Publications

A novel fast method to update the object texture of the triangular mesh hologram is proposed. The angular spectrum of the three-dimensional object represented in triangular meshes is calculated with various pre-defined spectrum shifts. These shifted angular spectrums are added with appropriate coefficients to synthesize the hologram with arbitrary texture on the three-dimensional object in an enhanced speed. © 2013 Optical Society of America.

The implementation of optical systems, based on rare-earth doped fibers, in space environments adds a powerful new dimension of functionality to the design of space-based systems, particularly when high power and bandwidth, high fidelity, and low susceptibility to electromagnetic interference are desired. As these specialty fibers are often the most sensitive components of an optical system, extensive use requires considerable insight into the ionizing-radiation-induced changes experienced by the fibers during their operational lifetime. In this research, a suite of aluminosilicate fibers singly or co-doped with erbium and ytterbium ions was deployed into low-Earth orbit for approximately 18 months as part of the Materials International Space Station Experiment (MISSE) 7 mission. Optical spectroscopy performed on the retrieved fibers is compared to control data from pristine, unirradiated fibers, revealing colorcenter generation in the visible portion of the spectrum consistent with silica-related and aluminum-related absorption centers, with band-tailing into the near-infrared. Results suggest that visible to near infra-red (NIR) absorption experienced by the co-doped fiber is less-pronounced than in its singly-doped counterparts, likely a result of the lower aluminum concentration of this fiber. The data were also compared to data from terrestrial 60Co irradiation of the same fiber types and it was found that the overall trends observed in the space-irradiated fibers in the near-infrared were accurately, although not identically, reproduced. The resultant information is important for the design and testing of radiation-hardened optical-fiber-based laser and amplifier systems. © 2013 Published by Elsevier B.V.

We report a passively Q-switched all-fiber laser using a large mode area (LMA) Yb3+-doped fiber cladding-pumped at 915 nm and an unpumped single-mode Yb3+-doped fiber as the saturable absorber (SA). The saturable absorber and gain fibers were first coupled with a free-space telescope to better study the composite system, and then fusion spliced with fiber tapers to match the mode field diameters. ASE generated in the LMA gain fiber preferentially bleaches the SA fiber before depleting the gain, thereby causing the SA fiber to act as a passive saturable absorber. Using this scheme we first demonstrate a Q-switched oscillator with 40 μJ 79 ns pulses at 1026 nm using a free-space taper, and show that pulses can be generated from 1020 nm to 1040 nm. We scale the pulse energy to 0.40 mJ using an Yb3+-doped cladding pumped fiber amplifier. Experimental studies in which the saturable absorber length, pump times, and wavelengths are independently varied reveal the impact of these parameters on laser performance. Finally, we demonstrate 60 μJ 81 ns pulses at 1030 nm in an all fiber architecture using tapered mode field adaptors to match the mode filed diameters of the gain and SA fibers. © 2013 Copyright SPIE.

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Recent advances in power scaling of Yb+ 3-doped fiber lasers to the kilowatt level suggest a need to examine the performance of Yb + 3-doped silica at temperatures well above ambient. We report experimental results for the absorption coefficient, emission cross-section, fluorescence lifetime, and slope efficiency of a Yb3+-doped large mode area (LMA) silica fiber for temperatures spanning 23 °C-977 °C. To the best of our knowledge these are the highest temperatures to date for which these optical properties have been measured. We find a sharp reduction in the energy storing capability and lasing performance of Yb+ 3:SiO 2 above 500 °C that coincides with the onset of non-radiative transitions in the excited state manifold (thermal quenching). As the temperature increases from room temperature to 977 °C, absorption in the 1020-1120 nm operating band increases monotonically, concurrent with a reduction in absorption at the 920-nm and 977-nm pumping bands. Conversely, the spectral weight of the emission cross-section shifts from transitions above 1010 nm to those below, with the exception of the 977-nm emission band. © 2011 Elsevier B.V. All rights reserved. © 2011 Elsevier B.V. All rights reserved.

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