High efficiency frequency doubled diode laser for precision spectroscopy of Single Ba* ions at 493 nm

Abstract

Un!versii8l Innsbruck lnsliiul for EXDenmenfalDhVSlkPrecision spectroscopy of single trapped Barium ions requires a narrowband. drin-free light SOUI M at 493 nm. We have built c frequency doubled diode laser which produces 60 mW of light at 493 nm with a Spectra bandwidth of less than 30 kHz. The Bystem consists of a 986 nm diode laser in a Lmmann cavny configuration, PoUnd-Drever.stabilv& lo a reference cavily. and an external doubling resonator with a KNbO, crptai. Pound-DreVer-Stabiiiled to the frequency of the 966 nm iight. We employ an SDL laser diode with 150 mW maximum output power. E 4-minor doubling resonator in ring geometry, and 80 dB isolation between the laser cavity and the doubling resonator. We achieve a conversion of 94 mW before the doubler Into 60 mW frequency doubled light, coneoponding to an efficiency of 63%.For finding stable reference iines and demonstrating a spectroscopic application of the system. we carried aut Doppler-free madulatlon transfer spectroscopy (MTS) [l] on Te2 in a 12 GHz interval near thE S,,, to PI,^ resonance line of Ba' a 4 9 3 nm. A scan of the region, together with the signal from a Ba hollow cathode lamp is shown in Fig.1. It exhibits 16 Te, lines of which two (20261 534 cm.' and 20261 801 cm.0 have been previously ldentrfied [z]. For further investigalion we scanned Over the strong line al 20261.801 cm~' with higher Spectral resolution. The recorded MTS signal is shown in Fig.2 together with a calc~lat~on [ l ] using lhree fit parameters, the linewidth of the Banstlion I, the demodulation phase 8, and an overall scaling factor. i I 40 20 0 20 40 eo I Laser Detuning a t 493 nm (MHz) Rg 1: Tez MTS signal showing 16 resoFig.2. MTS signal of Te, h e and nance lines, and Ba hollow cathode signal theoretical fit calculated with y r4.3 MHz showing the SIi2 to PI,* transition in Ea'.and g = 95". The iaser system, completed with a second grating stabilized diode laser at 650 nm which has 100 kHz bandwidth, is used for quantum optical measurements and precision spectroscopy on single trapped Ba' ions in a Paul trap. We pesent tis application for the observation of non-classical correiatlons and motional effects in the single ion resonance fluorescence.(1) L S Maetal.App1.Phys 857, 159(1993). [2] $0 a 6 I 2 0 I Frequency In GHz J Cariou. P. Luc, CNRS 11, Orsay, France (1980).