1 files changed, 28 insertions, 0 deletions
diff --git a/axial/beamradius.m b/axial/beamradius.m
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+% Returns the field radius of the beam at any point z along a Gaussian beam
+%
+% SYNTAX: [w,R,zR]=beamradius([w0,z0,lambda],z);
+% 
+% w0 = waist size
+% z0 = position of waist
+% lambda = wavelength
+%
+% w  = spot size (field radius) at z
+% R  = curvature of phasefront at z
+% zR = Raleigh length.
+%
+%-------------------------------------------------------------------
+% SYNTAX: [w,R,zR]=beamradius([w0,z0,lambda],z);
+%-------------------------------------------------------------------
+
+function [w,R,zR]=beamradius(params,z)
+
+w0=params(1);                           % beam (field) width at waist [meters]
+z0=params(2);                           % waist position [meters]
+lambda=params(3);                       % wavelength [meters]
+zR=pi*w0^2/lambda;                      % Raleigh length [meters]
+
+w=w0.*sqrt(1+((z-z0)/zR).^2);           % beam width at z [meters]
+
+if nargout>=2
+    R=z.*(1+(zR./z).^2);                % beam phasefront curvature at z
+end
+\ No newline at end of file