We demonstrate an optical chromatic aberration correction method for virtual reality (VR) displays using cost-efficient flat optics. The fabricated ultra-broadband liquid crystal thin-film polymer lens is based on the Pancharatnam-Berry phase and manifests over 97% first-order diffraction efficiency over the display spectrum. By cascading the fabricated polymer lens with the conventional Fresnel VR lens, the lateral color breakup in the near-eye display system can be reduced by more than 10 times. Both optical designs and experimental results are presented and discussed.
Homogeneous, flexible light sources with pure, deep red color and sufficiently high power densities are necessary for more effective and widely used photodynamic therapy (PDT), but have been difficult to achieve with lasers or LED arrays at reasonably low cost. Quantum dot light emitting diodes (QLEDs) have outstanding wavelength tunability, ideal color purity, sufficient power density and unique form factors as thin, flexible, light weight and uniformly large area light sources, which will meet the pressing needs for PDT.
Here we report QLEDs fabricated with emission wavelengths precisely tuned to match the absorption peaks of several FDA approved photosensitizers. Preliminary in-vitro studies with rigid on-glass QLEDs as photosensitizer activators demonstrate they can kill cancerous A431 cells or Methicillin-resistant Staphylococcus aureus (MRSA) with efficiency comparable or better than control LED sources, indicating their potential for PDT treatments of cancers or infections. Computer simulation of light propagation in a tissue mimicking phantom suggests that about 50% of the QLED power can be delivered to a depth of about 4 mm from the treated surface. Recent progress on the fabrication of low-cost flexible QLEDs will be presented. Finally, the perspectives of using these devices for PDT to address medical conditions such as cancer treatment, wound repair or cosmetic dermatology will be discussed.