Robert E. Miklos

Development of low-loss IR transmitting chalcogenide glass fibers

We have fabricated long lengths of low loss sulphide and telluride glass fibers for the 1 - 6 and 3 - 12 micrometers regions, respectively. Minimum losses for core/clad fibers are approximately 0.6 and 0.7 dB/m, respectively, while core-only fibers have exhibited losses of about 0.1 dB/m. The measurements have been performed on long lengths, typically 7 - 50 meters. Fiber strengths are reasonable for many short length applications, but improved processing will lead to stronger fibers for long length applications. These fibers are candidates for chemical sensors and for IR laser power delivery.

Infrared optical fibers and their applications

Chalcogenide glass fibers based on sulphide, selenide, telluride and their rare earth doped compositions are being actively pursued at the Naval Research Laboratory (NRL) as well as world-wide. Great strides have been made in reducing optical losses using improved chemical purification techniques, but further improvements are needed in both purification and fiberization technology to attain the theoretical optical losses. Despite this, current singlemode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, scanning near field microscopy/spectroscopy, and fiber IR sources/lasers and amplifiers.

IR fiber optics development at the Naval Research Laboratory

We report the first technology demonstration of the use of an IR fiber cable in an IRCM system for missile jamming. The IR fiber cable contains sulphide glass fibers which possess low loss, high strength and high threshold to laser damage. The fiber cable was used to transmit the output from a laser operating in the 2 - 5 micrometers atmospheric window to a Jam Head located remote from the laser. The demonstration was successful and fiber cable performed remarkably well and without damage.

IR-GRIN optics for imaging

Infrared (IR) transmitting gradient index (GRIN) materials have been developed for broad-band IR imaging. This material is derived from the diffusion of homogeneous chalcogenide glasses has good transmission for all IR wavebands. The optical properties of the IR-GRIN materials are presented and the fabrication methodologies are discussed. Modeling and optimization of the diffusion process is exploited to minimize the deviation of the index profile from the design profile.

Effect of temperature on the loss of the As-S-Se and Ge-As-Se-Te chalcogenide glass fibers

The change in the absorption loss relative to room temperature of the IR-transmitting sulfur-based (As-S-Se) and tellurium-based (Ge-As-Se-Te) glass fibers in the temperature range of-110°C? T? 110°C was investigated. For the sulfur-based (As-S-Se) glass fibers, the change in loss relative to room temperature was slightly affected by temperature in the wavelength region of 1-5 ?m. For ? ? 6 ?m, the change in loss was mainly due to multiphonon absorption. For the tellurium-based (Ge-As-Se-Te) glass fibers, the attenuation increased significantly at T 40°C. This is mainly attributed to thermally activated free carriers associated with the semi-metallic character ofthe Te atom. For ? ? 4.2 ?m, the loss due to electronic and free carrier absorption was strongly affected by temperature. In the wavelength region of 5 - 11 ?m, the loss was mainly due to free carrier absorption. Beyond ?? 1 1 ?m, multiphonon absorption dominated the loss spectrum at T ? 60°C while free carrier absorption contributed mainly to the total loss at T 80°C.

Fabrication and Properties of Ceramic Laser Materials

We have developed a novel sintering process using in-house prepared powders to make transparent ceramics such as Yb:Y2O3. The properties of this material indicate that it is suitable for making a high power laser.