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Commit b705ae7b authored by Sean Leavey's avatar Sean Leavey
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Added cavity scan example, which is 100% pure PyKat

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# -*- coding: utf-8 -*-
"""
Fabry-Perot cavity scan example.
]--------(=========================)---->
laser ITM 10m cavity ETM photodiode
The simulation sets up a parameter list in the form of a Python dictionary,
then populates PyKat with the experimental setup directly (without using
a .kat file input - 100% PyKat).
The cavity is then scanned by tuning the ETM, and the results are plotted.
Some terminology:
ITM: initial test mass
ETM: end test mass
HR: highly reflective
AR: anti-reflective
Sean Leavey
s.leavey.1@research.gla.ac.uk
January 2014
"""
import pykat
import pylab as pl
import numpy as np
#######################
# set some parameters #
#######################
parameters = {
'laser': {
'power': 30, # input laser power [W]
'frequency_offset': 0,
'phase': 0
},
'cavity': {
'length': 10.8, # cavity length [m]
'itm': { # ITM
'radius': 0.023225, # [m]
'radius_of_curvature': {
'inner': { # inner (concave) surface
'x': -5.7, # [m]
'y': -5.7 # [m]
},
'outer': { # outer (convex) surface
'x': -1.7763, # [m]
'y': -1.7763 # [m]
}
},
'thickness': 0.027, # [m]
'reflectivity': { # power reflectivity
'inner': 0.995, # inner (concave) surface
'outer': 0.001 # outer (convex) surface
},
'transmission': { # power transmission
'inner': 0.005,
'outer': 0.999
},
'tuning_angle': { # phi
'inner': 0,
'outer': 0
},
'misalignment': { # mirror misalignment [rad]
'inner': {
'x': 0,
'y': 0
},
'outer': {
'x': 0,
'y': 0
}
}
},
'etm': { # ETM
'radius': 0.023225, # [m]
'radius_of_curvature': {
'inner': { # inner (concave) surface
'x': 5.7, # [m]
'y': 5.7 # [m]
},
'outer': { # outer (convex) surface
'x': 1.7763, # [m]
'y': 1.7763 # [m]
}
},
'thickness': 0.027, # [m]
'reflectivity': { # power reflectivity
'inner': 0.995, # inner (concave) surface
'outer': 0.001 # outer (convex) surface
},
'transmission': { # power transmission
'inner': 0.005,
'outer': 0.999
},
'tuning_angle': { # phi
'inner': 0,
'outer': 0
},
'misalignment': { # mirror misalignment [rad]
'inner': {
'x': 0,
'y': 0
},
'outer': {
'x': 0,
'y': 0
}
}
},
},
'materials': {
'bulk': {
'silica': {
'refractive_index': 1.45
}
}
}
}
###############################################
# instantiate PyKat object and add components #
###############################################
# instantiate PyKat object
kat = pykat.finesse.kat()
# laser
kat.add(
pykat.components.laser(
'laser', # name
'n1', # node
parameters['laser']['power'],
parameters['laser']['frequency_offset'],
parameters['laser']['phase']
)
)
# add a 1m space between laser and ITM
kat.add(
pykat.components.space(
'space1', # name
'n1', # node 1
'n2', # node 2
1 # length [m]
)
)
##################
# ITM definition #
##################
# This involves three 'components':
# * a mirror to represent the convex AR surface;
# * a space representing the thickness of the mirror, with correct refractive index;
# * a mirror representing the concave HR surface
# AR coating
kat.add(
pykat.components.mirror(
'M_ITM_AR',
'n2',
'n3',
parameters['cavity']['itm']['reflectivity']['outer'],
parameters['cavity']['itm']['transmission']['outer'],
parameters['cavity']['itm']['tuning_angle']['outer'],
parameters['cavity']['itm']['radius_of_curvature']['outer']['x'],
parameters['cavity']['itm']['radius_of_curvature']['outer']['y'],
parameters['cavity']['itm']['misalignment']['outer']['x'],
parameters['cavity']['itm']['misalignment']['outer']['y'],
0,
parameters['cavity']['itm']['radius'] * 2
)
)
# bulk mirror material
kat.add(
pykat.components.space(
'M_ITM_BULK',
'n3',
'n4',
parameters['cavity']['itm']['thickness'],
parameters['materials']['bulk']['silica']['refractive_index']
)
)
# HR coating
kat.add(
pykat.components.mirror(
'M_ITM_HR',
'n4',
'n5',
parameters['cavity']['itm']['reflectivity']['inner'],
parameters['cavity']['itm']['transmission']['inner'],
parameters['cavity']['itm']['tuning_angle']['inner'],
parameters['cavity']['itm']['radius_of_curvature']['inner']['x'],
parameters['cavity']['itm']['radius_of_curvature']['inner']['y'],
parameters['cavity']['itm']['misalignment']['inner']['x'],
parameters['cavity']['itm']['misalignment']['inner']['y'],
0,
parameters['cavity']['itm']['radius'] * 2
)
)
##########
# cavity #
##########
kat.add(
pykat.components.space(
'space2',
'n5',
'n6',
parameters['cavity']['length']
)
)
##################
# ETM definition #
##################
# This involves three 'components', just like the ITM definition.
# HR coating
kat.add(
pykat.components.mirror(
'M_ETM_HR',
'n6',
'n7',
parameters['cavity']['etm']['reflectivity']['inner'],
parameters['cavity']['etm']['transmission']['inner'],
parameters['cavity']['etm']['tuning_angle']['inner'],
parameters['cavity']['etm']['radius_of_curvature']['inner']['x'],
parameters['cavity']['etm']['radius_of_curvature']['inner']['y'],
parameters['cavity']['etm']['misalignment']['inner']['x'],
parameters['cavity']['etm']['misalignment']['inner']['y'],
0,
parameters['cavity']['etm']['radius'] * 2
)
)
# bulk mirror material
kat.add(
pykat.components.space(
'M_ETM_BULK',
'n7',
'n8',
parameters['cavity']['etm']['thickness'],
parameters['materials']['bulk']['silica']['refractive_index']
)
)
# AR coating
kat.add(
pykat.components.mirror(
'M_ETM_AR',
'n8',
'n9',
parameters['cavity']['etm']['reflectivity']['outer'],
parameters['cavity']['etm']['transmission']['outer'],
parameters['cavity']['etm']['tuning_angle']['outer'],
parameters['cavity']['etm']['radius_of_curvature']['outer']['x'],
parameters['cavity']['etm']['radius_of_curvature']['outer']['y'],
parameters['cavity']['etm']['misalignment']['outer']['x'],
parameters['cavity']['etm']['misalignment']['outer']['y'],
0,
parameters['cavity']['etm']['radius'] * 2
)
)
##############
# photodiode #
##############
# photodiode looking at cavity transmitted light
kat.add(
pykat.detectors.photodiode(
'pd1',
'n9'
)
)
###########################
# Gaussian beam parameter #
###########################
# set q value 1m from ITM, i.e. at the n1 node
# use the utility method for this purpose
kat.space1.n1.q = pykat.utilities.optics.gaussian_beams.gauss_param(q = 1.050412 + 24.243836j)
# you can alternatively set w0 and z with gauss_param(w0 = #, z = #)
##############################
# define what we want to see #
##############################
# scan cavity from 0 to 360 degrees
kat.add(pykat.commands.xaxis('lin', [0, 360], kat.M_ETM_HR, kat.M_ETM_HR.phi, 360))
# set maximum TEM mode to model
kat.maxtem = 3
#######################
# run script and plot #
#######################
# run simulation
r = kat.run()
# output the raw FINESSE file that PyKat has generated
scriptList = kat.generateKatScript()
print ''.join(scriptList)
# calculate and print cavity finesse
r1r2 = np.sqrt(parameters['cavity']['itm']['reflectivity']['inner']) * np.sqrt(parameters['cavity']['etm']['reflectivity']['inner'])
finesse = np.pi / (2 * np.arcsin((1 - r1r2) / (2 * np.sqrt(r1r2))))
print "Cavity finesse: {0:.0f}".format(finesse)
# create plot
pl.plot(r.x, r.y)
# show grid
pl.grid(True)
# set plot limits
pl.xlim((0, 360))
# make plot visible
pl.show()
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