In this paper, we present a low loss optical resonator platform based on the aluminum nitride (AlN) material, which can be used to sense the temperature, chemical, and mechanical variations. The platform is built by use of the AlN rib-waveguide structures deposited on top of a thick oxide layer. Applications of temperature sensing, chemical sensing, and mechanical sensing of the AlN optical resonators are simulated.

AlN is a promising material for integrated opto-mechanics. It has not only excellent optical properties, such as ultra-low absorption at near infrared region, but also shows large piezoelectric coefficient, which allows efficient control of optomechanical systems by electrical means. It promises a high sensitive on-chip detection by optical method ^[1-3]. In this work, an AlN rib waveguide based opto-resonator is reported. The AlN rib waveguide is on top of a 3 µm thick oxide layer as shown in Fig. 1(a). Figure 1 (b) shows the designed AlN optical resonator structures.

The field distribution of the optical mode of the AlN optical resonator is simulated using the finite element method (FEM) tool by COMSOL. Figure 2 illustrates the optical field distribution of AlN rib waveguide. The dependence of n_eff of the rib waveguide on temperature, chemical and mechanical stress are also obtained using COMSOL, as shown in Fig. 3. The responses of the AlN rib waveguide to temperature, chemical, and mechanical stress are obtained via simulation.

Figure 4 show the scanning electron microscope (SEM) images of fabricated AlN rib waveguide. A rough surface of the sidewall and rib is achieved using an optimized etching recipe. The propagation loss of the AlN rib waveguide is greatly reduced with the merits of ultra-low optical scattering.

This paper reports a preliminary study of electric field induced (EFI) optical rectification (OR) in (001), (110) and (111) surface layers of germanium (Ge). It is well known that the second-order nonlinear optical effects are theoretically absent in Ge due to the inverse symmetry. In fact, space charge regions (SCRs) exist in surface layers of Ge, and electric fields in SCRs can break the inverse symmetry and induce the so-called “EFI OR”. OR is an important mechanism to be used in terahertz (THz) generation. A. Urbanowicz et al. indicated that EFI OR played an important role in the observed THz emission from Ge surfaces [1]. Besides, EFI OR can be used to characterize surface properties of crystals with symmetry centers such as Si [2]. We have demonstrated EFI OR in Si(001) surface layers in previous work [3]. However, there are few relative researches on OR in Ge.

The samples used in experiments are all near-intrinsic Ge single crystals, sandwiched between two metal electrodes. The structures, sizes and orientations of the sample are shown in Fig. 1, as well as the measurement system. The thickness of Ge(001) and Ge(110) crystals is 3 mm and the resistivity is about 60 Ω×cm. The thickness of Ge(111) crystals is 1 mm and the resistivity is more than 35Ω×cm. The light source is a fiber laser with the wavelength of 1964 nm. A chopper is used to input a reference signal into the lock-in amplifier. The polarization of the polarizer is along the x axis. If the azimuth of linearly polarized light with respect to the x axis is θ, when the light propagated along the y axis, the dc polarization along the z axis can be expressed as,

                                                                                                                                    (1)

where  is the permittivity of Ge,  is the optical electric field of the probing beam, and  and  are the components of the effective second-order susceptibility tensor. By rotating the half-wave plate, we measured the dependence of OR signals on the azimuth θ. The OR signals in Ge(001), Ge(110) and Ge(111) surface layers are shown in Fig. 2 to Fig. 4. According to fitted curves, OR signals all show cosine dependences on the azimuth θ. In Fig. 2, the fitted curve can be written as,

                                                                                                                                     (2)

If any contribution to OR signals from absorption is neglected, according to Eqs. (1) and (2), the ratio of  in Ge(001) surface layer is calculated to be about 0.91, which means that the two susceptibilities are close. Therefore, the sum of the two susceptibilities is much larger than the difference and there is a large background in the measured OR signals. Using the same method, the ratio of  in Ge(110) and Ge(111) surface layers are calculated to be 0.91 and 1.07.

We also measured the distribution of OR signals in Ge(001) surface layers along the surface normal direction. The result is shown in Fig. 5, as well as the simulation curve, which agrees well with the experimental data. Distance between the two peaks of OR signals is 2920 μm, which is consistent with the thickness of crystal after being polished. According to the simulation, the ratio of the maximum electric field intensities and the ratio of the width of SCRs in No. 1 and No. 2 Ge(001) surface layers are both deduced to be 1:0.966. It is proved that EFI OR is a method to analysis the surface properties of crystals with symmetry centers, such as Ge and Si.

The current medical measurement of human blood glucose concentration is invasive. In order to relieve the suffering of patient and improve the efficiency, a non-invasive optical glucose sensor is required. Based on these advantages, this paper designs a filter based on basic two-dimensional Photonic Crystals [1-5] structure by using different array structure. Based on Rsoft simulation software, the dimensional photonic crystal models are built. By changing the lattice structure and the depth of the apertures, the power transmission of the structure is analyzed.

Compared with invasive glucose sensor, optical noninvasive glucose sensor can reduce the pain of frequent sampling. However, the optical testing of glucose concentration is still influenced by the noise from body fluid and organic structure. According to this situation, the Photonic Crystals of multi-period array is proposed. Photonic crystals can enhanced the intensity of the light selectively in the form of increasing the characteristic peak value which can read out the glucose concentration. By comparison and comprehensive analysis, the effective high-precision optical signal can be chosen from the noise. The wavelength of the infrared light source is from 5 to 15μm. The minimum size of the fabrication processing is 0.5μm which ensures the higher precision without increasing the costs. The project will provide new point about the non-invasive optical glucose sensor by the way of multiple characteristic peak comprehensive analysis.

There has been a growing interest in the study of Photonic Crystals because of their unique abilities to control light propagation [6-8]. Recently, significant progress has been made in the fabrication and characterization of Photonic Crystals [9-10], and towards the development of Photonic Crystals applications in the fields of photonic circuits. In these cases, the photonic band structure mainly depends on the lattice constant and refractive index that varies in response to the design changes.

The structure of the two Photonic Crystals are shown in Fig. 1 and Fig. 2. The first structure is designed as Fig. 1 shown. The surface structure is aperture arrays with a diameter of 5µm and lattice constant of 10µm. The depth of the aperture array in the Photonic Crystal is 2µm. The structure of the lattice structure is square. The second surface structure is aperture arrays with a diameter of 5µm and lattice constant of 8µm. The structure of the lattice structure is equal triangle as shown in Fig. 2. The relationship between the transmission power and the wavelength of the input light is shown in Fig. 3 and Fig. 4. The SEM image of the equal triangle lattice Photonic Crystal is shown in Fig. 5. The surface structure is aperture arrays with a diameter of 5µm and lattice constant of 8µm. The depth of the aperture is 2µm.

This paper reports a cavity optomechanical signal amplifier driven by optical force in photonic circuit platform, with an amplification factor as high as 4. High amplification resolution is obtained through the precise optical force control. Different with conventional optical amplifier, the proposed design realizes the optical amplification using an optical force actuated nano-structure. The signal amplifier consists of a tunable ring resonator, an actuation ring resonator and a mechanical beam. Utilizing the nano-structure deformation by the optical force, a small input optical signal is amplified to a large output signal. An amplification factor as high as 4 is obtained experimentally and the modulating frequency is up to 4.2 MHz.

Currently, manufactures are focusing on developing sensor products featured with increased miniaturization and lower cost. Several current technology trends are driving the need for miniaturization, compactness and low power consumption sensor solutions. On the other hand, benefitted from the significant progress in the development of advanced silicon photonics and MEMS technologies, silicon nanophotonic sensing devices become candidates to meet the high sensitivity sensor requirement, and to be used across a broad range of applications, including environmental monitoring, safety hazard detection, health monitoring and industry applications.

The particular truth, making silicon nanophotonic sensors to be attractive, is that environmental changes could be represented as a change in frequency of the light detected, as well as the change of the signal strength. It much benefits the detection system with high sensitivity and resolution. For instance, working as multifunction and smart gas sensors, the detection of concentration becomes possible by measuring the influence on the optical properties of silicon nanophotonic sensors such as micro-ring resonator and optomechanical resonator, etc., is an excellent transducer for environmental sensing (including temperature, humidity, chemical, carbon dioxide gases, etc.) due to their intrinsic advantages of high Q-factor, large extinction ratio, and high compactness. Meanwhile, their transmission spectra heavily depend on the resonator’s surrounding environment. In this paper, different types of silicon nanophotonic sensors will be highlighted and their potential applications in environmental protection, safety hazard detection, health monitoring, etc., will be discussed. Silicon nanophotonic sensors offer advantages over conventional sensors for low cost, low power consumption, small size and high sensitivity etc. 

We experimentally demonstrate optical filtering, polarization splitting and rotating, and mode (de)multiplexing and switching in silicon devices.

We firstly demonstrate silicon photonic filters based on Sagnac loop reflectors, including a wavelength and bandwidth-tunable comb filter, and two compact interleavers in the Michaelson interferometer and interfering loop configurations with compact footprints.

We then discuss a high extinction-ratio (30 dB) silicon polarization beam splitter (PBS) based on a grating-assisted contra-directional coupler (GACC), and an ultra-compact silicon polarization splitter and rotator (PSR) with a short coupling length of 8.77 micron.

We further talk about optical switching in wavelength, mode, and polarization. We demonstrate a 2x2 nanobeam thermal-optic switch with ultra-small mode volumes, a high tuning efficiency of 1.23 nm/mW and an ultra-low switching power of 0.16 mW. We then propose a mode- and polarization-selective switch (MPSS) architecture for next generation high capacity switching systems, and demonstrate 1x2 and 2x2 on-chip MPSS switches.

Silicon photonics circuits are playing more and more important role in optical communication and interconnect fields [1, 2]. Many silicon CMOS technique compatible photonics integrated devices are reported [3, 4]. Most of those silicon components are based on optical waveguide. But conventional integrated optical waveguide is without memory feature. One hand, which makes us in trying to change the refractive index of the optical waveguide, must continually support energy to maintain the state of the waveguide, such as optical switch and modulators. And other hands, memory functional PIC into computer memory system, will solve van Neumann bottleneck issue.

In this presentation, I will introduce our group recent works that experimentally demonstrate two solutions for overcome those issues [5, 6]. First one is a non-volatile optical waveguide structure. It consists of a floating gate above an optical waveguide with a separated source and drain configuration.

For checking the memory functionality, we made a microring resonator by memory optical waveguide. By measuring the optical spectrum, the memory properties of maintain and retention are proved. And using different pulse voltage to drive electrons will cause multi-level state in the optical spectrum. Theoretically, this can be increased up to ~400 times using a 100 nm free spectral range broadband light source.

Another solution is using memristor device to control the optical waveguide property. Experimentally, we demonstrated SONOS (silicon-oxide-nitride-oxide-silicon) transistor as the memory cell, monolithically integrated with optical sense circuits (microring resonator, MRR).  The SONOS series connect with P-N junction optical waveguide. The memristor situation determines the series current, thus change the optical waveguide states. Similarly, we fabricate a microring resonator with P-N junction waveguide. SONOS controlled current to modify the microring resonator’s oscillation wavelength. From optical spectrum, we will know the SONOS status. Results show that the effective reading speed can be enhanced by 1200 times with 100 nm spectrum ranges.

On-chip sensing is an important application of silicon photonics. In this talk, silicon-based passive optical devices for on-chip sensing systems will be presented in two parts, the sensors and the supporting devices. The first part highlights the research on sensitivity enhancement, athermalization, and cost reduction of silicon photonic sensors while the other part presents the needed passive functional devices for a sensing system, including grating couplers, power splitters, polarization beam splitters, polarization rotators, and strip-slot waveguide mode converters.

       This paper reports a novel hybrid broadband micro vibration energy harvester (EH), which consists of an AlN MEMS piezoelectric vibration EH unit and a PTFE based single-electrode mode triboelectric EH unit. AlN piezoelectric vibration EH was a hot research topic of MEMS EH owing to its high energy density, high stability, and CMOS compatibility. In recent years, the study of the high-performance AlN piezoelectric film (Barth et al. 2016^[1], Minh et al. 2015^[2]), the novel structure design (Guido et al. 2016^[3], Sharma et al. 2015^[4], Wang et al. 2014^[5]), and the piezo vibration bandwidth expanding (Jackson et al. 2014^[6]) were the focal points on the enhancement of the device power output. The EH device discussed in this paper features its broad work bandwidth by placing an stopper underneath the vibrating proof mass for amplitude limiting, at the mean time, another part of energy was efficiently collected through mutual collision between the proof mass and stopper utilizing triboelectric mechanism. As a result, a higher power output density is realized by this hybrid mechanism method.
      A schematic diagram of the hybrid broadband vibration micro EH device is illustrated in Fig. 1 and the device optical image is shown in Fig.2. Figure 3 shows the SEM of the cross-section image of AlN-Si piezoelectric cantilever beam, the AlN piezo film with crystal orientation (002) deposited by pulsed-DC magnetron sputtering. The output performance of hybrid broadband vibration micro EH device is shown in Table 1, which shows that the open-circuit voltage (V_oc) and short-circuit current (I_sc) of AlN piezo vibration EH unit can reach 1.52 V and 11.5 µA before amplitude limiting and 0.7 V and 8.2 µA after amplitude limiting. The V_oc and I_sc of the amplitude limiting unit of single- electrode mode triboelectric EH unit can reach 10 V and 0.7 µA, respectively. The work bandwidth of AlN piezo vibration EH expands from ~1 Hz to ~9 Hz (Fig.4), which makes it more adaptable to the surrounding environmental frequency change. Experimental results show that the prototype can achieve the output power of 5.066 μW and 1.32 μW of AlN piezo EH unit and PTFE tribo EH unit, the work bandwidth of ~9 Hz, respectively, at the acceleration of 1g and the frequency of 204.3 Hz (Fig.5). This hybrid broadband vibration micro EH paves a way for new generation of high power density EH development and it potentially accelerate the deployment of the wireless sensor network.

  This paper reports a novel biosensor based on shear horizontal surface acoustic wave(SH-SAW) applied in biological detection. we designed a surface acoustic wave resonator as biosensor and integrated it with a waterproof fixture, in which there is a micro-fluidic channel insuring the smooth of liquid flowing, and guarantee the stability during the biological reaction. In this paper, we have studied the feature of the device in liquid-phase, the experimental result indicates that a larger value of phase shift (3 degree) is realized compared with pioneer works[1].
  SAW biosensors, as core part of the bio-detection system are powerful and promising in various fields. Particularly for clinical analysis and biochemical, the SH-SAW biosensors are good candidates benefiting from high sensitivity and good repeatability in liquid phase. In this paper, we present a novel SH-SAW biosensor, the device geometry schematically is shown in Fig.1. A 36° rotated Y-cut X propagation lithium tantalate (LiTaO3) piezoelectric single crystal chip is selected as substrate and Au is selected for IDT fingers, electrode and the area of bio-probe grow respectively. In addition, the microfluidics inlet and outlet channels were fabricated by PDMS micro molding technique to insure the smooth flowing of the liquid flow in the sensitive area. Fig.2 and 4 show the inner structure of the PDMS micro-fluidics channel layer and the assembled fixture respectively. Compared to our group's previous research output[1-2], the SH-SAW biosensor reported in this paper posses several advantages: (1) avoid the volatilization of the solution; (2) ease of device miniaturization; (3) the fixture we have designed offers a confined space, which minimizes the air influence , and hence guarantees more enough times of biological reactions performed at certain volume solution provided each time.
  The SH-SAW based bio-chip (Fig.1) consists of two sets of gold input and output IDTs mounted on the surface of the LiTaO3 substrate. The SH-SAW is excited by an input electrical signal applied at the input IDTs, and then propagates on the piezoelectric substrate through the delay line and is converted back to an electrical signal[3], while the wave is potentially sensitive to the mass loading on the surface, therefore, the signal phase will shift when the aptamers are fixed on the surface through Au-S bond. The main displacement component of the SH-SAWs is perpendicular to the direction of the propagation and parallel to the propagation surface, and the longitudinal waves will not be reflected at the solid/liquid interface[4], as the biological reactions occur in liquid-phase, so the waves can propagate with minimal dissipation of energy to a liquid at the surface[5]. The detailed parameter of the device can be found in table Ι.
The measurement system(Fig.7) consists of an Aglient E5080A network analyzer connected to SMA adapter, the spectrogram of the bio-chip is shown in Fig.5. In the experiments, we fixed the aptamers on the sensitive area by sulfhydryl self-assembled method, the phase shift data was analyzed by Matlab and the picture is shown in Fig.6, the phase shift is about 4.5°, and the stability time is less than 10 minutes, which is better than our previous research.