[OPTICAL REVIEW Vol. 6, No. 2 (1999) 124-130]
A New Approach to the Design of Hybrid Lenses for Integrated Optics
Michele A. FORASTIERE and Giancarlo C. RIGHINI*
Optoelectronic Technologies Group, Istituto di Ricerca sulle Onde Elettromagnetiche “Nello Carrara” (IROE-CNR) Via Panciatichi 64-50127 Firenze, Italy
(Received November 16, 1998; Accepted January 4, 1999)
The Fresnel lens is one of the most extensively studied components in both classical and integrated optics. This structure is free from axial spherical aberration, but is heavily affected by both off-axis and chromatic aberrations. The latter can be compensated by introducing a refractive component, whose chromatic behavior is the opposite of that of the diffractive lens. This hybrid refractive-diffractive structure, however, is not able to deal effectively with off-axis aberrations, namely, with coma. In this work, a novel methodology for the design of corrected hybrid lenses is proposed which allows for correction of both chromatism and coma. The design method is based on a ray-optics variational approach which provides a range of possible achromatic solutions. An optimization procedure is performed by means of a series of beam propagation method numerical calculations which make it possible to simulate the lens operation and thus to find the best solution.
Key words : Integrated optics, diffractive structures, hybrid lens, optical design, numerical modeling, BPM, achromatism, aberration correction