Intra-Cavity UV Laser Structure With SHG and Birefringent Extraction
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Solution Overview
Problem
Current UV lasers lack efficient methods for stable generation and control of ultraviolet light, particularly in diode-pumped solid state media, and effective extraction and polarization control of UV light within the laser cavity.
Innovation Solution
The development employs a diode-pumped solid state laser with intra-cavity second harmonic generation using a birefringent crystal for UV light extraction, combined with optical bonding and volume Bragg gratings to enhance optical efficiency and control the polarization of UV light, while using a combination of nonlinear crystals and waveplates for wavelength selection and locking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If intra-cavity second harmonic generation is used for UV light extraction, then UV light generation efficiency is improved, but device complexity increases due to additional nonlinear crystals and optical components
Solution Approach 1:
The patent combines the second harmonic generation process within the laser cavity itself, merging the frequency conversion function with the laser oscillation system. The nonlinear crystal is integrated into the cavity structure, allowing simultaneous laser operation and UV generation without separate external conversion systems, thus improving efficiency while managing complexity through functional integration.
Solution Approach 2:
The laser cavity is designed to serve multiple functions: generating the fundamental laser wavelength, providing the optical field for second harmonic generation, and enabling UV light extraction. The same optical components (mirrors, cavity structure) serve both the fundamental wavelength operation and the harmonic generation process, reducing the need for additional specialized components.
2Ease of operation
If birefringent crystal is used for UV light extraction, then polarization control is improved, but manufacturing precision requirements increase due to precise crystal orientation needs
Solution Approach 1:
The patent utilizes the birefringent properties of the crystal by carefully selecting and controlling the orientation parameters (crystal cut angle, polarization direction) to achieve the desired UV extraction and polarization control. By optimizing these parameters during the design phase, the system achieves good polarization control while setting realistic manufacturing precision requirements.
Solution Approach 2:
The birefringent crystal acts as an intermediary element that converts the polarized fundamental wavelength light into UV light with controlled polarization. The crystal's birefringence serves as the mechanism to achieve polarization control in the UV output, mediating between the pump laser polarization and the desired UV polarization state.
3Loss of energy
If volume Bragg gratings are used to enhance optical efficiency, then energy utilization is improved, but device complexity increases due to additional optical components
Solution Approach 1:
The volume Bragg grating is pre-configured within the cavity to selectively reflect and enhance specific wavelengths before the laser oscillation fully develops. This preliminary wavelength selection and enhancement action improves optical efficiency by directing energy into the desired modes from the beginning, reducing energy losses that would occur without such pre-conditioning of the optical field.
Solution Approach 2:
The patent replaces traditional mechanical wavelength selection methods (such as rotating etalons or adjustable mirrors) with a fixed volume Bragg grating structure that provides wavelength selection through its inherent photorefractive or holographic properties. This substitution eliminates the need for moving parts while maintaining wavelength control, improving efficiency without proportionally increasing operational complexity.
4Power
If multiple cavity frequencies are supported, then power output is improved, but stability control becomes more difficult due to frequency selection challenges
Solution Approach 1:
The patent employs dynamic frequency selection mechanisms such as tunable etalons, piezoelectrically controlled mirrors, or acousto-optic modulators that can adaptively select and stabilize the desired cavity frequencies. These dynamic elements allow the system to maintain multiple frequency modes for high power output while actively controlling frequency drift and mode hopping to preserve stability and reliability.
Solution Approach 2:
The system incorporates feedback mechanisms where detectors monitor the output frequencies and power levels, and this information feeds back to control elements (such as piezoelectric actuators on cavity mirrors or etalon spacing) to automatically adjust and stabilize the operating frequencies. This closed-loop control enables the system to maintain multiple frequencies for high power while ensuring frequency stability through continuous monitoring and correction.
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 approach results in a stable and efficient generation of UV light with improved optical efficiency and precise control over polarization, enabling reliable operation with multiple cavity frequencies and enhanced power output.
Implementation Method 1
uses an intra-cavity second harmonic generation (SHG) and a birefringent crystal (BC) to extract the UV light
Implementation Method 2
A nonlinear crystal (NLC) 114 that is disposed inside the laser cavity provides second harmonic generation (SHG) and converts the visible light into UV light
Implementation Method 3
The interfaces between the cavity mirrors, the gain media, the nonlinear crystal, and the birefringent crystal may be optically bonded
Data Source
AI summary
Devices, systems, and methods for generating ultraviolet lasers are disclosed. Schematics and arrangements of a combination structure implementation that often uses an intra-cavity second harmonic generation (SHG) element and a UV extractor often with a birefringent crystal (BC) to extract the UV light are described and disclosed. A Nonlinear crystal (NLC) may serve as the SHG element and volume Bragg gating (VBG) may be included to control pump light characteristics.