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OSCAR

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08 Jul 2008 (Updated )

An optical FFT code to simulate Fabry Perot cavities with arbitrary mirror profiles

E_Field
classdef E_Field
    % E_Field, this class represents an electric field defined on a grid
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    % E = E_Field( Grid_name , 'w', 0.1)     Create a fundamental
    % Gaussian beam at the waist with a waist size of 10 cm
    % E = E_Field(Grid_name , 'w', 0.1,'R',-2000)    Create a fundamental mode with a defined beam radius of 10 cm and
    % wavefront radius of curvature of -2 km, so the beam propagates toward the waist
    % E = E_Field(Grid_name , 'w0', 0.1,'Z',-60)    Create a fundamental mode with a defined beam waist of 10 cm and
    % we are are 60m from the waist, so the beam propagates toward the waist
    % E = E_Field(Grid_name , 'q',-100 + 425*1i)    Create a fundamental
    % mode defined with the complex q parameter
   %  E = E_Field(Grid_name , 'w0', 0.1,'mode','LG m n') Create a mode Hermitte Gauss of order m,n
   %  E = E_Field(Grid_name , 'w0', 0.1,'mode','LG m n')  Create a mode Laguerre Gauss helicoidal d'ordre
    % p,l
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    properties
        Grid
        Field
        Field_SBl
        Field_SBu
        
        Refractive_index = 1;
        Wavelength = 1064E-9;
        Frequency_Offset = 0;
        Mode_name
        
        k_prop
    end
    
    %     events
    %         Nan_present
    %     end
    
    methods
        function E = E_Field(Grid_in,varargin)
            p  = inputParser;
            E.k_prop = (2*pi/E.Wavelength);
            
            p.FunctionName = 'E_field creator';
            
            % Check if the first argument is a grid
            p.addRequired('Grid_in', @(x)isa(x, 'Grid'));
            
            % enter either the size of the beam radius and the complex
            % radius of curvature
            p.addParamValue('w',[],@(x)isnumeric(x) && x>0);
            p.addParamValue('R',1E99,  @(x)isnumeric(x));
            
            % can also enter the size of the waist and the distance from
            % the waist
            p.addParamValue('w0',[],  @(x)isnumeric(x) && x>0);
            p.addParamValue('z', 0,  @(x)isnumeric(x));
            
            % or enter the complex radius of curvature
            p.addParamValue('q',[],  @(x)isnumeric(x));
            
            % Check if the power of the beam is given
            p.addParamValue('P',1, @(x)isnumeric(x) && x>0);
            
            % Mode
            p.addParamValue('mode','HG 0 0', @(x)ischar(x));
            
            p.parse(Grid_in,varargin{:});
            
            % check of what is entered
            
            if ( isempty(p.Results.q) && isempty(p.Results.w) && isempty(p.Results.w0))
                error('E_Field(): at least the parameter w,w0 or q must be given to define the laser beam')
            end
            
            if  ~isempty(p.Results.w)
                q_start = 1/(1/p.Results.R - 1i*(E.Wavelength)/(pi*p.Results.w^2));
                beam_radius = p.Results.w;
            elseif ~isempty(p.Results.w0)
                q_start = p.Results.z + 1i*pi*p.Results.w0^2/E.Wavelength;
                beam_radius = sqrt( 1/(-imag(1/q_start)*pi/(E.Wavelength)) );
            else
                q_start =  p.Results.q;
                beam_radius = sqrt( 1/(-imag(1/q_start)*pi/(E.Wavelength)) );
            end
            
            [family m n] = Read_mode_name(p.Results.mode);
            E.Grid = Grid_in;
            
            if strcmp(family,'HG')
                
                E.Field = exp(-1i*E.k_prop*E.Grid.D2_square/(2*q_start));
                
                E.Field =  E.Field  .* HermitePolynomial(m, sqrt(2)/beam_radius * E.Grid.D2_X) .*...
                    HermitePolynomial(n, sqrt(2)/beam_radius * E.Grid.D2_Y);
                
            elseif strcmp(family,'LG')
                
                E.Field = exp(-1i*E.k_prop*E.Grid.D2_square/(2*q_start));
                
                E.Field =  E.Field  .* (2* E.Grid.D2_square / beam_radius^2) .^ (abs(n)/2);
                E.Field =  E.Field  .* LaguerrePolynomial(m, abs(n), 2* E.Grid.D2_square / beam_radius^2);
                E.Field =  E.Field  .* exp(1i * n*atan2(E.Grid.D2_Y,E.Grid.D2_X));
                
            else
                error('E_Field():the mode name must be HG or LG')
            end
            
            E.Mode_name = p.Results.mode;           
            E = Normalise_E(E,p.Results.P);
            
        end
        
        function value = get.Field(obj)
            value = obj.Field;
        end
    end
    
end

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