Kang Xiong

25 Gbit/s silicon microring modulator based on misalignment-tolerant interleaved PN junctions

A high-speed depletion-mode silicon-based microring modulator with interleaved PN junctions optimized for high modulation efficiency and large alignment tolerance is demonstrated. It is fabricated using standard 0.18 μm complementary metal-oxide-semiconductor processes and provides low V(π)L(π)s of 0.68 V·cm to 1.64 V·cm with a moderate doping concentration of 2 × 10(17) cm(-3). The measured modulation efficiency decreases by only 12.4% under ± 150 nm alignment errors. 25 Gbit/s non-return-zero modulation with a 4.5 dB extinction ratio is experimentally realized at a peak-to-peak driving voltage of 2 V, demonstrating the excellent performance of the novel doping profile.

44-Gb/s Silicon Microring Modulators Based on Zigzag PN Junctions

We experimentally demonstrate silicon microring modulators with >;40-Gb/s modulation speed based on the carrier-depletion mechanism in reverse-biased PN junctions. A novel zigzag PN junction providing a modulation efficiency of 3.85× 10-5/V and a resistance-capacitance bandwidth of 51 GHz is proposed and demonstrated. The moderate Q factor of ~ 8000 and the operation wavelength detuning are optimized to relieve photon-lifetime-induced bandwidth limitation. Finally, with a voltage swing of 3 V, high-speed modulation of 20 and 44 Gb/s is experimentally demonstrated with the extinction ratio of 3.45 and 3.01 dB, showing great potential in the application of ultrahigh-capacity optical interconnects.

High-speed silicon modulator based on cascaded microring resonators

A high-speed silicon modulator based on cascaded double microring resonators is demonstrated in this paper. The proposed modulator experimentally achieved 40 Gbit/s modulation with an extinction ratio of 3.9 dB. Enhancement of the modulator achieves with an ultra-high optical bandwidth of 0.41 nm, corresponding to 51 GHz, was accomplished by using cascaded double ring structure. The described modulator can provides an ultra-high-speed optical modulation with a further improvement in electrical bandwidth of the device.

Systematic investigation of coupling-modulated microring resonators based on interleaved p-n junctions

We systematically investigate the optical effects and the optical functions of coupling-modulated microring resonators (CMR) based on interleaved p-n junctions. The optical effect of coupling-induced frequency shifts (CIFS) is firstly observed experimentally. Due to the CIFS and thermal-optical effect, the resonance spacing is tuned as large as 0.182 nm (corresponding to 22.8 GHz), the extinction ratio is continuously modulated between 0 dB to as large as 35 dB.

Single-mode silicon-on-insulator elliptical microdisk resonators with high Q factors

We propose and demonstrate a novel elliptical microdisk resonator which enables single-mode operation with high quality (Q) factor. Such elliptical microdisk resonators with pedestal, which consist of plenty of smoothly changing bends with modified curvature radii, can easily achieve single-mode operation due to selective losses introduced by mode transmission mismatches and small curvature radii portion inside the elliptical microdisks. We fabricated the devices on silicon-on-insulator (SOI) platform. Single-mode resonance with high quality factor (Q) of ~105 was experimentally realized. Besides, the proposed elliptical microdisk provides larger coupling strength compared to normal circular microdisk, and hence enables critical coupling with easy-to-fabricate gaps.

Modeling and analysis of silicon-on-insulator elliptical microring resonators for future high-density integrated photonic circuits

We propose a novel resonator containing an elliptical microring based on a silicon-on-insulator platform. Simulations using the three-dimensional finite-difference time-domain method show that the novel elliptical microring can efficiently enhance the mode coupling between straight bus waveguides and resonator waveguides or between adjacent resonators while preserving relatively high intrinsic quality factors with large free spectral range. The proposed resonator would be an alternative choice for future high-density integrated photonic circuits.

Research on SOI-based micro-resonator devices

SOI (silicon-on-insulator)-based micro-resonator is the key building block of silicon photonics, which is considered as a promising solution to alleviate the bandwidth bottleneck of on-chip interconnects. Silicon-based sub-micron waveguide, microring and microdisk devices are investigated in Institute of Semiconductors, Chinese Academy of Sciences. The main progress in recent years is presented in this talk, such as high Q factor single mode microdisk filters, compact thirdorder microring filters with the through/drop port extinctions to be ~ 30/40 dB, fast microring electro-optical switches with the switch time of < 400 ps and crosstalk < -23 dB, and > 10 Gbit/s high speed microring modulators.

25Gbit/s fully CMOS-compatible silicon modulator based on interleaved PN junctions

We present a kind of depletion-mode silicon modulators based on cascade interleaved PN junctions, which simultaneously provide high modulation efficiency and large modulation bandwidth. The interfaces of the PN junctions are vertical to the waveguides propagation direction and tolerant with ± 150nm junction misalignment on the cost of little degradation on the modulation efficiency. The device was fabricated with standard 0.18μm CMOS process, and provides a VπLπ < 1V • cm and an intrinsic bandwidth 39GHz. Over 10GHz electro-optical modulation bandwidth of the device was experimentally obtained. High speed non-return-zero modulation with a bit rate up to 25Gbit/s was finally demonstrated.

Continuously tunable time delay and advance in coupling-modulated microring resonators

We experimentally demonstrate continuously tunable optical time delay and advance using coupling-modulated microring resonators (CMR) with a 15-μm radius. By modulating the coupling coefficient through thermo-optical effect based on micro-heater, the coupling state of the microring is flexibly controlled; as a result, a large dynamic time tuning range (from time advance to delay) is achieved. The CMR device based on SOI is fabricated with commercial 0.18-μm CMOS technology. A novel micro-heater structure was firstly used to thermally tune the coupling state of the micoring. Pulse delay and advance from -15 ps to 85 ps is experimentally realized.