Abstract

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⁺ 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

Diffractive optical elements with continuous relief fabricated by focused ion beam for monomode fiber coupling

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