{
  "cells": [
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "\n# Gaussian beam\n\nBasic example of computation of the field emitted by a coherent Gaussian beam.\n"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Import required libraries\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "import matplotlib.pyplot as plt\nimport numpy as np\n\nimport pysrw as srw"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Starts creating a coherent Gaussian beam with a waist of 20 um.\nWe leave the default initial position and angle of the source (all zero)\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "sigma = 20e-6\ngsnBeam = srw.emitters.GaussianBeam(xSigma=sigma, ySigma=sigma)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Create a 10 mm x 10 mm observation mesh, with a resolution of 100 um, \nplaced 1 m downstream of the source\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "observer = srw.wavefronts.Observer(centerCoord=[0, 0, 1],\n                                   obsXextension=10e-3, \n                                   obsYextension=10e-3,\n                                   obsXres=100e-6,\n                                   obsYres=100e-6)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Compute the wavefront at the observation wavelength of 600 nm.\nThe multiprocessing version is reported for comparison\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "wl = 600\nwfr = srw.computeGsnBeamWfr(gsnBeam, observer, wavelength=wl)\nwfr_mp = srw.computeGsnBeamWfrMultiProcess(4, gsnBeam, observer, wavelength=600)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Compute the corresponding optical intensity\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "intensity = wfr.getWfrI()\nintensity_mp = wfr_mp.getWfrI()"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Plot the 2D intensity distribution\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "srw.plotI(intensity)\nsrw.plotI(intensity_mp)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Extract cross-cut using :py:func:`~pysrw.tools.extractCrossCuts`\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "crosscuts = srw.extractCrossCuts(intensity)\nxax = crosscuts[\"xax\"]\nxcut = crosscuts[\"xdata\"]"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Compare the intensity profile with the theoretical distribution.\nFor a Gaussian beam $\\sigma \\cdot \\sigma' = \\lambda / 4 \\pi$.\nWe omit the spherical attenuation as it's negligible with respect to the \ndecay due to the finite divergence of the beam\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "sigma_p = wl*1e-9 / (4 * np.pi * sigma) #rad\nxcut_theo = srw.gaussian1p(xax, sigma_p * observer.zPos)"
      ]
    },
    {
      "cell_type": "markdown",
      "metadata": {},
      "source": [
        "Summary plot of the intensity cuts\n\n"
      ]
    },
    {
      "cell_type": "code",
      "execution_count": null,
      "metadata": {
        "collapsed": false
      },
      "outputs": [],
      "source": [
        "fig, ax = plt.subplots()\nax.plot(xax * 1e3, xcut, label=\"sim\")\nax.plot(xax * 1e3, np.max(xcut) * xcut_theo, linestyle=\"--\", label=\"theo\")\nax.set_xlabel(\"x position [mm]\")\nax.set_ylabel(\"Intensity [ph/(s mm^2 0.1%BW)]\")\nax.legend()\nplt.show()"
      ]
    }
  ],
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      "display_name": "Python 3",
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      "file_extension": ".py",
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      "pygments_lexer": "ipython3",
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