Structured Illumination Chip Based on Integrated Optics

A compact structured illumination chip based on integrated optics is proposed and fabricated on a silicon-on- insulator platform. Based on the simulation of Caussian beam interference, we adopt a chirped diffraction grating to achieve a specific interference pattern. The experimental results match well with the simulations. The portability and flexibility of the structured illumination chip can be increased greatly through horizontal encapsulation. High levels of integration, compared with the conventional structured illumination approach, make this chip very compact, with a footprint of only around 1 mm2. The chip has no optical lenses and can be easily combined with a microfluidic system. These properties would make the chip very suitable for portable 3D scanner and compact super-resolution microscopy applications.

Integrated Optics Acoustooptic Receiver

The recent advances on the research and the applications of the integrated optics acousto-optic spectrum analyzer(IOSA) are reviewed. The operating principle, architecture, characteristics and technology, and future development of the different receivers are described.

Design and simulation of a silicon-based hybrid integrated optical gyroscope system

By combining a silicon-based lithium niobate modulator and a silicon-based Si3N4resonator with silicon-based photonics technology,a highly systematic design of a hybrid integrated optical gyroscope with enhanced reciprocity sensitivity and a dual micro-ring structure is proposed for the first time in this paper.The relationship between the device's structural parameters and optical performance is also analyzed by constructing a complete simulation link,which provides a theoretical design reference to improve the system's sensitivity.When the wavelength is 1550 nm,the conversion frequency of the dual-ring optical path is 50 MHz,the coupling coefficient is 0.2,and the radius R is 1000μm,the quality factor of the silicon-based Si_(3)N_(4)resonator is 2.58×10^(5),which is 1.58 times that of the silicon-on-insulator resonator.Moreover,the effective number of times the light travels around the ring before leaving the micro-ring is 5.93,which is 1.62 times that of the silicon-on-insulator resonator.The work fits the gyro dynamic output diagram,and solves the problem of low sensitivity at low speed by setting the phase offset.This results provide a basis for the further optimization of design and chip processing of the integrated optical gyroscope.

Asymmetrical Fabry-Perot cavity slot micro-ring resonator and its sensing characteristics

To achieve high quality factor and high-sensitivity refractive index sensor,a slot micro-ring resonator(MRR)based on asymmetric Fabry-Perot(FP)cavity was proposed.The structure consisted of a pair of elliptical holes to form an FP cavity and a microring resonator.The two different optical modes generated by the micro-ring resonator were destructively interfered to form a Fano line shape,which improved the system sensitivity while obtaining a higher quality factor and extinction ratio.The transmission principle of the structure was analyzed by the transfer matrix method.The transmission spectrum and mode field distribution of the proposed structure were simulated by the finite difference time domain(FDTD)method,and the key structural parameters affecting the Fano line shape in the device were optimized.The simulation results show that the quality factor of the device reached 22037.1,and the extinction ratio was 23.9 dB.By analyzing the refractive index sensing characteristics,the sensitivity of the structure was 354 nm·RIU−1,and the detection limit of the sensitivity was 2×10−4 RIU.Thus,the proposed compact asymmetric FP cavity slot micro-ring resonator has obvious advantages in sensing applications owing to its excellent performance.

S-type Er-Yb Co-doped Phosphate Glass Waveguide Amplifier Integrated with Cascaded Multilayer Medium Thin Film Filter

A new S-type of erbium-ytterbium co-doped phosphate glass waveguide amplifier integrated with cascaded multilayer medium thin film filter is proposed,this S-type geometry waveguide structure is used to achieve a long path in a compact chip,and obtained higher gain with lower Er-doped concentration. The cascaded multilayer medium thin film filter is utilized to achieve a broader flattening gain bandwidth.The intrinsical gain spectrum is obtained by solving rate and power propagation equations,the effect of transmittance spectrum of thin film filter on flattening gain is discussed.

Compact TE-pass polarizer based on lithium-niobate-on-insulator assisted by indium tin oxide and silicon nitride

An indium tin oxide(ITO) and silicon nitride(Si_(3)N_(4)) assisted compact TE-pass waveguide polarizer based on lithiumniobate-on-insulator is proposed and numerically analyzed.By properly designing the ITO and Si_(3)N_(4) assisted structure and utilizing the epsilon-near-zero effect of ITO,the TM mode is strongly confined in the ITO layer with extremely high loss,while the TE mode is hardly affected and passes through the waveguide with low loss.The simulation results show that the polarizer has an extinction ratio of 22.5 dB and an insertion loss of 0.8 dB at the wavelength of 1.55 μm,and has an operating bandwidth of about 125 nm(from 1540 nm to 1665 nm) for an extinction ratio of>20 dB and an insertion loss of<0.95 dB.Moreover,the proposed device exhibits large fabrication tolerances.More notably,the device is compact,with a length of only 7.5 μm,and is appropriate for on-chip applications.

Research progress of integrated optical gyroscope

Integrated optical gyroscopes(IOGs)have been an efficient tool for numerous applications in various fields,including inertial navigation,flight control,and earthquake monitoring.Here,we review the progress of integrated optical gyroscopes based on two categories of integrated interferometric optical gyroscopes(IIOGs)and integrated resonant optical gyroscopes(IROGs).

Design and Fabrication of Thermo-Optic 4×4 Switching Matrix in Silicon-on-Insulator

A rearrangeable nonblocking thermo-optic 4×4 switching matrix,which consists of five 2×2 multimode interference-based Mach-Zehnder interferometer(MMI-MZI) switch elements,is designed and fabricated.The minimum and maximum excess loss for the matrix are 6.6 and 10.4dB,respectively.The crosstalk in the matrix is measured to be between -12 and -19.8dB.The switching speed of the matrix is less than 30μs.The power consumption for the single switch element is about 330mW.

Tapered Multimode Interference Combiners for Coherent Receivers

A new tapered multimode interference （MMl）-based coherent lightwave combiner is reported. A comprehensive theoretical analysis of mode behaviors in the tapered MMI waveguide is presented, and the output characteristics of the tapered MMI combiners with various structures are demonstrated. The combiner is fabricated on a silicon-on-insulator （SO1） substrate. Due to its advantages of having no end-facet reflection,easy extension to a multi-port configuration, high tolerance for fabrication errors, and compact size, the tapered MMI is a good candidate for a coherent lightwave combiner to be used in large-scale photonic integrated circuits.

A 1×4 Polymeric Digital Optical Switch Based on the Thermo-Optic Effect

We present a 1 × 4 Y-branch digital optical switch in which S-bend variable optical attenuators are integrated. The S-bend waveguides, which are always introduced to connect the switch and the standard fiber array, are made use of and designed as variable optical attenuators. A compact device with low crosstalk and larger branching-angle is obtained. The device is fabricated on the thermo-optic polymer materials,and the performance of the device is measured. With an applied driving power of less than 200mW, the device has a low crosstalk of less than - 35dB at a wavelength of 1.55 μm.

Triplexers Based on SOI Flattop AWGs

Triplexers are designed based on SOl flattop arrayed waveguide gratings （AWGs）. Three wavelengths （1310, 1490,and 1550nm） operate at three diffraction orders of AWGs. Simulation shows that the 3dB bandwidth,crosstalk, and loss are 6nm,less than -40dB, and 5dB, respectively. The output optical fields of the device fabricated in our laboratory are clear and show a good triplexing function.

Fabrication and Evaluation of Bragg Gratings on Optimally Designed Silicon-on-Insulator Rib Waveguides Using Electron-Beam Lithography

The fabrication of Bragg gratings on silicon-on-insulator （SOI） rib waveguides using electron-beam lithography is presented. The grating waveguide is optimally designed for actual photonic integration. Experimental and theoretical evaluations of the Bragg grating are demonstrated. By thinning the SOl device layer and deeply etching the Bragg grating, a large grating coupling coefficient of 30cm^-1 is obtained.

EFFECTIVE INDEX PROFILE ALONG THE DEPTH DIRECTION OF Ti∶LiNbO 3 STRIP WAVEGUIDE

Based on the quasi analytical technique, an analytical expression for the effective index profile in the depth direction in Ti:LiNbO 3 strip waveguide is theoretically derived. It is very useful for the research into the propagation characteristics of the strip waveguides with metal clad. From this expression, the field distributions and modal indices in typical waveguides are calculated. In addition, the method of how to get the position where the mode field has the maximum value is yielded in this paper. It is very important to the optical coupling between two waveguides or between the waveguide and the fiber.

A 2×3 Photonic Switch in SiGe for 1.55μm Operation

A silicon-based photonic switch is proposed and simulated based on the multimode interference （MMI） principle and the free-carrier plasma dispersion effect in silicon-germanium. The proposed switch, designed for 1.55μm window operation,is useful for DWDM optical networks. The switch consists of two input single-mode ridge waveguide ports,a MMI section, and three output single-mode ridge waveguide ports. In the MMI section, two index-modulation regions are placed to divert input optical signals from the two input ports to each of the three output ports. Switching characteristics are demonstrated theoretically by a beam propagation method for 1.55μm operation. The simulated results show that the insertion loss of the switch is less than 1.43dB, and the crosstalk is between - 18 and - 32.8dB.

Integrated sources of photon quantum states based on nonlinear optics

The ability to generate complex optical photon states involving entanglement between multiple optical modes is not only critical to advancing our understanding of quantum mechanics but will play a key role in generating many applications in quantum technologies.These include quantum communications,computation,imaging,microscopy and many other novel technologies that are constantly being proposed.However,approaches to generating parallel multiple,customisable bi-and multi-entangled quantum bits(qubits)on a chip are still in the early stages of development.Here,we review recent advances in the realisation of integrated sources of photonic quantum states,focusing on approaches based on nonlinear optics that are compatible with contemporary optical fibre telecommunications and quantum memory platforms as well as with chip-scale semiconductor technology.These new and exciting platforms hold the promise of compact,low-cost,scalable and practical implementations of sources for the generation and manipulation of complex quantum optical states on a chip,which will play a major role in bringing quantum technologies out of the laboratory and into the real world.

Chip-Based High-Dimensional Optical Neural Network

Parallel multi-thread processing in advanced intelligent processors is the core to realize high-speed and high-capacity signal processing systems.Optical neural network(ONN)has the native advantages of high parallelization,large bandwidth,and low power consumption to meet the demand of big data.Here,we demonstrate the dual-layer ONN with Mach-Zehnder interferometer(MZI)network and nonlinear layer,while the nonlinear activation function is achieved by optical-electronic signal conversion.Two frequency components from the microcomb source carrying digit datasets are simultaneously imposed and intelligently recognized through the ONN.We successfully achieve the digit classification of different frequency components by demultiplexing the output signal and testing power distribution.Efficient parallelization feasibility with wavelength division multiplexing is demonstrated in our high-dimensional ONN.This work provides a high-performance architecture for future parallel high-capacity optical analog computing.

Review of micromachined optical accelerometers:from mg to sub-μg

Micro-Opto-Electro-Mechanical Systems(MOEMS)accelerometer is a new type of accelerometer which combines the merits of optical measurement and Micro-Electro-Mechanical Systems(MEMS)to enable high precision,small volume and anti-electromagnetic disturbance measurement of acceleration.In recent years,with the in-depth research and development of MOEMS accelerometers,the community is flourishing with the possible applications in seismic monitoring,inertial navigation,aerospace and other industrial and military fields.There have been a variety of schemes of MOEMS accelerometers,whereas the performances differ greatly due to different measurement principles and corresponding application requirements.This paper aims to address the pressing issue of the current lack of systematic review of MOEMS accelerometers.According to the optical measurement principle,we divide the MOEMS accelerometers into three categories:the geometric optics based,the wave optics based,and the new optomechanical accelerometers.Regarding the most widely studied category,the wave optics based accelerometers are further divided into four sub-categories,which is based on grating interferometric cavity,Fiber Bragg Grating(FBG),Fabry-Perot cavity,and photonic crystal,respectively.Following a brief introduction to the measurement principles,the typical performances,advantages and disadvantages as well as the potential application scenarios of all kinds of MOEMS accelerometers are discussed on the basis of typical demonstrations.This paper also presents the status and development tendency of MOEMS accelerometers to meet the ever-increasing demand for high-precision acceleration measurement.

Hybrid 2D–3D optical devices for integrated optics by direct laser writing

Integrated optical chips have already been established for application in optical communication.They also offer interesting future perspectives for integrated quantum optics on a chip.At present,however,they are mostly fabricated using essentially planar fabrication approaches like electron-beam lithography or UV optical lithography.Many further design options would arise if one had complete fabrication freedom in regard to the third dimension normal to the chip without having to give up the virtues and the know-how of existing planar fabrication technologies.As a step in this direction,we here use three-dimensional dip-in direct-laser-writing optical lithography to fabricate three-dimensional polymeric functional devices on pre-fabricated planar optical chips containing Si3N4 waveguides as well as grating couplers made by standard electron-beam lithography.The first example is a polymeric dielectric rectangular-shaped waveguide which is connected to Si3N4 waveguides and that is adiabatically twisted along its axis to achieve geometrical rotation of linear polarization on the chip.The rotator’s broadband performance at around 1550 nm wavelength is verified by polarization-dependent grating couplers.Such polarization rotation on the optical chip cannot easily be achieved by other means.The second example is a whispering-gallery-mode optical resonator connected to Si_(3)N_(4) waveguides on the chip via polymeric waveguides.By mechanically connecting the latter to the disk,we can control the coupling to the resonator and,at the same time,guarantee mechanical stability of the three-dimensional architecture on the chip.

Electrically pumped metallic and plasmonic nanolasers

In recent years, there have been a significant number of demonstrations of small metallic and plasmonic lasers. The vast majority of these demonstrations have been for optically pumped devices. Electrically pumped devices are advantageous for applications and could demonstrate concepts not amenable for optical pumping. However, there have been relatively few demonstrations of electrically pumped small metal cavity lasers. This lack of results is due to the following reasons： there are limited types of electrically pumped gain media available; there is a significantly greater level of complexity required in the fabrication of electrically pumped devices; finally, the required components for electrical pumping restrict cavity design options and furthermore make it intrinsically more difficult to achieve lasing. This review looks at the motivation for electrically pumped nanolasers, the key issues that need addressing for them to be realized, the results that have been achieved so far including devices where lasing has not been achieved, and potential new directions that could be pursued.

CMOS compatible highly efficient grating couplers with a stair-step blaze profile

A novel grating coupler with a stair-step blaze profile is proposed. The coupler is a CMOS process compatible device and can be used for light coupling in optical communication. The blaze profile can be optimized to obtain a high efficiency of 66.7% for the out-of-plane coupling at the centre wavelength of 1595 nm with a 1 dB bandwidth of 41 nm. Five key parameters of the stair-step blaze grating and their effects on the coupling are discussed for the application in L band telecommunication.