Mie Simulator GUI Running Application - VirtualPhotonics/MieSimulatorGUI GitHub Wiki

This document provides a brief description of inputs, outputs, and execution of the Mie Simulator GUI tool.

The Mie Simulator GUI tool has one input panel (input selection panel) and five output panels (µ_s, µ_s', number density, phase function and anisotropy panels) as shown below.

Depending on the application, users have to select either Mono-Disperse (spherical particles of uniform size) or Poly-Disperse (spherical particles of different size) in this panel. In Mono-Disperse distribution, the analysis is restricted to spherical scatterers with similar attributes (size and refractive index). In Poly-Disperse distribution, users can simulate spherical scatters with different attributes.

Diameter: The current version supports sphere diameters from 0.1nm to 300μm. The diameter (2 x Radius) of spheres must be specified in micrometers (μm).

Concentration/Volume Fraction: Users can either specify the concentration (number density) or the volume fraction. The concentration must be specified as a number of spheres in a cubic millimeter. When the product of the concentration and the sphere volume exceeds one cubic millimeter, an error message may appear. The volume fraction that provides the ratio between total sphere volume and the cubic volume can be calculated by multiplying sphere concentration and sphere volume. When the volume fraction is greater than 1, an error message will appear. After running a simulation, if users want to see the changes to the results with minor tweaks, they can use the ±5Margin slider to increase or decrease the concentration or the volume fraction.

Refractive index: Users can input the refractive index of the sphere and the medium. The tool computes the relative refractive index and uses it in the calculation. The refractive index of the sphere can be either real or complex (real and imaginary). When it is complex, the ‘negative’ imaginary part is related to the non-dimensional representation of light absorption. We considered the following sign convention in the simulations (van de Hulst 1957).

m_sphere = m_real – j m_imag

Wavelength: Specify the wavelength in vacuum/air (λ_vacuum) and the medium refractive index (n_med). The tool does the conversion. Users can specify the starting and the ending wavelengths and the wavelength step. A single wavelength can be assigned by specifying similar values in "Start" and "End" boxes. This tool is limited to wavelengths from 50nm to 3000nm (3µm).

Poly-Disperse selection allows three distributions; “Log Normal”, “Gaussian” and “Custom”.

"Log Normal" or "Gaussian" distribution selection:
Mean Diameter, Std. Deviation and Number of Spheres: Users can assign these parameters in "Log Normal" and "Gaussian" distribution selections. After setting parameters, users can click on "Show Distribution" button to check the number density distribution (number of spheres in a volume of 1mm3). In Log Normal and Gaussian selection, different spheres could not have different refractive indexes.

Custom Selection:
In this selection, users have the freedom to specify different refractive indexes for different spheres. Details about custom infile format and samples are given here.

Concentration/Volume Fraction, Refractive index and Wavelength: These items have already been discussed in "Parameters for Mono-Disperse Selection".

Plot Scale Y-Axis: "Log10" selection will change the scale of the y-axis to log10.

Click the “Run Simulation” button to compute the results. Use the “Display Data” button to display the results in a text window. The “Save Data” button will allow users to save selected results. The "Close" button will close the application.

This panel displays the number of spheres used in the simulation. Users can visualize the sphere size distribution in poly-disperse selection. The second tab displays the "Size Parameter" (=2πR n_med / λ_vacuum) data.

Bohren and Huffman's Mie algorithm computes the scattering efficiency (Q_sca), the extinction efficiency (Q_ext) and the backscattering efficiency (Q_back). The Mie simulator computes Q_sca, Q_ext, Q_back and multiplies them by the cross section (πR²) to obtain the scattering cross section (C_sca), extinction cross section (C_ext) and backscttering cross section (C_back) respectively. In mono-disperse, the scattering coefficient is computed by multiplying C_sca and N_s (number density). In poly-disperse distribution, the simulator considers Schmitt and Kumar's discrete particle model (Schmitt, App. Opt., 37(13), 1998) to compute the scattering coefficient.

The phase function describes the amount of light scattered into different angles. Users can either use the "Phase Function (Polar)" plot or the "Phase Function (Linear)" plot. The components of the scattering amplitude matrix (S1 and S2) are given in the S1/S2 plot. Use wavelength slider to find Phase function or S1/S2 data at a specific wavelength. To change the resolution of the phase function and S1/S2, the "dtheta(dθ)" selection can be changed.

µ_s×(1-g) provides the reduced scattering cross section (µ_s'). Users can use µ_s' Power Law Fitting tab to compute the fitting parameters, f_Ray and b_Mie for the fitting function given in Steve L. Jacques's review paper (Jacques, Phys. Med & Bio., 58(14), 2013).

Anisotropy panel displays the average cosine of the phase function. The second tab displays the forward and backward scattering percentages.

This example shows a single wavelength simulation for mono-disperse spheres with a complex refractive index. The results from the Mie Simulator GUI show excellent agreement with Scott Prahl's Mie Scattering Calculator.

Sphere Diameter: 1.0microns
Refractive Index of Medium: 1.0
Real Refractive Index of Sphere: 1.5
Imaginary Refractive Index of Sphere: -0.5
Wavelength: 632.8nm
Number Density:1e8spheres/mm3
Number of Angles: 360 (dtheta = π/360 = 0.5˚)

Comparison:

Edited: March 28, 2024