Date of Award
Doctor of Philosophy (PhD)
The chalcogenide glass, Ge28Sb12Se60, is a promising material platform for compact, low-threshold nonlinear optical devices operating in the near- to mid-infrared. It is particularly attractive given its wide range of transparency, large Kerr coefficient, and relatively weak multi-photon absorption. The nonlinear optical properties of Ge28Sb12Se60 were investigated in bulk and waveguide forms, over a range of wavelengths from 1.0 to 3.5 μm. From z-scan measurements at 1.03 µm, using circularly polarized, 200 fs pulses at 374 kHz, bulk Ge28Sb12Se60 glass was found to have a nonlinear refractive index ~130 times that of fused silica and a two-photon absorption coefficient of 3.5 cm/GW. Ge-Sb-Se waveguides and microresonators were designed and characterized, laying groundwork for the development of efficient, compact nonlinear devices such as frequency combs and optical switches. In particular, single-mode Ge-Sb-Se strip waveguides, fabricated by photo- or e-beam lithography, followed by thermal evaporation and lift-off, were demonstrated with average propagation losses of 11.8 dB/cm at 1.03 µm and 4.0-6.1 dB/cm at 1.55 µm. Nonlinear optical waveguides were characterized with measurements of spectral broadening and intensity-dependent transmission, revealing a large measured nonlinear figure of merit of 5.2±1.6 at 1.55 µm. Hybrid chalcogenide-silica wedge microresonators were characterized from 1500-1630 nm, with loaded quality factors up to 1.5x105 and thermal resonant shifts ~60.5 pm/˚C. Finally, planar chalcogenide-based ring resonators were designed for operation at 1.55 and 3.5 µm, simulating dispersion and optimizing waveguide dimensions for maximum four-wave mixing conversion efficiency. Ring resonators with 6- and 20-µm radii were demonstrated with intrinsic quality factors of 1-2x104 and 8.3x104, respectively.
Krogstad, Molly Rebecca, "Ge-Sb-Se Chalcogenide Glass for Near- and Mid-Infrared Nonlinear Photonics" (2018). Physics Graduate Theses & Dissertations. 263.