Waveguide Laser Multi-Wavelength Conversion via Segmented QPM
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Solution Overview
Problem
Existing wavelength conversion lasers face a challenge in achieving both a wide fundamental wave conversion wavelength band and high conversion efficiency simultaneously, as the conversion efficiency is lower when the polarization inversion period pitch is gradually varied.
Innovation Solution
A waveguide laser is designed with a wavelength selecting element that selectively reflects laser beams of different oscillation modes, and a wavelength conversion element that converts these beams to harmonics using a quasi phase matching structure with a fixed or varying polarization inversion period, ensuring high efficiency across multiple wavelengths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the polarization inversion period pitch is gradually varied to achieve a wide fundamental wave conversion wavelength band, then the wavelength conversion bandwidth is improved, but the conversion efficiency deteriorates
Solution Approach 1:
The wavelength conversion element is divided into multiple sections, each with a different fixed polarization inversion period pitch. Each section is optimized for specific wavelength bands, allowing high conversion efficiency at multiple discrete wavelengths without the efficiency loss associated with gradual pitch variation.
Solution Approach 2:
Different sections of the wavelength conversion element have different polarization inversion period pitches tailored to specific wavelength ranges. This local optimization ensures that each section operates at high efficiency for its designated wavelengths while collectively covering a broad spectrum.
2Loss of energy
If a fixed polarization inversion period is used to maintain high conversion efficiency, then the conversion efficiency is improved, but the wavelength conversion bandwidth is limited
Solution Approach 1:
The wavelength conversion element is designed with multiple polarization inversion regions, each optimized for different wavelength bands. This multi-functional design allows a single device to efficiently convert multiple wavelength bands simultaneously, achieving both high efficiency and broad bandwidth coverage.
Solution Approach 2:
The wavelength conversion element combines multiple nonlinear optical material regions with different polarization inversion period pitches. This composite structure enables the device to handle multiple wavelength bands with high conversion efficiency, effectively combining the advantages of fixed-period high efficiency with broad bandwidth coverage.
3Adaptability or versatility
If multiple laser oscillation modes are converted simultaneously, then the versatility of the laser device is improved, but the phase matching control becomes more complex
Solution Approach 1:
The wavelength conversion element is segmented into multiple sections, each optimized for specific laser oscillation modes and wavelength bands. This segmentation simplifies phase matching control by allowing independent optimization of each section for its target modes, avoiding the complexity of controlling a single continuously varying pitch for all modes.
Solution Approach 2:
The polarization inversion period pitch is discretely changed across different sections rather than continuously varied. This parameter discretization simplifies the control and design process for multi-mode conversion, as each section can be independently designed and optimized for specific modes without complex inter-sectional coordination.
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 allows for high-efficiency wavelength conversion at multiple wavelengths using a material with a wide gain band, optimizing the conversion efficiency by maintaining the polarization inversion periods within the phase matching band for each laser oscillation mode.
Implementation Method 1
converts the fundamental wave laser beams to the second harmonics with half the wavelengths (double frequency) using a nonlinear material (SHG: Second Harmonic Generation)
Implementation Method 2
a wavelength selecting element that selectively reflects laser beams with wavelengths λ = λ 0 , λ 1 , λ 2 , ..., λ n (n ≥ 1) of different laser oscillation modes from among fundamental oscillation wavelengths
Implementation Method 3
a quasi phase matching (QPM) wavelength conversion element using a periodic structure is known, for example. The QPM wavelength conversion element has an optical waveguide formed in a periodically poled lithium niobate (PPLN) which is a nonlinear optical crystal, and inverts its polarization periodically along the waveguide direction
Data Source
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AI summary
A laser includes a wavelength selecting element 14 that selectively reflects laser beams with wavelengths λ = λ0, λ1, λ2, ..., λn (n ≥ 2) of different laser oscillation modes from among fundamental oscillation wavelengths of laser beams passing through a wavelength conversion element 13, and the wavelength conversion element 13 that converts the laser beams with the wavelengths λ = λ0, λ1, λ2, ..., λn (n ≥ 2) of different laser oscillation modes reflected by the wavelength selecting element 14 to harmonics. When using a material with a wide gain band as a laser medium 121 of a solid-state laser element 12, a waveguide laser is implemented capable of carrying out high-efficiency wavelength conversion at a plurality of wavelengths within the gain band.