Abstract
Silicon Nitride (SiN) is emerging as a promising material for a variety of integrated photonic applications. Given its low index contrast however, a key challenge remains to design efficient couplers for the numerous platforms in SiN photonics portfolio. Using a combination of bottom reflector and a chirp generating algorithm, we propose and demonstrate high efficiency, grating couplers on two distinct SiN platforms. For a partially etched grating on 500 nm thick SiN, a calculated peak efficiency of −0.5 dB/coupler is predicted, while for a fully etched grating on 400 nm thick SiN, an efficiency of −0.4 dB/coupler is predicted. Experimentally measured coupling efficiencies are observed to be −1.17 and −1.24 dB/coupler for the partial and fully etched grating couplers respectively in the C-L band region. Furthermore, through numerical simulations, it is shown that the chirping algorithm can be implemented in eight additional combinations comprising SiN film thickness between 300–700 nm as well as alternate claddings, to achieve a per coupler loss between −0.33 to −0.65 dB.
Highlights
Silicon Nitride (SiN) is emerging as a promising material for a variety of integrated photonic applications
Our analysis reveals that the under-etching of the front-end narrow trenches, which is more prominent in design B, to be the likely cause of this mismatch
We have demonstrated a novel scheme for grating couplers on SiN photonic chips
Summary
Silicon Nitride (SiN) is emerging as a promising material for a variety of integrated photonic applications. Using a combination of bottom reflector and a chirp generating algorithm, we propose and demonstrate high efficiency, grating couplers on two distinct SiN platforms. Several reasons are attributed to this, such as SiN exhibiting a wideband spectral transparency encompassing visible to mid-infrared, having higher tolerance to fabrication imperfections owing to a moderate index contrast and its near total absence of two photon absorption Such vast potential has paved way for the emergence of several SiN platforms that cater to applications ranging from passive wavelength division multiplexing (WDM), spectroscopy, sensing as well as integrated nonlinear photonics. There are principally two ways of enabling this task, which are in-plane and out-of-plane coupling The former typically consists of edge couplers and is known to deliver high coupling efficiency as well as a broad bandwidth. By using a combination of a bottom reflector and a chirping generator, we show a sub-dB coupling loss on two distinct platforms, which are, a 500 nm thick SiN with an air cladding and a 400 nm thick SiN on SiO2 cladding
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
