Fast Tunable Integrated Laser Using Vernier Ring Resonators
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Solution Overview
Problem
Current tunable lasers are large, expensive, and sensitive to vibrations due to moving parts, with slow tuning speeds and poor linewidths, making them unsuitable for applications requiring speed and precision, and III-V material-based lasers are costly and have short coherence lengths.
Innovation Solution
A wavelength-tunable laser using a combination of slow and fast tunable optical filters in a silicon-based implementation, where a heater-tuned optical ring resonator is serially coupled with a carrier-injection-tuned Mach-Zehnder interferometer, allowing for rapid and dense scanning of wavelengths across a broad spectral range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If commercial tunable lasers use moving parts for wavelength tuning, then wavelength tuning capability is achieved, but the device becomes sensitive to vibrations, experiences hysteresis, suffers from nonlinear sweeps, and degrades over time
Solution Approach 1:
The patent replaces mechanical moving parts with an integrated photonic circuit implementation using the Vernier effect between two optical ring resonators. This eliminates mechanical components entirely, substituting them with optical resonance-based wavelength tuning mechanisms that are inherently more reliable and vibration-resistant.
Solution Approach 2:
The patent utilizes the resonant phase transition properties of optical ring resonators, where small changes in refractive index (via thermal or carrier injection) cause large shifts in resonance wavelength. This enables precise wavelength tuning without mechanical movement, resolving the contradiction between tuning capability and mechanical reliability.
2Device complexity
If thermo-optic tuning mechanisms are used in integrated tunable lasers, then integration is achieved, but tuning speed becomes slow (microsecond time scale)
Solution Approach 1:
The patent changes the tuning mechanism from slow thermo-optic effects to fast carrier injection effects in semiconductor materials. By injecting carriers into the ring resonators, the refractive index changes rapidly (nanosecond scale), enabling fast tuning while maintaining integration. This parameter change in the physical mechanism resolves the speed-integration contradiction.
3Adaptability or versatility
If III-V material lasers are used for tuning, then material-based wavelength control is achieved, but fabrication cost increases and coherence length decreases due to broad linewidth
Solution Approach 1:
The patent employs a composite material approach by integrating III-V semiconductor gain sections with silicon photonic circuit ring resonators. This hybrid structure combines the wavelength tuning capability of III-V materials with the low-loss, high-coherence advantages of silicon photonics, resolving the contradiction between material-based control and manufacturing quality.
Solution Approach 2:
The patent segments the laser system into distinct functional modules: III-V gain sections for wavelength control and silicon ring resonators for filtering and coherence enhancement. This segmentation allows each material to perform its optimal function while mitigating the drawbacks of using either material alone.
4Speed
If fast tunable optical filters with carrier depletion tuning are used, then tuning speed increases (sub-nanosecond), but cavity length becomes long resulting in small free spectral range
Solution Approach 1:
The patent merges two ring resonators with different free spectral ranges into a Vernier configuration. The combined system achieves both fast tuning (from carrier injection) and broad wavelength coverage (from the Vernier effect), resolving the contradiction between fast tuning and limited spectral range that would result from a single long cavity.
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 solution enables fast and wide tunability with narrow linewidths, overcoming the limitations of existing tunable lasers by achieving nanosecond-scale tuning speeds and covering a large wavelength range with low propagation loss, making it suitable for applications like LIDAR and optical coherence tomography.
Implementation Method 1
a heater-tuned optical ring resonator
Implementation Method 2
a carrier-injection-tuned Mach-Zehnder interferometer
Data Source
AI summary
An apparatus includes a wavelength-tunable laser and an electronic controller. The electronic controller is configured to control the wavelength-tunable laser such that an output wavelength of the wavelength-tunable laser performs a zigzag in time. The wavelength-tunable laser is capable of rapidly and densely scanning wavelengths across a broad spectral range.