Diode Laser Beam Quality Stabilization via Segmented Current Control
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Solution Overview
Problem
Current high power diode lasers used for pumping Ti:sapphire lasers suffer from low beam quality and high cost, complexity, and inefficiency due to their broad area design and the need for precise alignment, which limits the applications of Ti:sapphire lasers.
Innovation Solution
A method and apparatus that control the beam quality and stability of diode lasers by independently adjusting the current and temperature of separate sections, optimizing the power content of the dominant lobe of the radiation to improve beam quality and conversion efficiency through iterative monitoring and adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power broad area diode lasers are used for pumping, then output power is sufficient, but beam quality deteriorates
Solution Approach 1:
The diode laser is divided into multiple independent sections (first section, second section, etc.), each with separate current injection. This segmentation allows independent optimization of each section's contribution to the beam profile while maintaining high total power output, resolving the contradiction between power and beam quality.
Solution Approach 2:
Different sections of the diode laser are controlled with different current levels to optimize local beam characteristics. By adjusting the current distribution across sections, the patent achieves superior overall beam quality while maintaining high total power, as each section contributes optimally to the final beam profile.
2Shape
If frequency doubled DPSS lasers are used as pump sources, then beam quality is good, but device complexity and cost increase
Solution Approach 1:
The patent extracts and eliminates the complex frequency doubling cavity and alignment-sensitive optics from the pump source design. By using directly diode-generated frequencies with proper beam shaping through segmented current control, the system achieves good beam quality without the complexity of DPSS frequency doubling systems.
Solution Approach 2:
The patent replaces expensive, complex DPSS laser systems with simpler, more cost-effective diode laser sections that can be independently controlled. This substitution reduces system complexity and cost while maintaining or improving beam quality through electronic control of multiple sections.
3Productivity
If precise alignment is required for pump sources, then pumping efficiency is maximized, but ease of operation decreases
Solution Approach 1:
The patent introduces dynamic electronic control of multiple diode sections with independent current adjustment. This allows real-time optimization of beam properties and pumping efficiency without mechanical alignment adjustments, making the system easier to operate while maintaining high efficiency through electronic rather than mechanical control.
4Loss of energy
If high power diode lasers are used, then conversion efficiency should be high, but beam quality reduces leading to lower overlap with cavity beam
Solution Approach 1:
By segmenting the diode laser into multiple independently controlled sections, the patent optimizes the beam profile to achieve better overlap with the cavity beam mode. This segmentation allows the high power output to be delivered with improved spatial distribution, increasing conversion efficiency while maintaining the advantages of high power diode operation.
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 high stability and improved beam quality of the frequency-converted radiation, reducing noise and increasing efficiency, making the diode laser system more suitable for various applications, including ultrafast laser systems and medical diagnostics.
Implementation Method 1
a frequency conversion unit configured to frequency-convert the first radiation from the diode laser and to output the frequency-converted radiation, the frequency-converted radiation having at least a second wavelength different from the first wavelength
Data Source
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Figure 3
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AI summary
A method of controlling beam quality and stability of a laser apparatus, the laser apparatus comprising, a diode laser (10) providing first radiation of at least a first wavelength, and a frequency conversion unit (12) configured to frequency-convert the first radiation from the diode laser and to output the frequency-converted radiation (213), the frequency-converted radiation having at least a second wavelength different from the first wavelength, the diode laser (10) comprising at least a first and a second section (222,223), a first contact (220) for injecting a first current (I1) into the first section (222), a second contact (221) for injecting a second current (I2) into the second section (223), and means for controlling a temperature of the diode laser; wherein the method comprises monitoring a first parameter indicative of the power content of a dominant lobe of the first radiation; iteratively determining a combination of respective values of the first current, the second current and the temperature at which combination of respective values the monitored first parameter and a stability parameter indicative of a fluctuation over time of the monitored first parameter each fulfils a respective predetermined optimization criterion; and setting the first current, the second current, and the temperature to the determined combination of respective values.