Electromagnetic field calculations for microlens optical systems

Microlenses are becoming more widely used in modern optical equipment. When the microlens diameter is comparable with the incident electromagnetic illumination wavelength, diffraction effects through the microlens aperture dominate and significantly affect the microlens optical properties leading to differences from that predicted by ordinary geometrical optics theory. In this work, the continuous-profile symmetrical biconvex microlens is selected for investigation. Its optical properties, with both monochromatic plane wave and TEM00 mode Gaussian beam illumination, are studied using the full-field Separation-of-Variables method (SVM) in the oblate spheroidal coordinate system by calculating the electromagnetic field distributions inside of and adjacent to the microlens. The microlens optical properties are also compared with the corresponding geometrical optics theory.;The investigations and discussions include the focusing properties of a single microlens with monochromatic plane wave illumination, the beam transformation properties of a single microlens with monochromatic TEM00 mode Gaussian beam illumination, the axial combination properties of dual microlenses with monochromatic plane wave and TEM00 mode Gaussian beam illumination, the interference properties between dual parallel-arranged microlenses with monochromatic plane wave illumination, and the imaging properties of a single microlens with monochromatic plane wave and TEM00 mode Gaussian beam illumination. The optical properties of microlens optical systems are found to be similar to that given by the geometrical optics theory. The microlens actual focal length is measured for different profile and diameter microlenses and is compared with its corresponding geometrical focal length. It is shown that the microlens actual focal length is an important parameter and can be used to describe and approximately formulate the microlens optical properties. The transmitted beam waist position through a microlens calculated using the Rayleigh Range method (RRM) with the microlens actual focal length closely matches the exact value determined using the Separation-of-Variables method in the oblate spheroidal coordinate system. The axial combination properties of dual microlenses with monochromatic plane wave illumination and the imaging properties of a single microlens can also be described using the geometrical imaging formula with the microlens actual focal length.