finesse.gaussian.ws_overlap_grid

finesse.gaussian.ws_overlap_grid(qp, woffset, soffset, wpts=200, spts=200)

Computes the WS phase space overlap with the primary beam parameter qp over a grid of W, S data.

See ws_overlap() for a definition of the overlap quantity.

The $W$ and $S$ spaces are formed by creating arrays around the BeamParam.w and BeamParam.S values of qp, according to the offsets given in woffset and soffset, respectively.

Parameters:

qpBeamParam

The primary “mode” which overlapping modes are calculated against.

woffsetfloat, sequence

A single number, or size 2 sequence. Defines the offsets (lower, upper) from the primary mode beamsize to use for the W space.

soffsetfloat, sequence

A single number, or size 2 sequence. Defines the offsets (lower, upper) from the primary mode beamsize to use for the S space.

wptsint, optional; default: 200

Number of points for the W space array.

sptsint, optional; default: 200

Number of points for the S space array.

Returns:

Wnumpy.ndarray

The W space (as a 2D grid).

Snumpy.ndarray

The S space (as a 2D grid).

OLnumpy.ndarray

The overlap as a function of the WS phase space (as a 2D grid).

Examples

In the following example, we compute the overlap to a primary mode which has a 6 mm beam size and a defocus of 0 m (i.e. at the waist).

import finesse
finesse.configure(plotting=True)

import finesse.gaussian as gaussian
from finesse.plotting.plot import ws_phase_space

import matplotlib.pyplot as plt

# Make a beam parameter with w = 6 mm, S = 0 m
qp = gaussian.BeamParam(w=6e-3, S=0)

# Compute the WS phase space overlap with qp, using
# maximum offset of 1 mm in beam size and 1 cm in defocus
W, S, OL = gaussian.ws_overlap_grid(qp, woffset=1e-3, soffset=1e-2)

# Now plot this as contours of overlap with custom levels
fig, ax = ws_phase_space(
    W, S, OL,
    levels=[0.6, 0.8, 0.84, 0.88, 0.92, 0.94, 0.96, 0.98, 0.995, 0.999],
)