A pin-like beam is a kind of structured light with a special intensity distribution that can be against diffraction, which can be seen as a kind of quasi-nondiffracting beam (Q-NDB). Due to its wide applications, recently, numerous researchers have used optical lenses or on-chip integrated optical diffractive elements to generate this kind of beam. We theoretically verify and experimentally demonstrate an all-fiber solution to generate a subwavelength inverted pin beam by integrating a simple plasma structure on the fiber end surface. The output beams generated by two kinds of plasma structures, i.e., nanoring slot and nanopetal structure, are investigated and measured experimentally. The results show that both the structures are capable of generating subwavelength beams, and the beam generated using the nanopetal structure has the sidelobe suppression ability along the x-axis direction. Our all-fiber device can be flexibly inserted into liquid environments such as cell cultures, blood, and biological tissue fluids to illuminate or stimulate biological cells and molecules in them. It provides a promising fiber-integrated solution for exploring light–matter interaction with subwavelength resolution in the field of biological research.
As a continuously tunable laser with high-sweeping linearity, narrow linewidth lasers have excellent coherence properties that make them indispensable for the improvement of the spatial resolution of optical frequency domain reflection (OFDR) technology. In order to investigate the linewidth characteristics of narrow linewidth lasers with high-sweep linearity, this paper reviews the measurement and calculation methods of linewidth. The theoretical analysis of the linewidth is also carried out, and a delayed self-heterodyne measurement system based on the non-equilibrium Mach-Zehnder (M-Z) interferometer structure is built. The experimental results show that the steady-state linewidth of the laser is 178 kHz, and the fluctuation range of the dynamic linewidth is 150-200 kHz. In order to balance the speed and accuracy of linewidth measurement, the linewidth values at receiver bandwidth of 10 kHz, 30 kHz and 100 kHz are analyzed. Analyze the linewidth spreading generated by the laser during continuous frequency tuning, compensate the deviation between the real value of linewidth and the measured value by controlling the step amount of the laser wavelength tuning to keep the output power stable and reduce the measurement error caused by the linewidth spreading. This study not only improves the knowledge of linewidth characteristics, but also have important practical significance for OFDR research.
Conference Committee Involvement (1)
29th International Conference on Optical Fiber Sensors
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