Fred Kung

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.

Chalcogenide fiber based mid-IR sources and applications

In the visible and near-IR, silica fiber high power lasers, amplifiers, fiber combiners, couplers, fiber optic switches and attenuators have demonstrated impressive performance and have become critical technologies for many applications such as telecommunications, spectroscopy, sensing, laser machining, and directed energy. As mid-IR and long-wave IR applications become more prolific, the need for analogous devices in the IR becomes important. Chalcogenide fiber shows great promise for meeting the source and device needs for applications in the IR. Chalcogenide fiber has a broad transmission range out to 12 μm, depending upon composition, and is ideal for transmission of light in these wavelength ranges. In addition, chalcogenide fibers can be doped with rare earth ions or the high nonlinearity of chalcogenide glasses can be exploited to fabricate sources in the mid and long-wave-IR. In work to date, we have demonstrated an all-fiber broadband supercontinuum source in the mid-IR from 1.9 to 4.8 μm and have scaled up the power to >500 mW in this wavelength range [1]. We have also demonstrated a microchip laser pumped mid-IR supercontinuum source from 3.65 to 4.9 μm [2], IR fiber Raman amplification [3], and broad band mid-IR rare earth doped fiber sources [4]. Passive optical devices that we have demonstrated include chalcogenide fiber based optical attenuators [5], registered coherent imaging bundles [6] and multimode fiber combiners for power and wavelength combining of quantum cascade lasers [7]. In addition, we have developed methods to fabricate high power anti-reflection surface structures on chalcogenide fibers [8], splicing methods for chalcogenide fibers, and cabling and termination methods for fibers to allow the fiber sources and devices to be packaged for applications. Environmental testing and power testing has been performed on chalcogenide fiber and devices to determine the operational limits of these technologies. In this paper, we will review our prior and recent work on chalcogenide based mid-IR sources and devices and the packaging, characterization and applications of these sources and devices.

Thermal and vibration testing of ruggedized IR-transmitting fiber cables

We present successful results obtained for thermal/ vibration testing of ruggedized, IR-transmitting chalcogenide glass fiber cables using a government facility with state-of-the-art equipment capable of MIL-SPEC environmental testing. We will also present results of a direct imprinting process to create novel “moth eye” patterned surfaces on the IR fiber cable ends that significantly reduces endface reflection losses from 17% to less than 3%. The cables with these imprinted “moth eye” ends transmit much higher IR laser power without damage than was obtained for previous cables with traditional AR coatings.

Delivery of FEL laser energy at 6.1 /spl mu/m and 6.45 /spl mu/m with chalcogenide fibers

Summary form only given. Laser energy at 6.45 /spl mu/m, which corresponds to the Amide II band of protein, has been shown to be effective for soft tissue surgery while laser energy at 6.1 /spl mu/m, which corresponds to the bending mode of water, has been shown to be effective for bone surgery. These wavelengths enable efficient ablation of tissue and bone with little collateral damage. The Vanderbilt-free-electron laser (FEL), operating in the 2-9 /spl mu/m region, is being developed as a surgical tool at these wavelengths. In order to be an effective surgical tool, however, the FEL energy must be delivered to the patient in such a way that the surgeon can readily control application of the energy to the tissue. In this paper, we demonstrate that chalcogenide fibers are capable of handling the power levels necessary for laser surgical applications.