Highly sensitive plasmonic sensor based on eccentric-core photonic crystal fibers.

To further reduce the fabrication difficulty of optical fiber sensors and improve the sensing performance, this study introduced the surface plasmon resonance (SPR) effect into optical fiber sensing technology and designed an eccentric-core photonic crystal fiber (EC-PCF). We investigated the characteristics of the two fundamental modes in the fiber core and the surface plasmon polariton (SPP) modes on the surface of the gold film. We also investigated the influence of the structural parameters, such as gold film coating area and thickness, air hole diameter, and eccentricity, on the confinement loss and achieved a refractive index (RI) sensitivity of 31.25 µm RIU-1 in the RI range of 1.29-1.43, corresponding to a figure of merit (FOM) of 521.6 per RIU. When the resolution of the optical spectrum analyzer was 0.1 nm, the EC-PCF could achieve a refractive index resolution of 3.2 × 10-6 RIU. Moreover, we performed tests with two typical sensing types, one in which the sensor was directly in contact with adulterated gasoline to achieve kerosene-concentration detection, and another in which the sensor was coated with a layer of polydimethylsiloxane (PDMS), whose RI is sensitive to the temperature field, to achieve temperature sensing. The EC-PCF demonstrated excellent sensing performance and offers obvious manufacturing advantages, providing a new and easily fabricated structural design idea for optical fiber sensing.

A high-performance cell-phone based polarized microscope for malaria diagnosis.

We present a cell-phone based polarized microscope for diagnosing malaria through hemozoin recognition over a wide field-of-view (FOV) accompanied with decent image performance. The system is constructed based on attachment method using a lens assembly as objective, two mobile phones and two linear polarizers. A ~0.92 µm resolution across a FOV of ~3.27 mm × 3.27 mm with high imaging quality is realized, demonstrating an increased resolving power, four times improvement in FOV and better imaging quality over mobile-optical-polarization imaging device. Importantly, we also demonstrate it has capability of recognizing hemozoin within the sample for malaria diagnosis by imaging malaria-infected blood samples with similar sensitivity comparable to Leica microscopy. It is more compact, portable, and insensitive to alignment, making it highly suitable for malaria detection in a portable, easy to setup and use way in low-resource areas.

A wide-field microscope utilizing two cellphones for health-care applications.

In this report, we report a wide field-of-view (FOV) bright field (BF) microscope with compact and portable optical components, mechanically attached to the existing camera unit of the cellphone. A white screen displayed on a cellphone as the illumination source to pump the sample of interest uniformly for the purpose of the reduction in assembly complexity and alignment. It offers a large FOV of 4.36 × 3.27 mm without digital zoom and a spatial resolution of 1.5 µm. Furthermore, we also have demonstrated the potential application for diseases diagnosis and screening by imaging malaria-infected blood sample and iron deficiency anemia blood sample in resource-constrained settings where mobile phone infrastructure is already ubiquitous but microscope is notoriously scarce.