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.
Optical performance of aluminium nitride micro-ring resonators
Background:
Aluminium nitride stands out among semiconductors due to its large band gap, making it attractive for optical applications ranging from the UV to mid-infrared range. Consequently, it has been used in both linear and nonlinear optical devices over the past decade. The performance of the latter has significantly improved since it became possible to grow crystalline substrates, reducing defect density and consequently the optical losses of its sputtered counterpart. However, the influence of material properties on the quality of the final devices is still not well documented in the literature. A deeper understanding of the limiting factors is necessary to further advance this platform.
Project Description:
The semester project focuses on the linear characterization of optical ring resonators fabricated in the CMi and IPHYS cleanrooms, using crystalline substrates grown in LASPE reactors on the EPFL campus. The student will be introduced to fundamental techniques for measuring optical coupling and propagation losses in photonic devices. This will be achieved by becoming familiar with the exploitation of tuneable telecom lasers and both fibered and free-space optical components. By post-processing the collected data, the student will identify which samples exhibit the best optical performance, providing crucial feedback for refining photonic chip design and fabrication protocols.
If you are interested, please contact Samantha Sbarra ([email protected]) for more information.
References:
-
Liu, X., Bruch, A. W. & Tang, H. X. Aluminum nitride photonic integrated circuits: from piezo-optomechanics to nonlinear optics. Adv. Opt. Photonics 15, 236 (2023).
-
Liu, X. et al. Integrated High- Q Crystalline AlN Microresonators for Broadband Kerr and Raman Frequency Combs. ACS Photonics 5, 1943–1950 (2018).
-
Bruch, A. W. et al. 17 000%/W second-harmonic conversion efficiency in single- crystalline aluminum nitride microresonators. Appl. Phys. Lett. 113, 0–5 (2018).