ceramics prepared from rare-earth-doped nanopowders. Output powers and efficiencies of ceramic lasers have been reported to compare very well with those of crystal laser systems, causing interest both in nanoscale and macro-scale optical ceramics. In this paper, we first describe highly scattering oxide powders that generate continuous-wave random laser action, are able to store light, exhibit quantum size effects, and sinter to transparency at exceptionally low temperatures. Quantum size effects and modified dopant interactions in transparent ceramics processed from these powders are then considered, and their potential relevance to problems in laser cooling and the engineering of nanostructured ceramics for solid state lasers and nonlinear optics are evaluated.
We present results on the first application of upconversion dynamics for short pulse generation in visible solid state lasers. We also describe prospects for passive mode-locking mechanisms based on cooperative nonlinearities and instabilities.