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rINSTCONTROL/Measurement and analysis routines/g0Cal/Myg0Cal.m
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Myg0Cal.m
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% Calibration routine for the vacuum optomechanical coupling rate g0
classdef Myg0Cal < MyAnalysisRoutine
properties (Access = public, SetObservable = true)
% Thermomechanical spectrum
Data MyTrace
% Cursors for the selection of calibration tone
CalCursors MyCursor
cal_range = [0, 0]
% Cursors for the integration of thermomechanical noise
MechCursors MyCursor
mech_range = [0, 0]
% Fitting routine used in the method is 'fit'
LorFit MyLorentzianFit
% method of finding the area under the mechanical noise peak,
% integration or fit
method = 'integration'
% Calibration parameters set by the user
beta = 0.1 % Phase modulation depth of the reference tone
T = 300 % Temperature (K)
% Correction for dynamic backaction. Requires 'fit' method
% and reference quality factor.
correct_dba = false
ref_Q = 0
% Calibration result, g0l = g0/2pi
g0l = 0
end
properties (GetAccess = public, SetAccess = protected, ...
SetObservable = true)
Axes
Gui
% Parameters of the fitted mechanical Lorentzian
Q = 0
lw = 0
freq = 0
end
properties (Access = protected)
Psl % listener to the PostSet event of 'method' property
end
methods (Access = public)
function this = Myg0Cal(varargin)
p = inputParser();
addParameter(p, 'Data', MyTrace());
addParameter(p, 'Axes', matlab.graphics.axis.Axes.empty(), ...
@isaxes);
addParameter(p, 'enable_gui', true, @islogical);
parse(p, varargin{:});
this.Data = p.Results.Data;
this.Axes = p.Results.Axes;
if ~isempty(this.Axes)
% Add two sets of vertical cursors for the selection of
% integration ranges
xlim = this.Axes.XLim;
x1 = xlim(1)+0.4*(xlim(2)-xlim(1));
x2 = xlim(1)+0.45*(xlim(2)-xlim(1));
this.CalCursors = ...
[MyCursor(this.Axes, x1, 'orientation', 'vertical', ...
'Label','Cal 1', 'Color', [0, 0, 0.6]), ...
MyCursor(this.Axes, x2, 'orientation', 'vertical', ...
'Label','Cal 2', 'Color', [0, 0, 0.6])];
x1 = xlim(2)-0.45*(xlim(2)-xlim(1));
x2 = xlim(2)-0.4*(xlim(2)-xlim(1));
this.MechCursors = ...
[MyCursor(this.Axes, x1, 'orientation', 'vertical', ...
'Label','Mech 1', 'Color', [0.6, 0, 0]), ...
MyCursor(this.Axes, x2, 'orientation', 'vertical', ...
'Label','Mech 2', 'Color', [0.6, 0, 0])];
end
% This listener handles the initialization of fitting routine
% when the method is switched to 'fit' for the first time
this.Psl = addlistener(this, 'method', 'PostSet', ...
@(~,~)initFit(this));
% Gui is created right before the construction of object
% is over
if p.Results.enable_gui
this.Gui = Guig0Cal(this);
end
end
function delete(this)
if ~isempty(this.Psl)
delete(this.Psl);
end
if ~isempty(this.CalCursors)
delete(this.CalCursors);
end
if ~isempty(this.MechCursors)
delete(this.MechCursors);
end
if ~isempty(this.LorFit)
delete(this.LorFit)
end
end
% Calculate g0
function calcg0(this)
cr = this.cal_range;
% Find the frequency of calibration tone
ind = (this.Data.x>cr(1) & this.Data.x<=cr(2));
cal_tone_freq = sum(this.Data.x(ind) .* this.Data.y(ind))/ ...
sum(this.Data.y(ind));
% Calculate area under the calibration tone peak
cal_tone_area = integrate(this.Data, cr(1), cr(2));
mr = this.mech_range;
if isequal(this.method, 'integration')
mech_area = integrate(this.Data, mr(1), mr(2));
% Estimate mechanical frequency
ind = (this.Data.x>mr(1) & this.Data.x<=mr(2));
this.freq = sum(this.Data.x(ind) .* this.Data.y(ind))/ ...
sum(this.Data.y(ind));
elseif isequal(this.method, 'fit')
% Select data within the mechanics range
ind = (this.Data.x>mr(1) & this.Data.x<=mr(2));
this.LorFit.Data.x = this.Data.x(ind);
this.LorFit.Data.y = this.Data.y(ind);
fitTrace(this.LorFit);
% Extract fitted parameters
this.lw = this.LorFit.param_vals(2); % Linewidth in Hz
this.freq = this.LorFit.param_vals(3); % Frequency in Hz
this.Q = (this.freq/this.lw); % Q in millions
% Our Lorentzian is normalized such that the area under
% the curve is equal to the amplitude parameter
mech_area = this.LorFit.param_vals(1);
if this.correct_dba
% Apply correction for the cooling or amplification
% of mechanical motion by dynamic backaction
mech_area = mech_area*this.ref_Q/this.Q;
end
end
% Boltzmann and Planck constants
k_b = 1.3806e-23; % J/K
h = 6.62607e-34; % m^2*kg/s
% Equilibrium thermal occupation of the oscillator
n_th = k_b*this.T/(h*this.freq);
% Calculate g0
this.g0l = this.beta*cal_tone_freq* ...
sqrt(mech_area/(cal_tone_area*4*n_th));
end
end
methods (Access = protected)
% Initialize a new fit object if it was not created yet and if the
% method is 'fit'
function initFit(this)
if isequal(this.method, 'fit')
% Make sure that the fit object is initialized
if isempty(this.LorFit) || ~isvalid(this.LorFit)
% Select data within the mechanics range
ind = (this.Data.x>this.mech_range(1) & ...
this.Data.x<=this.mech_range(2));
this.LorFit = MyLorentzianFit('Axes', this.Axes, ...
'x', this.Data.x(ind), 'y', this.Data.y(ind), ...
'enable_range_cursors', false, ...
'enable_gui', false);
end
genInitParams(this.LorFit);
else
if ~isempty(this.LorFit) && isvalid(this.LorFit)
% Remove the fit curve from the plot
clearFit(this.LorFit);
end
end
end
end
methods
function set.method(this, val)
assert(ischar(val), ...
'Value assigned as ''method'' must be a character string')
val = lower(val);
assert(isequal(val, 'integration') || isequal(val, 'fit'), ...
'''method'' must be ''integration'' or ''fit''')
this.method = val;
end
% Get the integration range for the calibration tone
function val = get.cal_range(this)
if ~isempty(this.CalCursors) && all(isvalid(this.CalCursors))
% If cursors exist, return the range between the
% cursors
xmin = min(this.CalCursors.value);
xmax = max(this.CalCursors.value);
val = [xmin, xmax];
else
% Otherwise the value can be set programmatically
val = this.cal_range;
end
end
% Get the range for the mechanical peak
function val = get.mech_range(this)
if ~isempty(this.MechCursors) && all(isvalid(this.MechCursors))
% If cursors exist, return the range between the
% cursors
xmin = min(this.MechCursors.value);
xmax = max(this.MechCursors.value);
val = [xmin, xmax];
else
% Otherwise the value can be set programmatically
val = this.mech_range;
end
end
end
end
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