Electro-optic Tuning of On-Chip Optical Transparency

Abstract- We demonstrate electro-optic tuning of coupled resonator induced transparency on a silicon chip. We tune the quality factor of the transparency mode between 20000 and 6000. On-Chip coherent manipulation of light at room temperature for storing, delaying, stopping and time reversing of light pulses has profound implications for optical communications and quantum information processing. We have recently shown the ability to produce an optical transparency window on-chip using ring resonators [1]. Such optical transparency would enable the breaking of traditional limits imposed by the delay-bandwidth product [2]. Here, we demonstrate, for the first time, electro-optic tuning of such optical transparency on chip. The optical transparency, resulting from coherent interaction of ring resonators is tuned using free carrier dispersion [3]. In light of the recent demonstrations of high speed electrooptic devices integrated into resonators [4] this integration would enable electrically controlled delay, storage, stopping of optical pulses on an integrated silicon chip. A. Device Description The device consists of two micro-ring resonators of 14 µm diameter coupled to a pair of parallel waveguides. The coupling waveguides and rings are formed by waveguides of width 560 nm and height 250 nm. The center-to-center (CTC) distance between the waveguides forming the rings and the straight waveguides is 720 nm. The CTC distance between the rings is 22 µm. A small difference in circumference between the rings is introduced to detune the two ring resonances. Fig. 1: a) top view schematic double ring resonators embedded in PIN diodes b) Cross section of a waveguide embedded into a PIN diode Each ring is embedded in PIN diodes formed by concentric doped layers. The doping levels and dimensions of the device are shown in Fig 1. The structure operates by active charge injection and extraction enabling transitions times of 10s of picoseconds [4]. Fig. 2: Top view microscope picture of double ring resonators embedded i