Laser Diode Pump Module Switching for Wavelength Stability
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Solution Overview
Problem
High power laser systems face inefficiencies in power mode switching due to wavelength fluctuations of pump energy, leading to reduced lasing energy conversion efficiency and potential damage from unabsorbed pump energy, especially when rapidly switching between power modes.
Innovation Solution
A pump module with a controller and light combining optics that switches laser diodes between activated and deactivated states to maintain pump energy within a specific wavelength range (874-881 nm) across multiple power levels, ensuring efficient absorption by the gain medium.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If pump current is varied to rapidly switch between different power output modes, then power mode switching speed is improved, but pump energy wavelength strays outside the operating band of the gain medium causing reduced conversion efficiency
Solution Approach 1:
The pump module is divided into multiple independent laser diodes that can be individually controlled. Instead of varying the current to a single pump source, the system segments the pump source into multiple diodes where each can be independently activated or deactivated. This segmentation allows rapid power mode switching by simply turning individual diodes on/off without changing the operating current of active diodes, thereby maintaining wavelength stability and conversion efficiency.
Solution Approach 2:
The system dynamically reconfigures which laser diodes are active based on the desired power output mode. The controller dynamically switches between different combinations of laser diodes to achieve different power levels, rather than dynamically adjusting the current level. This dynamic reconfiguration of active components enables fast switching while maintaining each diode at its optimal operating wavelength.
2Power
If pump current is increased to achieve high power output, then power output level is improved, but thermal fracture occurs in the gain medium due to rapid absorption of pump energy
Solution Approach 1:
The pump energy delivery is segmented across multiple laser diodes and their corresponding optical paths. By distributing the pump energy input across multiple spatial locations within the gain medium (each diode pumping a different region), the localized thermal load on any single point of the gain medium is reduced. This spatial segmentation of pump energy input prevents the rapid energy absorption in a small volume that causes thermal fracture, while still achieving high overall power output.
Solution Approach 2:
Different regions of the gain medium are pumped by different laser diodes, creating local quality variations in the pump energy distribution. Each laser diode operates at its optimal current level, providing localized pump energy at the appropriate intensity. This local optimization ensures that no single region of the gain medium experiences excessive energy density that would cause thermal damage, while the cumulative effect of all diodes achieves the desired high power output.
3Ease of manufacture
If side-pumping is used to pump the gain medium, then pump energy delivery is simplified, but conversion of pump energy into laser output is low at relatively high pump energies
Solution Approach 1:
The system merges the advantages of both side-pumping and end-pumping configurations. Multiple laser diodes are arranged to deliver pump energy to the gain medium through a combination of lateral (side) and longitudinal (end) paths. This merged approach maintains the structural simplicity of side-pumping while achieving the high conversion efficiency of end-pumping, as the pump energy is delivered efficiently to the gain medium from multiple directions simultaneously.
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
Enables rapid and efficient switching between power modes while maintaining high pump energy to lasing light conversion efficiency, preventing damage from unabsorbed energy and ensuring stable operation across a wide range of power levels.
Implementation Method 1
The laser diodes receive current from the power source and output light when in the activated state
Implementation Method 2
The light combining optics are configured to combine the light from the activated laser diodes and output the combined light as pump energy
Implementation Method 3
The gain medium absorbs the pump energy and emits laser light responsive to the absorbed energy
Implementation Method 4
The laser resonator operates to generate a harmonic of the laser light
Data Source
AI summary
In a method, a laser pump module is set to a first power mode and pump energy is output at a first power level through the activation of a first subset of laser diodes. Laser light is emitted from a gain medium at the first power level in response to absorption of the pump energy. An operator input corresponding to a power mode setting is received. The laser pump module is switched to a second power mode and pump energy is output at a second power level through the activation of a second subset of the laser diodes. Laser light is emitted from the gain medium at the second power level in response to absorption of the pump energy.