A Multi-foci Sparse-Aperture Metalens.

Multi-foci lenses are essential components for optical communications, virtual reality display and microscopy, yet the bulkiness of conventional counterparts has significantly hindered their widespread applications. Benefiting from the unprecedented capability of metasurfaces in light modulation, metalenses are able to provide multi-foci functionality with a more compact footprint. However, achieving imaging quality comparable to that of corresponding single-foci metalenses at each focal point poses a challenge for existing multi-foci metalenses. Here, a polarization-independent all-dielectric multi-foci metalens is proposed and experimentally demonstrated by spatially integrating single-foci optical sparse-aperture sub-metalenses. Such design enables the metalens to generate multiple focal points, while maintaining the ability to capture target information comparable to that of a single-foci metalens. The proposed multi-foci metalens is composed of square-nanohole units array fabricated by two-photon polymerization. The focusing characteristic and imaging capability are demonstrated upon the illumination of an unpolarized light beam. This work finds a novel route toward multi-foci metalenses and may open a new avenue for dealing with the trade-off between multi-foci functionality and high-quality imaging performance.

Efficacy and safety of (32)P-nanocolloid for treatment of distant lymph node metastasis in VX2 tumor-bearing rabbits.

BACKGROUND: Eradication of micrometastases present in lymph nodes of cancer patients improves their prognosis significantly. Radionuclide therapy possesses the potential to eliminate such metastases. OBJECTIVE: This study was performed to evaluate the efficacy and safety of (32)P-nanocolloid therapy in the treatment of distant carcinoma cell metastases in lymph nodes of VX2 tumor-bearing rabbits. METHODS: To obtain VX2 tumor micrometastases in right armpit lymph nodes of 12 male New Zealand white rabbits, VX2 tumors were implanted by hypodermal inoculation into the right anterior limb. Animals were randomly divided into therapy (n = 6) and control (n = 6) groups. (32)P-nanocolloid (0.5 mCi), 95% of which was >50 nm in diameter, was administered to the therapy group, and saline was administered to the control group. Injections were given once weekly for 4 weeks. RESULTS: 2-Deoxy-2[(18)F]-fluoro-D -glucose positron emission tomography revealed that the number of involved lymph nodes and the maximum standardized uptake value decreased in the (32)P-nanocolloid therapy group as compared with the baseline or saline control group (P < 0.05). The expression of the lymphangiogenesis factors vascular endothelial growth factors (VEGF)-C and VEGF-D by VX2 tumor cells present in lymph nodes was significantly lower in the therapy group as compared with the control group. Additionally, apoptotic VX2 tumor cell death was significantly greater in lymph nodes of the therapy as compared with the control group (P < 0.01). With the exception of a decrease in white blood cells of peripheral blood (P < 0.05), standard laboratory values were unaffected throughout the course of therapy with (32)P-nanocolloid. CONCLUSIONS: These findings support treatment with (32)P-nanocolloid as a safe and effective approach for eradication of lymph node micrometastases.