b) FM spectroscopy and top-of-fringe locking
An alternative method is based on the principle of frequency modulation (FM) spectroscopy. The laser frequency is modulated, e.g. by modulating the laser…
Quite generally, generating an error signal consists of two steps. The first step is to create an optical signal using an optical setup involving a reference, e.g. one of those presented in the…
The goal of error signal generation is to create an electronic signal that is proportional to the laser´s deviation from a certain set frequency or phase which will be called lock point in the…
This application note deals with the question of how to generate an error signal for phase and frequency stabilization of lasers. First, general schemes which are independent of the choice of…
a) Atomic or Molecular Transitions – Spectroscopy
For many applications, a good and simple way to stabilize a laser´s frequency is to compare it to an atomic or molecular transition. One advantage…
The concept of phase and frequency stabilization relies on the possibility to detect changes of the quantity that is wished to be stabilized. To do so this quantity has to be measured continuously,…
The application note “Error-Signal Generation” describes how to generate an electronic signal which indicates how much the laser phase or frequency has deviated from a set value. Different schemes…
There are many ways to lock a laser´s phase or frequency. They do, however, all follow the same basic principles based on a feedback loop, which is diagrammatically sketched in Figure 1. Each…