Application Gallery

The edge coupler is a key device that enables efficient coupling between optical fibers and on-chip waveguides at the chip facet. It is widely used in low-loss fiber-to-chip coupling interfaces, optical input/output (I/O) at chip facets, and optical probe coupling in wafer-level testing. This example, based on reference [1], uses the finite-difference eigenmode (FDE) solver and the eigenmode expansion (EME) solver to model and simulate an edge coupler operating at 1550 nm that achieves efficient coupling between a standard SMF-28 single-mode fiber and a chip.

A phase-shifted Bragg grating (PSBG) is an optical device formed by introducing one or more phase jump points into the periodic structure of a conventional Bragg grating. It can open one or more extremely narrow transmission windows within the stopband of the grating's transmission spectrum, and can be used as a narrowband bandpass filter and wavelength selector in optical fiber communications, lasers, sensing, and other fields. This example uses the EME solver to simulate a phase-shifted Bragg grating, calculate its transmission spectrum, and analyze the influence of the number of periods on the grating's filtering characteristics.

Waveguides are fundamental components in integrated photonic chips, used to transmit optical signals within the chip. However, the mode field sizes of waveguides and optical fibers typically differ significantly, leading to high coupling losses when directly connected. Therefore, a Spot Size Converter (SSC) is often employed as an intermediate transition structure. Based on reference [1], this example simulates a spot size converter using a tapered waveguide with a polymer overlay, utilizing the EME solver.

A polarization rotator (PR) is a special waveguide structure that enables mutual conversion between polarization states by accumulating the phase difference between the TE and TM modes. It is widely used in coherent optical communications, polarization‑division multiplexed photonic integrated circuits, and quantum information processing. This example introduces the simulation method for a polarization rotator and demonstrates two approaches for calculating the rotation length using the FDE and EME solvers.

For laterally uniform multilayer structures with refractive index variations only in the thickness direction, the stack script provides an efficient analytical calculation method. Based on the transfer matrix method (TMM), the stack script associates each layer with a transfer matrix, multiplies the matrices sequentially to obtain the overall transfer matrix, and then solves for the reflectance, transmittance, and field distribution of the structure. Using a four-layer dielectric structure as an example, this page compares the transmittance and reflectance at different incident angles obtained from the stackrt script and the FDTD method. In addition, the stackrt script is used to analyze the effect of a 5 nm thickness variation in the middle layers on the reflectance.

The tapered-waveguide-type polarization converter achieves efficient polarization conversion by enabling smooth energy coupling between different polarization modes through a gradually varying waveguide cross-section along the propagation direction. This structure offers advantages such as broad bandwidth, low loss, and high tolerance to fabrication errors, making it widely used in optical communications, polarization multiplexing, and polarization control in silicon photonic chips. In this example, the FDE solver is first used to sweep the waveguide width and analyze the variation of the effective refractive index of the TM1 and TE0 modes, identifying the region where the two modes intersect to guide the design range of the tapered waveguide. Subsequently, the FDTD and EME solvers are employed to perform three-dimensional simulations of the entire structure to calculate the light propagation and polarization conversion efficiency within the tapered waveguide. By comparing the speed and accuracy of the two solvers, the unique advantages of EME in planar waveguide design are validated.

Fiber Bragg Grating (FBG) is an optical filtering device formed by introducing a periodic refractive index modulation in the fiber core, widely used in optical fiber communications, fiber sensing, laser frequency stabilization, and other fields. In this example, the Eigenmode Expansion (EME) solver is employed to simulate the fiber Bragg grating. Through conventional parameter sweep and wavelength sweep, the computational efficiency advantage of EME in handling periodic grating structures is demonstrated.

Solar cells are the core devices for photoelectric conversion. The basic principle is that when sunlight illuminates a semiconductor material with photovoltaic effect, the semiconductor absorbs photons and generates photogenerated carriers, which then form a photocurrent under the built-in electric field or electrode action. As the complexity of solar cell designs increases, accurate numerical simulation becomes a key means to predict and optimize cell performance. By importing the photogenerated carrier generation rate into the FDCharge solver for electrical simulation, key metrics of the solar cell can be obtained. This case study demonstrates the calculation of current–voltage characteristics and other metrics by importing optical results.

The directional coupler is a passive four-port device widely used in RF, microwave, and optical communication fields. Its core function is to extract a small portion of a signal proportionally and directionally without disturbing the main signal transmission. This case takes the directional coupler described in Section 3.1 of Liu et al. as an example, and carries out a comparative simulation in SimWorks, Lumerical, and Tidy3D. Through reasonable control of variables, it is demonstrated that the three software tools agree closely on key performance indicators.

In this case, we apply the topology optimization (TO) method to the design of a two-dimensional Y‑branch splitter. By directly optimizing the material distribution within the design region and allowing the algorithm to explore freely throughout the design space, we demonstrate the powerful capability of topology‑based inverse design in both structural generation and performance optimization of photonic devices.