Variable Lasing Output via Modal Index Modulation
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Solution Overview
Problem
Existing photonic circuits using ring resonators face challenges with high energy consumption and undesirable wavelength shift when modulating lasing output, particularly due to varying injection current, which affects power consumption and modulation speed.
Innovation Solution
The approach involves selectively varying the evanescent coupling between a ring waveguide and input/output waveguides by modulating the modal index of a coupling section, allowing for direct modulation of lasing output without changing the injection current or device geometry, thereby reducing power consumption and minimizing wavelength shift.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If injection current is varied to modulate lasing output, then modulation depth is achieved, but power consumption increases and wavelength shift occurs
Solution Approach 1:
The patent changes the physical parameter used for modulation from injection current to modal index. By varying the modal index of the coupling section through refractive index changes (via thermal, electro-optic, or other mechanisms), the evanescent coupling is modulated without changing the injection current, thereby achieving modulation while maintaining constant power consumption and avoiding wavelength shift.
Solution Approach 2:
The patent divides the waveguide into distinct sections: a coupling section and non-coupled portions. Only the coupling section is subjected to modal index modulation, while the rest of the waveguide remains unchanged. This segmentation allows localized modulation that affects only the coupling efficiency, leaving the laser's operating point and wavelength stable.
2Ease of operation
If injection current is varied to modulate lasing output, then modulation is achieved, but modulation speed is limited
Solution Approach 1:
The patent switches from current-based modulation to modal index-based modulation. Changes in modal index can be achieved rapidly through electro-optic effects, thermal effects, or other mechanisms that directly alter the refractive index, enabling faster modulation speeds compared to the inertial limitations of current-driven carrier recombination in traditional laser modulation.
3Power
If evanescent coupling is modulated by changing device geometry, then coupling coefficient changes, but device complexity increases
Solution Approach 1:
Instead of mechanically changing the geometry (such as moving waveguides or changing gaps), the patent modulates the modal index of the coupling section. This can be achieved through material properties changes (refractive index modulation via temperature, electric field, or other means) while maintaining fixed physical geometry, thereby simplifying the device structure while still achieving coupling modulation.
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 method achieves lower power consumption, higher-speed modulation, and minimal chirp, maintaining a stable resonator temperature and bias point, enabling reliable optical signaling for digital communications with improved power efficiency.
Implementation Method 1
A ring waveguide is coupled to a bus waveguide based on evanescent coupling to exchange power therebetween
Data Source
AI summary
An example device in accordance with an aspect of the present disclosure includes a ring waveguide and bus waveguide. The ring waveguide has a first coupled portion associated with a first modal index, and the bus waveguide includes a second coupled portion associated with a second modal index. The second coupled portion is evanescently coupleable to the first coupled portion. A laser outcoupling and associated lasing output of the device is variable based on varying a difference between the first modal index and the second modal index to vary coupling between the first coupled portion and the second coupled portion, without varying modal indices of non-coupled portions of the ring waveguide and bus waveguide.