Resonance control of a silicon micro-ring resonator modulator under high-speed operation using the intrinsic defect-mediated photocurrent

Abstract

A method to stabilize the resonance wavelength of a depletion-type silicon micro-ring resonator modulator during high-speed operation is described. The method utilizes the intrinsic defect-mediated photo-absorption of a silicon waveguide and results in a modulator chip fabrication process that is free of heterogeneous integration (for example using germanium), thus significantly reducing the complexity and cost of manufacture. Residual defects, present after p-n junction formation, are found to produce an adequate photocurrent for use as a feedback signal, while an integrated heater is used to compensate for thermal drift via closed-loop control. The photocurrent is measured by a source-meter, which simultaneously provides a DC bias to the integrated heater during high-speed operation. A drop-port or an integrated extrinsic detector is not needed. This feedback control method is experimentally demonstrated via a computer-aided proportional-integral-differential loop. The resonance locking is validated for 12.5 Gb/s intensity modulation in a back-to-back bit-error-rate measurement. The stabilization method described is not limited to a specific modulator design and is compatible with speeds greatly in excess of 12.5 Gb/s, in contrast to the bandwidth limitation of other stabilization methods that rely on intrinsic photo-carrier generation through non-linear processes such as two-photon-absorption. Further, the use of intrinsic defects present after standard fabrication insures that no excess loss is associated with this stabilization method.

Photoconductive heaters enable control of large-scale silicon photonic ring resonator circuits

“…In order to demonstrate that we can automatically route any input-port to any cross/bar-port, we chose to automatically align the resonances of the 31 rings along the longest route of the switch (labeled as diagonal in Fig. 5) from input-port I 1 to cross-port C 16 . This was accomplished by sequentially tuning the rings along the diagonal, starting from the ring nearest to the input-port to maximize the photocurrent in each ring.…”

OE-CAM: A Hybrid Opto-Electronic Content Addressable Memory

“…However, thermal interactions between on-chip heat-sources and ring resonators can limit this number, as the micro-ring resonators are extremely sensitive to temperature-induced changes in refractive index. In order to mitigate this effect two main strategies could be considered: (1) Computer aided resonance locking [61]; (2) Thermal-aware Integration strategies [62]. Even if the latter still enables high-speed modulation it requires a great deal of additional power, therefore we believe that integration strategies aiming to minimize cross-talk and thermal effect, using for instance thermal polymers [63] would give a pathway for a high speed modulation using ring resonators without trading off energy consumption.…”

Enhancing bulk defect-mediated absorption in silicon waveguides by doping compensation technique

“…Li 10 microring/PN diodeModulator2.2/3.6 @−3/−5 VZ. Wang 11 microring/PN diodeModulator0.18 @−4VD. J. Thomson 12 straight wg/PIN diode4 MeV B + implantation6~10J.…”

“…For example, responsivities of SiWG PDs by using residual defects in carrier-depletion-based modulators are usually on the order of several mA/W 8–11 . A weak photocurrent is adverse to build a simple, fast and robust feedback control loop.…”

“…The bulk defect-mediated absorption (BDA) usually relies on dedicated ion-implantation and annealing steps to induce lattice defects in silicon waveguides 12 – 18 . On the other hand, it is also observed that after the ion-implantations to embed the PN junction and the subsequent annealing to repair lattice damages, there are still residual lattice defects in silicon carrier-depletion-based modulators which provide a substantial photosensitivity to photons at C band 8 – 11 . This effect lends itself to monitor operation points of silicon PICs containing modulators very well since no additional processing steps are required.…”