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% Accepts the q factor of a Gaussian beam and plots the 1/e^2 intensity envelope.
%
% SYNTAX: [handle,xend,yend]=beamplot(q,z,<,x,y,theta,n,lambda,...
% attitudes,plotsuppress>);
%
% INPUT ARGUMENTS:
% q = Gaussian beam complex radius of curvature "q".
% If q is a vector, a beam is plotted for each element.
% z = vector along beam axis over which to plot the envelope
% x,y = position of the point at which q is specified, default=0,0.
% theta = rotation of optic axis counterclockwise relative to x-axis,
% defaul=0 (degrees)
% n = index of medium in which the beam propagates
% lambda = wavelength, default=1064 nm or 4.189e-5 inches
% plotsuppress = set to 1 to suppress plotting, default 0.
%
% OUTPUT ARGUMENTS:
% handle = handle of the trace plotted
% xend,yend = position of the end of the optic axis over which the beam
% was plotted.
%
% Last Modified: June 23, 2004 by Andri M. Gretarsson.
%
%--------------------------------------------------------------------------------
% SYNTAX: [handle,xend,yend]=beamplot(q,z,<,x,y,theta,n,lambda,plotsuppress>);
%--------------------------------------------------------------------------------
function [handle,xend,yend]=beamplot(q,z,varargin)
if nargin>=3, x=varargin{1}; else x=0; end
if nargin>=4, y=varargin{2}; else y=0; end
if nargin>=5, theta=varargin{3}*pi/180; else theta=0; end
if nargin>=6, n=varargin{4}; else n=1; end
if nargin>=7, lambda=varargin{5}; else lambda=1064e-9; end
if nargin>=9, plotsuppress=varargin{7}; else plotsuppress=0; end
if size(z,1)>size(z,2)
z=transpose(z);
end
if size(q,1)<size(q,2)
q=transpose(q);
end
lambda=lambda/n;
w0=sqrt(imag(q).*lambda/pi);
L=-real(q).*ones(size(w0));
w_upper=zeros(length(L),length(z)); w_lower=w_upper; xend=zeros(length(L)); yend=xend;
handle=zeros(2,length(L)); plotcolors=colormap;
for s=1:length(L)
w_upper=w0(s)*sqrt(1+(lambda*(z-L(s))/pi/w0(s)^2).^2);
w_lower=w_upper;
upperenv=[z;w_upper];
lowerenv=[z;-w_lower];
rotmat=[[cos(theta), -sin(theta)];[sin(theta), cos(theta)]];
rotupperenv=rotmat*upperenv;
rotupperenv(1,:)=rotupperenv(1,:)+x;
rotupperenv(2,:)=rotupperenv(2,:)+y;
rotlowerenv=rotmat*lowerenv;
rotlowerenv(1,:)=rotlowerenv(1,:)+x;
rotlowerenv(2,:)=rotlowerenv(2,:)+y;
xend=max(z)*cos(theta)+x;
yend=max(z)*sin(theta)+y;
if plotsuppress~=1
if s==1,
orighold=get(gca,'nextplot');
handle(:,s)=plot(rotupperenv(1,:),rotupperenv(2,:),'b-',rotlowerenv(1,:),rotlowerenv(2,:),'b-');
set(handle(:,s),'color',plotcolors(mod(s,end)+1,:));
else
set(gca,'nextplot','add');
handle(:,s)=plot(rotupperenv(1,:),rotupperenv(2,:),'b-',rotlowerenv(1,:),rotlowerenv(2,:),'b-');
set(handle(:,s),'color',plotcolors(mod(s,end)+1,:));
end
if s==length(L)
set(gca,'nextplot',orighold);
end
end
end
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