Optical gas sensors play an increasingly important role in many applications. Sensing techniques based on mid-infrared absorption spectroscopy offer excellent stability, selectivity and sensitivity, for numerous possibilities expected for sensors integrated into mobile and wearable devices. Here we review recent progress towards the miniaturization and integration of optical gas sensors, with a focus on low-cost and low-power consumption devices.

https://www.mdpi.com/1424-8220/19/9/2076/pdf

Towards Integrated Mid-Infrared Gas Sensors.

Abstract The tremendous growth of data traffic has spurred a rapid evolution of optical communications for a higher data transmission capacity. Next-generation fiber-optic communication systems will require dramatically increased complexity that cannot be obtained using discrete components. In this context, silicon photonics is quickly maturing. Capable of manipulating electrons and photons on the same platform, this disruptive technology promises to cram more complexity on a single chip, leading to orders-of-magnitude reduction of integrated photonic systems in size, energy, and cost. This paper provides a system perspective and reviews recent progress in silicon photonics probing all dimensions of light to scale the capacity of fiber-optic networks toward terabits-per-second per optical interface and petabits-per-second per transmission link. Firstly, we overview fundamentals and the evolving trends of silicon photonic fabrication process. Then, we focus on recent progress in silicon coherent optical transceivers. Further scaling the system capacity requires multiplexing techniques in all the dimensions of light: wavelength, polarization, and space, for which we have seen impressive demonstrations of on-chip functionalities such as polarization diversity circuits and wavelength- and space-division multiplexers. Despite these advances, large-scale silicon photonic integrated circuits incorporating a variety of active and passive functionalities still face considerable challenges, many of which will eventually be addressed as the technology continues evolving with the entire ecosystem at a fast pace.

/pdf/scaling-capacity-of-fiber-optic-transmission-systems-via-ds4kmihb4k.pdf

Scaling capacity of fiber-optic transmission systems via silicon photonics

Compact and smart optical gas sensors have attracted significant attention over the past few decades. Among the materials used for developing such gas sensors, group-IV materials, including silicon...

On-Chip Optical Gas Sensors Based on Group-IV Materials

/pdf/a-review-of-silicon-subwavelength-gratings-building-break-54chaj4osh.pdf

A review of silicon subwavelength gratings: building break-through devices with anisotropic metamaterials

On-chip mode-manipulation is one of the most important physical fundamentals for many photonic integrated devices and circuits. In the past years, great progresses have been achieved on subwavelength silicon photonics for on-chip mode-manipulation by introducing special subwavelength photonic waveguides. Among them, there are two popular waveguide structures available. One is silicon hybrid plasmonic waveguides (HPWGs) and the other one is silicon subwavelength-structured waveguides (SSWGs). In this paper, we focus on subwavelength silicon photonic devices and the applications with the manipulation of the effective indices, the modal field profiles, the mode dispersion, as well as the birefringence. First, a review is given about subwavelength silicon photonics for the fundamental-mode manipulation, including high-performance polarization-handling devices, efficient mode converters for chip-fiber edge-coupling, and ultra-broadband power splitters. Second, a review is given about subwavelength silicon photonics for the higher-order-mode manipulation, including multimode converters, multimode waveguide bends, and multimode waveguide crossing. Finally, some emerging applications of subwavelength silicon photonics for on-chip mode-manipulation are discussed.

/pdf/subwavelength-silicon-photonics-for-on-chip-mode-6u1e9gvhzt.pdf

Subwavelength silicon photonics for on-chip mode-manipulation

The performance of on-chip gas sensors using absorption spectroscopy are currently limited by the small overlap and reduced interaction length between the light and the analyte. Here, the use of slow-light in subwavelength grating (SWG) waveguide integrated on a silicon photonic chip is proposed to improve methane sensing by tunable diode laser absorption spectroscopy in the near infrared. Such SWG waveguide increases the interaction by two means. First, close to the photonic bandgap edge, a SWG waveguide no longer acts as a metamaterial with a homogeneous index, but rather as a 1D photonic crystal in which slow-light effect enhances the light-analyte interaction. Second, the subwavelength segmentation of the waveguide increases the modal overlap with the air. These two enhancement mechanisms results in a six-fold improvement of the interaction with respect to strip waveguides. In this paper, we discuss how to engineer the group index of SWG waveguides to exploit slow-light effect for the first time. Design guidelines for minimizing propagation loss and disorder effect are discussed considering limitations of typical fabrication processes. SWG waveguides could improve the sensitivity and the limit of detection of on-chip trace-gas sensors that provide a compact, fabrication tolerant, inexpensive, and selective sensing technology.

https://corpus.ulaval.ca/jspui/bitstream/20.500.11794/33345/2/Gervais_2019_JSTQE.pdf

Design of Slow-Light Subwavelength Grating Waveguides for Enhanced On-Chip Methane Sensing by Absorption Spectroscopy

Structural slow light is the dispersion engineering process by which the group velocity of light can be drastically reduced in a periodic waveguide structure. Enabling large group delay and enhancing the light-matter interaction on a subwavelength scale, on-chip slow light is of great interest in a vast array of fields such as non-linear optic, sensing, laser physics, telecommunication and computing. In this work, we experimentally demonstrate, for the first time, slow light in subwavelength grating waveguides on the silicon-on-insulator platform. We present a comprehensive numerical study in analytical modelling and 3-D FDTD. Multiple waveguides variations were fabricated using an electron-beam lithography process. Figures of merit such as group index, bandwidth and loss-per-delay are examined in both theory and experiment. A maximum measured group index of 47.74 with a loss-per-delay of 103.37 dB/ns has been achieved near the wavelength of 1550 nm. A broad bandwidth of 8.82 nm was measured, in which the group index remains larger than 10. We also show that the region of slow light operation can be shifted over a large wavelength span by controlling a single design parameter.

/pdf/slow-light-in-subwavelength-grating-waveguides-4x0w3uv5y0.pdf

Slow Light in Subwavelength Grating Waveguides

Commercial silicon photonic (SiP) biosensor architectures rely on expensive swept-tunable lasers that limit their use for widespread, point-of-care applications. An alternative is the use of fixed wavelength lasers integrated directly on a silicon photonic platform. This study investigates the design considerations of such architectures.

A silicon photonic evanescent-field sensor architecture using a fixed-wavelength laser

Slow-light is experimentally demonstrated in subwavelength grating waveguides integrated on a silicon photonic chip. At the band-edge, a group index up to 30 is measured. We show that the band-edge wavelength varies linearly with the subwavelength grating period and can be shifted by thermal tuning.

https://corpus.ulaval.ca/jspui/bitstream/20.500.11794/39210/1/Antoine_2019_GroupIV.pdf

Antoine Gervais

Papers

Scaling capacity of fiber-optic transmission systems via silicon photonics

Design of Slow-Light Subwavelength Grating Waveguides for Enhanced On-Chip Methane Sensing by Absorption Spectroscopy

Slow Light in Subwavelength Grating Waveguides

A silicon photonic evanescent-field sensor architecture using a fixed-wavelength laser

Tunable Slow-Light in Silicon Photonic Subwavelength Grating Waveguides