## Nanophotonics

### Simulation Tools

### **Molecular Foundry Photonics Toolkit**

** Stanford Stratified Structure Solver (S4) Simulation tool**

S4 is a frequency domain code to solve layered periodic structures. Internally, it uses Rigorous Coupled Wave Analysis (RCWA; also called the Fourier Modal Method (FMM)) and the S-matrix algorithm. S4 was developed by Victor Liu of the Fan Group in the Stanford Electrical Engineering Department. http://www.stanford.edu/group/fan/S4/#main

### **S4 Editor**

Edit a Lua script for the Stanford Stratified Structure Solver and visualize the output, all within the Jupyter Notebook environment in nanoHUB.

** nanoDDSCAT**

This tool calculates plasmonic properties of dielectric heterostructures, such as and is useful for people building bio-sensors based on refractive index sensing and plasmonic coupling, as well as people who wish to compute fields for SERS or other field enhanced spectroscopies. Through the use of the Discrete Dipole Approximation (DDSCAT version 7.3) users can study absorption, scattering, and electric fields around arrays of nanostructures, including nanobio systems, with varied properties. Spectra (absorption and scattering) and electrical near fields are calculated using classical electrodynamics.

This tool provides an interactive interface for user-input to the DDSCAT software package. Supported geometries include: rectangular prism, anisotropic ellipsoid, ellipsoid, concentric ellipsoids, isotropic cylinder, isotropic cylinder with hemispherical end-caps, and cylinder with unixial anisotropic dielectric tensor.

** DDSCAT Convert: A Target Generation Tool**

Convert .obj files to DDSCAT shape files

** nanoDDSCAT+**

Combines the Discrete Dipole Scattering (DDSCAT) tool with the DDAConvert tool for a single workflow for custom shapes.

This tool creates a single workflow for creating and processing a custom shape in Draine and Flatau's DDSCAT (v7.3).

**NanoDDSCAT+ Tutorial on YouTube**

### **Shape Generator for DDSCAT**

### **PhotonicsSHA-2D: Modeling of Single-Period Multilayer Optical Gratings and Metamaterials**

**PhotonicsSHA-2D: Modeling of Single-Period Multilayer Optical Gratings and Metamaterials** employs the 2-dimensional spatial harmonic analysis (2D SHA) method to model the optical responses of single-period multilayer gratings. The incident wave is a plane wave with arbitrary incident angles (with either TE or TM polarization), and the output results are the complex transmission and reflection coefficients for the zero diffraction order. The database of optical elemental materials stored in PhotonicsDB is integrated into this tool.

### **PhotonicsCL: Photonic Cylindrical Multilayer Lenses**

PhotonicsCL: Photonic Cylindrical Multilayer Lenses is used for designing and simulating circular cylindrical multilayered and graded index structures. The designed multilayered cylindrical structure can serve as a piecewise-constant approximation for a variety of ideal optical devices with continuous distribution of material constants, e.g., Eaton lenses, Luneburg lenses, and optical “black hole” devices (omnidirectional light concentrators and absorbers). Also the direct simulation of an ideal optical “black hole” is available. The tool allows for different types of light sources, including point sources, plane wave source, and multiple Gaussian beam sources. It also has a link to the material database and can use all the database materials, as well as a user-specified material, in the design.

### **Hyperlens Design Solver **

The Hyperlens Design Solver tool is intended to be used in conjunction with the Hyperlens Layer Designer tool to aid in the design and simulation of a hyperlens. The Hyperlens Design Solver tool allows users to upload designs created with the Hyperlens Layer Designer tool, make a new design, or select from several pre-existing designs. The tool then simulates the performance of the design and outputs several plots of the resulting field intensities. By using these two tools, users can experiment with different designs and evaluate performance to find the optimal design before beginning fabrication.

### **Hyperlens Layer Designer**

Recent research has been done in regards to optically imaging using metamaterials. One such project is the hyperlens, which aims to overcome the classical diffraction limit and project a magnified image into the far field. The potential applications for this device range from nanolithography to bioimaging.

The Hyperlens Layer Designer tool is intended to be used in conjunction with the Hyperlens Solver tool to aid in the design and simulation of a hyperlens. The Hyperlens Layer Designer allows users to quickly and easily create hyperlens designs and save them for later use in the Hyperlnes Solver. By using these two tools, users can experiment with different designs and evaluate performance to find the optimal layout before beginning fabrication.

### **PhotonicsRT: Wave Propagation in Multilayer Structures**

**PhotonicsRT: Wave Propagation in Multilayer Structures** calculates the electromagnetic field for a plane wave incident at an arbitrary incident angle on a multilayer material stack using the T-matrix approach. The outputs of the tool are real and imaginary part of reflection coefficient (r), real and imaginary part of transmission coefficient (t), reflectance (R), transmittance (T) and absorption (A).

** Meep**

Meep implements the finite-difference time-domain (FDTD) method for computational electromagnetism. This is a widely used technique in which space is divided into a discrete grid and then the fields are evolved in time using discrete time steps. As the grid and the time steps are made finer and finer, this becomes a closer and closer approximation for the true continuous equations, and one can simulate many practical problems essentially exactly. Though many quantities can be calculated, major applications include transmission and reflection spectra, resonant modes and frequencies, and field pattern.

For detailed description and tutorials, please refer to: http://ab-initio.mit.edu/wiki/index.php/Meep

### **MIT Photonic Bands**

This application computes the band structures and electromagnetic modes of periodic dielectric structures. The program uses fully-vectorial and three-dimensional frequency domain methods. It is designed for the study of photonic crystals. For a more detailed description, please visit: http://ab-initio.mit.edu/wiki/index.php/MIT_Photonic_Bands

** PhotonicVASEfit: VASE fitting tool**

PhotonicVASEfit is a tool to fit optical constants of materials to the data obtained with Variable Angle Spectroscopic Ellipsometry (VASE). The tool is initially designed to retrieve the surface conductivity of a single layer graphene sheet deposited on a substrate. Built-in support includes a graphene specific integral model - RPA (Random Phase Approximation). Among general built-in models are Splines and Critical Points (CP) model (relaxed Lorentz oscillators). Furthermore, any custom user-defined material model (defined as a Matlab function) could be used. Current version supports a structure of 2D material layer on a substrate. Extensions to a more general geometry and support for more materials are expected in next versions.

** PhotonicsPOS: Particle on Substrate**

PhotonicsPOS: Core-shell Particles on Layered Planar Substrates provides the scattering solutions for a plane wave at an arbitrary angle incident on a core-shell particle on a planar lamellar substrate. The tool uses a modified version of the standard Mie solution in order to account for the reflection of scattered spherical waves from the planar substrate. Full control is give to the user, allowing them to select the material parameters of each layer, obtained from PhotonicsDB, as well as providing a two-parameter sweep functionality. The tool first solves for the optical cross sections and maximum modes for the given geometry, and then provides the field maps in Cartesian and cylindrical coordinates. The user has the opportunity to select a range of scattering modes for both the optical cross section and field maps. The tool also saves optical cross sections for solved geometries in a cache.