Chalcogenide glasses and structures for quantum sensing

Chalcogenide glasses are formed by combining chalcogen elements with IV-V elements. Among the family of glasses, As ₂S ₃, and As ₂Se ₃ are important infrared (IR) transparent materials for a variety of applications such as IR sensors, waveguides, and photonic crystals. With the promise of accessibility to any wavelengths between 3.5 and 16 μm using tunable quantum cascade lasers (QCL) and chalcogenides with IR properties that can be compositionally adjusted, ultra-sensitive, solid-state, photonic-based chemical sensing in mid-wave IR region is now possible. Pacific Northwest National Laboratory (PNNL) has been developing quantum cascade lasers (QCLs), chalcogenides, and all other components for an integrated approach to chemical sensing. Significant progress has been made in glass formation and fabrication of different structures at PNNL. Three different glass-forming systems, As-S, As-S-Se, and As-S-Ag have been examined for this application. Purification of constituents from contaminants and thermal history are two major issues in obtaining defect-free glasses. We have shown how the optical properties can be systematically modified by changing the chemistry in As-S-Se system. Different fabrication techniques need to be employed for different geometries and structures. We have successfully fabricated periodic arrays and straight waveguides using laser-writing and characterized the structures. Wet-chemical lithography has been extended to chalcogenides and challenges identified. We have also demonstrated holographic recording or diffraction gratings in chalcogenides.