An external-cavity 1560-nm diode laser was frequency doubled in a 3-cm-long periodically poled LiNbO(3) waveguide doubler with 120% W(-1) conversion efficiency. The 780-nm light was used to detect the D(2) transitions of Rb, and the laser frequency was locked to Doppler-broadened lines of Rb. Furthermore, the ~1 microW of second-harmonic power was sufficient for detecting the sub-Doppler lines of Rb, and the laser was locked to a (87)Rb crossover line.
The frequency stability of a 1560-nm diode laser, whose second harmonic was locked to (87)Rb sub-Doppler lines, was characterized by measuring the beat frequency relative to a 780-nm reference laser that was locked to sub-Doppler lines of another rubidium cell. The square root of the Allan variance reached a minimum value of 7.5 x 10(-12) in 1 s, which corresponded to frequency variations of 1.44 kHz for the 1560-nm laser. The frequency reproducibility of the system was approximately 1 x 10(-9). These values are better than those that can be achieved by locking to Doppler-broadened transitions at the 1550-nm wavelength band.
Two diode-pumped tunable Nd:YAG lasers locked to sub-Doppler transitions of (127)I(2) and (133)Cs(2) are used as a source for two-wavelength interferometry. The synthetic wavelength is highly stable and accurate, owing to the frequency stability of the locked lasers and the precise determination of the frequency difference between Cs(2) and I(2) transitions. The dense spectra of the two molecular absorbers allows selection of synthetic wavelength A over a wide range, between 8.5 mm and more than 1 m, thus enabling distance measurements with a large nonambiguity range. Fringe contrast and phase-shifting methods are used to measure the synthetic phase. An accuracy of 70 µm is achieved for synthetic wavelength Λ ~ 19 mm, corresponding to a phase interpolation accuracy ofΛ/260.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.