Laser Mirror Microstructures for Beam Divergence Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High power lasers often exhibit large divergence angles, shallow depth of focus, and high power density loss during long distance transmission due to their multi-mode nature, making them unsuitable for precise industrial and military applications.
Innovation Solution
The design incorporates a total reflective mirror with a spherical body and a metal film coated with microstructures, such as concave ring-shaped or concentric microstructures, within a resonant cavity to produce a laser beam with a small divergence angle and long depth of focus, minimizing power density loss during transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If high power multi-mode lasers are used to achieve high power levels, then power output is improved, but beam divergence angle increases and depth of focus decreases
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of microstructures on the reflective surface. The microstructures are concentrated in the center region rather than being uniformly distributed, which selectively affects the central portion of the laser beam to reduce divergence while maintaining the overall high power output capability of the multi-mode laser system.
Solution Approach 2:
The patent employs spherical microstructures (such as micro-spheres or micro-domes) on the reflective surface to modify the laser beam. These curved microstructural elements help to collimate the diverging beams from different modes, reducing the overall beam divergence angle while preserving the high power output through constructive interference of the reflected modes.
2Power
If high power multi-mode lasers are used to achieve high power levels, then power output is improved, but depth of focus becomes shallow
Solution Approach 1:
By concentrating microstructures in the central region of the reflective surface, the patent selectively modifies the phase and direction of the central beam portions that contribute most to the focused spot. This local modification extends the depth of focus for the high-power central region without requiring uniform modification across the entire beam profile, thus maintaining power output while improving focus characteristics.
Solution Approach 2:
The spherical shape of the microstructures acts as a lens-like element that helps to refocus the diverging laser modes. This curvature effect extends the depth of focus by creating a more gradual convergence of beams, allowing the high power output to be maintained over a longer axial distance while preserving a small spot size at the focus.
3Power
If high power multi-mode lasers are used to achieve high power levels, then power output is improved, but power density loss increases during long distance transmission
Solution Approach 1:
The non-uniform distribution of microstructures optimizes the beam quality for the central high-power region, which carries the majority of the power. By focusing the beam modification efforts on this critical region, the patent reduces divergence and spot size for the main power-carrying portion of the beam, thereby minimizing power density loss during long-distance transmission while maintaining high overall power output.
Solution Approach 2:
The spherical microstructures function as distributed lens elements that collimate and refocus the laser beam during propagation. This reduces beam divergence and maintains a smaller spot size over distance, directly reducing the power density loss that occurs during long-distance transmission while preserving the high power output capability of the multi-mode 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
The solution results in a high-quality laser beam with a long depth of focus and low power density loss, suitable for applications like cutting and welding, especially over long distances.
Implementation Method 1
The microstructures have a width relating to a working wavelength of the laser. In one embodiment, the width is in a range from about 0.5λ to about 2λ
Implementation Method 2
The microstructures are concaved from the reflective surface by a depth relating to a working wavelength of the laser
Data Source
AI summary
A laser includes a total reflective mirror, an output mirror, a discharge lamp, and an active laser medium. The total reflective mirror, the output mirror, and the discharge lamp define a resonant cavity. The active laser medium is filled in the resonant cavity. The total reflective mirror includes a microstructure. The microstructure is concave ring-shaped structure. The concave ring-shaped structure has a depth and a width, and both the depth and the width are in a range from about 0.5λ to about 2λ, while λ is a working wavelength of the laser.