Thulium-Doped Fiber Laser Frequency Quadrupling for Underwater Sensing
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Solution Overview
Problem
Conventional lasers for generating high-power blue-green or blue light are costly, inefficient, and fragile, requiring multiple nonlinear conversion steps, which limits their effectiveness for underwater communications, imaging, and sensing applications.
Innovation Solution
A fiber-laser system that uses a thulium-doped fiber laser for generating high-power infrared light, which is then frequency-quadrupled to produce blue light through a nonlinear wavelength conversion device, enabling efficient underwater communications, imaging, and object detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional lasers are used to generate high-power blue-green light, then the output power can be achieved, but the system becomes costly, inefficient, and fragile due to requiring multiple nonlinear conversion steps
Solution Approach 1:
The patent segments the laser system into distinct functional modules: a thulium-doped fiber laser oscillator generating infrared light at 1900nm, followed by separate frequency doubling stages. This modular segmentation allows each component to be optimized independently, reducing overall system complexity while maintaining high output power capability
Solution Approach 2:
The patent introduces an intermediate infrared wavelength (1900nm from thulium-doped fiber laser) as a mediator between the pump source and the final blue-green output. This intermediary wavelength enables more efficient frequency conversion compared to direct blue-green generation, reducing system complexity and improving overall efficiency
2Illumination intensity
If multiple nonlinear conversion steps are used to generate blue-green light, then the desired wavelength can be achieved, but the system efficiency decreases
Solution Approach 1:
The patent changes the operating parameters by using a thulium-doped fiber laser operating at 1900nm instead of conventional wavelengths. This parameter change enables more efficient nonlinear frequency conversion to blue-green wavelengths, reducing energy loss while achieving the desired illumination intensity
3Reliability
If conventional laser systems are used for underwater applications, then the basic function can be performed, but the signal strength is reduced and noise increases
Solution Approach 1:
The patent skips the conventional approach of direct blue-green laser generation and instead uses infrared generation followed by frequency conversion. This skipping of the conventional path enables achieving higher signal strength with reduced noise, improving underwater communication reliability
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 system provides a cost-effective, compact, and efficient means for generating high-power blue light, suitable for deep underwater applications, with improved signal strength and reduced noise, enabling effective data transmission and imaging in seawater.
Implementation Method 1
a fiber ring laser that includes a thulium-doped gain fiber
Implementation Method 2
the first output beam is passed through a wavelength-conversion device to generate a second output beam at a second blue or blue-green wavelength that is one-quarter the wavelength of the first signal wavelength
Data Source
AI summary
An apparatus, method and associated fiber-laser architectures for high-power pulsed operation and pumping wavelength-conversion devices. Some embodiments generate blue laser light by frequency quadrupling infrared (IR) light from Tm-doped gain fiber using non-linear wavelength conversion. Some embodiments use a fiber MOPA configuration to amplify a seed signal from a semiconductor laser or ring fiber laser. Some embodiments use the frequency-quadrupled blue light for underwater communications, imaging, and/or object and anomaly detection. Some embodiments amplitude modulate the IR seed signal to encode communication data sent to or from a submarine once the modulated light has its wavelength quartered. Other embodiments transmit blue-light pulses in a scanned pattern and detect scattered light to measure distances to objects in a raster-scanned underwater volume, which in turn are used to generate a data structure representing a three-dimensional rendition of the underwater scene being imaged for viewing by a person or for other software analysis.