Maoqing Xin

Breakdown delay-based depletion mode silicon modulator with photonic hybrid-lattice resonator.

A compact silicon electro-optic modulator that operates in the breakdown delay based depletion mode is introduced. This operation mode has not previously been utilized for optical modulators, and represents a way to potentially achieve much higher modulation speeds and carrier extraction efficiencies without sacrificing energy efficiency, which is a critical criterion for realizing miniaturized sub-THz modulation components in silicon. Our study shows a speed of at least 238 GHz modulation is achievable along with an ultra-low energy consumption of 26.6 fJ/bit in a simple planar P+PNN+ diode example structure, which is embedded in a 2D hybrid photonic lattice mode gap resonator. The optical resonator itself is only 69 µm2 in footprint and is designed for optimized electro-optic sensitivity and conversion efficiency with reduced carrier scattering. Both the static and dynamic device performance are backed up by fully integrated 3D optical and 3D electrical numerical results. The compact device dimensions and low energy consumption are favorable to high density photonic integration.

A high speed electro-optic phase shifter based on a polymer-infiltrated P-S-N diode capacitor

A polymer-infiltrated P-S-N diode capacitor configuration is proposed and a high speed electro-optic phase shifter based on a silicon organic hybrid platform is designed and modeled. The structure enables fast carrier depletion in addition to the second order nonlinearity so that a large electro-optic overlapped volume is achievable. Moreover, the device speed can be significantly improved with the introduction of free carriers due to a reduced experienced transient capacitance. The advantages of the diode capacitor structure are highly suitable for application to a class of low aspect ratio slot waveguides where the RC limitation of the radio frequency response is minimized. According to our numerical results, by optimizing both the waveguide geometry and polarization mode, at least 269 GHz 3-dB bandwidth with high efficiency of 5.5 V-cm is achievable. More importantly, the device does not rely on strong optical confinement within the nano-slot, a feature that gives considerable tolerance in the use of nano-fabrication techniques. Finally, the high overlap and energy efficiency of the device can be applied to slow light or optical resonance media for realizing photonic integrated circuits-based green photonics.

Hybrid silicon organic high speed electro-optic phase shifter

We study a hybrid silicon organic high speed electro-optic phase shifter based on polymer infiltrated P-S-N (“S” refers to the slot) diode capacitor structure. This optical phase shift is realized based on index perturbation both inside the slot via Pockels nonlinearity and within the silicon ridges via the free carrier effect (carrier depletion). The combination of the polymer diode capacitor configuration with the low aspect ratio slot waveguide system leads to a promising method of constructing sub-THz speed optical modulators without sacrificing either modulation efficiency or energy consumption. By optimizing the waveguide geometry in terms of balancing effective index shift and device speed, at least 269 GHz bandwidth can be achieved with a high modulation efficiency of 5.5 V-cm when the diode capacitor is reverse biased by an external radio frequency (RF) voltage signal between the electrodes (optical propagation loss is acceptably low at 4.29 dB).

A compact depletion mode silicon modulator based on a photonic hybrid-lattice mode-gap resonator

A high speed silicon electro-optic modulator is proposed based on a hybrid-lattice mode-gap resonator. The device surface area is only 10 μm by 4.5 μm and both injection and depletion mode operation have been studied. Our full 3D optical and electrical numerical result shows the device is capable of a modulation speed of 238 Gb/s at a 10 dB extinction ratio when it is operated in the depletion mode by an embedded P+PNN+ diode. More importantly, its energy consumption is ultra-low at 26.6 fJ per bit. The fabricated hybrid-lattice resonator demonstrates a resonance peak around 1600 nm with quality factor ~7800, which agrees well with the optical numerical results from 3D FDTD methods. The dynamic characterization of the device is still in progress. The compact device dimension and ultra-low energy consumption are favorable to high density photonic integration.

Resonator-Based Silicon Electro-Optic Modulator with Low Power Consumption

This paper demonstrates, via simulation, an electro-optic modulator based on a subwavelength Fabry–Perot resonator cavity with low power consumption of 86 µW/µm. This is, to the best of our knowledge, the lowest power reported for silicon photonic bandgap modulators. The device is modulated at a doped p–i–n junction overlapping the cavity in a silicon waveguide perforated with etched holes, with the doping area optimized for minimum power consumption. The surface area of the entire device is only 2.1 µm2, which compares favorably to other silicon-based modulators. A modulation speed of at least 300 MHz is detected from the electrical simulator after sidewall doping is introduced which is suitable for sensing or fiber to the home (FTTH) technologies, where speed can be traded for low cost and power consumption. The device does not rely on ultra-high Q, and could serve as a sensor, modulator, or passive filter with built-in calibration.

A Resonator-based Silicon Electro-optic Modulator with Ultra-low Power Consumption and Optimized Modulation Performance

This paper demonstrates, via simulation, an electro-optic modulator based on a subwavelength Fabry-Perot resonator cavity with ultra-low power consumption. The device is modulated at a doped p-i-n junction overlapping the cavity in a silicon waveguide perforated with etched holes, with the doping area optimized for minimum power consumption. The surface area of the entire device is only 2.1 mum2. Our optical and electrical simulations demonstrate a resonance peak shift of 12 nm with 0.5 mW power consumption. Transient results indicate that the modulation depth exceeds 10 dB at a modulation speed of 100 MHz with the power consumption comparing favorably to a previous report [1]. This speed can be further improved to 250 MHz by using an optimized driving signal [2]. Finally, the etched holes forming the cavity have been tapered [3], [4] to maximize insertion, and the etching depth of those holes is tuned to reduce fabrication complexity. The device does not rely on ultra-high Q, and the huge peak shift detected could be applied to a sensor [5]-[7], modulator, or passive filter with built-in calibration.

Resonator-based Silicon Electro-optic Modulator with Ultra-low Power Consumption

This paper demonstrates, via simulation, an electro-optic modulator based on a subwavelength Fabry-Perot resonator cavity with ultra-low power consumption. The device is modulated at a doped p-i-n junction overlapping the cavity in a silicon waveguide perforated with etched holes, with the doping area optimized for minimum power consumption. The surface area of the entire device is only 2.1 μm. Our optical and electrical simulations demonstrate a resonance peak shift of 12 nm with 0.5 mW power consumption. Transient results indicate that the modulation depth exceeds 10 dB at a modulation speed of 100MHz with the power consumption comparing favorably to a previous report [1]. The etched holes forming the cavity have also been tapered [2] to optimize insertion. The device does not rely on ultra-high Q, and could serve as a sensor, modulator, or passive filter with built-in calibration.