Throughout the project LIGENTEC is responsible for the fabrication of SiN PICs as part of Work-Package (WP) 2 “Fabrication Development”. Here we demonstrate that we have fabricated the SiN PICs to a high standard. Through multiple fabrication runs, the process has been improved to meet the specifications required by the FEMTOCHIP partners. The SiN chips have integrated heaters to allow for thermo-optic tuning. SiO2 is locally removed from above the SiN waveguide so that light can be transferred into the gain material in specific parts of the chip. The SiN PICs are designed and laid out in WP4 “Integrated mode-locked laser” and WP5 “Development of Amplifier” and submitted to LIGENTEC for design rule checks and compliance before fabrication. These chips will be used in the final implementation of the on-chip femtosecond laser. Both the mode locked laser and the amplifier use the demonstrators as the base platform from which the device is built. The chips have been sent to the project partners for characterisation and deposition of gain materials.
The PIC demonstrator consists of SiN waveguides, metal heating lines and large sections of locally removed cladding. Figure (1) shows the design in WP4 which required a larger region of unclad waveguides (chip size of 20 mm x 10 mm). Figure (2) shows the chips fabricated for WP5 (dimensions are 5 mm x 10 mm), the locally removed cladding can be seen in the centre of the chips.