Here are some projects offered by PHOSL, the exact content can be adapted to match semester or master projects time commitments. Feel free to contact us, there might also be other possibilities!
Optical Characterization of Periodically-Poled Thin-Film Lithium Niobate Waveguides
Background:
Thin-film lithium niobate is one of the most promising materials for a standardized PIC platform capable providing optimum conditions for a multitude of photonic processes. Conventionally, lithium niobate crystal has been a favourable due to its high electro-optic coefficient, high intrinsic nonlinearities, and wide transparency window. Devices based on lithium niobate have already showed superior performance on nonlinear frequency conversion via periodic poling compared to other materials platforms. With the recent advances on microfabrication, thin-film lithium niobate can now be directly etched to form low-loss waveguides and resonators. High index contrast between lithium niobate and the cladding enables the propagation of high intensity modes with strong confinement through the nonlinear medium, giving optimal conditions for efficient frequency conversion.
Project Description:
The project will focus on second-order nonlinearities within periodically-poled lithium niobate (PPLN), more specifically on second-harmonic generation and difference-frequency generation. We aim to optimize these fundamental building blocks to achieve broadband operation and/or high conversion efficiency. Tasks for this project can include(but not limited to) optical measurements on PPLN waveguides, characterizing the response at different pump/signal wavelengths & temperatures. In addition, the student will also be involved in the post-processing of these measurements for experimentally extracting waveguides intrinsic properties properties.
If you are interested, please contact Yesim Koyaz ([email protected]) for detailed information.
References:
[1] Zhu, Di, et al., Advances in Optics and Photonics 13.2 (2021): 242-352.
[2] Rao, Ashutosh, et al., Optics express 27.18 (2019): 25920-25930.
[3] Ledezma, Luis, et al, Optica 9.3 (2022): 303-308.
Linear and nonlinear characterization of gallium nitride optical devices
Background:
Gallium nitride (GaN) is a III-V direct bandgap semiconductor which combines mid-infrared transparency, a large bandgap (3.4 eV) and high Kerr and second-order nonlinearity up to 20 pm/V. This has led to the demonstration of efficient second harmonic generation [1], four-wave mixing [2] and micro-resonator solitons [3], and supercontinuum generation [4] on integrated GaN devices. Many other nonlinear processes exploiting optical and electro-optical properties of this material remain to be explored by engineering integrated optical devices such as waveguides, micro-resonators, and modulators.
Project Description:
The semester project focuses on the characterization of GaN optical waveguides, ring resonators and modulators fabricated by Hexisense*. First, the student will need to verify the linear behavior of photonic devices by testing coupling and propagation losses. Subsequently, the nonlinear response of waveguides under continuous and pulsed regimes, as well as the electro-optic modulation of optical resonators, will be explored.
If you are interested, please contact Christian Lafforgue ([email protected]) and/or Samantha Sbarra ([email protected]) for more information.
References:
- Roland, I. et al. Phase-matched second harmonic generation with on-chip GaN-on-Si microdisks. Sci Rep 6, 34191 (2016).
- Munk, D. et al. Four-wave mixing and nonlinear parameter measurement in a gallium-nitride ridge waveguide. Opt. Mater. Express, OME 8, 66–72 (2018).
- Zheng, Y. et al. Integrated Gallium Nitride Nonlinear Photonics. Laser & Photonics Reviews 16, 2100071 (2022).
- Fan, W. et al. Supercontinua from integrated gallium nitride waveguides. Optica, OPTICA 11, 1175–1181 (2024).
*https://hexisense.com/