Mutlilayer Wedge Disks CROW for an Optical Delay Line

Optical delay lines are vital for the development of all optical telecommunications, optical computers and for many nonlinear and quantum optics processes. Periodic structures such as coupled resonator optical waveguides (CROW) achieve high delays in a compact manner and with a large bandwidth. Wedge disk resonators have demonstrated high quality factors compared to rectangular disks and rings while remaining integrable on chip. Vertical coupling is needed since the optical mode is pushed toward the disk center by the wedge. We propose an optical delay line made of wedge disks arranged in two overlapping layers. Disks are made of silicon dioxide on silicon pillars. Numerical calculations of the device performance and an experimental proof of concept are presented. A maximum delay of 85 ps for eleven disks is achieved with a loss per cavity of 3.91 dB. This is a first proof of concept of a CROW structure made of wedge disk coupled vertically.