From 1de42f53fd7eae56442d96b98861f252ae01b5a0 Mon Sep 17 00:00:00 2001
From: Charlotte Bond <czb@star.sr.bham.ac.uk>
Date: Tue, 19 Nov 2013 17:52:11 +0000
Subject: [PATCH] adding function which uses the FT_LG_clipping_loss analytic
function for clipping of an LG mode to find the radius of a circular aperture
which causes a given amount of clipping
---
src/new/FT_find_radius_for_clipping_loss.m | 63 ++++++++++++++++++++++
1 file changed, 63 insertions(+)
create mode 100644 src/new/FT_find_radius_for_clipping_loss.m
diff --git a/src/new/FT_find_radius_for_clipping_loss.m b/src/new/FT_find_radius_for_clipping_loss.m
new file mode 100644
index 0000000..acbaec8
--- /dev/null
+++ b/src/new/FT_find_radius_for_clipping_loss.m
@@ -0,0 +1,63 @@
+%
+%--------------------------------------------------------------------------
+% function [R_out,cl_out] = FT_find_radius_for_clipping_loss(cl_in,p,l,w,R_in)
+%
+% A function for Matlab which attempts to find the required radius of a
+% mirror to give a specified clipping loss for a particular LG beam. The
+% function uses a fitting function, fminsearch, to try and minimise the
+% difference between the actual and required clipping.
+%
+% cl_in: required clipping loss
+% p,l: indices of the LG beam
+% w: beam radius at the mirror
+% R_in: initial guess for the radius of the mirror. Care
+% should be taken when choosing this. If the
+% resulting clipping doesn't match the requirements
+% well repeat the function using the outputted
+% radius, R_out.
+%
+% R_out: radius required for given clipping, output of the
+% fitting routine.
+% cl_out: clipping loss given by R_out.
+%
+% Charlotte Bond 18.12.2010
+%--------------------------------------------------------------------------
+
+function [R_out,cl_out] = FT_radius_for_clipping_loss(cl_in,p,l,w,R_in)
+
+
+ params=[R_in];
+
+
+ % set options for fminsearch ('help optimset' gives the list of options)
+ options=optimset('Display','off', 'TolX', 1e-08, 'TolFun',1e-10, 'MaxIter', 10000);
+
+ % create link to test function below
+ f=@testfunc;
+
+ % run the fitting algorithm
+ params=fminsearch(f,params,options,cl_in,p,l,w);
+
+ % assign new radius of mirror
+ R_out=params(1);
+
+ cl_out=FT_LG_clipping_loss(p,l,w,R_out);
+
+end
+
+
+
+% test function for fminsearch
+function [y]=testfunc(params,cl_in,p,l,w)
+
+ R=params(1);
+
+ % Use clipping loss function
+ cl=FT_LG_clipping_loss(p,l,w,R);
+
+ y=abs(cl-cl_in);
+
+end
+
+
+
\ No newline at end of file
--
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