D. Gibson

Single crystal fibers for high power lasers

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 35m 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.

IR Imaging Bundles for HWIL Testing

We report on development and characterization of square registered infrared imaging bundles fabricated from As2S3fiber for HWIL applications. Bundle properties and cross-talk measurements are presented.

Non-linearity in chalcogenide glasses and fibers, and their applications

High nonlinearity and large IR transparency make chalcogenide fibers well suited for compact Raman amplifiers, supercontinuum generation and other mid-IR sources. As2S3 fiber has record high theoretical gain compared with silica fiber for slow-light applications.

Desorption electrospray ionization-mass spectrometric analysis of low vapor pressure chemical particulates collected from a surface.

The collection of a low vapor pressure chemical simulant triethyl phosphate sorbed onto silica gel (TEP/SG) from a surface with subsequent analysis of the TEP/SG particulates using desorption electrospray ionization-mass spectrometry (DESI-MS) is described. Collection of TEP/SG particulates on a surface was accomplished using a sticky screen sampler composed of a stainless steel screen coated with partially polymerized polydimethylsiloxane (PDMS). DESI-MS analysis of TEP/SG particulates containing different percentages of TEP sorbed onto silica gel enabled the generation of response curves for the TEP ions m/z 155 and m/z 127. Using the response curves the calculation of the mass of TEP in a 25 wt% sample of TEP/SG was calculated, results show that the calculated mass of TEP was 14% different from the actual mass of TEP in the sample using the m/z 127 TEP ion response curve. Detection limits for the TEP vapor and TEP/SG particulates were calculated to be 4 μg and 6 particles, respectively.

Progress of Chalcogenide Glass Fibers

High nonlinearity and large IR transparency make these fibers well suited for compact Raman amplifiers, supercontinuum generation and other mid-IR sources. As2S3 fiber has record high theoretical gain compared with silica fiber for slow-light applications.

Collection method for chemical particulates on surfaces with detection using thermal desorption-ion trap mass spectrometry

Successful analysis of particulate/low vapor pressure analytes such as explosives and toxic chemicals, and commercial pesticides require new sampling tools that enable detection of these analytes using current vapor phase detection instruments. We describe a sampling approach that uses stainless steel screens coated with a sticky polydimethyl siloxane (PDMS) coating to capture particulates from surfaces. Preliminary results for the collection of dimethyl methylphosphonate (DMMP) sorbed onto silica gel (SG) particulates (DMMP/SG) from a surface with subsequent analysis by thermal desorption-cylindrical ion trap mass spectrometry (TD-CITMS) are reported.

Fusion splicing of highly dissimilar YAG crystal fiber and silica fiber with reaction bonding

Splices between materials with dissimilar thermal expansion and melting points are particularly difficult to create. We have developed a method for splicing YAG single crystal fiber to silica fiber. Optical losses associated with the splices were measured for multimode fibers to be 0.33 dB. The splices display greater than 50 kPsi of tensile strength with reaction bonding at the interface. Study of the elemental composition at the splice interface showed formation of a stable intermediate material that provides mechanical strength to the splice. This is a major step toward developing very high power integrated and compact laser systems based on crystals and glass despite their stark dissimilarities in physical and material properties.

Index change of chalcogenide materials from precision glass molding processes

With the increase in demand for infrared optics for thermal applications and the use of glass molding of chalcogenide materials to support these higher volume optical designs, an investigation of changes to the optical properties of these materials is required. Typical precision glass molding requires specific thermal conditions for proper lens molding of any type of optical glass. With these conditions a change (reduction) of optical index occurs after molding of all oxide glass types and it is presumed that a similar behavior will happen with chalcogenide based materials. We will discuss the effects of a typical molding thermal cycle for use with commercially and newly developed chalcogenide materials and show results of index variation from nominally established material data.

Recent advancements in transparent ceramics and crystal fibers for high power lasers

In this paper, we present our recent progress in the development of rare-earth (Yb3+ or Ho3+) doped Lu2O3 and Y2O3 sesquioxides for high power solid state lasers. We have fabricated high quality transparent ceramics using nano-powders synthesized by a co-precipitation method. This was accomplished by developments in high purity powder synthesis and low temperature scalable sintering technology developed at NRL. The optical, spectral and morphological properties as well as the lasing performance from our highly transparent ceramics are presented. In the second part of the paper, we discuss our recent research effort in developing cladded-single crystal fibers for high power single frequency fiber lasers has the potential to significantly exceed the capabilities of existing silica fiber based lasers. Single crystal fiber cores with diameters as small as 35μm have been drawn using high purity rare earth doped ceramic or single crystal feed rods by the Laser Heated Pedestal Growth (LHPG) process. Our recent results on the development of suitable claddings on the crystal fiber core are discussed.

Crystal fibers for high power lasers

In this paper, we present our recent progress in developing single crystal fibers for high power single frequency fiber lasers. The optical, spectral and morphological properties as well as the loss and gain measured from these crystal fibers drawn by Laser Heated Pedestal Growth (LHPG) system are also discussed. Results on application of various cladding materials on the crystal core and the methods of fiber end-face polishing are also presented.