A pulse is generated when the heart pumps blood into the arterial system. The heart pumps blood only when it contracts, not when it relaxes; therefore, blood enters the arterial system in a cyclical form. Artery beating is visible in some parts of the body surface, such as the radial artery of the wrist. This paper mainly uses the feature in which near-infrared spectroscopy penetrates skin to construct a non-invasive measurement system that can measure small vibration in the subcutaneous tissue of the human body, and then uses it for the pulse measurement. This measurement system uses the optical moiré principle, together with the fringe displacement made by small vibration in the subcutaneous tissue, and an image analysis program to calculate the height variation from small vibrations in the subcutaneous tissue. It completes a measurement system that records height variation with time, and that together with a fast Fourier transform (FFT) program, they can convert the pulse waveform generated by vibration (time-amplitude) to heartbeat frequency (frequency-amplitude). This is a new and non-invasive medical assistance system for measuring the pulse of the human body, with the advantages of being simple, fast, safe and objective.

Ion implantation is widely used to fabricate advanced optical and optoelectronic materials and devices. However, nanoscale defects generated during the ion implantation process severely affect the quality and properties of the material and device. Here, combining computational simulations and experiments, we investigate the mechanism for defect repair in fused silica after Cu ion implantation using femtosecond laser irradiation with an energy fluence much lower than the ablation threshold. Atomic force microscopy demonstrates no unexpected ablation. The optical absorption spectra show that various types of defects with formation energies between 1.9 and 6.2 eV can be repaired successfully via an athermal procedure. The Raman spectra imply that the broken chemical bonds reconnect after femtosecond laser irradiation. Our study reveals that low-energy femtosecond laser irradiation can transfer the appropriate energy needed to repair defects; thus it could be useful in fabricating nonlinear optical devices due to its high spatial selectivity and convenience.

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We explore the terahertz (THz) wave generation based on surface-emitted difference frequency generation (SEDFG) in periodically-inverted GaAs crystals. One scheme applying collinear quasi phase matching (QPM) is proposed. The wave propagation of the higher frequency pump wave is parallel to the wave propagation of the lower frequency pump wave, and both of them are perpendicular to the domain wall of the nonlinear crystal. The THz wave is emitted perpendicular to the surface of the nonlinear crystal. We calculated the grating period of periodically-inverted GaAs at the range of 100-1000μm (0.3-3THz). Our estimates illustrate that THz wave output corresponds to the power conversion efficiency of 0.015% at a frequency of 1THz. The result is shown that this scheme is efficient to obtain THz wave.