MATLAB
`W = IrradianceCovariancePathWeight(xi,d,wvl,L,sourceStr,[LAMBDA],[THETA])`

Computes weighting of Cn2 (turbulence strength) over propagation path for the irradiance covariance. Handles plane, spherical, and Gaussian beam cases (can be numerically unstable in beam wave cases). Uses the weak turbulence assumption.

 Parameters Description xi [vector] Normalized location along the propagation path. d [scalar] Magnitude of the separation of points in the observation plane. wvl [scalar] Optical wavelength (m). L [scalar] Propagation distance (m). sourceStr [string] Type of optical field source. Either 'plane', 'spherical', or 'beam'. LAMBDA [scalar] (Optional) Gaussian beam target plane diffraction parameter. Defaults to 0 (infinite beam). THETA [scalar] (Optional) Gaussian beam target plane refraction parameter. Defaults to 0 (focused).
 Return Values Description W [vector] Path weighting evaluated along the path

• L. C. Andrews and R. L. Phillips, Laser Beam Propagation through Random Media, 2nd ed. Bellingham, Wash.: SPIE Press, 2005.

>> G = SimpleGeom(0, 2e4, 0);

>> NZ = 100;

>> Atm = AtmStruct(G, NZ, 'Cn2', 'HV57');

>> wvl = 0.5e-6;

>> d = 2e-2; % points separated by 2 cm at the pupil

>> x = Atm.z / Atm.L;

>> W = IrradianceCovariancePathWeight(x, d, wvl, Atm.L, 'spherical');

• Path weighting function for irradiance covariance with wavelength of 500 nm, point source at 20 km propagating straight down, pupil-plane separation 2 cm, and atmospheric model Atm.

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