A stabilized laser continuously tunable over a range of 1.5 GHz

We demonstrate a method to stabilize laser frequency which can be continuously tuned over a range of 1.5 GHz. It is based on saturated absorption spectroscopy (SAS) generated by an external-cavity diode laser (ECDL) which is modulated by an electro-optic amplitude modulator (EO-AM). The spectra consist of not only the original peaks corresponding to resonant and crossover lines of ¹³³Cs D₂ line, but also signals introduced by sidebands from an EO-AM. Thus, the laser frequency can be locked to any point within the range of the spectra. Furthermore, the tuning range of the laser can be doubled compared to the coverage of common SAS by fixing the frequency of the pumping laser. The best stability of the locked laser induced by the EO-AM is 1.27 × 10^-11 over an integrating time of 125 s. This method may be applied for more precise and flexible manipulation of atoms and molecules.