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Modified script to plot multiple RIN curves.

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Karthik 2024-09-16 15:18:43 +02:00
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Time-Series-Analyzer/computeAndcompareRIN.m Normal file
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% Script to compute the Relative Intensity Noise of a laser by recording the y-t signal
% by Mathias Neidig in 2012
% modified for DyLab use by Karthik in 2024
% The RIN is defined as
%
% RIN = 10* log10 [Single-sided power spectrum density / (average power)]
%
% and is given in [RIN] = dB/Hz
clear all
close all
%% Set the directory where the data is
dirDCData = 'C:\\Users\\Karthik\\Documents\\GitRepositories\\Calculations\\Time-Series-Analyzer\\Time-Series-Data\\20240915\\After_AOD\\DC_Coupling\\';
dirACData = 'C:\\Users\\Karthik\\Documents\\GitRepositories\\Calculations\\Time-Series-Analyzer\\Time-Series-Data\\20240915\\After_AOD\\AC_Coupling\\';
%% Load the files which contain: - the DC coupled y-t signal to obtain the averaged power
% - the AC coupled y-t signal to obtain the fluctuations
% - the AC coupled y-t signal with the beam blocked to obtain the background fluctuations
%------------------------------------------------------------------------- %
bgsignal = load( [ dirACData '20240915_Background_AC'] ); %
dcsignal = load( [ dirDCData '20240915_1V_-3Mod_DC_PID_Inactive'] ); %
acsignal_1 = load( [ dirACData '20240915_1V_-3Mod_AC_PID_Inactive'] ); %
acsignal_2 = load( [ dirACData '20240915_1V_-3Mod_AC_PID_Active'] ); %
label_0 = 'Background'; %
label_1 = 'Power = 1 V, Modulation = -3.0 V, PID Inactive'; %
label_2 = 'Power = 1 V, Modulation = -3.0 V, PID Active'; %
%------------------------------------------------------------------------- %
%% Read out the important parameters
dcdata = dcsignal.A;
acdata_1 = acsignal_1.A;
acdata_2 = acsignal_2.A;
bgdata = bgsignal.A;
N = length(dcdata); % #samples
f_s = 1/dcsignal.Tinterval; % Sample Frequency
delta_f = f_s/N; % step size in frequency domain
delta_t = 1/f_s; % time step
%% Custom Control Parameters
% Choose smoothing parameter; has to be odd
%----------------%
span = 21; %
%----------------%
%% Computes the RIN
% compute the average power (voltage^2)
average_P = mean(dcdata.*dcdata);
% compute the power spectrum density FFT(A) x FFT*(A)/N^2 of the source & the bg
psd_src_1 = fft(acdata_1) .* conj(fft(acdata_1))/N^2;
psd_src_2 = fft(acdata_2) .* conj(fft(acdata_2))/N^2;
psd_bg = fft(bgdata) .* conj(fft(bgdata))/N^2;
% converts the psd to the single-sided psd --> psd is symmetric around zero --> omit
% negative frequencies and put the power into the positive ones --> spsd
for i = 1 : N/2+1
if i>1
spsd_src_1(i) = 2*psd_src_1(i);
spsd_src_2(i) = 2*psd_src_2(i);
spsd_bg(i) = 2*psd_bg(i);
else
spsd_src_1(i) = psd_src_1(i);
spsd_src_2(i) = psd_src_2(i);
spsd_bg(i) = psd_bg(i);
end
end
% smooths the spsd by doing a moving average
spsd_src_smooth_1 = smooth(spsd_src_1,span,'moving');
spsd_src_smooth_2 = smooth(spsd_src_2,span,'moving');
spsd_bg_smooth = smooth(spsd_bg, span,'moving');
% calculates the RIN given in dB/Hz; the factor delta_f is needed to convert from dB/bin into dB/Hz
RIN_src_smooth_1 = 10*log10(spsd_src_smooth_1/(average_P*delta_f));
RIN_src_smooth_2 = 10*log10(spsd_src_smooth_2/(average_P*delta_f));
RIN_bg_smooth = 10*log10(spsd_bg_smooth /(average_P*delta_f));
% creates an array for the frequencies up to half the sampling frequency
f = f_s/2 * linspace(0,1,N/2+1);
f_smooth = smooth(f,span,'moving');
%
% Calculates the shot noise limit of the used PD given the wavelength of the light source and
% incident average power
PlanckConstant = 6.62607015E-34;
SpeedOfLight = 299792458;
WavelengthOfLaserLight = 1064E-9;
FrequencyOfLaserLight = SpeedOfLight / WavelengthOfLaserLight;
QuantumEfficiencyOfPD = 1;
AverageIncidentPower = 0.001; % (in W)
ShotNoiseLimit = 10*log10((2 * PlanckConstant * FrequencyOfLaserLight) / (QuantumEfficiencyOfPD * AverageIncidentPower));
%% Plots the RIN
% Plots the RIN vs frequency
f_ = clf;
figure(f_);
set(gcf,'Position',[100 100 950 750])
semilogx(f_smooth, RIN_bg_smooth, LineStyle = "-", Color = [.7 .7 .7])
hold on
semilogx(f_smooth,RIN_src_smooth_1,'r-')
semilogx(f_smooth,RIN_src_smooth_2,'b-')
ax = gca(f_);
ax.XAxis.FontSize = 14;
ax.YAxis.FontSize = 14;
xlabel('Frequency [Hz]', FontSize=16)
ylabel('RIN [dBc/Hz]', FontSize=16)
xlim([10 5E6]);
ylim([-140 -25]);
title('\bf Intensity noise of Arm 1 of the ODT as measured by an Out-of-loop PD', FontSize=14)
legend(label_0, label_1, label_2, 'Location','NorthWest', FontSize=12);
grid on
% optional: save the picture without editing wherever you want
%------------------------------------------%
% saveas(f_,'FileName','png'); %
%------------------------------------------%