{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Group index"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "import numpy as np\n",
    "import matplotlib.pyplot as plt\n",
    "import modes\n",
    "import opticalmaterialspy as mat"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "ms = modes.group_index?"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "ms = modes.group_index"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "wavelength = np.arange(1500, 1600, 10)*1e-3\n",
    "widths = np.arange(400, 601, 50)*1e-3\n",
    "\n",
    "plt.figure(1)\n",
    "\n",
    "for i, width in enumerate(widths):\n",
    "    ng = [modes.group_index(w, width=width) for w in wavelength]\n",
    "    \n",
    "    plt.plot(wavelength, ng, label=f'{width*1e3}')\n",
    "    \n",
    "plt.legend()\n",
    "plt.xlabel('Wavelength (um)')\n",
    "plt.xlabel('ng')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "w = wavelength[0]\n",
    "modes.group_index(w, width=width)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "widths = np.array([490, 500, 510])*1e-3\n",
    "ng = [modes.group_index(w, width=width)[0] for width in widths]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "np.diff(ng)/np.diff(widths) # dng/dw [/um]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "thicknesss = np.array([200, 220, 240])*1e-3\n",
    "ng = [modes.group_index(w, thickness=thickness)[0] for thickness in thicknesss]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "np.diff(ng)/np.diff(thicknesss) # dng/dh [/um]"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": [
    "plt.plot(thicknesss*1e3, ng, '-o')\n",
    "plt.ylabel('ng')\n",
    "plt.xlabel('thickness (nm)')"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
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