def gaussian_beam(fwhm=10):
"""Display a Gaussian beam at the given fwhm.
Parameters
----------
fwhm : float
Full width at half maximum (for intensity not amplitude) (µm).
"""
w = fwhm / np.sqrt(2 * np.log(2))
bpm = Bpm(1, 1, 1, 1, 1, 1, 1)
bpm.x = np.linspace(-1.5*fwhm, 1.5*fwhm, 500)
x = bpm.x
plt.figure("Beam")
plt.title("Width definition of a gaussian beam with FWHM=%s µm" % fwhm)
plt.xlabel("x (µm)")
plt.plot(x, bpm.gauss_light(fwhm, 0), label='field')
plt.plot(x, (bpm.gauss_light(fwhm, 0))**2, label='intensity')
plt.plot(x, [1/2]*x.size, '-.', label='1/2')
plt.plot([fwhm/2]*x.size, np.linspace(0, 1, x.size),
'--', label='fwhm/2')
plt.plot(x, [np.exp(-1)]*x.size, '-.', label='1/e')
plt.plot(x, [np.exp(-2)]*x.size, '-.', label='1/$e^2$')
plt.plot([w]*x.size, np.linspace(0, 1, x.size),
'--', label='$w_0$=%.2f' % w)
plt.legend()
plt.show()
def guides_x():
"""Display a Gaussian guide, two super-Gaussian guides and a flat-top guide
to illustrate the width definition."""
width = 10
bpm = Bpm(1, 1, 1, 1, 1, 1, 1)
bpm.x = np.linspace(-15, 9.1, 500)
x = bpm.x
plt.figure("guide_x")
plt.title("Different waveguides shape available")
plt.plot(x, bpm.gauss_guide(width, 1)(x), label='Gaussian')
plt.plot(x, bpm.gauss_guide(width, 4)(x), label='super-Gaussian P=4')
plt.plot(x, bpm.gauss_guide(width, 10)(x), label='super-Gaussian P=10')
plt.plot(x, bpm.squared_guide(width)(x), label='Flat-top')
plt.plot([width/2]*x.size, np.linspace(0, 1, x.size), '--',
label='width/2')
plt.plot(x, [np.exp(-1)]*x.size, '-.', label='1/e')
plt.legend()
plt.show()