We report on an air-clad large-core single-transverse-mode ytterbium-doped photonic crystal fiber with a mode-field-diameter of 35 microm, corresponding to a mode-field-area of ~1000 microm(2). In a ...first experiment this fiber is used to amplify 10-ps pulses to a peak power of 60 kW without significant spectral broadening due to self-phase modulation allowing for the frequency up-conversion of these pulses using narrow-bandwidth phase matched nonlinear crystals.
We report on a 2.3 m long air-clad ytterbium-doped large-mode-area photonic crystal fiber laser generating up to 80 W output power with a slope efficiency of 78%. Single transverse mode operation is ...achieved with a mode-field area of 350 /spl mu/m/sup 2/. No thermo-optical limitations are observed at the extracted /spl sim/35 W/m, therefore such fibers allow scaling to even higher powers.
We report on the generation of linearly chirped parabolic pulses with 17-W average power at 75 MHz repetition rate and diffraction-limited beam quality in a large-mode-area ytterbium-doped fiber ...amplifier. Highly efficient transmission gratings in fused silica are applied to recompress these pulses down to 80-fs with an efficiency of 60%, resulting in a peak power of 1.7 MW. Power scaling limitations given by the amplifier bandwidth are discussed.
We report on a novel ytterbium-doped fiber design that combines the advantages of rod and fiber gain media. The fiber design has outer dimensions of a rod laser, meaning a diameter in the range of a ...few millimeters and a length of just a few tens of centimeters, and includes two important waveguide structures, one for pump radiation and one for laser radiation. We obtained 120-W output power in single-mode beam quality from a 48-cm-long fiber cane that corresponds to an extracted power of 250 W/m. The fiber has significantly reduced nonlinearity, which therefore allows for scalability in the performance of a high-peak-power fiber laser and amplifier system.
We report on the experimental demonstration of an all fiber CPA system based on a step-index fiber stretcher and an air-guiding photonic crystal fiber compressor. The ultrafast fiber laser system ...producing an average power of 6.0 W with 100-fs pulses at 73 MHz, what corresponds to a peak power out of the compressor fiber of 0.82 MW. This completely fiber integrated approach has the potential to be scaled to significantly higher peak powers.
We report on the investigation of the thermo-optical behavior of air-clad ytterbium-doped large-mode-area photonic crystal fiber lasers. Analytical and numerical models are applied to calculate the ...heat distribution and induced stresses in a microstructured fiber. The results are compared to conventional double-clad fiber lasers and design guidelines are provided to ensure maximum heat dissipation and scalability to power levels of several kWs.
We report on the generation of a high average power, flat supercontinuum using a compact ytterbium-doped fiber amplifier. The femto- and picosecond pulses delivered by the amplifier are coupled into ...two different photonic crystal fibers. By using picosecond pulses the highest output power of 5 W with a spectrum ranging from below 500 nm up to above 1800 nm is obtained. Numerical simulations are compared with the experimental spectra and it is shown that the main part of the broadening mechanism is a soliton effect even for picosecond pulses. Furthermore, second and third harmonic processes leading to some sharp spectral lines in the visible region are investigated.
Dental implants are now considered the standard of care for supporting dental restorations in edentulous areas. The purpose of this study was to explore the attitudes and practices of dental ...hygienists in the United States regarding dental implant assessment and maintenance care.
A 34-item quantitative survey was developed and distributed nationally to a randomly selected sample of 10,000 dental hygienists from the American Dental Hygienists' Association (ADHA) email database. Responses were collected and analyzed via an online software program using frequency distributions for categorical variables.
A total of 2,018 dental hygienists participated for a response rate of 21%. The majority of respondents (98%) provided care to patients with dental implants. While the majority of respondents reported routinely assessing patients for bleeding/exudate, mobility, plaque/calculus, and tissue color around implants, 34% rarely/never checked for cement around implants, 31% rarely/never probed, and 54% rarely/never checked the occlusion. Nearly half of the respondents (44%) reported that they were unable to remove plaque as effectively from dental implants as from natural teeth. A majority (60%) reported using plastic/resin scalers, however only 7% of those who use plastic/resin scalers felt they were effective. While only 5% reported using air-polishers, 71% of the users felt they were effective. An oral irrigator was the most commonly recommended self-care hygiene aid for patients with implants and continuing education courses were the primary source of implant-related knowledge among respondents.
The wide variation in implant-related assessment and maintenance care practices among dental hygiene respondents indicates a need for greater emphasis on evidence-based practices in dental hygiene curricula and in continuing education to ensure optimal care for patients with dental implants.
In a fiber amplifier, spectral compression due to self-phase modulation is demonstrated for ultrashort pulses. We report the generation of near-transform-limited picosecond pulses with peak powers of ...several kW at a repetition rate of 74 MHz and diffraction-limited beam quality in a Yb-doped fiber amplifier when seeding with a negative chirped pulse.
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