2ND-HARMONIC GENERATION OF A 1560-NM DISTRIBUTED-FEEDBACK LASER BY USE OF A KNBO3 CRYSTAL FOR FREQUENCY LOCKING TO THE RB-87 D(2) LINE AT 780 NM

Second-harmonic generation of a semiconductor distributed-feedback las er at 1560 nm is described. It is produced by use of a 4.8-mm-long KNb O3 crystal at room temperature. As much as 2.2 nW of power at 780 nm i s obtained for 11.3 mW of fundamental power incident upon the crystal. This signal is used to interrogate a component of the linear absorpti on profile of the D2 line in Rb-87 (780.241 nm) and to produce an erro r signal used to frequency lock the 1560-nm distributed-feedback laser . Such a system can therefore be a candidate for establishing an absol ute wavelength standard at 1560 nm.