From e75e6f968d620fde5d5596092e6c6b0f2cc4aa94 Mon Sep 17 00:00:00 2001
From: Eugeniy Mikhailov <evgmik@gmail.com>
Date: Wed, 13 Apr 2011 11:10:28 -0400
Subject: beam propagation function renamed and moved to separate files

Ignore-this: 972fa9dce2f57e8ddb1624bab32be1ed

darcs-hash:20110413151028-067c0-a7e6d0c98e2856fdff930d4bf3216056eb937367
---
 gbeam_propagation.m | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)
 create mode 100644 gbeam_propagation.m

(limited to 'gbeam_propagation.m')

diff --git a/gbeam_propagation.m b/gbeam_propagation.m
new file mode 100644
index 0000000..524d4ae
--- /dev/null
+++ b/gbeam_propagation.m
@@ -0,0 +1,41 @@
+function q = gbeam_propagation(x_pos, q_in, x_in,  optics_elements)
+% calculate the 'q' parameter of the Gaussian beam propagating through optical
+% 'optics_elements' array along 'x' axis at points 'x_pos'
+%  takes the gaussian beam with initial q_in parameter at x_in
+% x_pos must be monotonic!
+
+	q=0*x_pos; % q vector initialization
+
+	if any(x_pos >= x_in)
+		% Forward propagation to the right of x_in
+		q(x_pos >= x_in) = gbeam_propagation_froward_only(x_pos(x_pos>=x_in), q_in, x_in,  optics_elements);
+	end
+
+	if any(x_pos < x_in)
+		% Backward propagation part the left of x_in
+		% do it as forward propagation of the reverse beam
+		x_backw=x_pos(x_pos<x_in);
+		% now let's reflect the beam with respect to x_in
+		% and solve the problem as forward propagating.
+		x_backw=x_in-x_backw;
+		% now we need to flip x positions
+		x_backw=fliplr(x_backw);
+		% reflected beam means inverted radius of curvature or real part of q parameter
+		q_in_backw = -real(q_in) + 1i*imag(q_in);
+		optics_elements_backw=optics_elements;
+		% we need to flip all optics elements around x_in as well
+		for i=1:length(optics_elements_backw)
+			optics_elements_backw{i}.x=x_in-optics_elements_backw{i}.x;
+		end
+
+		q_backw = gbeam_propagation_froward_only(x_backw, q_in_backw, 0,  optics_elements_backw);
+		% now we need to flip the radius of curvature again
+		q_backw =  -real(q_backw) + 1i*imag(q_backw);
+
+		% final assignment of the backwards propagating beam 
+		% which we need to flip back
+		q(x_pos<x_in) = fliplr(q_backw);
+	end
+
+endfunction
+
-- 
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