Laser Surface Treatment for Optical Materials
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Solution Overview
Problem
Existing methods for forming fine periodic structures on optical materials using laser beams face challenges such as high accuracy requirements for beam interference and difficulty in treating large areas, leading to increased reflection loss due to refractive index differences between optical mediums.
Innovation Solution
A laser surface treatment process involving the formation of a metal film on a substrate, followed by its removal using an ultra-intense short-pulse laser beam to create a fine periodic structure, which reduces reflection loss without relying on beam interference, allowing for controlled periodic intervals and reduced laser energy density to prevent thermal damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If two femtosecond-pulse laser beams are interfered to form a periodic microstructure, then a fine periodic structure with minimum average size of 5 to 200 nm can be obtained, but the positional adjustment of the optical system must be performed with high accuracy and large area treatment is difficult
Solution Approach 1:
The patent extracts the metal film formation step as a separate preliminary action before laser irradiation. By forming a metal film on the substrate first, then using ultra-intense short-pulse laser irradiation to remove the metal film and create the periodic structure, the method eliminates the need for complex beam interference alignment while achieving fine periodic structures with controllable pitch.
Solution Approach 2:
The metal film is formed in advance on the substrate before laser irradiation. This preliminary action creates a layer that enhances laser absorption and facilitates the formation of periodic structures during subsequent laser processing, simplifying the overall process and reducing optical system complexity.
2Manufacturing precision
If laser beam interference is used to form periodic structures, then fine periodic structures can be created, but large area treatment becomes difficult
Solution Approach 1:
The patent removes the beam interference mechanism from the process by using direct ultra-intense short-pulse laser irradiation on a metal-coated substrate. This extraction of the interference step eliminates the limitation on treatment area, allowing large area periodic structure formation while maintaining fine precision through controlled laser parameters.
Solution Approach 2:
The patent changes the laser parameters to ultra-intense short-pulse conditions with specific energy density ranges. By controlling laser pulse duration, energy density, and scanning speed, fine periodic structures can be formed across large areas without relying on beam interference, thus resolving the contradiction between precision and treatment area.
3Manufacturing precision
If substrate is treated by laser irradiation in the absence of metal film, then fine periodic structure can be formed, but high laser energy density is required causing thermal damage
Solution Approach 1:
The patent introduces a metal film as an intermediary layer between the laser beam and the substrate. This metal film acts as a mediator that absorbs laser energy and facilitates periodic structure formation at lower energy densities, preventing direct thermal damage to the substrate while enabling precise periodic structure creation.
Solution Approach 2:
The patent changes the laser irradiation parameters by using ultra-intense short-pulse conditions with optimized energy density in the presence of metal film. This parameter optimization allows periodic structure formation at lower effective energy densities compared to direct substrate irradiation, reducing thermal damage while maintaining manufacturing precision.
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 process effectively reduces reflection loss and improves transmission factors by forming fine periodic structures suitable for incident light wavelengths, enabling efficient treatment of large areas with minimal thermal damage and enhanced stability of the periodic structure.
Implementation Method 1
removing said metal film from the substrate by irradiation of an ultra-intense short-pulse laser beam having a pulse width of 1 femtosecond (fs) to 100 picoseconds (ps), so that a fine periodic structure having a periodic interval of 50 to 1000 nm is formed on the surface of the substrate exposed by the removal of the metal film
Implementation Method 2
forming a metal film on a surface of a substrate having optical transparency; and removing said metal film from the substrate by irradiation of an ultra-intense short-pulse laser beam
Data Source
AI summary
A laser surface treatment for reducing reflection loss on the surface of an optical material is provided. A metal film is formed on the surface of the optical material, and then the metal film is removed from the optical material by irradiation of an ultra-intense short-pulse laser beam having a pulse width of 1 femtosecond to 100 picoseconds, so that a fine periodic structure is formed on the surface of the optical material exposed by the removal of the metal film. The obtained fine periodic structure has asperities with a periodic interval of preferably 50 to 1000 nm, which can be controlled by changing the laser energy density.