Microresonator Self-Injection Locking for Tunable Narrow-Linewidth Lasers
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Solution Overview
Problem
Existing tunable, long coherent length lasers are costly and large, limiting their applications in spectroscopy, holographic metrology, quantum measurements, and medical imaging due to high mechanical tuning requirements.
Innovation Solution
A compact, low-cost tunable laser device using a multimode diode laser optically locked to a microresonator via self-injection feedback, with tunability achieved by controlling the laser temperature and polarization, and mechanically tuning the microresonator's Whispering Gallery Modes (WGMs).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Littman-Metcalf configuration is used to achieve highly tunable narrow linewidth lasers, then the laser performance is improved, but the device cost and size increase significantly
Solution Approach 1:
The patent replaces the mechanical Littman-Metcalf tuning system with an optical microresonator-based system. Instead of mechanically tuning a back reflector mirror, the invention uses optical feedback from a microresonator to achieve wavelength selection and tuning, thereby eliminating complex mechanical components while maintaining narrow linewidth performance
Solution Approach 2:
The patent achieves laser tuning by changing the temperature of the microresonator, which shifts the Whispering Gallery Modes (WGMs) and enables wavelength selection. This thermal parameter change replaces the mechanical movement required in traditional systems, reducing device complexity while maintaining tuning capability
2Adaptability or versatility
If mechanical tuning is used to achieve spectral tuning in lasers, then the tuning capability is improved, but the mechanical complexity and cost increase
Solution Approach 1:
The patent substitutes mechanical tuning mechanisms with thermal and electrical control methods. The microresonator's WGMs are tuned by controlling its temperature, and the laser source wavelength is adjusted by changing its temperature and polarization, eliminating the need for mechanical moving parts while achieving broad spectral tuning (>200 nm)
Solution Approach 2:
The invention achieves spectral tuning by changing physical parameters (temperature, polarization) rather than mechanical positions. The microresonator temperature controls the WGM wavelengths, and the laser source temperature and polarization control the emitted wavelength, providing a non-mechanical tuning approach that reduces complexity
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
Provides continuous tunability over a wide range with high side-mode suppression ratio, suitable for applications requiring non-uniformly spaced laser lines, and reduces mechanical complexity and cost.
Implementation Method 1
A multimode diode laser (with a single transverse mode) is optically locked to a single Whispering Gallery Mode (WGM) of a micro-resonator via self-injection feedback
Implementation Method 2
The tunability of the WGM-locked laser is achieved by locking the diode laser to different WGMs of the microresonator
Implementation Method 3
The WGMs are selected by tuning the temperature and polarization of the laser source
Implementation Method 4
The WGMs are selected by tuning the temperature and polarization of the laser source
Implementation Method 5
the WGMs are tuned mechanically, or by controlling the temperature of the microresonator using a feedback control system
Data Source
Figure 1~2
Figure 3
AI summary
A multimode diode laser (with a single transverse mode) is optically locked to a single Whispering Gallery Mode (WGM) of a microresonator via self-injection feedback. The tunability of the WGM-locked laser is achieved by locking the diode laser to different WGMs of the microresonator.