Design Of Optical Circuits Research Articles

Unidirectional hyperbolic whispering-gallery phonon-polariton excitation in boron nitride nanotubes.

In two-dimensional (2D) hyperbolic materials, energy is directed into their deep subwavelength polaritonic modes through four narrow beams. Hyperbolic whispering-gallery mode nanocavity-confined phonon polaritons (PhPs) display a strongly enhanced light-matter interaction in the infrared regime. Particularly, the unidirectional phonon-polarization excitation in nanocavities has a potential application value in an on-chip integrated optical circuit design, efficient optical sensors, and enhanced spectral technology. Here, we explore the hyperbolic whispering-gallery mode PhPs on the cross section of a hexagonal BN nanotube (BNNT) and demonstrate that efficient unidirectional excitation can be achieved using a circularly polarized electric dipole, combining with optical spin-orbit coupling. Our results demonstrated that the undirectionality of the hyperbolic polariton propagation in a nanocavity can be conveniently achieved, independent of the structure symmetry of the nanocavity, providing potential applications in nanoscale light propagation, on-chip optical devices, and communication.

Design of a 1 × 3 Power Splitter Based on Multimode Interference in a Parabolic-Type Slot-Waveguide Structure

Multimode interference (MMI) couplers based on silicon slot-waveguide structures have received widespread attention in recent years. The key issues that need to be addressed are the size and loss of such devices. This study introduces a 1 × 3 silicon-based slot-waveguide multimode interference power splitter. The device uses a gallium-nitride slot-waveguide structure to reduce the length of the coupling region and decrease additional losses. To reduce the width of the coupling region, the multimode interference coupling area is designed with a parabolic-shaped structure. The introduction of a tapered structure between the input/output waveguides and the coupling region improves additional losses and non-uniformity. Furthermore, we conducted an analysis of the fabrication tolerances of the coupling region. In this paper, we use mode solution to simulate the design of the device in the 1550 nm optical wavelength range. The eigenmode expansion method is used to simulate and optimize the parameters of the device. The device is simulated using the eigenmode expansion solver. The simulation results show that the total length of the coupling region for the device is only 4 μm. The normalized transmission of the device is 0.992, and its excess loss and imbalance are 0.036 dB and 0.003 dB, respectively. The proposed power splitter can be applied to integrated optical circuit design, optical sensing, and optical power measurement.

High-dimensional spatial mode sorting and optical circuit design using multi-plane light conversion

Multi-plane light converters (MPLCs) are an emerging class of optical devices capable of converting a set of input spatial light modes to a new target set of output modes. This operation represents a linear optical transformation—a much sought after capability in photonics. MPLCs have potential applications in both the classical and quantum optics domains, in fields ranging from optical communications to optical computing and imaging. They consist of a series of diffractive optical elements (the “planes”), typically separated by a free space. The phase delays imparted by each plane are determined by the process of inverse-design, most often using an adjoint algorithm known as the wavefront matching method (WMM), which optimizes the correlation between the target and actual MPLC outputs. In this work, we investigate high mode capacity MPLCs to create arbitrary spatial mode sorters and linear optical circuits. We focus on designs possessing low numbers of phase planes to render these MPLCs experimentally feasible. To best control light in this scenario, we develop a new inverse-design algorithm, based on gradient ascent with a specifically tailored objective function, and show how, in the low-plane limit, it converges to MPLC designs with a substantially lower modal cross-talk and higher fidelity than those achievable using the WMM. We experimentally demonstrate several prototype few-plane high-dimensional spatial mode sorters, operating on up to 55 modes, capable of sorting photons based on their Zernike mode or orbital angular momentum state, or an arbitrarily randomized spatial mode basis. We discuss the advantages and drawbacks of these proof-of-principle prototypes and describe future improvements. Our work points to a bright future for high-dimensional MPLC-based technologies.

Coupled microbeads for unidirectional cascade lasing transfer

One-way photonic devices are based around the concept of directionally-dependent propagation of light that can be used in the design of optical circuits. We demonstrate a straightforward method arising from cascade lasing transfer using a pair of coupled microcavities. The concept is based on consecutive down-converted laser transmission leading to net cross-cavity propagation in one direction. To describe this system, we first develop a simple, generalized coupled-cavity rate equation model to calculate the efficiency of the lasing cascade process. The basic idea is then demonstrated experimentally using a coupled resonator geometry. The two-cavity lasing design forms a basic three-wavelength microdevice that can change the original lasing wavelength or act as a one-way down-converting micro-lasing system.

An improved synthesis technique for optical circuits using MIG and XMG

The progress of fabrication technology in the photonics industry has achieved a significant milestone due to the practicability of performing functional computations on-chips using ultra-high-speed optical devices and low-power interconnects. These rapid advancements in the optical industry have generated a huge interest before the research community towards developing algorithms for efficient synthesis of optical circuits, and in the last few years several articles have come out in this field. Use of graph data structures like BDD, AIG is investigated as intermediate representations (IR) to perform scalable synthesis for logic functions. However, optimizing the generated circuits and developing efficient synthesis schemes remain a high priority in this highly growing field.Motivated by the rapid progress made in optical circuit design, in this work, we introduce an improved synthesis scheme based on two prominent graph data structures - MIG and XMG, where both the graphs act as IR in designing optical circuit. The synthesis steps are completed in two phases, wherein the first phase, we find the intermediate representation (IR) for the input function and then, we perform the technology mapping from the obtained IR to MZI circuit. This second phase also has two more sub-phases where first we run a template matching algorithm and then a set of optimization rules are executed to improve the cost. In our design, we use three primary optical components – MZI, beam combiner and splitter but as the use of beam splitter in circuits reduces the signal strength, we also have shown the way of transforming a normal circuit to splitter-free design. Our synthesis approach can handle large functions and have shown good results for a wide spectrum of benchmarks. Comparison with related state-of-the-art IR based approaches has registered some good improvements too.

Design of all-optical parallel multipliers using semiconductor optical amplifier-based Mach–Zehnder interferometers

Due to the benefits of low power, high bandwidth and complementary metal-oxide-semiconductor (CMOS) compatibility, the design of optical circuits has spurred great attention among researchers in the domain of electronic design automation. With this motivation, all-optical combinational and sequential circuits such as adders, multiplexers, multipliers and flip-flops have been explored in recent times. In this paper, we have explored the designs of all-optical array multiplier and four types of parallel multipliers (carry save adder multiplier, Wallace tree multiplier, Dadda multiplier and reduced area multiplier) using two different design approaches named as Design1 and Design2. In order to design these multipliers, semiconductor optical amplifier (SOA)-based Mach–Zehnder interferometers (MZIs) have been used as the basic optical component. The basic MZI switch, full adder and 2-bit multiplier have been simulated using OptiSystem software to analyze the power loss. Furthermore, an all-optical merged multiplier has been designed, which is often used in digital signal processors. In comparison with other designed multipliers, it is evident from the simulation results that the MZI-based reduced area multiplier of Design1 approach has the highest performance in terms of speed, while the MZI-based carry save adder (CSA) multiplier with Design1 approach has the least optical cost.

Coupled Mode Demonstration of Slow-Light Plasmonic Sensor Based on Metasurface at Near-Infrared Region

In this paper, we theoretically and numerically reported a dual plasmon-induced transparency and the relevant sensing property in a multi-cross metasurface by the coupled mode analysis. A phase coupling model was established to characterize the optical response of this plasmonic sensor. It was found that the transparency windows were sensitive to the resonance mode of each metal strip, which was well demonstrated by the theoretical model. Both the sensing property and the slow light in this structure were discussed. A high figure of merit of 223 and sensitivity of 850 nm/RIU were achieved. In addition, the 1170-nm near-infrared light can be slowed down by nearly two order of magnitude with group delay of 0.45 ps in this sensor. These results may provide guidance for light-matter interaction-enhanced slow-light sensor and integrated optical circuit design.

Plasmonic filter with highly selective wavelength in a fixed dimension based on the loaded rectangular ring cavity

Here we reported a compact plasmonic filter design based on the block-loaded rectangular ring cavity. The selected wavelength can be flexible modulated to longer ones without extending the filter dimension. Such filter was composed of a common rectangular ring and several loaded nanoblocks. This is attributed to the electrical field perturbation caused by the loaded block. The resonant mode was found sensitive to the nanoblock which located at the antinode position, and the proportional relationship was revealed between the selected wavelength and the nanoblock size and number, which ensured the accurate determination of the selected wavelength. In particularly, this proposed plasmonic filter possess a more compact size than the common used one for the same properties. These findings can be beneficial for the integrated optical circuit design and may improve the integration level.

All-optical control of polarization splitting with a dielectric-clad azobenzene liquid crystal.

We report the design, fabrication, and characterization of an optically switchable polarizing beam splitter with a prism/azobenzene liquid crystal/prism hybrid structure. The beam splitter can operate in the polarization-splitting mode and the non-splitting mode. The switching between the modes is realized by the photoisomerization-induced phase transitions in the azobenzene liquid crystal, featuring all-optical control, bistability, and fast response. Such an active polarization-handling element is highly desirable as it not only simplifies and compacts sophisticated optical systems but also increases the degree of freedom in optical circuit design.

Utilization of binary PSO algorithm and DDA method to investigate the plasmonic demultiplexer -based CPA filter

Here, we suggest the possibility of optical circuit design approach by employing the binary optimization of plasmonic nano disks. The proposed mechanism is based on combination of binary particle swarm optimization (BPSO) algorithm and discrete dipole approximation (DDA) method. BPSO, a group of birds including a matrix with binary entries responsible for controlling nano disks in the array, shows the presence with symbol of (‘1’) and the absence with (‘0’). The current research represents a nanoscale and compact 4 channels plasmonic Demultiplexer as optical circuit. It includes 8 coherent perfect absorption (CPA) –type filters. The operation principle is based on the absorbable formation of a conductive path in the dielectric layer of a plasmonic nano-disks waveguide. Since the CPA efficiency depends strongly on the number of plasmonic nano-disks and the nano disks location, an efficient binary optimization method based the BPSO algorithm is used to design an optimized array of the plasmonic nano-rod in order to achieve the maximum absorption coefficient in the ‘off’ state.

Combination of binary particle swarm optimization algorithm and discrete dipole approximation method to investigate the plasmonic circuit-based coherent perfect absorption filter

Here, we suggest the possibility of optical circuit design approach by employing the binary optimization of plasmonic nano rods. The proposed mechanism is based on combination of binary particle swarm optimization (BPSO) algorithm and discrete dipole approximation method. BPSO, a group of birds including a matrix with binary entries responsible for controlling nano rods in the array, shows the presence with symbol of (‘1’) and the absence with (‘0’). The current research represents a nanoscale and compact four channels plasmonic Demultiplexer as optical circuit. It includes eight coherent perfect absorption (CPA)—type filters. The operation principle is based on the absorbable formation of a conductive path in the dielectric layer of a plasmonic nano-rods waveguide. Since the CPA efficiency depends strongly on the number of plasmonic nano-rods and the nano rods location, an efficient binary optimization method based the BPSO algorithm is used to design an optimized array of the plasmonic nano-rod in order to achieve the maximum absorption coefficient in the ‘off’ state.

Circular grating coupler for creating focused azimuthally and radially polarized beams

We show a planar optical circuit design that takes light from an input waveguide and creates a focused azimuthally or radially polarized beam emanating from the surface of the substrate. It is implemented in silicon-on-insulator waveguides and does not require any external components to focus the beam. The focal spot size can be subwavelength and is potentially useful for lithography, imaging, optical data storage, optical trapping, optical excitation of molecules, or coupling to optical fibers.

Optical circuit design based on a wavefront-matching method

We propose an optical circuit design method for coherent waves as a boundary value problem. The method produces a very compact circuit in which the refractive index pattern is automatically synthesized for given input and output fields with a numerical calculation. We employ the method to design a 1.3/1.55 microm wavelength demultiplexer and also describe the features of a circuit generated by use of the method.

Loss in a rectangular optical waveguide induced by the crossover of a second waveguide

We calculate the loss induced in a single-mode rectangular optical waveguide by the presence of a second waveguide, perpendicular to the first, which crosses over the first waveguide at a variable distance d. Our calculation is applied to the analysis of several doped silica waveguides of practical importance for optical circuit design.

A 1.3/1.55-/spl mu/m wavelength-division multiplexing optical module using a planar lightwave circuit for full duplex operation

We developed a hybrid integrated optical module for 1.3/1.55-/spl mu/m wavelength-division multiplexing (WDM) full-duplex operation. The optical circuit was designed to suppress the optical and electrical crosstalk using a wavelength division multiplexing filter, and an optical crosstalk of -43 dB and an electrical crosstalk of -105 dB were achieved with a separation between the transmitter laser diode and the receiver photodiode of more than 9 mm. We used the optical circuit design to fabricate an optical module with a bare chip preamplifier in a package. This module exhibited a full duplex operation of 156 Mbit/s with a minimum sensitivity of -35.2 dBm at a bit error rate of 10/sup -10/.

Design of optical circuits for multiplex computing based on set-valued logic

A new computer architecture that uses multiwavelength optoelectronic integrated circuits is proposed that addresses problems caused by interconnection complexity. Multiwavelength-optoelectronicintegrated- circuit architectures, in which various wavelengths are employed as information carriers, provide the wavelength as an extra dimension of freedom for parallel processing; thus we can perform several independent computations in parallel in a single optical module. This multiplex computing enables us to reduce the number of interconnections on the chip and to improve interconnection complexity. The systematic synthesis of the optical circuits for multiplex computing is discussed on the basis of a set-valued switching algebra.

Refractive index decrease phenomena in SiO2–Ta2O5 waveguide films by CO2 laser irradiation

SiO2-Ta2O5 waveguide film exhibits a refractive index decrease up to 2% and a simultaneous film thickness increase proportional to the index decrease by CO2 laser irradiation. A partial restoration to the pre-irradiated state is observed by annealing in air at temperatures between 700 and 780 °C. The origin of the index decrease may be due to the density change with Ta2O5 crystallization. For application to the optical circuit design, the effective refractive indices of the index-decreased area are estimated, and a TE0-TE1 mode separation experiment by a 20°angle is done successfully, in order to examine the usefulness of the effective index.