This PDF file contains the front matter associated with SPIE Proceedings Volume 11556, including the Title Page, Copyright information and the Table of Contens

Metasurfaces are leading to the emergence of new optical components based on dispersion engineering of nanoscale structures, which enable circumventing the limitations of standard refractive and diffractive optics as well as entirely new functionalities. Broadband metasurface achromatic optics based on metasurface and on hybrid refractive/diffractive design will be presented, along with ultracompact spectrometers consisting of a single off axis metalens, where high resolution is achieved by designing chromatic dispersion and eliminating field curvature. New metaoptical components where different functionalities can be accessed by changing either the wavelength, the angle of incidence or the incidence polarization will be presented. As an example, using waveplates with designed arbitrary elliptical birefringence, the eigen-polarizations and the output polarization can be tuned continuously from linear to elliptical by changing the angle of incidence. A new approach to polarization optics will be presented, based on a powerful generalization of Fourier optics ( Matrix Fourier Optics), which leads to the replacement of conventional phase plates and analyzers, This has led to the demonstration of a compact, single shot, full Stokes polarization sensitive camera using a single metasurface, thus dramatically reducing the complexity of existing cameras and increasing their functionality. Finally taking inspiration from how jumping spiders capture their prey, a new depth sensing camera at video rates based on co-design of hardware (metalenses) and software, which requires far computational resources than stereo and time of flight cameras has been developed. It combines spatially multiplexed metalenses and efficient computations to measure depth from image defocus. Compared with previous passive artificial depth sensors, this bioinspired design is lightweight, single-shot, and requires much less computation.

Ge epitaxial layer is grown on a bonded Si-on-quartz (SOQ) wafer by ultrahigh vacuum chemical vapor deposition. A tensile strain as large as 0.4% is generated in Ge grown on SOQ, which is almost two times larger than ~0.2% in Ge grown on an ordinary Si-on-insulator (SOI) wafer. The enhancement of tensile strain is derived from an increased thermal expansion mismatch between the Ge layer and the base substrate of quartz in SOQ, whose thermal expansion coefficient of 0.5 × 10^-6 K^-1 is smaller than 2.6 × 10^-6 K^-1 for Si base substrate in SOI. Because of the strain-induced bandgap narrowing, the direct bandgap energy is reduced from ~0.77 eV for Ge on SOI to ~0.75 eV for Ge on SOQ. Performances are discussed when the strain-enhanced Ge layer on SOQ is applied to near-infrared photonic devices of photodetectors and light emitters.

In this work, an ultra-compact and high sensitivity ring resonator-based liquid sensor on a CMOS-compatible SOI platform, utilizing a horizontal slot hybrid plasmonic (HP) waveguide consists of the Cu plasmonic layer suspending above the Si channel waveguide as the sensing element, is proposed. Numerical results suggest that the waveguide sensitivity, 𝑆𝑤, of the proposed HP waveguide reaches as high as 0.84 with the propagation loss less than 0.06 dB/μm, showing a similar Sw and a lower propagation loss in comparison to the typical plasmonic waveguide. In addition, with the scenario of SOI photonic platform continuously standardizing with the established CMOS methodologies for taking the advantages of the CMOS technology, the proposed miniaturized liquid sensor employing the Cu plasmonic element indicates the potential for the monolithic electronic-photonic integration. The sensitivity of the proposed liquid sensor with a miniaturized radius of 2 μm is numerically demonstrated as 540.0 nm/RIU, which is approximately four times higher than that of the conventional Si ring resonator with the identical geometry. Meanwhile a larger FOM is also achieved in comparison to other reported HP ring sensors.

Silicon nitride material is widely used in photonics and other disciplines such as biology, life sciences, data communication, and sensing. These applications benefit from that silicon nitride has a much broader wavelength transparency range, lower propagation loss and lower thermo-optical coefficient compared with silicon material. However, it is very difficult to deposit thick silicon nitride films on large size wafer directly, which introduces a larger tensile stress and may produce cracks. In this paper, a process to fabricate crack-free 400-nm-thick silicon nitride films was discussed, leveraging 200- mm silicon photonics platform, which is compatible with CMOS process. The silicon nitride layer was deposited on the buried oxide layer via low-pressure chemical vapor deposition in two steps, followed by annealing separately, which can effectively overcome the problem of excessive stress in the films. Chemical mechanical polish technique was applied to planarize the silicon nitride layer and the oxide cladding layer. Annealing improves the uniformity and reduces the stress of the silicon nitride films. Using this process, 1-μm-wide strip waveguide was obtained with low propagation losses for the C-band (0.65 dB/cm). Furthermore, the propagation loss of 0.9-μm-wide strip waveguide was measured to be 0.7dB/cm; the insertion loss of 1×2 multi-mode interference was less than 0.3dB and the non-uniformity was smaller than 10%; the insertion loss of crossing was approximately 0.17dB and the crosstalk was lower than -40dB.

A low-loss and compact TM-pass polarizer on silicon is proposed using an asymmetrical directional coupler (ADC) consisted of a silicon wire waveguide and a sub-wavelength-grating (SWG) waveguide. To reduce the reflection loss and improve the extinction ratio (ER), tapered structure and sharp bending are introduced at the input and output port of the SWG waveguide, respectively. The TE input-mode is coupled into the SWG waveguide through the ADC, and then filtered out and absorbed by the Chromium wires located at two sides of the end of the bending. By properly selecting the structure parameters, the TM mode is cut-off in the SWG waveguide and thus directly passes through the silicon wire waveguide. Results show that a compact device length of 9.6μm with an ER of 18.3 dB and insertion loss of 0.16 dB is obtained at the wavelength of 1.55μm. To further improve the performance of the device, a cascaded scheme is constructed and analyzed. The total device length of the scheme is 40μm with an operating bandwidth of ~62nm for ensuring ER> 30dB. Similar concepts can also be used to produce a TE-pass polarizer by simply constructing a vertical ADC.

We recently reported an isotropic linear dispersion relation of a square-lattice photonic crystal slab fabricated in an SOI wafer. The linear dispersion of the square lattice generally suffers from the distortion due to a diffraction loss, which may reduce its performance in expected applications. We present a method to eliminate the diffraction loss and avoid the distortion by using triangular-lattice photonic crystal slabs with the six-fold rotational symmetry. The theoretical results on the dispersion and the angle-resolved reflection spectra obtained by the k-p perturbation theory and the finite element method will be compared with available experimental data.

Localized surface plasmon resonances (LSPR) in plasmonic nanostructures have shown high sensitivities for optical sensing and spectroscopy applications. Individual plasmonic nanoresonators are capable of detecting analytes in ultrasmall volumes. Light being diffraction limited results in weak coupling efficiency (approximately 1% extinction in free space) to the nanoresonator. Improving the signal to noise ratio (SNR) at the output requires a dark field microscope which makes the sensing system bulky. Light interaction with nanoantenna can be improved by using dielectric waveguides for interrogation. Besides this, compact and completely integrated on-chip biosensors can be realized with easier interrogation and multiplexed detection capabilities. Waveguide interrogated plasmonic nanoresonators have been investigated in the past for spectral shift based refractive index (RI) sensing modality. Such sensors require bulky spectrometers for obtaining the output spectrum. In contrast to it, intensity shift based RI sensors require photodetectors which are compact and easily integrable on chip. We propose a small footprint phase shifted Bragg grating (PSBG) waveguide made of silicon nitride loaded with a gold nanoresonator. Numerical investigation of the structure's optical response and its potential for intensity shift based refractometric sensing has been done in the visible wavelength range. The grating possesses a Fabry Perot cavity with a high Q-factor (1008) thus increasing the photon lifetime and interaction of light with the nanoantenna. Intensity shift based RI sensing results show sensitivity of 394%/RIU for PSBG excited nanoantenna compared to 57%/RIU observed in strip waveguide loaded with nanoantenna. Besides this, light coupling efficiency to plasmonic nanoresonator is 35% on excitation with PSBG waveguide in comparison to 12% observed in strip waveguide based excitation scheme. Strategies for further improvement in coupling efficiency are also reported.

Silver nanowires as one of the most important plasmonic waveguides, can support several different plasmonic modes. These surface plasmon polariton (SPP) modes have different electric field distributions, effective mode areas, propagation lengths and losses and thus can be used for different applications, from efficiently collecting single photons to carrying quantum entanglement. Therefore, the excitation and analysis of these different SPP modes are of pivotal importance for the development of subwavelength optical devices. In this work, we investigate different SPP modes on a suspended AgNW adhered to a fiber taper. Theoretical simulations and experimental results show that the desired SPP modes can be selectively excited by adjusting either the polarization of the excitation light or the coupling length between the fiber taper and the AgNW. Moreover, fundamental and higher-order SPP modes can be distinguished by means of a far-field method.

There is recent interest in integrating optics into neural computing systems considering the potential energy savings and speed enhancements. Optical neural networks relying on free-space diffractive effects can potentially permit the use of low resolution imagers and off load a portion of electronic computation. They are of interest in microscopy and edge computing applications. A numerical analysis of ideal few-layered diffractive optical neural networks with trainable phase masks (in real and Fourier spaces) under monochromatic coherent illumination is presented. Stacked all-dielectric transmissive metasurfaces are particularly suitable for the realization of such networks at optical frequencies. Six different kinds of networks (with and without Fourier space phase masks; electronic dense layers; and intensity-dependent optical nonlinearity) are considered for a comparative analysis. The networks are assessed on their testing accuracy on the MNIST, Fashion MNIST and the grayscale CiFAR-10 datasets. Optical variants were found to perform well on MNIST (≥96% testing accuracy) and F-MNIST (≥85%) datasets where objects are clearly demarcated from the background. However, the optical variants performed poorly on the CiFAR dataset (≈44%) in comparison to state-of-the-art electronic deep convolutional neural networks. The presence of electronic dense layers or optical nonlinearity provided marginal improvements of about 2% in test accuracy. Furthermore, network scaling by widening the phase plates and/or cascading more layers is found to only marginally improve test accuracy.

Dielectric resonators are generally applied for radio waves in the microwave and millimeter-wave regions. In this work, we investigate the properties of a novel dielectric resonator comprised of a finite two-dimensional (2D) photonic crystal (PhC) array and a high reflector. By the proper design of PhC band and size, multi-functions, such as highly efficient radiation, significant self-collimation, beam splitting, and zero phase shift, can be achieved simultaneously through the PhC resonator instead of zero refractive index metamaterials, which have important theoretical significance for promoting the application and development of the radiation technology of micro-nano dielectric resonators. We believe it will provide a theoretical basis and technical route for the development of new integrated multifunctional metamaterials and devices.

Nowadays, with 3D topographic features increasingly complicated and complex, scanning probe microscopes have widely been used of nano-scale dimensional measurement in the semiconductor manufacturing and space industry, which can create three-dimensional data over almost all solids in a wide range of ambient. Although scanning probe microscopes readily achieve nanometer level resolution images of measured surfaces, there are several aspects of their behavior that can cause them to yield large measurement errors. In this paper, according to possible traceability pathways for calibration of lateral axes and z axis, both pitch and step height measurements are respectively performed and axis error self-correction model is proposed. The influence of thermal stability on drift error is also discussed. Experimental results show that our method will be helpful for a fast performance evaluation test for scanning probe microscope.

This paper proposes a two-dimensional back-coupled grating waveguide coupler structure and its parameter optimization method. The WGC can split a part of the photons of the incident beam uniformly in four directions, and make the split photons back-coupled to the incident direction. The unique structure enables the WGC to be applied to an array laser light source that requires uniform back coupling of the beam in four directions. In addition, through the analysis of the parameter scanning results of the WGC, we found that although the coupling efficiency in two directions of the two-dimensional grating is affected by the combined impact of multiple directional parameters, but some of these effects are major and some are minor. Using this discovery, we have greatly reduced the amount of calculation required for parameter optimization for two-dimensional WGC, and provided a certain reference for later researchers.

With the rapid development of artificial intelligence, the traditional computer architecture can no longer meet the growing computing performance requirements. At the same time, with the chip manufacturing process approaching the physical limit, a single electronic technology cannot adapt the rapid development of artificial intelligence chips, so there is an urgent need for new computing chips. Photonic neural network chip, which combines artificial intelligence, silicon photonic, integrated circuit and other technologies, will get unprecedented opportunities for the development. Silicon based opto-electronic integration is a large-scale integration technology with optical signal as the main information carrier. It can integrate micro-nano-size optical and electrical devices on the silicon substrate, to form a new large-scale integration chip with comprehensive functions. At present, the development of silicon photonic devices is mainly focused on the field of optical communication and data center, while silicon photonic devices for photonic neural networks are still in the initial stage. Starting from the underlying unit devices, silicon-based photonic devices were studied deeply by combining the artificial neural network with the silicon photonic technology in this paper. Based on 200 mm CMOS process, a lot of process modules for photonic neural network were developed. According to the characteristics of photonic neural network architecture and the performance requirements for the basic unit devices, a series of silicon photonic devices, such as waveguides, grating couplers, MMI, thermal modulators, and other unit devices, were designed and developed. These devices provide important basic conditions for the implementation of high performance photonic neural network chips.

Detecting a single-molecule fluorescent spectrum with a low quantum yield needs to enhance the signal greatly overcome the noise disturbance. Based on plasmon-enhanced fluorescence method with single gold nanorods antenna, we measured the emission spectra of a single methylene blue or crystal violet molecules with an effective integration time of ~2.14 milliseconds at room temperature. These transient spectra have revealed the single-molecule spectral shape and intensity fluctuations. We found that the transient spectral shape is dominated by the molecule, while the plasmon resonance determines the averaged spectral shape. These fluctuations can be understood as transitions between metastable minima in the molecular potential-energy surface, as supported by complementary ab initio simulations.

It is a tradeoff between bandwidth and resolution for the on chip Fourier transform spectrometer. To solve this problem, a single ring filter enhanced on chip Fourier transform spectrometer was proposed recently. In this paper, the performance of the cascaded double-ring enhanced Fourier transform on chip spectrometer was investigated theoretically. The cascaded two tunable Micro-ring resonators forms a large narrow band filter with a larger free spectral range (FSR) than the single ring, which reduces the requirement of the Fourier transform spectrometer spectral resolution. The spectrum of the input is retrieved by the Fourier transform algorithm with dispersion correction. The cascaded doublering enhanced Fourier transform spectrometer has a high resolution (0.3 nm) and a large bandwidth (1500nm-1600nm). The fabrication process is compatibility with CMOS process. It can be easily integrated with other silicon-based optical devices.

In experiments, we demonstrated that luminescence quantum yield of single gold nanorods illuminated by continuous wave laser at wavelength of 532 nm depends on the excitation polarization, while that excited by 633 nm laser does not. The electrons in sp-band dominates the luminescence process when the 633 nm laser is applied, resulting in a constant quantum yield under different excitation polarizations. When the 532 nm laser is applied, both the electrons in d-band (interband transition) and sp-band (surface plasmon) involve in the luminescence process. The variation of quantum yield by the 532 nm laser is resulted from different efficiency of d-band interband transition and sp-band plasmon conversion into luminescence. Furthermore, we found that plasmon modes coupling effect can modulate strongly the plasmon emission efficiency by comparing the luminescence of two sets of the nanorods with different size. And smaller size GNRs often results in higher quantum yield of interband transition. These findings make a step to understand the luminescence process of plasmonic nanostructures and point out a rule to control it through plasmon mode coupling effect.

The article presents a study of the dependence of the change in the shape of the resonance transmission line for optical thin dielectric gratings. The result of changing the duty cycle for high and low medium contrast while maintaining the amount of substance has been demonstrated. The results of the effect of the filling factor on the resonance transmission width and the frequency position in the normal TE wave drop are numerically investigated. Results for various options of a angles of the falling bunch at various coefficients of filling are presented. The effect of refractive index contrast of this structure on the width and shape of resonance lines was analyzed. In the first approximation, effective refractive indices and effective thicknesses for such structures were calculated. Conclusions are drawn about the conditions under which the structure can be considered optically thin.

Biomaterial, such as proteins and deoxyribonucleic acid (DNA), which have many advantages such as biocompatibility and biodegradability, have been widely adopted as photonic device materials. In this study, we proposed and experimentally demonstrated an all-biomaterial whispering-gallery-mode (WGM) microbottle resonator. The quality factor of the fabricated protein microbottle resonator is on the order of 105. In addition, the entire process for preparing microbottle is simple and low-cost. Our work will open a door to explore various biomaterial and different bio-photonic device for biomedical applications.

In this work, the method of electrostatic doping is used to achieve the PL enhancement of large scale MoS2 grown by chemical vapor deposition (CVD) method. It has been found that the release of strain in the as-grown monolayers by the transfer process is essential for TMDCs PL enhancement. To ensure the low contamination level on the 2D materials, a dry-transfer technique based on polydimethylsiloxane (PDMS) was utilized to transfer monolayer MoS2. We found that the peak PL intensity of CVD-grown MoS2 showing an enhancement up to 200% by adding both positive and negative back-gate voltage (Vg). Compared with the chemical treatment method, electrostatic doping can realize the controllable process of PL, that is, the PL intensity is gradually tuned by the gate voltage. In addition, covering the sample with PMMA (polymethyl methacrylate) can isolate the influences of the external environment on the sample, which can improve the stability of the sample and enable more stable measurements.

We showed that the microresonators of whispering gallery modes on the surface of standard optical fibers can be shaped by introducing negative radius variations of effective radius instead of positive. To do this, the sample of optical fiber is irradiated with CO2 laser and heated to temperatures that are well below the transformation temperature. The method reduces the influence of the heated spot to the surrounding silica and makes the modification method simpler. Combining both positive and negative modification also expands the range of axial shapes of microresonators that can be introduced with CO2 laser heating.

Two-dimensional (2D)-material-based photodetectors have recently received great attention due to their potential as ultrathin and ultra-highly integrated devices. In this study, we demonstrated the application of MoTe2 as electrode material for photodetectors. An all-2D photodetector based on WS2 and MoTe2 is fabricated. Owing to the large Schottky barrier formed between WS2 and MoTe2, the avalanche effect can be realized because a large electrical field can be applied across the MoTe2–WS2–MoTe2 junctions before breakdown. Additionally, because of the existence of Schottky barrier, the dark current of device is greatly reduced. As a result, we achieved the enhanced performance of the ultrathin all-2D photodetector, with a photoresponsivity of 6.02 AW-1, an external quantum efficiency of 1406%, an avalanche gain of 587, and a low dark current of 93 pA in the broadband spectrum range from visible-to-NIR wavelengths.

All-dielectric nanophotonics is a branch of nano-optics that studies the interaction between high-refractive-index dielectric nanoparticles and light, which enables light manipulation at nanoscale. Nano-antenna and metasurfaces are widely studied technologies for light manipulation, but they can only work under a fixed single excitation condition. Recently, we have realized that coherent control is a novel way in which two or more beams of light are used to control the interaction between light and matter. Here, we study the the silicon nano-disk illuminate by two light beams. By controlling the angle, amplitude, and phase of beams to bring about the interference between electric dipole and magnetic dipole, we realized the directional control of scattered light. We performed simulations with the individual silicon nano-disk both in the air and the oil. We believe that our work will provide a new way for light manipulation, which is of great significance for future applications.

Single beam thermo-optical tweezers has been used for rotating particles continuously by 360o in pitch sense. The particle is rotated by placing it in a sample chamber with a thin layer of gold coated coverslip in an optical tweezers setup. The combined effects of convection current generated from heating of water and the optical trap rotate the particle in pitch sense near the hot spot present at the gold layer. This method works effectively until a water vapor bubble is formed due to continuous heating of the gold layer. We have tried to delay the onset of bubble formation by using viscoelastic medium instead of water. Viscoelastic medium is prepared by mixing polyacrylamide in water. Pitch rotation of hexagonal shaped particle has been observed for media having different concentrations of polyacrylamide. The frequency of rotation is measured at various concentrations. A suitable mathematical function is determined empirically which can describe the change in frequency while varying the concentration.