Fabrication of vertically curved Si surface optical coupler coupling with 5-μm-mode-field-diameter optical fiber

A vertically curved Si surface optical coupler for high-numerical-aperture optical fibers with 5-μm-mode-field-diameter was fabricated. The dome-like SiO
₂
coupler-top could be successfully formed, and the fabricated coupler showed optical coupling with loss of 5.2 dB and the 0.5-dB bandwidth of 110 nm.