Abstract
A CMOS compatible post-processing method to reduce optical losses in silicon nitride (Si(3)N(4)) integrated optical waveguides is demonstrated. Using thin layer atomic layer deposition (ALD) of aluminum oxide (Al(2)O(3)) we demonstrate that surface roughness can be reduced. A 40 nm thick Al(2)O(3) layer is deposited by ALD over Si(3)N(4) based strip waveguides and its influence on the surface roughness and the waveguide loss is studied. As a result, an improvement in the waveguide loss, from very high loss (60 dB/cm) to low-loss regime (~5 dB/cm) is reported for a 220 nm x 500 nm Si(3)N(4) wire at 900 nm wavelength. This opens prospects to implement very low loss waveguides.
Highlights
Silicon nitride (Si3N4) exhibits bulk material transparency in the visible and infrared part of the electro-magnetic spectrum [1,2]
Using thin layer atomic layer deposition (ALD) of aluminum oxide (Al2O3) we demonstrate that surface roughness can be reduced
A 40 nm thick Al2O3 layer is deposited by ALD over Si3N4 based strip waveguides and its influence on the surface roughness and the waveguide loss is studied
Summary
Silicon nitride (Si3N4) exhibits bulk material transparency in the visible and infrared part of the electro-magnetic spectrum [1,2]. Si3N4 leverages the advantages of the mature complementary-metal-oxide-semiconductor (CMOS) infrastructure to realize uniform and reproducible integrated optical devices within wafer and wafer-to-wafer [13] Together, these factors have contributed to interest shown by the industry and the academia towards Si3N4 technology platform for photonic applications, especially in the visible and very-near-infrared (VNIR) wavelength regime (400-1000 nm). Use of conformal ALD layers to reduce surface roughness and reduce loss in the infrared wavelength regime (λ = 1550 nm) for silicon and titania (TiO2) wire waveguides has been demonstrated [14,15]. The influence of scattering on the propagation loss is expected to be more pronounced in Si3N4 material system at visible-VNIR wavelengths vis-à-vis silicon photonics in the infrared regime. We report the influence of ALD deposition of a thin layer of Al2O3 on the surface roughness and loss in a 220 nm X 500 nm Si3N4 based wire waveguide
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