Non-diffracting beam generated from a photonic integrated circuit based axicon-like lens.

Area of Science:

• Photonics and Optical Engineering
• Nanofabrication
• Integrated Optics

Background:

• Non-diffracting beams offer extended propagation distances, crucial for optical manipulation and sensing.
• Generating these beams on-chip requires advanced fabrication techniques for precise optical element design.

Purpose of the Study:

• To demonstrate an on-chip silicon-on-insulator (SOI) device for generating non-diffracting beams.
• To improve the penetration depth of diffractive axicon-like lenses using grating apodization.

Main Methods:

• Fabrication of a diffractive axicon-like lens using deep-ultraviolet lithography (200 nm feature size).
• Implementation of a seven-stage multimode interferometer with azimuthally apodized circular gratings.
• Characterization using a swept source laser (1300±50 nm) and balanced homodyne detection.

Main Results:

• Generation of a non-diffracting beam with an approximate length of 850 µm.
• Apodization technique increased grating penetration depth from ≈5 µm to ≈60 µm.
• Output lobe position showed minimal spectral dependence.

Conclusions:

• The developed SOI device successfully generates non-diffracting beams with enhanced penetration depth.
• Azimuthal apodization is an effective method for improving grating performance in integrated photonic devices.
• The device shows wavelength stability, suitable for various photonic applications.