Low-loss, low-background aluminium oxide waveguide platform for UV-visible applications

A versatile photonic integrated circuit platform capable of operating across a broad spectral range - from ultraviolet to infrared - is vital for the advancement of on-chip optical microscopy, spectroscopy, and emerging quantum technologies. Such a platform should offer low propagation loss, minimal autofluorescence background, and a high refractive index contrast to enable compact, high-performance designs. In this work, we present Al₂O₃ waveguide platform fabricated using atomic layer deposition that meets these key criteria. At wavelengths of 375 nm and 405 nm, the Al₂O₃ strip waveguide exhibits low propagation loss below 0.75 dB/cm and 0.50 dB/cm, respectively, together with exceptionally low autofluorescence compared to conventional Si₃N₄ and Ta₂O₅ waveguides. These features make the Al2O3 platform a highly promising candidate for next-generation, ultra-sensitive on-chip bioimaging, spectroscopy, and trapped-ion quantum computing applications.