Refractive index sensing method based on silicon ring resonator is used to build the sensing platform, for its potential to be CMOS compatible and can be easily integrated with other sensors and control elements [1]. An integrated volatile organic compounds (VOC) sensor is presented in this paper. Current device is tested with acetone vapor, and the detection limit reached 200 ppm, which is lower than the human safety level [2]. By making a ring resonator array, the proposed sensor has a potential to detect and distinguish different gas species. 

Figure 1(a) shows the sensing platform with silicon ring resonator as the key component. A straight waveguide is used to couple laser into the ring structure. The width and height of the waveguide and the ring is 450 and 220 nm, respectively. The ring structure is coated by a thin absorption layer and covered in a microfluidic channel, acting as the main sensing unit. Figure 1(b) shows the SEM image of one of the sensing ring.

After light passing through the resonator, resonance peaks can be seen on the output spectrum. As shown in Figure 2(a), the linewidth of each peak is less than 30 pm, which offers a Q-factor of more than 5×10⁴. This resonance peak, however, is very sensitive to the refractive index and thickness of the absorption layer. Gas absorb inside the layer will affect the resonance peak position. Figure 2(b) shows the mode distribution in the waveguide after the absorption layer coating. The strong light field in the absorption layer will make the device sensitive to refractive index and thickness change.

To demonstrate this sensing performance, a 20-nm polydimethylsiloxane is spin coated on top of the device to absorb VOC vapor. Acetone is chosen as the target gas. Gas is injected to the chip surface via a microfluidic channel. Figure 3(a) shows the monitored peak position as a function of time. The periods with white background represents the condition when pure N₂ gas is injected to the channel. On the other hand, the periods with gray background represents the condition when different concentrations of acetone vapor are injected in the channel. Stable performance and fast response is observed. The response time constant is about 20 s. Figure 3(b) indicates a linear relationship between acetone concentration and resonance peak position. Based on the experimental results, the sensitivity is 1.7 pm/1000 ppm and the detection limit is 200 ppm.

In conclusion, a gas sensor for VOC based on silicon photonics ring resonator system is presented in this paper. Sensitivity of 1.7 pm/1000 ppm and detection limit of 200 ppm are achieved, which is lower than the human safety level. This makes it a potential application for indoor air quality detection and monitoring.

This paper presents a novel chemical sensor using a metamaterial absorber, which is composed of an Au Bottom layer, a microfluidic channel, a FR4 substrate and a split-square-cross-resonator (SSCR). The resonance generated by SSCR is extraordinarily sensitive to changes of the effective dielectric constant around the capacitive gap. Furthermore, the effective dielectric constant of the dielectric substrate is under the influence of microfluidic channels by using an infinitesimal quantity of a liquid. The proposed sensor exhibits an outstanding sensitivity by a creative SSCR structure and the Au Bottom layer. In addition, the relationship between the absorption frequency and chemical concentration is demonstrated by simulation.

Recombinant protein biologics have replaced small molecules as the major blockbuster drugs in the therapeutic pharmaceutical market, comprising a current world-wide market of over $140B per year.  We have developed a new technology platform which significantly increases the precision and reduces the time and investment required to discover novel therapeutic proteins. This innovation combines fluidic miniaturization, image processing, and rapid, proprietary single cell analysis and isolation; enabling screening of millions of protein-expressing cells in less than an hour, using a device the size of a silver dollar. In addition to antibody discovery, this transformative “million well microtiter plate” allows high-throughput drug screening applications currently not accessible with other technologies, including discovery of protein and peptide modulators that activate or inhibit biochemical pathways, and the development of novel enzyme catalysts.  The technology platform also has broad reaching impact for other biotechnology and medical applications where single cell analysis and isolation is critical.  I will discuss several examples of applications of this new platform in antibody engineering, the development of new protein fluorophores, and novel enzymes.

Directional Coupler is a passive optical device used to couple electromagnetic powers in a transmission line to a port enabling the signal to be used in another circuit, which is a key component widely used in chip-integrated quantum simulation and communication devices working as a quantum operation gate. The fundamental parameter for the directional coupler is the splitting ratio of the reflection and transmission signal, which is mainly decided by the operation wavelength, gap, coupling length, cross-section size and material. Here, we design the silicon direction coupler waveguide working at the wavelength of 1550 nm to meet the splitting ratio of R/T=1:1 and 1:2 by adjusting the coupling length based on FDTD method with the aid of Lumerical software. The coupler gap is 200 nm with cross-section width of 450 nm, height of 600 nm. The theoretical coupling length calculated for each ratio is 12.12 um and 14.74 um and the optimization process is to adjust this length to compensate for the effect caused by waveguide curvature at the beginning and ending of the coupling region, aiming to conclude the curvature equivalence, effective coupling length and empirical equation as an instruction for further coupler design.

Fabless access to silicon photonics technology is moving silicon photonics closer to becoming a mainstream technology for both of research and industry. Several wafer-scale fabrication platforms have been developed in Europe and America that allow for sub-micron silicon photonic waveguide based circuits, such as imec in Belgium, CEA-Leti in France, IME in Singapore and AIM in America. A new 200mm platform in the Institute of Microelectronics of Chinese Academy of Sciences is introduced. The measurement results of the passive devices, carrier-based modulators and photodiodes are demonstrated, which meet the requirements for 30 Gbps data-communication applications. The other developing CMOS platform compatible for silicon photonics in China are introduced as well.

In recently years, asymmetric evanescent coupling systems have become more and more important as silicon photonics is developing, because of the ultra-high index contrast and an ultra-small cross section of silicon nanophotonic waveguides. Asymmetric evanescent coupling systems on silicon have been developed successfully to enable ultra-small high-performance polarization-handling devices, special power splitting, as well as multi-channel mode conversion/(de)multiplexing. This paper will give a review for the recent progresses of asymmetric evanescent coupling systems on silicon.

In this paper, we demonstrated several AWG-based silicon photonics devices fabricated with deep UV lithography on SOI platform, including cascaded AWG, AWG-based receiver with fiber-to-waveguide converters, AWG-based OADM and folded AWG with ring-reflectors. In a thin top silicon layer, the silicon nanowire AWG has a performance of relative high crosstalk. In order to reduce the crosstalk, we designed and fabricated a 4-channel cascaded AWG. Compared to the normal single silicon photonics arrayed waveguide grating with a crosstalk of ~ -12.5 dB, the crosstalk of more than 20 dB has been dramatically improved in this cascaded AWG. The AWG-based OADM device is composed of two 1×8 AWGs, MZI thermo-optic switch array and crossing array, by which 8 signals can be loaded or uploaded. The channel spacing is around 3.2 nm at the wavelength of 1550nm and the crosstalk is less than -20 dB. The dynamic extinction is around 15 dB by thermal effect and the power consumption for a single channel is less than 12.3 mW. The 8-channel receiver was designed and fabricated on a SOI wafer with 1µm-thick top silicon layer, which was composed of 5×8 AWG and 8 Ge-based butt-coupled photodetector array. The AWG device was designed on a thick SOI wafer for a good crosstalk performance. However, The silicon waveguide with a height of 1µm has a coupling issue with a cleaved standard optical fiber. In order to reduce the coupling loss with the cleaved fiber, a new cantilevered fiber-to-waveguide converter was designed to integrate at the output/input waveguide of this receiver. The measured coupling loss of this converter is around 2.4dB/facet by using a cleaved single mode fiber. The 3dB-bandwidth of this butt-coupled photodetector is more than 30 GHz at a reverse bias of -1V. The transmission capability of this receiver is more than 400Gbps. Compared to other silicon photonics devices, the AWG size is not small. A 1×4 folded silicon photonics AWG was designed and fabricated on a SOI wafer with 340nm-thick top silicon layer. This folded AWG was integrated with ring-mirrors at the end of arrayed waveguides. The optical signals are launched into the input waveguide and coupled into the arrayed waveguides through the input slab waveguides. At the end of arrayed waveguides, the signals are reflected by the ring-mirrors. The reflected signals go back to the arrayed waveguides and the input slab waveguide in sequence, and then they are separated into the four output waveguides. The measured transmission loss of this folded AWG is about 3.5 dB and the crosstalk is around 20 dB. The measured channel spacing is 6.7 nm. This size of the demonstrated arrayed waveguide grating is only half of the normal arrayed waveguide grating.

Acknowledgment： This work was supported by the National Natural Science Foundation of China (No. 61674072, No. 61565011 and No. 51304097).

Chip-level integration in Silicon Photonics (SiP) technology of complex optical communication systems, like WDM or PAM systems, is the key to both power and cost efficient implementation of next generation Datacom applications. Semiconductor Mode-Locked-Lasers (MLL) [1] and Resonant Ring Modulators (RRM) [2,3] are considered elegant building block solutions for an efficient transceiver architecture. We have recently demonstrated a single channel link with 14G and 25G On-Off-Keying (OOK) modulation based on a single section MLL and RRMs [4,5]. Here, we will report on the latest progress towards a fully integrated 8 channel WDM Datacom transceiver system. The system features a SiP-PIC with a hybrid integrated MLL, a wideband filter for line selection, and 8 channels of high speed RRMs on the Tx side, as well as an 8 channel OADM DeMUX, and Ge-integrated waveguide photodiodes as well as flip-chip photodiodes on the receiver side. Figure 1 shows a micrograph and a block diagram of the transceiver SiP-PIC before assembly.

The SiP-PIC is assembled on a module PCB together with 8x 25G modulator drivers and 8x 25G transimpedance amplifiers (TIA) and packaged in a module housing. Figure 2 shows a test system assembly with an external MLL and SOA.

Gas detection is relative with industry safety, indoor ventilation, medical and health, etc, in which many applications require the detection limitation down to ppb level. That is quite challenges for most of conventional miniature gas sensors in the market. Although some equipment can achieve ppb-level detection accuracy, e.g. gas chromatography and tunable diode laser spectrometry (TDLS), they are too bulky and expensive to be adopted widely [1]. And, they need a big sample gas volume that results of long time consuming and lower accuracy because in real cases the gas concentration always changes as time going on. Here, we demonstrate a new ppb-level detection approach based on photonics waveguides. The detection limitation down to around 200 ppb - level, and the gas volume for one test is less than 1 mL.

Figure 1 shows the schematic of the gas detection system. A low-cost blackbody radiation light source is used to generate a broad-band spectrum (from visible light to long-wavelength infrared) that promises this system can be used as a universal gas detection platform. The output light passes a bandpass filter and is coupled into an optical fiber. At one end of the fiber, a waveguide with a detector is connected. The waveguide exposes in the air to sense the target gas molecules in the surrounding, in which no pump is needed. Insert shows the principle of the gas sensing by use of waveguide.

Figure 2 shows the detection limitation analysis. In the experiment, we use carbon dioxide as a verification gas whose absorption spectrum is around 4.26 µm. The sensitivity of the system is around 15.91 mV/100ppm, while the noise floor is only 0.03 mV.  Thus, the detection limitation is around 188 ppb.

In recent times, silicon photonics have received much attention mainly for applications in data centres and communications. This work reports our recent results in a number of pertinent components necessary to realise successful implementation on silicon-on-insulator platform. We report design, modeling, and fabrication of inverse taper couplers, broadband directional couplers and polarization beam splitters. We achieved fiber-to-chip coupling loss of <2dB, ~50% splitting over bandwidth of 100 nm and polarisation extinction ratios ~40dB (both TE and TM) were obtained respectively. Furthermore, we report design and simulation of ring resonator modulators and silicon-germanium detectors with an extinction ratio of ~20dB and dark currents of ~100 nA and responsivity of 0.9A/W were obtained. Additionally, we also report polarization-independent configurations for slot waveguides that are suitable for sensing applications.