Wide continuous tuning LDs using hybrid resonant optical reflector

The application technology, in which coherent light was used, has been studied vigorously as the next generation optical communication and optical measurement systems. The LD source having the linewidth below 100 kHz and the tuning range over 10 nm is necessary for the coherent optical communication. The coherent light source having the more narrow linewidth and the more wide continuous tuning range is necessary for the optical measurement systems than the coherent optical communication. It is insufficient with present LD source in the performance target. The narrow linewidth and the wide continuous tuning range should be realized at the same time. Therefore, the design for the external cavity LD source is adopted in a ROR (Resonant Optical Reflector) structure and a sine-bar mechanism. The phase adjustment condition by the cavity length and the angle adjustment of the grating must be performed at the same time in the continuous tuning. Therefore, the sine-bar mechanism is used. The sine-bar mechanism adjusts automatically the angle of the grating, when adjusting the cavity length. The LD source is excellent in continuous tuning condition, when an equation presented is satisfied by the sine-bar mechanism. It could be continuously tuned in the wavelength range of 1511.2 nm - 1482.8 nm by the sine-bar mechanism. The minimum linewidth of 2.3 kHz was obtained by the ROR structure. A more wide continuous tuning range can be expected by improving the wavelength dispersion of the optical parts and the mechanics.<>