% Polarizer calibration / Rana's lab
% Tobin Fricke 2007-10-26

% Experimental setup:
%                                [Dump]   
%                                  |
%  +-------+                       |
%  | Laser |-------|lambda/2|----|PBS|----[Power Meter]
%  +-------+ 
%  

set(0, 'DefaultLineLineWidth', 3);

% The data (written in lab notebook, 2007-10-23)
theta = 40:2:98;

power = [0.922 0.688 0.153 0.095 0.332 0.966 1.735 3.154 4.546 ...
	 5.83 8.02 9.89 10.62 12.72 16.88 19.34 22.38 23.64 25.32 27.91 ...
	 29.99 31.15 32.07 33.50 34.25 34.62 34.61 34.19 33.55 32.42];

% Fitting function
fcn = @(a, x)  (a(1)/2)*(1 + sind(a(2)+4*x))
a = lsqcurvefit(fcn, [35 0], theta, power)

% Plot

theta2 = linspace(min(theta), max(theta), 100);

hold on;
h = [0 0];
h(2) = plot(theta2, fcn(a, theta2), '-', 'Color', [0 0.5 0]);
h(1) = plot(theta, power, 'bo', 'MarkerSize', 6);
hold off;

xlabel('Polarizer angle [degrees]');
ylabel('Power measured through beamsplitter [Watts]');

grid on;

legend(h, 'data', ...
       sprintf('fit to model: %3.1f*(1 + sin(4\\theta + %3.1f))/2', a(1), a(2)), ...
       'Location', 'NorthWest');

%% Make a table of power --> polarizer angle

P=0:2:34;
P = [P a(1)]; % Make sure the maximum power is on the list

theta3 = (asin((P*2/a(1))-1)*180/pi - a(2))/4 + 90

format bank;
[P ; theta3 ]' 

h = text(0.65, 0.4, [sprintf(' Power  Angle\n') ...
		     sprintf('%4.0f W %4.0f\\circ\n', [P ; theta3 ])],...
 'Units', 'Normalized')

set(h, 'FontName', 'Courier', ...
       'Background', 'white');

print(gcf, '-dpdf', 'polarizer.pdf');