Optical head employing a concentric-circular focusing grating coupler.

Area of Science:

• Optoelectronics
• Optical Engineering
• Nanofabrication

Background:

• Aberrations in optical systems, particularly those caused by wavelength and effective index deviations, limit performance.
• Efficient light coupling and focusing are critical for integrated optical devices.

Purpose of the Study:

• To propose and characterize a new optical head design utilizing concentric-circular grating couplers.
• To theoretically address and experimentally validate the removal of aberrations in the optical head.
• To demonstrate the fundamental optical functionalities of the proposed device.

Main Methods:

• Theoretical analysis based on optimizing an annular aperture to mitigate aberrations.
• Fabrication of concentric-circular grating coupler (CGC) and concentric-circular focusing grating coupler (CFGC) using electron-beam-writing.
• Experimental validation of light input, waveguiding, output, and convergence characteristics.

Main Results:

• Theoretical aberration removal was achieved through annular aperture optimization.
• The fabricated CGC and CFGC demonstrated fundamental optical functionalities.
• An elliptical focusing spot with half-intensity widths of 1.8µm and 4.0µm was experimentally achieved.

Conclusions:

• The proposed optical head design effectively addresses aberrations.
• The developed grating couplers are suitable for integrated optical applications.
• The device shows promise for high-performance optical coupling and focusing.