Investigation of Grating Growth Characteristics in Planar Lightwave Circuits for External Cavity Laser

We fabricated Bragg gratings in planar lightwave circuits and investigated their growth characteristics. The refractive index modulation of the gratings grew in the PLC with total fluence F by the power law δ n = AF^B with A = 8.6 ± 0.9 × 10^-8 and B = 1.47 ± 0.02. The PLC gratings as external reflectors for ECLs were controlled reasonably well by adjusting the writing conditions based on the power law and the coupled mode theory. The properties of fabricated PLC gratings were closely matched to the design parameters of the PLC grating. The single longitudinal mode oscillations of the ECLs were also demonstrated at 1309.5 nm and 1550.5 nm.