This paper examines the evolution of DUI (Driving Under the Influence) education, particularly th... more This paper examines the evolution of DUI (Driving Under the Influence) education, particularly the shift from traditional inperson classes to online platforms.
Fiber lasers rely on clad pump architectures where double clad designs are used. Currently, polym... more Fiber lasers rely on clad pump architectures where double clad designs are used. Currently, polymers are used successfully as pump claddings on Yb-doped laser fibers. In order to transition to resonantly pumped fiber lasers at eye safer wavelengths, polymer pump claddings must have low absorption at those wavelengths. There is currently no suitable low index, low absorption, thermally stable, and high thermal conductivity polymer to act as a low-index coating. This work presents a new class of polymers, termed fluorinated polymer composites (FPCs), which possess improved thermal properties. The FPCs are fabricated by incorporating ceramic nanoparticles into fluorinated polymers. Ultimately, the FPCs could enable further use of fiber lasers at commonly used wavelengths, as well as at eye-safer wavelengths.
We investigate high-energy pulse amplification in a counter-directionally cladding-pumped partly-... more We investigate high-energy pulse amplification in a counter-directionally cladding-pumped partly-quenched heavily erbium-doped fiber. Despite the quenching, we reach a pulse energy of 0.38 mJ, which is several times the saturation energy at the 1563-nm signal wavelength.
At the Naval Research Laboratory (NRL), we are developing infrared glasses, ceramics and optical ... more At the Naval Research Laboratory (NRL), we are developing infrared glasses, ceramics and optical fibers for many active and passive applications. The chalcogenide glasses transmit from approximately 1 μm to 12 μm in the important infrared wavelength region. Fibers have been developed for passive applications, including light-pipes for remote chemical sensor systems for environmental pollution monitoring, exo-planet discovery, scanning near field optical microscopy and aircraft protection systems. Active applications have also been developed to exploit the high optical nonlinearity of the fibers to generate broadband IR supercontinuum sources and Raman wavelength shifters. In addition, rare earth doping has been used to create bright sources in the IR for applications such as dynamic IR scene projection systems. More recent developments have focused on fabricating hollow core negative curvature fiber with waveguide loss 100X lower than the material loss in the infrared. Additionally fiber devices and components have been designed and fabricated. Examples include IR fiber combiners utilized to couple the output from several QCLs in the MWIR and LWIR into a single output fiber, thereby enabling efficient power and wavelength scaling. Robust splicing between different types of fibers has also been demonstrated.
We report results for high quality transparent ceramic window materials (spinel and β-SiC) and hi... more We report results for high quality transparent ceramic window materials (spinel and β-SiC) and high power solid state laser materials (Yb: YO and Yb: LuO). Spinel ceramic demonstrates a record low absorption loss of 6 ppm/cm at 1.06 μm. We also report optical ...
In this paper, we present our recent results in developing cladded-single crystal fibers for high... more In this paper, we present our recent results in developing cladded-single crystal fibers for high power single frequency fiber lasers significantly exceeding the capabilities of existing silica fiber based lasers. This fiber laser would not only exploit the advantages of crystals, namely their high temperature stability, high thermal conductivity, superior environmental ruggedness, high propensity for rare earth ion doping and low nonlinearity, but will also provide the benefits from an optical fiber geometry to enable better thermal management thereby enabling the potential for high laser power output in short lengths. Single crystal fiber cores with diameters as small as 35m have been drawn using high purity rare earth doped ceramic or single crystal feed rods by Laser Heated Pedestal Growth (LHPG) process. The mechanical, optical and morphological properties of these fibers have been characterized. The fibers are very flexible and show good overall uniformity. We also measured the optical loss as well as the non-radiative loss of the doped crystal fibers and the results show that the fibers have excellent optical and morphological quality. The gain coefficient of the crystal fiber matches the low quantum defect laser model and it is a good indication of the high quality of the fibers.
This dataset supports the article entitled "110 W High-Efficiency Er-Nanoparticle-Doped Fibe... more This dataset supports the article entitled "110 W High-Efficiency Er-Nanoparticle-Doped Fiber Laser", published at Conference on Lasers and Electro-optics 2018, San Jose, United States, 13-18 May 2018.
Holmium doped fiber lasers (HoDFL) are attractive candidates for high energy lasers used in direc... more Holmium doped fiber lasers (HoDFL) are attractive candidates for high energy lasers used in directed energy applications because they operate at wavelengths that are safer to the eye. The common solution-doping technique for making HoDFs can result in the incorporation of hydroxyl (OH) impurity in the active fiber core. The HoDFL operational wavelength of ~2.0 µm is near the 2.2 µm combination absorption band of the OH fundamental mode and the SiO4 tetrahedron vibration, so the OH concentration must be <1 ppm to prevent degradation of the laser performance. We have routinely fabricated HoDF with [OH] < 0.5 ppm. We have developed an ultralow OH processing technique based on both atmospheric exclusion from the silica core soot preform and careful, extensive drying. We report a resonantly-pumped solution doped Ho3+ fiber laser with a slope efficiency of 74%, and an output power of 96W. We are also investigating nanoparticle (NP) doping, where the holmium ions are encaged in a nanoparticle host selected for properties such as low phonon energy, where they are shielded from the Silica lattice. By optimizing variables such as precursor concentrations, NP ripening times, and surfactant selection during synthesis we have been able to increase the Ho NP concentration levels in Silica fiber cores. This has also allowed us to increase concentrations of otherwise incompatible low phonon energy host materials into the cores of the fibers. Cores comprising Ho doped LaF3 and Lu2O3 nanoparticles exhibited slope efficiencies as high as 85% at 2.06 µm in a MOPA configuration.
We computationally study two-layer motheye nanostructures fabricated on MgAl2O4 spinel ceramic wi... more We computationally study two-layer motheye nanostructures fabricated on MgAl2O4 spinel ceramic windows. We investigated the parameters of the structure, including height, width, and shape, in order to optimize its power transmission efficiency over a broad bandwidth. We found a two-layer motheye structure in which the cones of the upper structure have a concave shape that can theoretically achieve more than 99.8% transmission at normal incidence in the wavelength range between 0.4 μm and 5.0 μm.
A nanoparticle (NP) doping technique was developed for fabricating erbium (Er)- and holmium (Ho)-... more 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.
It has been experimentally observed that moth-eye antireflective microstructures at the end of As... more It has been experimentally observed that moth-eye antireflective microstructures at the end of As<sub>2</sub>S<sub>3</sub> fibers have an increased laser damage threshold relative to thin-film antireflective coatings. In this work, we computationally study the irradiance enhancement in As<sub>2</sub>S<sub>3</sub> moth-eye antireflective microstructures in order to explain the increased damage threshold. We show that the irradiance enhancement occurs mostly on the air side of the interfaces and is minimal in the As<sub>2</sub>S<sub>3</sub> material. We give a physical explanation for this behavior.
This paper examines the evolution of DUI (Driving Under the Influence) education, particularly th... more This paper examines the evolution of DUI (Driving Under the Influence) education, particularly the shift from traditional inperson classes to online platforms.
Fiber lasers rely on clad pump architectures where double clad designs are used. Currently, polym... more Fiber lasers rely on clad pump architectures where double clad designs are used. Currently, polymers are used successfully as pump claddings on Yb-doped laser fibers. In order to transition to resonantly pumped fiber lasers at eye safer wavelengths, polymer pump claddings must have low absorption at those wavelengths. There is currently no suitable low index, low absorption, thermally stable, and high thermal conductivity polymer to act as a low-index coating. This work presents a new class of polymers, termed fluorinated polymer composites (FPCs), which possess improved thermal properties. The FPCs are fabricated by incorporating ceramic nanoparticles into fluorinated polymers. Ultimately, the FPCs could enable further use of fiber lasers at commonly used wavelengths, as well as at eye-safer wavelengths.
We investigate high-energy pulse amplification in a counter-directionally cladding-pumped partly-... more We investigate high-energy pulse amplification in a counter-directionally cladding-pumped partly-quenched heavily erbium-doped fiber. Despite the quenching, we reach a pulse energy of 0.38 mJ, which is several times the saturation energy at the 1563-nm signal wavelength.
At the Naval Research Laboratory (NRL), we are developing infrared glasses, ceramics and optical ... more At the Naval Research Laboratory (NRL), we are developing infrared glasses, ceramics and optical fibers for many active and passive applications. The chalcogenide glasses transmit from approximately 1 μm to 12 μm in the important infrared wavelength region. Fibers have been developed for passive applications, including light-pipes for remote chemical sensor systems for environmental pollution monitoring, exo-planet discovery, scanning near field optical microscopy and aircraft protection systems. Active applications have also been developed to exploit the high optical nonlinearity of the fibers to generate broadband IR supercontinuum sources and Raman wavelength shifters. In addition, rare earth doping has been used to create bright sources in the IR for applications such as dynamic IR scene projection systems. More recent developments have focused on fabricating hollow core negative curvature fiber with waveguide loss 100X lower than the material loss in the infrared. Additionally fiber devices and components have been designed and fabricated. Examples include IR fiber combiners utilized to couple the output from several QCLs in the MWIR and LWIR into a single output fiber, thereby enabling efficient power and wavelength scaling. Robust splicing between different types of fibers has also been demonstrated.
We report results for high quality transparent ceramic window materials (spinel and β-SiC) and hi... more We report results for high quality transparent ceramic window materials (spinel and β-SiC) and high power solid state laser materials (Yb: YO and Yb: LuO). Spinel ceramic demonstrates a record low absorption loss of 6 ppm/cm at 1.06 μm. We also report optical ...
In this paper, we present our recent results in developing cladded-single crystal fibers for high... more In this paper, we present our recent results in developing cladded-single crystal fibers for high power single frequency fiber lasers significantly exceeding the capabilities of existing silica fiber based lasers. This fiber laser would not only exploit the advantages of crystals, namely their high temperature stability, high thermal conductivity, superior environmental ruggedness, high propensity for rare earth ion doping and low nonlinearity, but will also provide the benefits from an optical fiber geometry to enable better thermal management thereby enabling the potential for high laser power output in short lengths. Single crystal fiber cores with diameters as small as 35m have been drawn using high purity rare earth doped ceramic or single crystal feed rods by Laser Heated Pedestal Growth (LHPG) process. The mechanical, optical and morphological properties of these fibers have been characterized. The fibers are very flexible and show good overall uniformity. We also measured the optical loss as well as the non-radiative loss of the doped crystal fibers and the results show that the fibers have excellent optical and morphological quality. The gain coefficient of the crystal fiber matches the low quantum defect laser model and it is a good indication of the high quality of the fibers.
This dataset supports the article entitled "110 W High-Efficiency Er-Nanoparticle-Doped Fibe... more This dataset supports the article entitled "110 W High-Efficiency Er-Nanoparticle-Doped Fiber Laser", published at Conference on Lasers and Electro-optics 2018, San Jose, United States, 13-18 May 2018.
Holmium doped fiber lasers (HoDFL) are attractive candidates for high energy lasers used in direc... more Holmium doped fiber lasers (HoDFL) are attractive candidates for high energy lasers used in directed energy applications because they operate at wavelengths that are safer to the eye. The common solution-doping technique for making HoDFs can result in the incorporation of hydroxyl (OH) impurity in the active fiber core. The HoDFL operational wavelength of ~2.0 µm is near the 2.2 µm combination absorption band of the OH fundamental mode and the SiO4 tetrahedron vibration, so the OH concentration must be <1 ppm to prevent degradation of the laser performance. We have routinely fabricated HoDF with [OH] < 0.5 ppm. We have developed an ultralow OH processing technique based on both atmospheric exclusion from the silica core soot preform and careful, extensive drying. We report a resonantly-pumped solution doped Ho3+ fiber laser with a slope efficiency of 74%, and an output power of 96W. We are also investigating nanoparticle (NP) doping, where the holmium ions are encaged in a nanoparticle host selected for properties such as low phonon energy, where they are shielded from the Silica lattice. By optimizing variables such as precursor concentrations, NP ripening times, and surfactant selection during synthesis we have been able to increase the Ho NP concentration levels in Silica fiber cores. This has also allowed us to increase concentrations of otherwise incompatible low phonon energy host materials into the cores of the fibers. Cores comprising Ho doped LaF3 and Lu2O3 nanoparticles exhibited slope efficiencies as high as 85% at 2.06 µm in a MOPA configuration.
We computationally study two-layer motheye nanostructures fabricated on MgAl2O4 spinel ceramic wi... more We computationally study two-layer motheye nanostructures fabricated on MgAl2O4 spinel ceramic windows. We investigated the parameters of the structure, including height, width, and shape, in order to optimize its power transmission efficiency over a broad bandwidth. We found a two-layer motheye structure in which the cones of the upper structure have a concave shape that can theoretically achieve more than 99.8% transmission at normal incidence in the wavelength range between 0.4 μm and 5.0 μm.
A nanoparticle (NP) doping technique was developed for fabricating erbium (Er)- and holmium (Ho)-... more 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.
It has been experimentally observed that moth-eye antireflective microstructures at the end of As... more It has been experimentally observed that moth-eye antireflective microstructures at the end of As<sub>2</sub>S<sub>3</sub> fibers have an increased laser damage threshold relative to thin-film antireflective coatings. In this work, we computationally study the irradiance enhancement in As<sub>2</sub>S<sub>3</sub> moth-eye antireflective microstructures in order to explain the increased damage threshold. We show that the irradiance enhancement occurs mostly on the air side of the interfaces and is minimal in the As<sub>2</sub>S<sub>3</sub> material. We give a physical explanation for this behavior.
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