Free-Space Characterization Setup for Low-loss Aluminum Oxide Waveguides at 261 nm

Abstract

We present a methodology for the characterization of deep-ultraviolet (UV) photonic integrated circuits (UV-PICs) based on polycrystalline Al2O3, operating at a wavelength of 261 nm. The platform enables low-loss propagation in the deep UV, and we demonstrate an image-based analysis pipeline for estimating waveguide attenuation using free-space coupling and scattered-light imaging. The characterization approach combines spatial calibration of the imaging system, background analysis, and controlled exposure conditions to extract the exponential decay of scattered light along the propagation direction. Preliminary measurements suggest propagation losses on the order of 4.6 dB/cm for 600 nm wide waveguides, while narrower waveguides exhibit higher attenuation due to increased scattering and reduced mode confinement. This work primarily documents the experimental setup and analysis methodology used for deep-UV characterization, providing a foundation for further validation and refinement of propagation-loss measurements in integrated photonic devices operating in the deep-ultraviolet regime.

Figures (4)

• Figure 1: Characterization of UV 261 chips: (a) Camera based waveguide loss measurement setup at a wavelength of 261 nm and (b,c) spectrometer data before and after the UV filter.
• Figure 2: (a) Exponential decay of scattered intensity along a 200 nm wide waveguide at 261 nm, with the solid line representing the exponential fit. (b) Captured image showing 261 nm light propagation in the 200 nm waveguide.
• Figure 3: (a) Measured propagation losses at 261 nm for waveguide widths of 200, 400, 600, and 800 nm. (b) Example of 261 nm light propagation in a 2000 nm wide waveguide.
• Figure 4: Measured propagation losses at 261 nm across various waveguide widths. The exponential fit is included for visualization purposes only.