The paper presents a novel approach to designing subwavelength-thick, polarization-insensitive micro-lenses with high numerical apertures and large focusing efficiency. These lenses, based on high contrast transmitarrays (HCTAs), can achieve focal spots as small as 0.57 wavelengths and focusing efficiencies up to 82%. The HCTAs, composed of silicon nano-posts on glass, enable control of optical phase fronts with subwavelength spatial resolution. The design method and trade-offs between efficiency and spot size are discussed. The fabrication process, using high-throughput photo or nanoimprint lithography, makes these lenses suitable for widespread adoption. The authors demonstrate the versatility of HCTAs by designing and fabricating high numerical aperture micro-lenses with exotic phase profiles, optimized for specific tasks such as microscopy and high-density data recording. The measured performance of the micro-lenses agrees well with simulations, confirming the effectiveness of the design technique.The paper presents a novel approach to designing subwavelength-thick, polarization-insensitive micro-lenses with high numerical apertures and large focusing efficiency. These lenses, based on high contrast transmitarrays (HCTAs), can achieve focal spots as small as 0.57 wavelengths and focusing efficiencies up to 82%. The HCTAs, composed of silicon nano-posts on glass, enable control of optical phase fronts with subwavelength spatial resolution. The design method and trade-offs between efficiency and spot size are discussed. The fabrication process, using high-throughput photo or nanoimprint lithography, makes these lenses suitable for widespread adoption. The authors demonstrate the versatility of HCTAs by designing and fabricating high numerical aperture micro-lenses with exotic phase profiles, optimized for specific tasks such as microscopy and high-density data recording. The measured performance of the micro-lenses agrees well with simulations, confirming the effectiveness of the design technique.