Abstract
In this Letter, we report suspended silicon waveguides operating at a wavelength of 7.67μm with a propagation loss of 3.1±0.3 dB/cm. To our knowledge, this is the first demonstration of low-loss silicon waveguides at such a long wavelength, with loss comparable to other platforms that use more exotic materials. The suspended Si waveguide core is supported by a sub-wavelength grating that provides lateral optical confinement while also allowing access to the buried oxide layer so that it can be wet etched using hydrofluoric acid. We also demonstrate low-loss waveguide bends and s-bends.
Highlights
In this Letter, we report suspended silicon waveguides operating at a wavelength of 7.67 μm with a propagation loss of 3.1 0.3 dB∕cm. This is the first demonstration of low-loss silicon waveguides at such a long wavelength, with loss comparable to other platforms that use more exotic materials
The suspended Si waveguide core is supported by a sub-wavelength grating that provides lateral optical confinement while allowing access to the buried oxide layer so that it can be wet etched using hydrofluoric acid
In [20,21], we presented an alternative approach, consisting of a strip waveguide with subwavelength grating (SWG) holes that provide lateral optical confinement as well as access to the buried oxide (BOX)
Summary
In this Letter, we report suspended silicon waveguides operating at a wavelength of 7.67 μm with a propagation loss of 3.1 0.3 dB∕cm. The suspended Si waveguide core is supported by a sub-wavelength grating that provides lateral optical confinement while allowing access to the buried oxide layer so that it can be wet etched using hydrofluoric acid. An alternative approach to changing the material is to use SOI wafers, but to limit the optical mode overlap with SiO2, such as by suspending the Si waveguide core or by substantially increasing the Si core size [13].
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