chapter  7
17 Pages

Mode-Lock Phenomenon

WithChandrasekhar Roychoudhuri

The pulse generation from a laser cavity is a collaborative and evolving interaction process between EM waves and the intracavity phase locker, which enforces the evolution of the phase-locking process between the allowed cavity modes. This chapter presents a simple experiment to generate phase-lock-like behavior out of a continuous wave (CW) He-Ne laser by using a fast photodetector. This is to underscore again that a fast photodetector with broad quantum absorption bands can sum the joint stimulations due to all the E-vectors of the modes of a CW laser and generate mode-lock-like pulsed photo current if the phase stability between the modes last longer than the integration time of the phtodetector. The chapter also presents another experiment to test whether simple superposition of a set of periodically spaced frequencies with steady phase can automatically generate mode-lock pulses. It shows that interactions between phase-steady mode amplitudes do not create the pulse train out of a mode-locked laser.