new chirped modulator with alpha setting

dp_sync is softened

Classes/02_optical/EML.m

@@ -15,6 +15,7 @@ classdef EML
         u_pi
         randomkey
         randomstream
+        alpha
 
         %on instance creation
         field
@@ -38,6 +39,7 @@ classdef EML
                 options.lambda;
                 options.power;
                 options.linewidth = 0;
+                options.alpha = 0;
                 options.ampl_imbal = 0;
                 options.pha_imbal = 0;
                 options.bias;
@@ -101,9 +103,21 @@ classdef EML
             end
             
             %modulate the laserfield with the electrical signal
-            opt_out = obj.externalmodulation(laserfield,elec_in);
+            laserfield = obj.externalmodulation(laserfield,elec_in);
 
+            % add chirp
+            opt_out = obj.chirp(laserfield);
 
+        end
+
+        function chirped_field = chirp(obj,laserfield)
+
+            % Chirp
+            p = abs(laserfield.^2);
+            derv_p = [0; diff(p)];
+            delta_phi = derv_p./(4*pi*p).*obj.alpha;
+            delta_phi = cumsum(delta_phi);
+            chirped_field = laserfield.*exp(1i*2*pi*delta_phi);
 
         end