Plasma Optical Shutter for Precise Laser Pulse Width Control
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Solution Overview
Problem
Conventional picosecond or femtosecond lasers have fixed pulse widths and wavelengths, limiting their application and being costly, with existing control methods unable to achieve the required fast shutter speeds for precise pulse width adjustment, especially for ultra-precision machining and measurement where minimal thermal energy generation is crucial.
Innovation Solution
A device and method using plasma-induced shuttering, where a laser beam is split into target and shutter pulses, with adjustable plasma forming units to intersect and focus the shutter pulse, allowing for precise control of pulse width through inverse-Bremsstrahlung photon absorption, enabling fast response speed without electrical signal delays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If conventional nanosecond laser is used, then device cost is low and device complexity is simple, but pulse width cannot be adjusted to picosecond or femtosecond range and shutter speed is limited by electrical signal delay
Solution Approach 1:
The patent replaces the conventional electrical signal-based mechanical shutter system with a plasma-based optical shutter. The plasma is generated by focusing a pump laser beam onto a target material, creating a plasma plume that optically absorbs the probe laser beam. This substitution eliminates the need for fast electrical shutters and enables picosecond or femtosecond-level pulse width control without the limitations of electrical signal propagation delays.
Solution Approach 2:
The patent utilizes changes in plasma density and optical absorption characteristics as control parameters. By adjusting the pump laser energy, focal position, and target material properties, the plasma density can be controlled to achieve variable optical absorption. This allows dynamic adjustment of the effective pulse width by controlling when and how the plasma forms to absorb the probe beam, enabling precise temporal control without mechanical moving parts.
2Manufacturing precision
If picosecond or femtosecond laser is used for ultra-precision ablation machining, then manufacturing precision is improved and thermal impact is reduced, but device cost increases significantly and application flexibility is limited due to fixed wavelength
Solution Approach 1:
The patent introduces a plasma plume as an intermediary medium between the pump laser and the workpiece. The plasma absorbs specific wavelengths of the probe laser through inverse Bremsstrahlung absorption, effectively filtering and shaping the laser spectrum. This allows a broadband or multi-wavelength laser source to be used while achieving the precise temporal characteristics of picosecond or femtosecond pulses, thereby maintaining manufacturing precision while improving wavelength flexibility.
3Speed
If mechanical shutter or optical element is used to control laser characteristics, then ease of operation is improved, but response time is limited to nanosecond unit and cannot achieve picosecond or femtosecond shutter speed
Solution Approach 1:
The patent replaces mechanical shutters and electro-optic modulators with a plasma-based optical shutter. The plasma formation and absorption process occurs on picosecond or femtosecond timescales, naturally providing the required shutter speed without mechanical inertia or electrical signal limitations. The system maintains ease of operation by controlling plasma formation through laser parameters that are already standard in laser systems.
4Device complexity
If laser pulse width is extended to nanosecond range, then device cost is reduced and device complexity is simplified, but thermal energy generation increases causing material deterioration
Solution Approach 1:
The patent uses the pump laser to create the plasma plume in advance before the probe laser arrives. By precisely controlling the timing and formation of the plasma through the pump laser, the system prepares the absorption medium beforehand. When the probe laser passes through the formed plasma, the inverse Bremsstrahlung absorption occurs, effectively shortening the pulse duration and reducing thermal energy deposition on the material, thus preventing material deterioration while using a simpler nanosecond-class laser system.
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 allows for precise and active control of high-energy single-wavelength laser pulse widths, reducing thermal impact on materials and enhancing the value of conventional laser devices by enabling picosecond or femtosecond pulse generation in nanosecond devices, thus improving precision and minimizing material deterioration.
Implementation Method 1
capable of forming the plasma induced from the shutter pulse to adjust the pulse width of the target pulse by the target pulse activating the inverse-Bremsstrahlung photon absorption propagation-induced within the plasma therein
Implementation Method 2
a focusing unit disposed on the path of the shutter pulse, and for focusing the shutter pulse so that the plasma induced from the shutter pulse is formed within the plasma forming unit
Implementation Method 3
when the laser pulse is focused, laser-induced plasma can be generated when the power density at the focal point exceeds a threshold
Data Source
AI summary
The present disclosure relates to a device and a method for adjusting a pulse width of a laser beam by using the plasma generated by being induced from laser as a shutter, and more particularly, to a device and a method for adjusting a laser pulse width, which can precisely and quickly adjust the laser pulse width by dividing the laser generated from a laser light source into a target pulse and a shutter pulse; converting the optical path of the divided laser; and chopping the target pulse by using the plasma induced from the shutter pulse as an optical shutter in a cell having adjustable internal pressure.