J. Keith Miller

Spectroscopic properties of Er-sesquoxides

The current effort reports on the spectroscopic properties (absorption, emission and fluorescence lifetime) as a function of varying Erbium concentration in Y₂O₃. Results show a non-linear behavior in the fluorescence lifetimes and the radiative-emission intensities for the ⁴I_11/2and the ⁴I_13/2 energy levels.

Transmitted beam profile for determining bulk scattering in transparent ceramics

Bulk scattering in polycrystalline laser materials (PLM), due to non-uniform refractive index distribution across the bulk, is regarded as the primary loss mechanism leading to degradation of laser performance with higher threshold and lower output power. There is a need for characterization techniques, towards identifying bulk scatter and assessing the quality. Assessment of optical quality and the identification of bulk scatter have been by simple visual inspection of thin samples of PLMs, thus making the measurements highly subjective and inaccurate. Transmitted Beam Wavefront Profiling (TBWP) allows for the direct and quick imaging of the distortions introduced by bulk scattering, which is a direct manifestation of the presence of refractive index inhomogeneities in the PLM sample. As a laser beam propagates through the PLM sample, different regions of the incident beam experience different refractive index profiles, which cause spatial distortions to the beam. TBWP is able to directly and quickly image these distortions introduced to a propagating laser beam caused by the presence of bulk scattering in the PLMs.

Pump Beam Engineering for Vortex Beam in a Ho:YAG Rod Amplifier

Different pump beam profiles are utilized for pumping optical vortex beams in a Ho:YAG amplifier. Pump beam profile engineering is discussed for the optimized amplification results.

Angle resolved scatter measurement of bulk scattering in transparent ceramics

Bulk scattering in polycrystalline laser materials (PLM), due to non-uniform refractive index across the bulk, is regarded as the primary loss mechanism leading to degradation of laser performance with higher threshold and lower output power. The need for characterization techniques towards identifying bulk scatter and assessing the quality. Assessment of optical quality and the identification of bulk scatter have been by simple visual inspection of thin samples of PLMs, thus making the measurements highly subjective and inaccurate. Angle Resolved Scatter (ARS) measurement allows for the spatial mapping of scattered light at all possible angles about a sample, mapping the intensity for both forward scatter and back-scatter regions. The cumulative scattered light intensity, in the forward scatter direction, away from the specular beam is used for the comparison of bulk scattering between samples. This technique employ the detection of scattered light at all angles away from the specular beam directions and represented as a 2-D polar map. The high sensitivity of the ARS technique allows us to compare bulk scattering in different PLM samples which otherwise had similar transmitted beam wavefront distortions.

Schlieren imaging of bulk scattering in transparent ceramics

Bulk scattering in polycrystalline laser materials (PLM), due to non-uniform refractive index across the bulk, is regarded as the primary loss mechanism leading to degradation of laser performance with higher threshold and lower output power. The need for characterization techniques towards identifying bulk scatter and assessing the quality. Assessment of optical quality and the identification of bulk scatter have been by simple visual inspection of thin samples of PLMs, thus making the measurements highly subjective and inaccurate. A modified white light Schlieren Imaging Setup utilizing variable focusing capability is demonstrated. The white light Schlieren Imaging Setup makes it possible to image the spatial variations in the refractive index in the PLMs regardless of dimensions, which are the cause of bulk scattering loss in a transparent material over the entire cross-sectional area of the sample. The high sensitivity of white light Schlieren provides the ability of directly imaging the local spatial variations in refractive index across the entire sample dimension and compare different samples.