Solar-pumped fiber laser using a solid-state luminescent solar collector.

We have developed a fully planar solar-pumped fiber laser using a solid-state luminescent solar collector (LSC). This laser does not use any focusing device, such as a lens or mirror; thus, it can lase without tracking the sun. Our developed device with an aperture of 30 cm emits 15 mW, corresponding to an optical-to-optical conversion efficiency of 0.023% and a collection efficiency of 0.21 W/m2. A 12-fold improvement over a previously developed liquid LSC is achieved by combining the total internal reflection of the solid-state LSC with dielectric multilayer mirrors. The observed laser power is in good agreement with that predicted via numerical simulation, demonstrating the effectiveness of our proposed method.

Theoretical concentration limit and maximum annual optical efficiency of static/low-concentration CPV for horizontal integration to vehicle bodies.

This study proposes an extended theoretical formula to characterize the relationship between the geometrical concentration ratio Cg and arbitrary incidence-angle range to objectively understand the theoretical limit performance of vehicle-integrated concentrator photovoltaics (VICPVs), i.e., static and low-concentration CPVs installed on a horizontal surface. Theoretical analysis revealed that the maximum annual optical efficiency (maximum annual solar energy yield) can be achieved by selectively collecting the sunlight incident only from a specific incidence-angle range of θ1-θ2 (θ1 ≠ 0°), regardless of the geographical location, which is associated with the angular distribution of the annual solar energy on the concentrator aperture. Moreover, the results of the solar concentrator design based on the obtained formula clarified that the annual optical efficiencies of the optical systems with aspheric lens or dielectric-filled crossed compound-parabolic-concentrator lens were 64-89% of the theoretical limit depending on the location for Cg = 3.5×. Nevertheless, the concentrator design can be further improved for practical applications.

Noncontact Blood Pressure Monitoring Technology using Facial Photoplethysmograms.

We propose noncontact blood pressure estimation technology using photoplethysmograms (PPGs) extracted from camera images of only user's face and this estimation can be realized without calibration, which usually needs to be performed for each individual. Proposed technology contains the pulse wave detection method robust to lighting conditions. The influence of users' body motions was evaluated by our experimental system. We also propose the method to reduce the blood pressure prediction error by classifying users according to their vascular conditions which can be detected from facial PPGs.