Abstract :
We successfully fabricated a step-type optical delay line using a silica-based planar light-wave circuit (PLC) technology with a total delay of 51.0 mm and an optical coherent crosstalk of -49.1 dB. For the purpose of applying it to a mode-locked Er3+-doped fiber ring laser, we aimed for: 1) an optical delay of several tens of mm so that any optical pulse repetition frequency could be set, 2) as-low-as-possible optical crosstalk so that the oscillation of the mode-locked ring laser would be stable, and 3) low optical insertion loss. We integrated an optical circuit consisting of eight optical delay units possessing three thermo-optic switches, which have a Mach-Zehnder interferometer configuration, and two waveguides. The difference in optical path length of the waveguides corresponds to the optical delay. We set the optical delay of each unit to 0.2, 0.4, 0.8, 1.6, 3.2, 6.4, 12.8, and 25.6 mm, respectively, to give a maximum delay of 51.0 mm. Moreover, the total insertion loss was 5.2 dB. Precision measurement of the optical delay of each unit gave good results, with a manufacturing error of <0.47%, Based on the above results, the fabricated PLC step-type optical delay line can be used in a mode locked ring laser
Keywords :
Mach-Zehnder interferometers; erbium; fibre lasers; laser mode locking; optical crosstalk; optical delay lines; optical planar waveguides; ring lasers; 49.1 dB; 5.2 dB; Er3+-doped fiber ring laser; Mach-Zehnder interferometer; coherent crosstalk; least squares method; manufacturing error; mode locked laser; optical crosstalk; optical delay; optical delay line; optical insertion loss; silica-based planar light-wave circuit; waveguides; Circuits; Delay lines; Fiber lasers; Laser mode locking; Laser stability; Optical crosstalk; Optical interferometry; Optical waveguides; Programmable control; Ring lasers;
