Single-pass Ring-Modulated Laser for Low-Power Silicon Photonics
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Solution Overview
Problem
Silicon high-speed optical modulators face challenges in achieving high-speed, low-power, and compact size with large ON/OFF extinction ratio, often requiring precise and dynamic tuning, which consumes significant power and involves complex control circuits.
Innovation Solution
An external cavity optical source is developed, comprising an optical gain chip and a silicon-on-insulator chip with a ring resonator and amplitude modulator, where the ring resonator provides dual-pass phase modulation and the amplitude modulator provides single-pass amplitude modulation, allowing for in-phase modulation and reduced tuning requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ring-resonator modulators are used to achieve large extinction ratio with weak phase modulation, then extinction ratio is improved, but precise and dynamic tuning is required which increases power consumption and device complexity
Solution Approach 1:
The patent combines the ring resonator and Mach-Zehnder interferometer into a single integrated device where the ring resonator provides both wavelength filtering and phase modulation, while the MZI provides amplitude modulation. This merging eliminates the need for separate tuning control circuits while maintaining large extinction ratio performance.
Solution Approach 2:
The ring resonator is designed to perform multiple functions simultaneously: wavelength filtering, phase modulation, and resonance enhancement. This multi-functionality reduces the need for additional dedicated tuning components and circuits, thereby reducing device complexity and power consumption.
2Device complexity
If MZI modulators are used to avoid precise tuning, then device complexity is reduced, but much stronger phase modulation is needed which increases modulator length and power consumption
Solution Approach 1:
The modulation function is segmented between two distinct components: the ring resonator handles phase modulation and wavelength filtering, while the MZI handles amplitude modulation. This segmentation allows each component to be optimized independently, reducing the overall modulator length while avoiding precise tuning requirements.
Solution Approach 2:
The device uses a composite structure combining ring resonator and MZI technologies, leveraging the strengths of both approaches. The ring resonator provides resonance enhancement for efficient phase modulation, while the MZI provides amplitude control without requiring precise tuning, resulting in a compact low-power device.
3Reliability
If stronger phase modulation is applied in MZI modulators to achieve large extinction ratio, then extinction ratio is improved, but power consumption and modulation voltage increase
Solution Approach 1:
The ring resonator's resonance condition is dynamically controlled to enhance phase modulation efficiency. By tuning the ring resonator to operate at its resonance wavelength, the device achieves large extinction ratio with minimal modulation power, as the resonance condition amplifies the modulation effect without requiring high voltages.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves improved optical modulation amplitude with low-power and high-speed modulation, aligned to the lasing wavelength without the need for excessive tuning, enhancing performance in silicon-photonic links and optical fibers.
Implementation Method 1
silicon high-speed optical modulators are based on the free-carrier plasma dispersion effect. Notably, the optical refractive index of silicon reduces with increased densities of electrons and holes (i.e., free carriers). In order to use this effect for data modulation, the carrier densities in an optical waveguide are usually electrically modulated, so that the optical refractive index is modulated, and thus the optical phase of the propagating laser light is modulated.
Implementation Method 2
Ring-resonator modulators often use strong resonances for modulation. Consequently, they can usually achieve large ER even with weak phase modulation.
Data Source
AI summary
An optical source may include an optical gain chip that provides an optical signal and that is optically coupled to an SOI chip. The optical gain chip may include a reflective layer. Moreover, the SOI chip may include: a first optical waveguide, a first ring resonator that selectively optically coupled to a second optical waveguide and that performs phase modulation and filtering of the optical signal, the second optical waveguide, an amplitude modulator, and an output port. Note that the reflective layer in the optical gain chip and the amplitude modulator may define an optical cavity. Furthermore, a resonance of the first ring resonator may be aligned with a lasing wavelength, and the resonance of the first ring resonator and a resonance of the amplitude modulator may be offset from each other. Additionally, modulation of the first ring resonator and the amplitude modulator may be in-phase with each other.