Numerical Analysis of Coupling Characteristics of Tunable Photonic Crystal Fiber Coupler for Nonlinear Optical Microscopy

As a kind of significant fiber device, an optical fiber coupler can make the nonlinear optical microscopy more compact and flexible for in vivo imaging. We numerically investigate the coupling efficiencies of side-polished large mode area endlessly single mode photonic crystal fiber coupler over the visible and near infrared wavelength range by using improved fully vectorial effective index method and weak-coupling theory. We find that appropriate combinations of the core distance and the angle between two side-polished fibers can accomplish a large mode area endlessly single mode photonic crystal fiber coupler to simultaneously deliver the near infrared laser for excitation and split the fluorescence for detection.