A micromachined platform for localized index modulation in chirped fiber Bragg gratings and its application to ultrafast optical pulse shaping

This paper reports the development of a micromachined platform that locally modifies the refractive index of a chirped fiber Bragg grating (CFBG). This platform, composed of an array of electrothermal actuators, has been used to make an ultrashort optical pulse shaper. The micromachined array, with a footprint of 5 mm × 1 mm, has 75 actuators spaced 60 μm apart, and has been used to demonstrate pulse shaping both in the time and frequency domain. A normalized intensity peak of 1.5 at 1550 nm is obtained by applying about 2 mN of force using a single actuator. The intensity peak can be shifted by over 3 nm to the edge of the CFBG spectrum by using different actuators. The pulse width is modulated from 1.5 ps to 4 ps by application of 500 mW of power. System simulations track experimental data that show the individual actuators addressing distinct frequency components. Thermal experiments verify that heat generated by the electrothermal actuators has no measurable effect on the optical pulse spectrum obtained.