Fluoride Fiber UV Laser with Single-Stage Wavelength Conversion
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Solution Overview
Problem
Conventional ultraviolet laser apparatuses are large in size, inefficient, and have short lifespans due to complex structures and multiple wavelength conversions, leading to reduced output stability and beam quality.
Innovation Solution
A compact ultraviolet laser apparatus utilizing a fluoride fiber laser medium excited by semiconductor lasers, with an external resonator incorporating a nonlinear optical crystal for single-stage wavelength conversion and phase conjugate mirror, and a thermally conductive housing to manage heat, ensuring efficient heat dissipation and alignment-free operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a He-Cd laser apparatus is used to generate ultraviolet light, then the laser can operate at the desired wavelength, but the apparatus becomes large in size and has very low efficiency
Solution Approach 1:
The patent changes the fundamental operating parameters by using a fiber laser at 445nm instead of He-Cd at 325nm, combined with wavelength conversion through nonlinear optical crystals. This parameter change enables compact size while maintaining ultraviolet output capability, achieving both small apparatus volume and reasonable efficiency
Solution Approach 2:
The patent replaces the gas-based He-Cd laser system with a solid-state fiber laser system. This substitution eliminates the need for large vacuum chambers and gas handling systems, dramatically reducing apparatus size while improving efficiency through direct diode pumping of the fiber laser medium
2Illumination intensity
If a YAG laser apparatus is used and wavelength conversion is performed multiple times, then ultraviolet light can be obtained, but the number of elements increases and costs increase while output stability and beam quality decrease
Solution Approach 1:
The patent combines multiple functions into fewer elements by using a single nonlinear optical crystal that performs both wavelength doubling and wavelength summing operations. The Type-II phase matching crystal simultaneously generates 222nm (second harmonic) and 203nm (sum frequency) wavelengths, eliminating the need for separate conversion stages and reducing overall system complexity
Solution Approach 2:
The nonlinear optical crystal serves multiple functions: it acts as a wavelength converter, a beam combiner, and a spatial filter all in one element. This multi-functionality reduces the number of optical components needed while maintaining high beam quality and output stability
3Productivity
If a fiber laser with silica glass base material is used, then high output and high beam quality are achieved, but the oscillation wavelength becomes near-infrared requiring two wavelength conversions
Solution Approach 1:
The patent changes the base material parameter from silica glass to fluoride glass, which has different transmission properties allowing direct lasing at 445nm. This single parameter change enables wavelength conversion to ultraviolet in just one stage while maintaining high output and beam quality
4Productivity
If the fiber temperature rises due to high output, then output saturation occurs and efficiency decreases, but using metal housing with matched thermal expansion coefficient improves heat radiation
Solution Approach 1:
The patent selects metal materials for the housing and ferrule whose thermal expansion coefficients closely match that of the fluoride fiber. This matching prevents thermal stress and damage during high-power operation while the metal's high thermal conductivity efficiently conducts heat away from the fiber, enabling sustained high output without saturation
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 apparatus achieves miniaturization, high luminance, and extended lifespan with improved efficiency and output stability, outputting ultraviolet light with high beam quality.
Implementation Method 1
an external resonator for wavelength conversion to perform wavelength conversion of a laser light oscillated in the fiber laser medium
Implementation Method 2
a semiconductor laser for excitation, a fiber laser medium to which an excitation laser light enters from the semiconductor laser for excitation
Data Source
AI summary
An ultraviolet laser apparatus includes: a semiconductor laser that emits an excitation laser light; a fiber laser medium to which the excitation laser light enters from the semiconductor laser and that causes laser oscillation; and an external resonator that: converts a wavelength of a laser light oscillated in the fiber laser medium, and outputs an ultraviolet region continuous wave of at least 0.1W.