Frequency control of semiconductor lasers

Frequency control of semiconductor lasers has become very important in recent years for several applications such as frequency standards, optical metrology, optical communication, and so on[1]. In the present work, a technique of electrical feedback was employed for the frequency control, because (a) stability and reliability of the feedback is high, (b) computer-aided-design (CAD) can be employed to realize the optimum feedback loop, and (c) magnitude of residual frequency fluctuations under the feedback can be reduced to a value which is far lower than that of the quantum noise limit of the free-running laser[2].