The design, microfabrication, and testing of a hybrid microdiffractive–microrefractive lens with a continuous relief that is used with a laser diode for monomode fiber coupling is discussed. The hybrid microlens with a diameter as small as 65 μm and a numerical aperture of 0.25 is fabricated directly onto a spherical surface by use of focused-ion-beam milling technology. A focused Ga<sup>+</sup> ion beam is used to mill the continuous relief microstructure at an acceleration voltage of 50 kV. From the test results a coupling efficiency of 71% (−1.49 dB) was achieved at room temperature. A diffraction efficiency of the main diffractive order, −1, was measured to as high as 90.5% at a wavelength of 635 nm. This indicates that the hybrid microlens was suitably designed within the application requirements and satisfactorily manufactured with focused-ion-beam milling.
© 2001 Optical Society of America
(050.1970) Diffraction and gratings : Diffractive optics
(060.2340) Fiber optics and optical communications : Fiber optics components
(220.0220) Optical design and fabrication : Optical design and fabrication
Yong-qi Fu and Ngoi Kok Ann Bryan, "Hybrid Microdiffractive-Microrefractive Lens with a Continuous Relief Fabricated by Use of Focused-Ion-Beam Milling for Single-Mode Fiber Coupling," Appl. Opt. 40, 5872-5876 (2001)