Use of Multi-focus laser sculpting for microstructured glass

 

Multi-focus laser sculpting is a technique used to shape materials using a laser beam. Instead of focusing on just one point, the laser is split into multiple focal points, so it can focus on several areas at the same time, making the process faster and more efficient.

Here, the Gaussian beam is manipulated using optical components Fresnel lenses and blaze gratings to create multiple laser spots.

For a Gaussian beam, the intensity is highest at the center (the beam's axis) and decreases as you move away from the center.

Gratings are made up of a microscopic, repeating structure of grooves. When light hits the grating, the structure causes the light to split into multiple beams that travel in different directions. 

A blaze grating is a type of diffraction grating that is designed to direct most of the light energy into a specific diffraction order, It enhances the brightness of wavelength or direction. 

Fresnel lenses consist of a series of concentric grooves.

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The equation for calculating the laser spot position, considering the refractive index of the glass, is given by:

zj is the target coordinate.

Equation for Correction of Blaze Grating and Fresnel Lens Deviations

where m is x or y denoting sectional displacement, zj is the z-direction displacement, the λ is the wavelength fOB is the focal length of objective, and pj is the period of blaze grating.

 f0 is the focal length of Fresnel lens for light modulation.

Low surface roughness is important for great application performance, which can be achieved by improving laser spot intensity uniformity and especially decreasing the point-to-point distance.

The energy at each laser point is adjusted by modifying the transmission function of the light as follows:

T is the transmission function for the light modulation( Light modulation is the process of controlling the intensity of light, or changing its wave features, such as its frequency, polarization, phase, or intensity)

A is the amplitude constant, j is the point number, ϕ is the phase forming the phase diagram for light modulation, Ij is normalized energy adjustment coefficient for each point,

px,j and py,j are the blaze grating period .Multi focus laser is used for precisely shaping glass microstructures and in fiber packaging devices.

Reference

https://www.oejournal.org//article/doi/10.29026/oea.2025.240082

https://en.wikipedia.org/wiki/Blazed_grating