Silicon Phase Shifter Research Articles

Phase-change material enabled silicon phase shifter actuated by a highly durable graphene microheater

Phase-change material enabled silicon phase shifter actuated by a highly durable graphene microheater

Low VπLπ and Driving Voltage Interleaved Silicon Phase Shifter for Modulation Applications

Interleaved doped Mach-Zehnder Modulators (MZMs) are one solution to attaining higher modulation efficiencies compared with lateral junction structures, due to greater modal overlap with the depletion regions of the PN junctions. In this work, we present an interleaved Si modulator device design and process simulation based on a three-step ion implantation process that aims to obtain a realistic PN junction doping profile using a Monte Carlo simulation method. A high doping concentration on the order of 5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">18</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−3</sup> for the P and N regions is explored. Device simulations to track the carrier motion under different voltage biases are performed. Using equivalent medium theory, we calculated the modulation efficiency V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> ·L <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">π</sub> of the interleaved Si modulator to be 0.19 V·cm under 1V reverse bias. This work is among the highest reported modulation efficiencies thus far in MZMs without photonic resonance structures.

Energy-efficient thermo-optic silicon phase shifter with well-balanced overall performance

Silicon photonic integrated circuits (PICs) show great potential for many applications. The phase tuning technique is indispensable and of great importance in silicon PICs. An optical phase shifter with balanced overall performance on power consumption, insertion loss, footprint, and modulation bandwidth is essential for harnessing large-scale integrated photonics. However, few proposed phase shifter schemes on various platforms have achieved a well-balanced performance. In this Letter, we experimentally demonstrate a thermo-optic phase shifter based on a densely distributed silicon spiral waveguide on a silicon-on-insulator platform. The phase shifter shows a well-balanced performance in all aspects. The electrical power consumption is as low as 3 mW to achieve a π phase shift, the optical insertion loss is 0.9 dB per phase shifter, the footprint is 67×28µm2 under a standard silicon photonics fabrication process without silicon air trench or undercut process, and the modulation bandwidth is measured to be 39 kHz.

Analysis of a process simulated graded-index strained silicon-germanium optical phase shifter

This paper analyzes the effect of germanium doping on the performance of an optical PN phase shifter in silicon photonics platform. The fabrication process flow is defined using a 2D process simulation tool to create the phase shifter structure. The mode, material, and loss parameters of the designed phase shifter are calculated and the performance is compared with a silicon phase shifter. A 1.84× higher phase shift, 1.27× lower absorption, and 1.50× lower insertion loss is obtained for the silicon-germanium phase shifter compared to silicon.

High-Efficiency Silicon Photonic Modulator Using Coupled Bragg Grating Resonators

In this, we propose a novel design of a silicon photonic modulator that has a high modulation efficiency and that is tolerant to temperature variations. A series of phase-shifted Bragg gratings are placed in each arm of a Mach–Zehnder interferometer in order to provide enhanced phase modulation. The slow light effect in these ultra-compact coupled resonators improves phase modulation efficiency compared to conventional silicon phase shifters. These Bragg grating cavities are designed such that the optical bandwidth is increased compared to other coupled resonators, such as micro-rings. This improved bandwidth reduces the temperature sensitivity of the devices. We present in detail how to optimize these modulators considering properties, such as modulation efficiency ( Vπ × L ), optical modulation amplitude, and optical bandwidth ( $\Delta \lambda _{BW}$ ); the latter property determines the operating temperature range (Δ T ). As examples, we present two designs that meet different target specifications for short-reach or long-haul applications. We further provide a model, based on the coupled mode theory, to investigate the dynamic response of the proposed modulators. A large signal analysis is performed using finite-difference time domain in order to simulate on/off keying modulation and eye diagrams up to 110 Gb/s.

Simplified modeling and optimization of silicon modulators based on free-carrier plasma dispersion effect.

In this paper, a simplified model of silicon phase modulators is presented that enables favorable accuracy together with a substantial reduction in computational effort and without the requirement of semiconductor TCAD device simulation software. This permits fast optimization of the different parameters of a modulator. The model was successfully implemented in Phoenix Optodesigner optical software allowing the optimization of silicon phase shifters for different applications. Moreover, this model presents a great potential for the simulation of modulators based on PN interdigitated junctions, which normally require complex and time consuming 3D simulations. Simulation time was reduced by a factor of 6 for the lateral PN junction based modulator, and two orders of magnitude reduction was obtained for interdigitated PN junctions based modulators.

Broadband linearized silicon modulator

A scheme to achieve a wideband linearized silicon Mach-Zehnder (MZ) modulator is proposed. The modulator consists of a single MZ interferometer with identical reverse-biased silicon diode phase shifters in both arms, driven in a push-pull configuration. It is shown that the 3rd order nonlinearity of the modulator can be eliminated by canceling the nonlinearities from the silicon phase shifters and the MZ transfer function against each other. The 2nd order nonlinearity is simultaneously eliminated by differential detection or operation away from the quadrature point. As a result, the linearity of the proposed silicon modulator greatly exceeds the linearity of a conventional MZ modulator with ideal, linear (e.g. LiNbO3) phase shifters. The simplicity and large optical and RF bandwidth of the proposed modulator make it attractive for analog photonic applications.

Wave-particle properties measured by neutron interferometry

Coherence phenomena of neutron waves have been investigated by means of perfect crystal interferometry. A perfect silicon phase shifter was used to obtain information on the longitudinal and transverse coherence lengths and to observe the strong variation of the phase shift near a Bragg direction. Interference experiments with pulsed beams displayed properties of the relative wave packet, and the self-interference character of experiments of this kind. Experiments with an absorber-detector in one coherent beam gave information about the unsharp particle-wave behaviour of neutrons.