Bragg scattering from a millimeter-scale periodic structure with extremely small aspect ratios.

Area of Science:

• Optics and Photonics
• Surface Science
• Diffraction Physics

Background:

• Periodic structures on optical surfaces influence beam characteristics.
• Quantitative analysis is crucial as eliminating microscopic structures is challenging.
• Large and complex optical elements exacerbate these effects.

Purpose of the Study:

• To experimentally investigate Bragg scattering from optical surfaces with micro-scale periodic structures.
• To quantify the impact of periodic surface structures on beam propagation and interference patterns.
• To establish a method for analyzing the effects of periodic structures via interference observation.

Main Methods:

• Experimental investigation of Bragg scattering.
• Utilizing optical surfaces with small aspect ratios (~10^-5) and low groove densities (0.5 lines/mm).
• Observing constructive interference patterns of 0th, 1st, and -1st order beam modes.

Main Results:

• Observed clear periodic constructive interference patterns.
• Demonstrated an intensity increase of >10 times for constructive interference compared to a flat surface.
• Correlated modulation depth (± 50 nm) with significant intensity enhancement.

Conclusions:

• Bragg scattering provides a viable method for analyzing periodic surface structures.
• The observed interference patterns allow for quantification of structural effects on beam propagation.
• This research opens new avenues for understanding and controlling optical surface impacts.