Abstract
In this work, we present metalenses (MLs) designed to enhance the luminous intensity of incoherent light-emitting diodes (LEDs) within the detection angles of 0° and 10°. The detection angle of 0° refers to the center of the LED. Because the light emitted from LEDs is incoherent and expressed as a surface light source, they are numerically described as a set of point sources and calculated using incoherent summation. The titanium dioxide (TiO2) and amorphous silicon (a-Si) nanohole meta-atoms are designed; however, the full 2π phase coverage is not reached. Nevertheless, because the phase modulation at the edge of the ML is important, an ML is successfully designed. The typical phase profile of the ML enhances the luminous intensity at the center, and the phase profile is modified to increase the luminous intensity in the target detection angle region. Far field simulations are conducted to calculate the luminous intensity after 25 m of propagation. We demonstrate an enhancement of the luminous intensity at the center by 8551% and 2115% using TiO2 and a-Si MLs, respectively. Meanwhile, the TiO2 and a-Si MLs with the modified phase profiles enhance the luminous intensity within the detection angle of 10° by 263% and 30%, respectively.
Highlights
Optical metasurfaces are made up of precisely designed structures, known as meta-atoms, that can modulate the phase [1,2], amplitude [3,4,5], and polarization [6,7] of incident light
We consider the Light-emitting diodes (LEDs) source composed of 3 × 3 micro-LED chips, and the light source is described by 3 × 3 points sources
Because the light emitted from the LED is partially spatial-coherent, the phase of light originating from each point source is random and interference effects are ignored
Summary
Optical metasurfaces are made up of precisely designed structures, known as meta-atoms, that can modulate the phase [1,2], amplitude [3,4,5], and polarization [6,7] of incident light. The intensity of light extraction efficiency of LEDs has been enhanced using microlens arrays [65,66,67], surface roughening [68,69,70,71], Nanomaterials 2022, 12, 153. Metasurfaces including MLs are difficult to use for LED sources, as the emitted light is incoherent [79,80]. The ML enhances the luminous intensity within the detection angles of 0◦ (center of the LED) and 10◦ by collimating the diverging light emitted from the LED. The phase profile of the ML is modified to spread out the transmitted light to the target detection angle
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