Optical Phase Modulator Using Bragg Grating Resonance
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Solution Overview
Problem
Existing optical phase modulators in semiconductor waveguides require long lengths or high bias voltages to achieve satisfactory phase modulation, leading to energy inefficiency and limited integration with other photonic components due to weak electro-optic effects in materials like silicon.
Innovation Solution
Incorporating series of phase shift units with Bragg gratings and cavities along the waveguide, enhancing first-order dispersion and group index through resonance effects, allowing for efficient phase modulation with reduced length and energy consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the length of semiconductor waveguide is increased to achieve satisfactory phase modulation, then phase modulation performance is improved, but device footprint and integration complexity increase
Solution Approach 1:
The patent changes the refractive index parameter of the semiconductor waveguide by introducing Bragg gratings with specific period lengths (e.g., 300-700 nm) and depths. This creates a periodic modulation of the refractive index that enhances the electro-optic effect, allowing satisfactory phase modulation to be achieved with shorter waveguide lengths compared to conventional uniform waveguides.
Solution Approach 2:
The patent creates a composite structure by combining the semiconductor waveguide material with Bragg grating features (periodic refractive index modulation). This composite structure leverages the electro-optic properties of the semiconductor while adding the dispersive effects of the periodic grating structure to enhance phase modulation efficiency.
2Reliability
If high bias voltage is applied to the semiconductor waveguide to achieve satisfactory phase modulation, then phase modulation performance is improved, but energy consumption increases
Solution Approach 1:
The Bragg grating structure modifies the dispersion relations of the waveguide modes, creating a steeper group velocity dispersion. This changes the operating parameters of the waveguide such that the electro-optic modulation efficiency is enhanced, allowing lower drive voltages to achieve the same phase modulation depth as conventional waveguides requiring high bias voltages.
3Reliability
If the length of semiconductor waveguide is increased to achieve satisfactory phase modulation, then phase modulation performance is improved, but ease of integration with other photonic components decreases
Solution Approach 1:
By changing the waveguide parameters through Bragg grating introduction, the patent achieves enhanced phase modulation performance in a compact length, making the device more suitable for integration with other photonic components on the same chip without requiring large footprint.
4Reliability
If high amplitude modulation signal is applied to the semiconductor waveguide to achieve satisfactory phase modulation, then phase modulation performance is improved, but energy consumption increases
Solution Approach 1:
The Bragg grating structure modifies the dispersion and group index of the waveguide, enhancing the sensitivity of the phase modulation to the modulation signal. This parameter change allows the system to achieve satisfactory phase modulation with lower signal amplitudes, reducing the energy consumption of the modulation driver circuitry.
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
The proposed design achieves efficient and sensitive phase modulation with reduced length, lower energy consumption, and temperature stability, enabling compact integration of photonic components.
Implementation Method 1
such series of phase shift units can cause the optical signal to experience a resonance effect which can sharply enhance a first-order dispersion of the semiconductor material of the semiconductor waveguide
Implementation Method 2
enhance a first-order dispersion of the semiconductor material of the semiconductor waveguide and which in turn can enhance its group index
Implementation Method 3
some semiconductor materials such as silicon typically have none or insignificant linear electro-optic effect
Implementation Method 4
the quadratic electro-optic, electro-absorption and plasma dispersion effects are all relatively weak. Accordingly, to achieve satisfactory phase modulation, the length of semiconductor waveguide which is driven with a bias voltage
Data Source
Figure 1
Figure 2~3B
Figure 4A~4D
AI summary
There is described an optical phase modulator generally having a substrate; a waveguide mounted to the substrate and extending along a path of the substrate, the waveguide having a first series of phase shift units distributed along the waveguide, each phase shift unit having two Bragg gratings being spaced apart from one another along the path and a cavity between the two spaced-apart Bragg gratings; and a modulation circuit configured for driving a length of the series of phase shift units of the waveguide in accordance with a modulation signal thereby modulating a refractive index of the waveguide to induce a phase shift to an optical signal propagating along the waveguide.