Light Absorption Filter for Stabilizing Second Harmonic Laser Output
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Solution Overview
Problem
Laser systems that generate second harmonic waves face instability due to high Pulse to Pulse (PTP) values, leading to significant variations in output energy when a fundamental wave with high PTP is incident on non-linear crystals, resulting in unstable second harmonic wave output.
Innovation Solution
An apparatus is designed with a light absorption filter placed behind non-linear crystals, allowing for selective placement on the laser path using moving means, which absorbs energy to stabilize the second harmonic wave output and enable user selection of high or low energy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a fundamental wave with high PTP value is incident on non-linear crystals to generate second harmonic wave, then the output energy of second harmonic wave is increased, but the PTP value of second harmonic wave becomes very high causing unstable output energy
Solution Approach 1:
A light absorption filter is introduced as an intermediary component between the non-linear crystal and the output. This filter selectively absorbs a portion of the second harmonic wave energy, acting as a mediator that reduces the PTP value while maintaining stable output. The filter serves as a buffer that smooths out energy fluctuations from the fundamental wave conversion process.
Solution Approach 2:
The invention changes the energy parameter of the second harmonic wave by using a light absorption filter with specific absorption characteristics. By selecting appropriate filter materials and thicknesses, the system transforms the high PTP value output into a low PTP value output, effectively controlling the output energy stability through parameter adjustment of the filter component.
2Reliability
If a light absorption filter is placed in the laser path to reduce second harmonic wave energy, then the PTP value is reduced and output stability is improved, but the output energy level is reduced
Solution Approach 1:
The light absorption filter is designed to be movable rather than fixed, allowing dynamic adjustment of its position in the laser path. This enables the system to switch between different operational states: when the filter is in the path, it reduces energy and PTP value for stable low-energy output; when removed, full energy output is achieved. This dynamic configuration resolves the contradiction by allowing user selection based on application needs.
Solution Approach 2:
The system achieves multi-functionality by incorporating a movable filter mechanism that allows the same laser system to operate in multiple modes: high-energy mode (filter removed) and stable low-energy mode (filter in path). This universal design enables the system to adapt to different application requirements, making it versatile for both high output energy scenarios and stable low PTP value scenarios.
3Reliability
If the fundamental wave energy is increased to achieve stable second harmonic wave output, then the PTP value of fundamental wave is reduced, but the system complexity increases due to need for energy adjustment mechanisms
Solution Approach 1:
Instead of modifying the fundamental wave generation system to adjust energy levels, the invention extracts the energy adjustment function to a separate component - the light absorption filter. This separates the frequency conversion function (non-linear crystal) from the energy control function (absorption filter), simplifying the overall system architecture while achieving the desired stability.
Solution Approach 2:
The light absorption filter serves as an intermediary that handles energy adjustment without requiring modifications to the fundamental wave laser system. By placing this passive optical component in the second harmonic wave path, the system achieves energy control and PTP reduction without adding complex active control mechanisms to the laser oscillator itself.
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 a low PTP value for the second harmonic wave, providing stable energy levels by adjusting the fundamental wave energy before conversion, allowing for flexible output energy selection.
Implementation Method 1
the wavelength of a laser pulse outputted from the common pulse laser oscillator (not shown) are converted into half the wavelength through non-linear crystals, such as KTP (KTiOPO4), LBO (LiB3O5), or BBO (BaB2O4). In the example shown in FIG. 1, a wavelength of 1064 nm is converted into a wavelength of 532 nm, which is called frequency doubling or generation of harmonic wave.
Implementation Method 2
a light absorption filter for outputting a second harmonic wave of a lower energy by absorbing some of the energy of the laser pulse having the second harmonic wave which has been converted by the non-linear crystals
Data Source
AI summary
The present invention relates to an apparatus for stabilizing second harmonic wave pulse output in a laser system operating by pulses. The apparatus of the present invention comprises: a pulse laser oscillating unit (110) which outputs a laser pulse; a nonlinear crystal (120) which converts the laser pulse of a first wavelength output by the pulse laser oscillation unit (110) into a second harmonic wave with a value that is half of the first wavelength, and outputs the converted second harmonic wave; and an optical absorption filter (130) which absorbs a portion of the energy of the converted second harmonic laser pulse from the nonlinear crystal (120) to output the second harmonic wave with a lower energy. The thus-configured apparatus of the present invention supplies a fundamental wave in a stable state and having a small PTP value and high level energy to the nonlinear crystal, in order to obtain the second harmonic wave which is in a more stable state and has a small PTP value and a variety of energies.