Curved laser microjet in near field

Area of Science:

• Optics and Photonics
• Nanotechnology
• Materials Science

Background:

• Diffraction phenomena are crucial for understanding light manipulation.
• Near-field optical microscopy enables sub-wavelength optical investigations.
• Controlling laser beam properties is essential for advanced applications.

Purpose of the Study:

• To investigate the generation of a laser jet from light diffraction by a glass corner step.
• To characterize the properties of the generated laser jet, including its shape, divergence, and intensity.
• To compare simulation results with experimental measurements.

Main Methods:

• Finite-difference time-domain (FDTD) based simulation.
• Scanning near-field optical microscopy (SNOM) with a metal cantilever tip.
• Optical characterization of a linearly polarized plane wave diffracted by a glass corner step of height 2λ.

Main Results:

• A low-divergence laser jet with a root-parabolic form was generated.
• The beam path shifted by 2.1λ on the optical axis over a distance of 4.7λ.
• The laser jet exhibited a Full Width at Half Maximum (FWHM) diameter of 1.94λ over 5.5λ and a depth of focus of 9.5λ.
• The intensity maximum was 5 times higher than the incident wave intensity.
• Discrepancy between analytical and experimental results was 11%.

Conclusions:

• The diffraction of light by a specifically designed glass corner step can generate a unique root-parabolic laser jet.
• The experimental and simulation results validate the generation and characteristics of this novel optical beam.
• This study demonstrates a method for creating controlled, high-intensity, low-divergence light beams with potential applications in nanophotonics.