Graded-index Fresnel lenses for integrated optics

Area of Science:

• Optics and Photonics
• Materials Science
• Waveguide Technology

Background:

• Fresnel lenses are essential diffractive optical elements.
• Waveguide integration offers miniaturization and enhanced functionality.
• Graded-index (GRIN) profiles enable sophisticated phase modulation.

Purpose of the Study:

• To demonstrate Fresnel waveguide lenses with a graded-index (GRIN) distribution.
• To investigate the focusing characteristics and efficiency of GRIN Fresnel waveguide lenses.
• To present the fabrication process and experimental results for these novel lenses.

Main Methods:

• Fabrication of GRIN Fresnel lenses in amorphous As(2)S(3) film waveguides.
• Utilizing electron-beam direct writing on a silicon substrate.
• Experimental characterization of focusing performance and optical efficiency.

Main Results:

• Demonstrated GRIN Fresnel lenses with segmented quadratic phase modulation.
• Achieved nearly diffraction-limited focusing characteristics.
• Obtained a high optical efficiency of 48%.

Conclusions:

• GRIN Fresnel waveguide lenses exhibit excellent focusing and high efficiency, limited only by diffraction.
• The electron-beam direct writing technique is suitable for fabricating these advanced optical components.
• These findings represent a significant step towards integrated photonic devices with superior optical performance.