Hi Aadil,
We can create a chaotic signal using an ideal single mode laser driven by a dc bias generator. Open up the dc bias generator and change the mode from normal to sweep then go into the parameter sweep window and change the spread to Gaussian. I gave the Gaussian distribution a nominal value 0.3 and standard deviation 0.1. This essentially makes the bias generator output random values and which will randomly vary the center frequency of the laser.
Regards,
Josh