Author
J. Wisdom
Bio: J. Wisdom is an academic researcher from Stanford University. The author has contributed to research in topics: Laser & Ceramic. The author has an hindex of 3, co-authored 6 publications receiving 136 citations.
Topics: Laser, Ceramic, Raman spectroscopy, Grain boundary, Quenching
Papers
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TL;DR: Using confocal Raman and fluorescence spectroscopic imaging in 3-dimensions, this paper showed direct evidence for Nd3+-Nd3+) interactions across grain boundaries (GBs) in Nd 3+:YAG laser ceramics.
Abstract: Using confocal Raman and fluorescence spectroscopic imaging in 3-dimensions, we show direct evidence for Nd3+-Nd3+ interactions across grain boundaries (GBs) in Nd3+:YAG laser ceramics. It is clearly shown that Nd3+ segregation takes place at GBs leading to self-fluorescence quenching which affects a volume fraction as high as 20%. In addition, we show a clear trend of increasing spatial inhomogeneities in Nd3+ concentration when the doping levels exceeds 3 at%, which is not detected by standard spectrometry techniques. These results could point the way to further improvements in what is already an impressive class of ceramic laser materials.
69 citations
TL;DR: Using confocal Raman and fluorescence spectroscopic imaging in 3-dimensions, direct evidence of inhomogeneous Nd(3+) distribution across grain boundaries (GBs) in Nd (3+):YAG laser ceramics is shown.
Abstract: Using confocal Raman and fluorescence spectroscopic imaging in 3-dimensions, we show direct evidence of inhomogeneous Nd3+ distribution across grain boundaries (GBs) in Nd3+:YAG laser ceramics. It is clearly shown that Nd3+ segregation takes place at GBs leading to self-fluorescence quenching which affects a volume fraction as high as 20%. In addition, we show a clear trend of increasing spatial inhomogeneities in Nd3+ concentration when the doping levels exceeds 3 at%, which is not detected by standard spectrometry techniques. These results could point the way to further improvements in what is already an impressive class of ceramic laser materials.
67 citations
08 Feb 2007
TL;DR: In this article, a 1.2 GHz YAG ceramic was used with an 808-nm laser diode, placed in a 2.92m cavity, and passively mode-locked at 1064-nm with a 1% modulation depth.
Abstract: We report a 1.2 at. % Nd:YAG ceramic pumped with an 808-nm laser diode, placed in a
1.92-m cavity, and passively mode-locked at 1064-nm with a 1% modulation depth
SESAM. At a pump power of 11.1 W, this laser produced 2.6 W of average power with a
slope efficiency of 27%. The pulse length was 26 ps at a repetition rate of 78 MHz. The
ceramic exhibited no peak power degradation during a 20-hour test of doubling efficiency
with periodically-poled, near-stoichiometric lithium tantalate.
4 citations
TL;DR: In this paper, a genetic-algorithm-based approach is presented that balances improvement in mode-overlap between excited state distribution and the signal laser beam against optical path length distortions.
Abstract: Edge-pumping Nd:YAG laser gain media is a convenient method to couple pump power into a laser cavity. A difficulty with this geometry is that for uniformly doped materials, pump power deposited near the edge of the gain medium cannot be efficiently extracted by a diffraction-limited beam. However, ceramic Nd:YAG with smooth changes in neodymium doping level (doping profiles) can now be fabricated to ameliorate this problem. A slab engineered with a doping profile that has a higher concentration of Nd in the center, and less at the edges, would allow more pump power to be efficiently extracted by a diffraction-limited laser beam. Yet this solution poses its own problem because variations in Nd concentration introduce optical path length distortions that can significantly reduce beam quality. The variations in optical path length are predominantly from changes in the refractive index of the host due to Nd doping and spatially varying temperatures. A genetic-algorithm-based approach is presented that balances improvement in mode-overlap between excited state distribution and the signal laser beam against optical path length distortions. A doping profile was found for an edge-pumped, zig-zag slab amplifier that is expected to yield a 39% improvement in extracted power delivered into a diffraction-limited spot compared to a uniformly doped slab.
16 May 2005
TL;DR: In this paper, the authors discuss the advantages such as the range of materials available and ways to implement them followed by some different test examples we been considered, and the important goal is an integrated system that avoids having to inject either laser or particle pulses into these structures.
Abstract: Laser driven particle accelerators require submicroncontrol of the laser field as well as precise electron-beam guiding so fabrication techniques that allow integrating both elements into an accelerator-on-chip format become critical for the success of such next generation machines. Micromachining technology for silicon has been shown to be one such feasible technology in PAC2003[1] but with a variety of complications on the laser side. However, fabrication of transparent ceramics has become an interesting technology that could be applied for laser-particle accelerators in several ways. We discuss the advantages such as the range of materials available and ways to implement them followed by some different test examples we been considered. One important goal is an integrated system that avoids having to inject either laser or particle pulses into these structures.
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TL;DR: Grain boundary complexion transitions are the root cause of a wide variety of materials phenomena such as abnormal grain growth, grain boundary embrittlement and activated sintering as discussed by the authors, which have defied mechanistic explanation for years.
662 citations
TL;DR: Transparent polycrystalline ceramics have found various applications, such as laser hosts, infrared windows/domes, lamp envelopes and transparent armors, due mainly to their processing flexibility in fabricating items with large sizes and complex shapes and more importantly costeffectiveness as mentioned in this paper.
453 citations
TL;DR: Efforts are under way to create perfectly dense ceramics for use in applications ranging from lasers to health care, according to the European Ceramics Agency.
Abstract: Efforts are under way to create perfectly dense ceramics for use in applications ranging from lasers to health care.
178 citations
TL;DR: In this paper, densification and grain growth in pure YAG, SiO 2 doped YAG and SiO 3 doped Nd:YAG sinters were explored.
Abstract: Densification and grain growth in pure YAG, SiO 2 doped YAG and SiO 2 doped Nd:YAG were explored. The activation energy for densification (235 kJ/mol) in pure YAG is lower than that of grain growth (946 kJ/mol) which is unusual in ceramic systems. Consequently, pure YAG sinters to near full density (>99.9%) at 1700 °C with little grain growth (1.2 μm average grain size). The remaining large pores (radius > 2 μm) were determined to be thermodynamically stable because their coordination number with grains was >6. The stability of these pores underscores the importance of powder processing and forming in fabricating transparent YAG. SiO 2 doped YAG sinters to near full density 100 °C lower than pure YAG because SiO 2 enables liquid phase sintering and the removal of large pores. The addition of Nd 2 O 3 further enhances both densification and grain growth at temperatures below 1700 °C. Above 1700 °C higher concentrations of Nd 3+ suppressed grain growth, possibly due to solute drag.
144 citations
TL;DR: The year 2010 marks the 50th anniversary of the invention of the first laser device, ruby laser and it is therefore an appropriate time to look back at the developments in the laser field since its inception and to try to map out its milestones.
138 citations