High-efficiency and wideband interlayer grating couplers in multilayer Si/SiO_2/SiN platform for 3D integration of optical functionalities

Abstract

We have designed interlayer grating couplers with single/double metallic reflectors for Si/SiO(2)/SiN multilayer material platform. Out-of-plane diffractive grating couplers separated by 1.6 μm thick buffer SiO(2) layer are vertically stacked against each other in Si and SiN layers. Geometrical optimization using genetic algorithm coupled with electromagnetic simulations using two-dimensional (2D) finite element method (FEM) results in coupler designs with high peak coupling efficiency of up to 89% for double- mirror and 64% for single-mirror structures at telecom wavelength. Also, 3-dB bandwidths of 40 nm and 50 nm are theoretically predicted for the two designs, respectively. We have fabricated the grating coupler structure with single mirror. Measured values for insertion loss and 3-dB bandwidth in the fabricated single-mirror coupler confirms the theoretical results. This opens up the possibility of low-loss 3D dense integration of optical functionalities in hybrid material platforms.

Expanding the Silicon Photonics Portfolio With Silicon Nitride Photonic Integrated Circuits

“…Moreover the manufacturing flexibility of SiN has been used to either stack multiple layers of SiN [74], [75] or combine SiN and SOI on a single platform [36], [76], [77]. This approach pavesthe way for low loss and high integration density PICs.…”

“…Approaches using directional couplers [74], grating couplers [77], inverted tapers [78] and reflector mirrors [79] are used to implement interlayer coupling in multilayer platforms. Typically the multiple layers in multilayer platforms are separated by an oxide layer.…”

Multilayer Silicon Nitride-on-Silicon Integrated Photonic Platforms and Devices

“…The optical transparency of SiN is high in the near-infrared and visible wavelength range [9], making it suitable for non-telecommunication applications, such as biosensors and frequency combs [10]- [13]. Because of these optical properties, several recent demonstrations have shown the integration of SiN waveguides onto SOI photonic platforms [14]- [17] or the integration of Si waveguides onto a SiN waveguide platform [18], [19] to combine the active and passive optical functionalities in Si-based integrated photonics.…”

Photonic Packaging: Transforming Silicon Photonic Integrated Circuits into Photonic Devices

“…In addition to Fiber-to-PIC coupling, grating-couplers can be used for optical proximity coupling or interlayer coupling [62][63][64], which allows for efficient vertical chip-to-chip and even board-to-chip connections (in conjunction with optical-PCBs mentioned above). Combined with low-loss waveguides for horizontal distribution, this vertical chip-to-chip optical connection allows for the possibility of true 3D integrated routing of light across optical-motherboards to multiple Si-PICs.…”