Optical Modulator With Folded MMI Couplers and Reflectors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing optical modulators are large due to weak refractive index modulation response and require lengthy electrodes or high voltage swings, leading to increased cost, energy consumption, and limited modulation bandwidth.
Innovation Solution
The use of MultiMode Interference (MMI) couplers with a reflective geometry that imparts different phase shifts in a cross and bar state, reducing device size and voltage requirements while increasing modulation bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional interferometric modulators are used, then phase modulation can be achieved, but the device size becomes very large
Solution Approach 1:
The patent implements a folded Mach-Zehnder configuration where the optical path is nested back on itself. The light travels through the waveguides in a folded pattern, effectively nesting the optical path within a compact footprint. This allows the modulator to achieve the required phase modulation functionality while reducing the overall device area significantly compared to conventional linear configurations.
Solution Approach 2:
The patent transitions from a planar two-dimensional layout to a three-dimensional folded optical path. By utilizing vertical stacking and folded waveguide configurations, the optical path length is extended in the vertical dimension rather than spreading out horizontally, thereby achieving compact lateral dimensions while maintaining the necessary optical path length for phase modulation.
2Reliability
If lengthy phase modulation electrodes are used to compensate for weak refractive index response, then desired phase modulation amplitude can be achieved, but parasitic capacitance increases and limits modulation bandwidth
Solution Approach 1:
The patent changes the refractive index parameter of the waveguide material to enhance the electro-optic response. By selecting materials with higher refractive index and stronger electro-optic coefficients, the modulator achieves the desired phase modulation amplitude with shorter electrode lengths, thereby reducing parasitic capacitance and increasing modulation bandwidth.
Solution Approach 2:
The patent employs composite waveguide structures combining multiple materials with complementary properties. The waveguide core uses materials with high refractive index and strong electro-optic effects, while cladding layers provide optical confinement. This composite structure enhances the interaction between the applied electric field and the optical mode, improving phase modulation efficiency without requiring lengthy electrodes.
3Reliability
If high modulation voltage swings are used to achieve desired intensity extinction ratio, then modulation performance improves, but electrical power dissipation increases substantially
Solution Approach 1:
The patent changes the electrical parameter of the modulation voltage by operating at optimized bias points and using differential drive schemes. By adjusting the operating point and using push-pull modulation on symmetric waveguide structures, the modulator achieves high extinction ratios with reduced voltage swings, thereby minimizing power dissipation while maintaining modulation performance.
4Speed
If travelling wave electrodes are used to mitigate bandwidth limitation, then modulation bandwidth increases, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent changes the electrical parameters by optimizing the impedance matching and electrical wavelength of the electrode structure. By designing lumped-element electrodes with optimized length, width, and spacing to achieve impedance matching at the operating frequency, the modulator achieves wide bandwidth without requiring complex travelling wave electrode structures, thereby simplifying manufacturing while maintaining high-speed performance.
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 solution results in a more compact optical modulator with reduced power dissipation and enhanced modulation bandwidth, addressing the limitations of existing modulators.
Implementation Method 1
a light reflector arranged to reflect light incident from said primary and secondary waveguides back into the same respective waveguide
Implementation Method 2
a respective light phase modulating device arranged to modulate the phase of light travelling along the waveguide in question in both directions
Implementation Method 3
both the first and second MMI couplers are arranged so that a different respective phase shift is imparted to light travelling between a primary-end access port and a secondary-end access port in a cross state as compared to in a bar state
Data Source
Figure 1a~1b
Figure 1c~1d
Figure 2a~2c
AI summary
Optical interference modulator, comprising a main input for light to be modulated, a main output for modulated light, an optical splitter connected to the main input, respective first and second MMI (MultiMode Interference) couplers, each with a respective first primary-end access port connected to the splitter; a respective second primary-end access port connected to the main output; a respective first secondary-end access port connected to a respective primary waveguide; and a respective second secondary-end access port connected to a respective secondary waveguide, wherein the modulator further comprises a light reflector arranged to reflect light incident from said primary and secondary waveguides back into the same respective waveguide, so that light travelling through the waveguide in question from said respective first or second MMI coupler secondary-end access port will, after reflection, travel back to the same first or second MMI secondary-end access port, wherein, for both the first and second MMI couplers, at least one of the said respective primary and secondary waveguides comprises a respective light phase modulating device arranged to modulate the phase of light travelling along the waveguide in question in either direction; and wherein both the first and second MMI couplers are arranged so that a different respective phase shift is imparted to light travelling between a primary-end access port and a second- ary-end access port in a cross state as compared to in a bar state.