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We experimentally demonstrate the heterogeneous integration of ferroelectric hafnium zirconium oxide (HZO) with a silicon photonic microring resonator and demonstrate two non-volatile states for data storage by switching the polarization of HZO. Capped by transparent conducting titanium doped indium oxide (ITiO), the device functions as a metal insulator semiconductor (MIS) capacitor and utilizes the refractive index modulation via carrier (hole) accumulation and the effect of trapped charges at the ferroelectric–silicon interface to create the non-volatile binary switching states. In contrast to electronic devices where trapped charges at the silicon–ferroelectric interface reduce the memory window, in our ferrophotonic device, trapped charges amplify the refractive index difference in the binary states due to effective screening of the silicon in inversion. By switching the applied bias from negative to positive, the optical power transmitted through the ring switches with 3.5 dB output power difference between the non-volatile set and reset states and 40 pJ switching energy at ±8 V. Preliminary results suggest a path toward achieving sub-1 V non-volatile ferrophotonic switching. 

We experimentally demonstrate slow light photonic crystal waveguide (PCW) and subwavelength waveguide (SWWG) loop terminated Mach-Zehnder interferometer (LT-MZI) sensors in a foundry-fabricated silicon-on-insulator (SOI) platform. We compare the experimental results on sensitivity and limit of detection (LOD) on the interferometer sensors with microcavity-type sensors. We show experimentally that 2-D PCW interferometers have higher phase sensitivities than SWWGs of the same length. Based on experimental results, 20- μ m-long 2-D PCW LT-MZI sensors and 200- μ m-long SWWG LT-MZI sensors achieve an LOD of 3.4×10−4 and 2.3×10−4 RIU, respectively, with nearly the same insertion losses in foundry-fabricated devices. We show that by considering the various sources of loss in our benchtop fiber-to-fiber photonic integrated circuit measurement system, it will be possible to reach 10−7 LOD in both slow light PCW and SWWG-based LT-MZI sensors with on-chip integrated light sources and detectors. We show via simulations and experiment that the LOD of a 20- μ m-long slow light PCW LT-MZI is equivalent to that of a 100- μ m-long SWWG LT-MZI, thus enabling more compact LT_MZI sensors when using slow light PCWs versus SWWGs 

Evanescent field silicon photonics in a silicon-on-insulator or silicon-nitride-on-insulator platforms have been effectively utilized to demonstrate chemical and biosensors over the past decade with applications in the detection of nucleic acids and protein biomarkers for cancers, viruses and infectious diseases, and environmental toxins. By balancing the requirements for efficient low-loss transmission through the waveguide and enhancing light-matter interaction such as with molecules binding on the high index material surfaces in resonant microcavities, slow light and interferometer geometries, various high sensitivity biosensors have been experimentally demonstrated down to few femtograms/ml. various slotted microcavities and waveguides have been experimentally demonstrated. In recent years, subwavelength waveguides have demonstrated high bulk spectral sensitivities approaching ~500nm/RIU (RIU=refractive index unit) in periodic structures with lattice constant (Λ) <<(λ/2n eff ) where n eff is the effective index at wavelength λ. While most experimental demonstrations have been in subwavelength ring resonator geometries, in this research, in addition to experimental demonstration of bulk spectral sensitivity ~775nm/RIU in subwavelength waveguides in interferometer configurations, we investigate optimized geometries that can reach sensitivities ~70,000nm/RIU in compact dimensions. In contrast to Mach-Zehnder interferometer (MZI) sensors of the same geometric interferometer arm lengths, the reflected path in Michelson interferometers (MI) doubles the optical path length, and thus effectively doubles the phase shift in the presence of an analyte. The interference fringe linewidths are narrowed compared to the equivalent MZI and would thus enable smaller changes in analyte concentration to be discerned from the fringe spectra. 

Changes in the real and imaginary parts of the waveguide effective index in the presence of analytes have been used in various microcavity and slow light devices for on-chip sensing and absorption spectroscopy respectively in diverse applications. Periodically patterned waveguide sensors in interferometer configurations can lead to small interferometer sizes comparable in dimensions to microcavity resonator sensors, and/or significantly higher sensitivities compared to resonator type sensors. We show our work with compact silicon photonic interferometer devices for on-chip biosensing and absorbance sensing, overcoming fabrication tolerances with post-fabrication phase trimming. 

We experimentally demonstrated slow wave enhanced phase and spectral sensitivity in asymmetric Michelson interferometer sensors with a phase sensitivity 277,750 rad/RIU-cm and theoretical phase sensitivity as high as 461,810 rad/RIU-cm. In the context of low-cost chip integrated photonic packaged sensors, in this paper we will experimentally demonstrate a method for active tuning of interferometer fringes using phase change materials that will potentially overcome fabrication induced variation of interference fringe wavelengths, thus allowing sensor chip packaging with a fixed wavelength laser and available integrated photodetectors. 

High quality graphene can efficiently be grown on large surface areas of copper foil through chemical vapor deposition (CVD). To transfer CVD graphene onto a substrate for use in nanoscale photonic devices a process called electrochemical bubble delamination is utilized. During the delamination and transfer procedure the CVD graphene is at its most susceptible. Therefore, the incentive to develop a minimal-contact and replicable process is high. The use of a mechanical stage controlled by an actuator is a promising method of avoiding significant mechanical defects like folding or tearing and is capable of ensuring the film is delaminated at the right speed and from bottom to top. The quality of the transferred graphene is varied with regions of high-quality graphene up to 80x80µm while the typical transfer region has a large presence of gaps, cracks, and PMMA residues. It is evident that extending the mechanical assistance to other parts of the transfer process may be valuable, however, the occurrence of mechanical and chemical defects in the transferred graphene is still a limiting factor in the use of electrochemical bubble delamination.