A review of some properties of chalcogenide glasses and the current status of their applications is given. Techniques to characterize the linear and non-linear properties of these glasses are introduced and used to measure the optical constants of chalcogenide glasses in the form of bulk, thin film and fiber. Different techniques for the fabrication of gratings and waveguides in these glasses are described. Achievable efficiencies of gratings, as well as propagation losses of fabricated waveguides, are presented. The possibilities of fabricating active devices, such as fiber amplifiers and lasers, are presented. Finally, a novel application of chalcogenide glasses, namely all-optical switching for the fabrication of efficient femtosecond switches, is introduced.

Optical properties and applications of chalcogenide glasses: a review

Fibre lasers in the mid-infrared regime are useful for a diverse range of fields, including chemical and biomedical sensing, military applications and materials processing. This Review summarizes the different rare-earth cations and host materials used in mid-infrared fibre laser technology, and discusses the future applications and challenges for the field.

Towards high-power mid-infrared emission from a fibre laser

Optical Waveguide Theory

The cost, size and availability of electron accelerators are dominated by the achievable accelerating gradient. Conventional high-brightness radio-frequency accelerating structures operate with 30-50 MeV m(-1) gradients. Electron accelerators driven with optical or infrared sources have demonstrated accelerating gradients orders of magnitude above that achievable with conventional radio-frequency structures. However, laser-driven wakefield accelerators require intense femtosecond sources and direct laser-driven accelerators suffer from low bunch charge, sub-micron tolerances and sub-femtosecond timing requirements due to the short wavelength of operation. Here we demonstrate linear acceleration of electrons with keV energy gain using optically generated terahertz pulses. Terahertz-driven accelerating structures enable high-gradient electron/proton accelerators with simple accelerating structures, high repetition rates and significant charge per bunch. These ultra-compact terahertz accelerators with extremely short electron bunches hold great potential to have a transformative impact for free electron lasers, linear colliders, ultrafast electron diffraction, X-ray science and medical therapy with X-rays and electron beams.

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Terahertz-driven linear electron acceleration

Chalcogenide glass fibers based on sulfide, selenide, telluride and their rare earth doped compositions are being actively investigated worldwide. 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 these problems, current single mode and multimode chalcogenide glass fibers are enabling numerous applications. Some of these applications include laser power delivery, chemical sensing, imaging, scanning near field microscopy/spectroscopy, fiber IR sources/lasers, amplifiers and optical switches. The authors assert that the research and development of chalcogenide glasses will grow in the foreseeable future, especially with respect to improvements in the optical quality of the fibers and the performance of the fibers in existing and future applications.

Active and passive chalcogenide glass optical fibers for IR applications: a review

We have synthesized a series of chalcogenide glasses from the As–S–Se system that is designed to have strong nonlinearities. Measurements reveal that many of these glasses offer optical Kerr nonlinearities greater than 400 times that of fused silica at 1.25 and 1.55 µm and figures of merit for all-optical switching greater than 5 at 1.55 µm.

Highly nonlinear As-S-Se glasses for all-optical switching.

The mid-wave IR and long-wave IR laser potential of rare-earth ions in chalcogenide glass fiber is reviewed. Spectroscopic data for the mid-wave and long-wave IR transitions for Pr/sup 3+/, Dy/sup 3+/, and Tb/sup 3+/ in chalcogenide glass is presented and used as a basis for discussion of laser potential in these glasses.

Mid-wave IR and long-wave IR laser potential of rare-earth doped chalcogenide glass fiber

Chalcogenide glasses have demonstrated high third-order Kerr (Χ (3) ) nonlinearities up to 1000x higher than silica glass which make them attractive for applications such as nonlinear switching, optical regeneration, Raman amplification, parametric amplification, and supercontinuum generation. Poling of chalcogenide glasses to induce an effective second order (Χ (2) ) nonlinearity has also been demonstrated and opens the possibility for the use of poled glass waveguides for applications such as frequency conversion or electro-optic modulation. Stimulated Brillouin scattering (SBS) has also been investigated in As 2 S 3 and As 2 Se 3 single-mode fibers. The threshold intensity for the stimulated Brillouin scattering process was measured and used to estimate the Brillouin gain coefficient. Preliminary results indicate record high values for the figure of merit and theoretical gain, compared to silica, which bodes well for slow-light based applications in chalcogenide fibers.

Nonlinear properties of chalcogenide glass fibers

High purity chalcogenide glasses were prepared in the series As 2 S (3− x ) Se x where x  = 0 to 3. The measured third order non-linearities increase with the value of x , and are up to about 1000 times larger than silica for As 2 Se 3 glass. We show that the anharmonic oscillator model, using the normalized photon energy, gives an excellent fit to the data over three orders of magnitude. Single mode optical fibers based on As 2 S 3 and As 2 Se 3 glasses have been fabricated using the double crucible technique and the Stimulated Brillouin Scattering (SBS) investigated. The threshold intensity for the SBS process was measured and used to estimate the Brillouin gain coefficient. Preliminary results indicate record high values for the figure of merit and theoretical gain, compared to silica, which bodes well for slow-light based applications in chalcogenide fibers.

Non-linear properties of chalcogenide glasses and fibers

Chalcogenide glass fibers based on sulphide, selenide, telluride and their rare earth doped compositions are being actively pursued both at the Naval Research Laboratory (NRL) and worldwide. 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, chalcogenide glass fibers are enabling numerous applications which include laser power delivery, chemical sensing, imaging, scanning near field microscopy/spectroscopy, IR sources/lasers, amplifiers and optical switches.

Leslie Brandon Shaw

Papers

Highly nonlinear As-S-Se glasses for all-optical switching.

Mid-wave IR and long-wave IR laser potential of rare-earth doped chalcogenide glass fiber

Nonlinear properties of chalcogenide glass fibers

Non-linear properties of chalcogenide glasses and fibers

Applications of chalcogenide glass optical fibers at nrl