In this paper, an ultrathin metalens has been proposed based on a holographic metasurface that consists of elongated apertures in 40 nm gold film, which exhibit intriguing properties such as on-and off-axis focusing and also can concentrate light into multiple, discrete spots for circularly polarized incident lights. First, the spatial transmission phase distributions of the designed metalens with arbitrary focusing can be obtained by computergenerated holography. Then, the discrete phase distributions can be continuously encoded by subwavelength nanoapertures with spatially varying orientations in gold film. The simulation results show that our designed metalens can work efficiently for different types of focusing. Finally, our metasurface shows superior broadband characteristics between 670 and 810 nm, and the corresponding focal lengths of the designed lenses also can be efficiently modulated with the incident lights at different wavelengths.

Determining the optical polarization properties of a skin lesion is a proposed method to differentiate melanoma from other skin lesions. We developed an in vivo Stokes polarimetry probe that fires a laser of known polarization at the skin and measures the Stokes parameters of the backscattered light in one shot. From these measured Stokes parameters, we can calculate the degree of polarization (DOP). Through testing on rough skin phantoms, a correlation between backscattered DOP and skin roughness was identified for both linear and circular input polarization, the latter of which was found to be more useful. In a pilot clinical trial of 69 skin lesions in vivo, it was found that the mean DOP for melanoma (linear input on melanoma: 0.46 AE 0.09) was greater than that of other lesions (linear input on all other lesions: 0.28 AE 0.01). This separation is greater for circular polarized input light, and it is likely that circular polarized light's greater sensitivity to surface roughness contributes to this result. In addition, all skin lesions demonstrated a stronger depolarizing effect on circular polarized light than linear polarized light. We have identified DOP as a potentially useful measurement to identify melanoma among other types of skin lesions.

This paper presents a micro Fourier transform infrared spectrometer (μFTIR), enabled by an H-shaped electrothermal microelectromechanical systems (MEMS) mirror. A special driving method was developed for obtaining a linear, uniform-speed motion of 186 μm, and the tilting angle of the MEMS mirror was as small as 0.06°, so there was no need of complex closed-loop control. A telecentric lens was employed in the interferometer of the μFTIR to reduce the influence of the MEMS mirror tilting effect. Also, a new phase interpolation algorithm, instead of the traditional fringe interval method, was applied in the process of the spectral reconstruction to improve the spectral stability. Finally, the new μFTIR was applied in the composition prediction of soybeans, and the experimental results show that it can accurately measure grain moisture, protein, and fat contents.

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