CLEANUP - changes to folder structure

Theory/Dissertation/mach_zehnder_nonlinearities_taylor.m

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+% MZM bias sweep (physical coefficients) + field & power transfer functions
+% Uses your notation:
+%   Pout/Pin = cos^2( (pi/2)*(v/Vpi) ),  v = Vbias + Δv
+% Taylor around Vbias:
+%   Pout/Pin ≈ a0 + a1 Δv + a2 Δv^2 + a3 Δv^3
+%
+% Coefficients (physical units):
+%   a0 [-], a1 [1/V], a2 [1/V^2], a3 [1/V^3]
+%
+% Also plots:
+%   Field TF amplitude:  Eout/Ein = cos( (pi/2)*(Vbias/Vpi) )
+%   Power TF:            Pout/Pin = cos^2( (pi/2)*(Vbias/Vpi) )
+
+clear; close all; clc;
+
+set(groot,'defaultLegendInterpreter','tex');
+set(groot,'defaultAxesTickLabelInterpreter','tex');
+set(groot,'defaultTextInterpreter','tex');
+
+%% Parameters
+Vpi = 3;                       % [V] device half-wave voltage
+xb  = linspace(0, 2, 2001);    % x_b = Vbias/Vpi
+Vbias = xb * Vpi;              % [V]
+
+%% Static transfer functions (at Vbias)
+H_field = cos((pi/2)*xb);        % field amplitude TF (balanced MZM)
+T_power = H_field.^2;            % intensity TF
+
+%% Taylor coefficients (physical units)
+a0 = T_power;
+a1 = -(pi/(2*Vpi))      .* sin(pi*xb);     % [1/V]
+a2 = -(pi^2/(4*Vpi^2))  .* cos(pi*xb);     % [1/V^2]
+a3 = +(pi^3/(12*Vpi^3)) .* sin(pi*xb);     % [1/V^3]
+A0 = a0;
+A1 = a1 * Vpi;
+A2 = a2 * Vpi^2;
+A3 = a3 * Vpi^3;
+
+%% Plot
+figure('Color','w'); clf;
+% --- (1) Field + power TF vs bias ---
+hold on; grid on;
+plot(xb, H_field, 'LineWidth', 1.4, 'DisplayName','Field','Color','black','LineStyle','--');
+% plot(xb, T_power, 'LineWidth', 1.4, 'DisplayName','Intensity','Color','black','LineStyle','-');
+
+
+% --- (2) Physical Taylor coefficients vs bias ---
+% nexttile; hold on; grid on;
+plot(xb, a0, 'LineWidth', 1.4, 'DisplayName','Intensity','Color','black','LineStyle','-');
+plot(xb, a1, 'LineWidth', 1.4, 'DisplayName','Linear');
+plot(xb, a2, 'LineWidth', 1.4, 'DisplayName','Even');
+plot(xb, a3, 'LineWidth', 1.4, 'DisplayName','Odd');
+
+xlabel('$V/V_\pi$','Interpreter','latex');
+ylabel('Transfer');
+title('Static transfer functions vs bias');
+xlim([min(xb) max(xb)]);
+ylim([-1.05 1.05]);
+legend('Location','best');
+
+% Optional: tighten y-limits to avoid a0 dominating the view
+% Comment out if you prefer auto-scaling.
+yl = ylim;
+ylim([min(yl(1), -max(abs([a1 a2 a3]))*1.1), max(yl(2), max(abs([a1 a2 a3]))*1.1)]);
+
+xticks([0:0.5:2]);