High-NA Chromatic-aberration-corrected Diffractive Lens for Broadband Focusing

Replacing bulky refractive lenses, a planar high-NA diffractive-lens is demonstrated to achieve apochromatic broadband focusing. For three-wavelength illumination (450nm, 538nm and 610nm), an average focusing efficiency of 66.6% is achieved with far-field-diffraction limited focal spots.