There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Silicon Photonics technology is rapidly maturing as a platform for larger-scale photonic circuits. As a result, the associated design methodologies are also evolving from componentoriented design to a more circuit-oriented design flow, that makes abstraction from the very detailed geometry and enables design on a larger scale. In this paper, we review the state of this emerging photonic circuit design flow and its synergies with electronic design automation (EDA). We cover the design flow from schematic capture, circuit simulation, layout and verification. We discuss the similarities and the differences between photonic and electronic design, and the challenges and opportunities that present themselves in the new photonic design landscape, such as variability analysis, photonic-electronic co-simulation and compact model definition. Silicon Photonics Circuit Design: Methods, Tools and

https://www.onlinelibrary.wiley.com/doi/epdf/10.1002/lpor.201700237

Silicon Photonics Circuit Design: Methods, Tools and Challenges

DOI: 10.1002/adom.201801433 Scientific American selects plasmonic sensing as the top 10 emerging technologies of 2018.[15] Almost every single new plasmonic or photonic structure would be explored to test its sensing ability.[16–29] These works tend to report the sensing performance of their own structure. Some declare that their sensitivity breaks the world record. However, there is still a missing literature on what the world record really is, the gap between the experiments and the theoretical limit, as well as the differences between metal-based plasmonic sensors and dielectric-based photonic sensors. To push plasmonic and photonic sensors into industrial applications, an optical sensing technology map is absolutely necessary. This review aims to cover a wide range of most representative plasmonic and photonic sensors, and place them into a single map. The sensor performances of different structures will be distinctly illustrated. Future researchers could plot the sensing ability of their new sensors into this technology map and gauge their performances in this field. In this review, we focus on optical refractive index (RI) sensors with no fluorescent labeling required. We will utilize two parameters to characterize and compare the performance of optical RI sensors: sensitivity to RI change (denoted by symbol SRI) and figure of merit (in short, FoM). For simplicity, we restrict our discussions to bulk RI change, where the change in RI occurs within the whole sample. There is another case where the RI variation occurs only within a very small volume close to the sensor surface. This surface RI sensitivity is proportional to the bulk RI sensitivity, the ratio of the thickness of the layer within which the surface RI variation occurs, and the penetration depth of the optical mode.[6] The bulk RI sensitivity defines the ratio of the change in sensor output (e.g., resonance angle, intensity, or resonant wavelength) to the bulk RI variations. Here, we limit our discussions to the spectral interrogations and the bulk RI sensitivity SRI is given by[3,5–7,30]

Optical Refractive Index Sensors with Plasmonic and Photonic Structures: Promising and Inconvenient Truth

Thanks to advanced semiconductor microfabrication technology, chip-scale integration and miniaturization of lab-on-a-chip components, silicon-based optical biosensors have made significant progress for the purpose of point-of-care diagnosis In this review, we provide an overview of the state-of-the-art in evanescent field biosensing technologies including interferometer, microcavity, photonic crystal, and Bragg grating waveguide-based sensors Their sensing mechanisms and sensor performances, as well as real biomarkers for label-free detection, are exhibited and compared We also review the development of chip-level integration for lab-on-a-chip photonic sensing platforms, which consist of the optical sensing device, flow delivery system, optical input and readout equipment At last, some advanced system-level complementary metal-oxide semiconductor (CMOS) chip packaging examples are presented, indicating the commercialization potential for the low cost, high yield, portable biosensing platform leveraging CMOS processes

Silicon Photonic Biosensors Using Label-Free Detection.

Standard silicon photonic strip waveguides offer a high intrinsic refractive index contrast; this permits strong light confinement, leading to compact bends, which in turn facilitates the fabrication of devices with small footprints. Sub-wavelength grating (SWG) based waveguides can allow the fabrication of low loss devices with specific, engineered optical properties. The combination of SWG waveguides with optical micro-resonators can offer the possibility of achieving resonators with properties different from the traditional SOI rings. One important property that SWG rings can offer is decreased light confinement in the waveguide core; this improves the resonator’s sensitivity to changes in the cladding refractive index, making the rings ideal for refractive index sensing applications. In this paper, we present the design and experimental characterization of SWG based rings realized on SOI chips without upper cladding (permitting their use as sensors). The fabricated rings offer quality factors in the range of ~1k-6k, depending on SWG parameters. Based on the comparison of experimental and simulated data we expect sensitivities exceeding 383 nm/RIU in water and 270 nm/RIU in air, showing excellent potential for use in sensing applications.

Design and fabrication of SOI micro-ring resonators based on sub-wavelength grating waveguides.

Silicon photonics biosensors continue to be an area of active research, showing the potential to revolutionize Labon-Chip applications ranging from environmental monitoring to medical diagnostics. As near-infrared light propagates through nano-scale silicon wires on an SOI chip, a portion of the light resides outside the waveguide and interacts with biomolecules and the biological matrix on the waveguide’s surface. This capability makes silicon photonics an ideal platform for label-free biosensing. Additionally, the SOI platform is compatible with standard CMOS fabrication processes, facilitating manufacturing at the economies of scale offered by today’s foundries. In this paper, we describe our efforts to improve the performance of SOI-based biosensors—specifically, TE and TM mode microring resonators, thin waveguide resonators, sub-wavelength grating resonators, as well as strip and slot Bragg gratings. We compare device performance in terms of sensitivity, intrinsic limit of detection, and their potential for biosensing applications in Lab-on-Chip systems.

Qian Wang

Papers

Improving the performance of silicon photonic rings, disks, and Bragg gratings for use in label-free biosensing