Abstract
Polymer photonic circuits offer a versatile platform for various applications, including communication, sensing and optical signal processing. Though polymers offer broadband, linear and nonlinear optical properties, the coupling between an optical fibre and a polymer waveguide has been a challenge. In this work, we propose and demonstrate a wafer-scale vertical coupling scheme for polymer waveguides. The scheme uses a silicon nitride grating coupler with an inverse taper to couple between an optical fibre and a SU8 polymer waveguide. We demonstrate a maximum coupling efficiency of -3.55 dB in the C-band and -2.92 dB in the L-band with a 3-dB bandwidth of 74 and 80 nm, respectively. A detailed design and simulation, fabrication, and characterisation results are presented. The scheme demonstrates a scalable and efficient surface grating approach for polymer photonic integrated circuits.
Highlights
Polymer based photonic circuits have attracted considerable attention for a host of applications in sensing and communication
We propose and demonstrate an efficient, scalable, and configurable grating-based coupling and polymer photonic circuit platform
The proposed approach couples light between a single-mode optical fibre and a SU8 waveguide using a combination of Silicon Nitride (SiN) grating and a spot size converter
Summary
Polymer based photonic circuits have attracted considerable attention for a host of applications in sensing and communication. One of the challenges in polymer photonic circuits is achieving efficient coupling between an optical fibre and a single-mode polymer waveguides. Both in-plane, as well as out-of-plane coupling mechanisms, have been explored. We propose and demonstrate an efficient, scalable, and configurable grating-based coupling and polymer photonic circuit platform. The proposed approach couples light between a single-mode optical fibre and a SU8 waveguide using a combination of Silicon Nitride (SiN) grating and a spot size converter. The proposal brings large volume CMOS compatible fabrication of SiN couplers with a configurable polymer waveguide platform Using this approach, we demonstrate a maximum fibre-to-polymer waveguide coupling of 2.92 dB/coupler with a 3-dB bandwidth of 80 nm in the telecommunication L-band wavelength. To the best of our knowledge, the coupling efficiency achieved is the best reported for a grating fibre-chip coupler in a polymer waveguide platform
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