Bragg reflector spectra calculation
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Bragg reflector spectra calculation

Provided are simulations of reflectance spectra for Bragg reflector structures. Two options are available:

 ·   "Simplified" option: Simulations are simplified by using fixed (wavelength - independent) refraction indexes, so checked values of indexes should be chosen to be exactly proper for the most important region of the spectra, typically the resonance region. Also for simplicity, the value of absorption coefficient is introduced as fixed, "effective" coefficient and basically average coefficient for the pair of Bragg layers at the resonant wavelength should be checked. The "0" value of absorption is set as default. Result spectra can be stored in the ASCII text format file. The calculation is available for perpendicular and no-perpendicular beam-surface configurations. If set is no-perpendicular appropriate polarisation should be checked.

 ·        "Advanced" option (uses "BRproject" module):  gives possibility to set arbitrary structure in details. Layers can be specified by single-value refractive indexes and absorption coefficients or by datasheets with (wavelength [nm], refractive index n) or (wavelength [nm], absorption coefficient [cm-1]) space separated pairs in two columns in text files form. Result spectra can be stored in the ASCII text file. The module provides also calculation of electro-magnetic field amplitude profile inside and around the structure. This profile can be displayed and stored in text file.

    - The module makes available also a "fitting session" to fit experimental and calculated spectra with estimation of selected thickness parameters.
I. To calculate reflectance spectra please:

   1. Specify the structure details clicking "Edit structure" button and than
   2. Click the "Plot spectra" button in the main software form.

   Spectrum can be saved in text file form. To save the spectrum click "File" menu.

II. To fit structure to experimental data do as follows:

   1. Click "Load spectrum" button in the main form to load experimental data file. This file should be in text file form with two columns - first one assigning wavelength (in micron), second one assigning measured absolute reflectance R (0<R<1).
   2. Click "Edit structure" button and set structure details.
   3. Choose thickness parameters to fit (maximum six thickness) - set for those thickness any arbitrary values in the table. Click "Options" button to specify thickness to fit. Click "OK" button.
   5. Run the fitting pressing "Run fit" button.
III. To calculate field profile:

   1. Calculate reflectance spectra according to above procedure I.
   2. Click the "Show profile" button.
 ·  To change wavelength set appropriate value and click "Show profile"  button in the "Amplitude profile" form.
 ·  Spectrum can be saved in text file form. To save the spectrum click "Save" button.
 -  Number of lines in the structure design table is limited to 100.