A new tracking technology for achieving high track density over 10 k tracks-per-inch (TPI) is developed. Two key technologies are incorporated. One is the application of optical disk technology to a magnetic disk to obtain a high quality servo signal with a trackwidth 1.5 to 2-mu-m. The other is the installation of a dual-stage actuator using a piezoelectric device for the fine acuator to gain higher servo performance in a bandwidth greater than 1 kHz. This paper describes the design of the optical servo system for the track pitch 1.5-mu-m, 17 k TPI, and experimental results including a comparison of magnetic heads.