Suspended nanomembrane silicon photonic integrated circuits

Leveraging the low linear and nonlinear absorption loss of silicon at mid-infrared(mid-IR)wavelengths,silicon photonic integrated circuits(PICs)have attracted significant attention for mid-IR applications including optical sensing,spectroscopy,and nonlinear optics.However,mid-IR silicon PICs typically show moderate performance compared to state-of-the-art silicon photonic devices operating in the telecommunication band.Here,we proposed and demonstrated suspended nanomembrane silicon(SNS)PICs with light-guiding within deep-subwavelength waveguide thickness for operation in the short-wavelength mid-IR region.We demonstrated key building components,namely,grating couplers,waveguide arrays,micro-resonators,etc.,which exhibit excellent performances in bandwidths,back reflections,quality factors,and fabrication tolerance.Moreover,the results show that the proposed SNS PICs have high compatibility with the multi-project wafer foundry services.Our study provides an unprecedented platform for mid-IR integrated photonics and applications.

Blazed subwavelength grating coupler

Short-wavelength mid-infrared(2–2.5 μm wave band) silicon photonics has been a growing area to boost the applications of integrated optoelectronics in free-space optical communications, laser ranging, and biochemical sensing. In this spectral region, multi-project wafer foundry services developed for the telecommunication band are easily adaptable with the low intrinsic optical absorption from silicon and silicon dioxide materials. However,light coupling techniques at 2–2.5 μm wavelengths, namely, grating couplers, still suffer from low efficiencies,mainly due to the moderated directionality and poor diffraction-field tailoring capability. Here, we demonstrate a foundry-processed blazed subwavelength coupler for high-efficiency, wide-bandwidth, and large-tolerance light coupling. We subtly design multi-step-etched hybrid subwavelength grating structures to significantly improve directionality, as well as an apodized structure to tailor the coupling strength for improving the optical mode overlap and backreflection. Experimental results show that the grating coupler has a recorded coupling efficiency of-4.53 dB at a wavelength of 2336 nm with a 3-dB bandwidth of ~107 nm. The study opens an avenue to developing state-of-the-art light coupling techniques for short-wavelength mid-infrared silicon photonics.

Integrated optoelectronics with two-dimensional materials

As we enter the post-Moore era,heterogeneous optoelectronic integrated circuits(OEICs)are attracting significant attention as an alternative approach to scaling to smaller-sized transistors.Two-dimensional(2D)materials,offering a range of intriguing optoelectronic properties as semiconductors,semimetals,and insulators,provide great potential for developing nextgeneration heterogeneous OEICs.For instance,Fermi levels of 2D materials can be tuned by applying electrical voltages,while their atomically thin geometries are inherently suited for the fabrication of planar devices without suffering from lattice mismatch.Since the first graphene-on-silicon OEICs were demonstrated in 2011,2D-material heterogeneous OEICs have significantly progressed.To date,researchers have a better understanding of the importance of interface states on the optical properties of chip-integrated 2D materials.Moreover,there has been impressive progress towards the use of 2D materials for waveguide-integrated lasers,modulators,and photodetectors.In this review,we summarize the history,status,and trend of integrated optoelectronics with 2D materials.