Tunable Fiber Laser Wavelength Scanning
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Solution Overview
Problem
Conventional tunable light sources face challenges in achieving high-speed wavelength scanning while maintaining high Q-value and narrow bandwidth, leading to unstable output and difficulty in continuous wavelength change, which is crucial for applications like optical coherent tomography and high-speed image processing.
Innovation Solution
A tunable fiber laser light source is designed with an optical fiber loop, a gain medium, a light branch incident section, a tunable optical filter incorporating an optical beam deflector and diffraction grating, and an optical coupler, allowing for continuous wavelength change and high-speed scanning by varying the incident angle to the diffraction grating, ensuring stable oscillation and narrow bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the length of the external resonator is kept short, then the device complexity is reduced, but the longitudinal mode interval becomes wide causing mode hopping and unstable output
Solution Approach 1:
The patent replaces the mechanical piezo-element control system with an all-optical solution using a fiber-based resonator and tunable filter. The fiber ring resonator eliminates mechanical components while the tunable filter provides wavelength selection without mechanical cavity length adjustment, resolving the contradiction between simple structure and stable single-mode operation.
Solution Approach 2:
The patent introduces dynamic wavelength tuning capability through a tunable filter in the fiber ring resonator. This allows the system to dynamically adjust the oscillation wavelength while maintaining stable single-mode operation, enabling continuous wavelength variation without mode hopping despite the compact resonator structure.
2Ease of operation
If the wavelength of the tunable filter is simply changed, then the operation is simplified, but mode hopping occurs and oscillation becomes multimode
Solution Approach 1:
The fiber ring resonator provides inherent feedback that stabilizes the oscillation mode. When the tunable filter wavelength is changed, the resonator's feedback mechanism ensures continuous single-mode oscillation by maintaining the phase and amplitude conditions for lasing, preventing mode hopping while keeping the operation simple.
3Reliability
If piezo-element control is used to control cavity length, then single mode oscillation can be maintained, but the device complexity increases and high-speed wavelength changing becomes difficult
Solution Approach 1:
The patent replaces the mechanical piezo-element control system with an all-optical solution using a fiber-based resonator and tunable filter. The fiber ring resonator eliminates mechanical components while the tunable filter provides wavelength selection without mechanical cavity length adjustment, resolving the contradiction between simple structure and stable single-mode operation.
4Device complexity
If a conventional bandpass filter is used, then the device complexity is reduced, but high-speed wavelength scanning cannot be achieved
Solution Approach 1:
The patent introduces dynamic wavelength tuning capability through a tunable filter in the fiber ring resonator. This allows the system to dynamically adjust the oscillation wavelength while maintaining stable single-mode operation, enabling continuous wavelength variation without mode hopping despite the compact resonator structure.
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 configuration enables high-speed wavelength scanning with continuous wavelength change without mode hopping, achieving stable and precise optical output suitable for applications requiring high-resolution imaging and dynamic analysis.
Implementation Method 1
a diffraction grating which receives light deflected by the optical beam deflector and reflects light of selected wavelength changing according to an incident angle in the same direction as the incident angle
Implementation Method 2
an optical beam deflector which changes a reflecting angle of an optical beam, obtained from the light branch incident section, periodically within a certain range
Implementation Method 3
a gain medium which is connected to the optical fiber loop and has a gain with respect to an oscillating wavelength
Data Source
AI summary
An optical fiber loop has a gain medium having a gain at an oscillation wavelength and optical circulators 13 and 14. Collimate lenses 22 and 24 enlarge light bean taken from the optical circulators 13 and 14. A polygon mirror 25 is provided on the light axis, and is rotated. A diffraction grating 27 is provided at the receiving position of the light reflected by the polygon mirror 25, and is of a Littrow configuration which reflects the light in the same direction as the incident light. A selected wavelength changes according to an incident angle to the diffraction grating 27, resulting in increase of selectivity owing to twice incident, thereby permitting to change an oscillation wavelength with narrow band even when changing the selected wavelength by rotating the polygon mirror 25 at high speed.