"""Collection of ABCD functions for standard optical components."""
import numpy as np
from finesse.exceptions import TotalReflectionError
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def none():
"""Unit matrix for no propagation."""
# Return object as it is used for symbolic matrix products not floating point
return np.array([[1.0, 0.0], [0.0, 1.0]], dtype=object)
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def space(L, nr=1):
"""Propagation along a physical length `L`
Parameters
----------
L : float
Length in metres
nr : float
refractive index of medium
Notes
-----
See :cite:`siegman`, table 15.1(a)
"""
return np.array([[1.0, L / nr], [0.0, 1.0]])
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def lens(f):
"""Propagation through a thin lens.
Parameters
----------
f : float
Focal lenth of thin lens in metres
Notes
-----
See :cite:`siegman`, table 15.1(b)
"""
return np.array([[1.0, 0.0], [-1.0 / f, 1.0]])
def _mirror_refl(Rc, nr=1):
return np.array([[1.0, 0.0], [-2 * nr / Rc, 1.0]])
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def mirror_refl_t(Rc, nr=1):
"""Tangential (in plane-of-incidence) reflection from a curved surface. Due to
coordinate system change on reflection the sagittal plane is reflected (parity
operation) and an additional minus sign is applied.
Parameters
----------
Rc : float
Radius of curvature of the surface being reflected from.
A positive Rc means the surface appears concave to the incident
beam.
nr : float
refractive index of medium in which the reflection occurs
Notes
-----
See :cite:`siegman`, table 15.1(c) and "Ray Inversion" section in 15.1
"""
return -1 * _mirror_refl(Rc, nr)
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def mirror_refl_s(Rc, nr=1):
"""Sagittal (perpendicular plane-of-incidence) reflection from a curved surface.
Parameters
----------
Rc : float
Radius of curvature of the surface being reflected from.
A positive Rc means the surface appears concave to the incident
beam.
nr : float
refractive index of medium in which the reflection occurs
Notes
-----
See :cite:`siegman`, table 15.1(c)
"""
return +1 * _mirror_refl(Rc, nr)
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def mirror_trans(Rc, nr1=1, nr2=1):
"""Transmission through a curved surface.
Parameters
----------
Rc : float
Radius of curvature of the surface being reflected from.
A positive Rc means the surface appears concave to the incident
beam.
nr1 : float
refractive index of medium the beam starts in
nr2 : float
refractive index of medium the beam ends up in
Notes
-----
See :cite:`siegman`, table 15.1(e)
"""
return np.array([[1.0, 0.0], [(nr2 - nr1) / Rc, 1.0]])
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def beamsplitter_refl_t(Rc, alpha, nr=1):
"""Tangential (in plane-of-incidence)reflection from a curved surface at a non-
normal angle of incidence. Due to coordinate system change on reflection the
sagittal plane is reflected (parity operation) and an additional minus sign is
applied.
Parameters
----------
Rc : float
Radius of curvature of the surface being reflected from.
A positive Rc means the surface appears concave to the incident
beam.
alpha : float
Angle of incidence in degrees
nr : float
refractive index of medium the reflection occurs in
Notes
-----
See :cite:`siegman`, table 15.1(d) and "Ray Inversion" section in 15.1
"""
alpha1 = np.radians(alpha)
Re = Rc * np.cos(alpha1)
C = -2 * nr / Re
return -1 * np.array([[1.0, 0.0], [C, 1.0]])
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def beamsplitter_refl_s(Rc, alpha, nr=1):
"""Sagittal (perpendicular plane-of-incidence) reflection from a curved surface at a
non-normal angle of incidence. Due to coordinate system change on reflection the
sagittal plane is reflected (parity operation) and an additional minus sign is
applied.
Parameters
----------
Rc : float
Radius of curvature of the surface being reflected from.
A positive Rc means the surface appears concave to the incident
beam.
alpha : float
Angle of incidence in degrees
nr : float
refractive index of medium the reflection occurs in
Notes
-----
See :cite:`siegman`, table 15.1(d) and "Ray Inversion" section in 15.1
"""
alpha1 = np.radians(alpha)
Re = Rc / np.cos(alpha1)
C = -2 * nr / Re
return np.array([[1.0, 0.0], [C, 1.0]])
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def beamsplitter_trans_t(Rc, alpha, nr1=1, nr2=1):
"""Tangential (in plane-of-incidence) transmission through a curved surface at an
angle of incidence.
Parameters
----------
Rc : float
Radius of curvature of the surface being reflected from.
A positive Rc means the surface appears concave to the incident
beam.
alpha : float
Angle of incidence in degrees
nr1 : float
refractive index of medium the beam starts in
nr2 : float
refractive index of medium the beam ends up in
Notes
-----
See :cite:`siegman`, table 15.1(f)
"""
alpha1 = np.radians(alpha)
# we get alpha2 from Snell's law
sin_alpha2 = (nr1 / nr2) * np.sin(alpha1)
if abs(float(sin_alpha2)) > 1:
raise TotalReflectionError("Total internal reflection")
alpha2 = np.arcsin(sin_alpha2)
cos_alpha1 = np.cos(alpha1)
cos_alpha2 = np.cos(alpha2)
# Tangential
A = cos_alpha2 / cos_alpha1
D = cos_alpha1 / cos_alpha2
delta_n = (nr2 * cos_alpha2 - nr1 * cos_alpha1) / (cos_alpha1 * cos_alpha2)
C = delta_n / Rc
return np.array([[A, 0.0], [C, D]])
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def beamsplitter_trans_s(Rc, alpha, nr1=1, nr2=1):
"""Sagittal (perpendicular plane-of-incidence) transmission through a curved surface
at an angle of incidence.
Parameters
----------
Rc : float
Radius of curvature of the surface being reflected from.
A positive Rc means the surface appears concave to the incident
beam.
alpha : float
Angle of incidence in degrees
nr1 : float
refractive index of medium the beam starts in
nr2 : float
refractive index of medium the beam ends up in
Notes
-----
See :cite:`siegman`, table 15.1(g)
"""
alpha1 = np.radians(alpha)
# we get alpha2 from Snell's law
sin_alpha2 = (nr1 / nr2) * np.sin(alpha1)
if abs(float(sin_alpha2)) > 1:
raise TotalReflectionError("Total internal reflection")
alpha2 = np.arcsin(sin_alpha2)
cos_alpha1 = np.cos(alpha1)
cos_alpha2 = np.cos(alpha2)
# sagittal
A = 1.0
D = 1.0
delta_n = nr2 * cos_alpha2 - nr1 * cos_alpha1
C = delta_n / Rc
return np.array([[A, 0.0], [C, D]])