Daniel L. Rhonehouse

New Er3+-doped phosphate glass for ion-exchanged waveguide amplifiers

A new Er 31 -doped phosphate glass exhibiting an excellent durability in both boiling water and NaNO3 molten salt is developed. The ion-exchange process of this glass is investigated by treating glass samples in a variety of salt baths with various exposure times. A planar waveguide with one mode at 1.54 mm and three modes at 632.8 nm is demonstrated. The spectral properties of Er 31 in this glass are charac- terized by measuring absorption and emission spectra and fluorescence lifetimes. The emission cross section of Er 31 in this glass is calculated to be 0.76310 20 cm 2 using McCumber theory.

Laser and thermal performance of a new erbium-doped phosphate laser glass

New erbium doped glass base compositions and sensitizer ion concentrations have been investigated. Laser, spectral, and thermo-mechanical properties have been tested. This study has resulted in a new erbium doped phosphate laser glass that exhibits improved thermal shock resistance and superior laser performance.

Ytterbium-doped phosphate laser glasses

Physical, spectral and laser properties of anew Yb3+ doped phosphate laser glass, QX/Yb, has been developed. This glass exhibits a low thermal expansion coefficient and a negative temperature coefficient of refractive index, resulting in an acceptable athermal behavior and an excellent thermal loading capability. The peak absorption and emission cross sections of Yb3+ were measured to be 1.06 X 10-20 cm2 and 0.903 X 10-20 cm2, respectively. The concentration quenching and the influence of the OH- content on fluorescence lifetimes were examined. Excellent laser performance with a slope efficient of 49 percent and a maximum output power of 400 mW was demonstrated.

Chemically stregthened Er3+, Nd3+ doped phosphate laser glasses

Significant enhancement of the thermal loading capability has been achieved with both Er3+ and Nd3+ doped inherently strong glasses by an ion-exchange chemical strengthening process. A free running laser with an average output power of 6.5 W and a Q-switched single mode laser with an energy of 5 mJ at a repetition rate of 15 Hz have been demonstrated at the 1.54 micrometers eye safe wavelength with strengthened QX/Er glass. An average output power of 110 W at 1.05 micrometers has been obtained employing a strengthened QX/Nd glass rod.

Infrared glass-based negative-curvature anti-resonant fibers fabricated through extrusion

Negative curvature fibers have been gaining attention as fibers for high power infrared light. Currently, these fibers have been made of silica glass and infrared glasses solely through stack and draw. Infrared glasses lower softening point presents the opportunity to perform low-temperature processing methods such as direct extrusion of pre-forms. We demonstrate an infrared-glass based negative curvature fiber fabricated through extrusion. The fiber shows record low losses in 9.75 - 10.5 µm range (which overlaps with the CO2 emission bands). We show the fibers lowest order mode and measure the numerical aperture in the longwave infrared transmission band. The possibility to directly extrude a negative curvature fiber with no penalties in losses is a strong motivation to think beyond the limitations of stack-and-draw to novel shapes for negative curvature fibers.

Nanoparticle doping for high power fiber lasers at eye-safer wavelengths

A nanoparticle (NP) doping technique was developed for fabricating erbium (Er)- and holmium (Ho)-doped silica-based optical fibers for high energy lasers. Slope efficiencies in excess of 74% were realized for Er NP doping in a single mode fiber based master oscillator power amplifier (MOPA) and 53% with multi-Watt-level output in a resonantly cladding-pumped power oscillator laser configuration based on a double-clad fiber. Cores comprising Ho doped LaF3 and Lu2O3 nanoparticles exhibited slope efficiencies as high as 85% at 2.09 µm in a laser configuration. To the best of the authors knowledge, this is the first report of a holmium nanoparticle doped fiber laser as well as the highest efficiency and power output reported from an erbium nanoparticle doped fiber laser.

High energy, high average and peak power phosphate-glass fiber amplifiers for 1micron band

Heavy doping of common silica gain fibers is not practical; therefore long fibers are required for efficient amplification (usually 5-10m). This is undesirable due to nonlinearities that grow with fiber length. In contrast, NP Photonics phosphate-glass based fibers can be heavily doped without any side-effects, and hence can provide very high gain in short lengths (less than 0.5m). This enables an ideal pulsed fiber amplifier for a MOPA system that maximizes the energy extraction and minimizes the nonlinearities. We demonstrate 1W average power, 200μJ energy, and >10kW peak power from a SBS-limited all-fiber MOPA system at 1550nm, and 32W average power, 90μJ energy, and 45kW peak power from a SRS and SPM limited all-fiber MOPA system at 1064 nm. These results were limited by the seed and pump sources.

High Verdet constant Faraday rotator glasses

Faraday rotator glasses with high Verdet constants are used for optical isolators and sensors. Based on the Tb2O3 -B2O3-Al2O3- SiO2 system and the effect of each component on glass formation, glass compositions were selected for development of new Faraday rotator glasses. Devitrification of Tb-glass was studied by microscopic morphology to establish the production process. Dispersion of Verdet constant and the influence of Tb3+ concentration on Verdet constant were investigated. Special technology was utilized for production of platinum-free glass. The quenching process is necessary to obtain crystal-free glass. Three kinds of Faraday rotator glass with higher Verdet constant than that of M16 have been developed. The higher Verdet constant glass is possible to obtain.

Ultra-wide mid-IR supercontinuum generation in W-type tellurite fiber pumped by 2 micron ultrashort laser

We have demonstrated heretofore ultra-wide mid-IR supercontinuum spanning from 0.9 µm to 4.2µm in a low-loss W-type tellurite based optical fiber. The W-fiber was pumped by passively mode-locked 2 micron Thulium doped fiber laser.

Development and characterization of a new Er3+-doped phosphate glass for planar waveguide lasers and amplifiers

A new Er3+ doped phosphate glass exhibiting an excellent durability in both boiling water and NaNO3 molten salt was developed. Ion-exchange process of this glass was investigated by treating glass samples in a variety of salt bathes with various exposure times. Planar waveguide with one mode at 1.54 micrometers and three modes at 632.8 nm was demonstrated. Spectral properties of Er3+ in this glass were characterized by measuring absorption and emission spectra, and fluorescence lifetimes. Emission cross section of Er3+ in this glass was calculated to be 0.76 X 10-20 cm2 using McCumber theory. Our preliminary experimental results indicate this new Er3+ doped glass is an excellent material for ion-exchanged waveguide lasers and amplifiers.