Wavelength-Dependent Varifocal Flat Lens

Varifocal lenses play an important role in zoom imaging system to make them more miniaturized and integrated. Varifocal lenses in existence, however, need drives or polarized light, which limits their integration into smaller imaging systems. Here, a wavelength-dependent varifocal flat lens (multi-level diffractive lens, MDL) with thickness of
$5~\mu \text{m}$
is proposed, which has characteristics of no drive and polarization independent. We demonstrate the proposed MDL achieves magnification imaging of
$\sim 2.3\times $
via changing wavelengths of incident light. Moreover, by combining the MDL with a microscope objective (
$10\times $
), we experimentally demonstrate the composite system achieves magnification imaging of
$\sim 10.4\times $
and
$\sim 24.2\times $
just via tunning wavelengths of incident light without lenses moving, which means this zoom approach based on the wavelength-dependent varifocal MDL has great potential in single wavelength integrated zoom imaging systems.