Scaling effect and its impact on wavelength-scale microlenses

We revisit the scaling laws in micro-optical systems to highlight new phenomena arising beyond a conventional optical regime, especially when the size of the system approaches to the operational wavelength. Our goal is to visualize the impact of the scaling effect in the micrometer-sized domain. First, we will show where the conventional optical regime fades away and unexpected responses arise. We will show this by using a ball-lens as an example. Second, we discuss the scaling effect in the Fresnel number of lens systems. Moving toward wavelength-scale microlenses, a specific value of Fresnel numbers leads to a giant focal shift with strong focal power. Our study will give comprehensive insights into the birth of unanticipated phenomena in miniaturized optical systems.