Equilibrium mode distribution

About: Equilibrium mode distribution is a research topic. Over the lifetime, 928 publications have been published within this topic receiving 14939 citations.

Fiber Fuse Propagation Characteristics of LP 01 and LP 11 Modes in Few-Mode Fiber

Abstract: We observe fiber fuse propagation in the LP11 mode in few-mode fiber by selective propagation mode launching via a PLC-based mode multiplexer. We focus on two fiber fuse propagation parameters, namely, the propagation power threshold ${\rm P_{th}}$ , and the diameter of the melted area ${\rm D_{melted}}$ . We confirm experimentally that ${\rm P_{th}}$ in the LP11 mode was higher than that in the LP01 mode. ${\rm P_{th}}$ of the LP01 and LP11 modes increases linearly with the Gaussian beam width, which is similar to the dependence of the mode field diameter of ${\rm P_{th}}$ in the LP01 mode. We also find a specific relationship between the power density and ${\rm D_{melted}}$ normalized by the Gaussian beam width regardless of input mode conditions and fiber type. Therefore, we believe that we can utilize the Gaussian beam width of the near field pattern of the LP 01 and LP11 modes for predicting the characteristics of fiber fuse propagation in both modes.

Investigation of the lowest-order TE mode of the parallel-plate metal waveguide for terahertz pulses

Abstract: We describe an experimental and theoretical study of the lowest-order transverse-electric (TE1) mode of the parallel-plate waveguide for the propagation of broadband THz pulses, and demonstrate undistorted THz pulse propagation via the TE1 mode. This demonstration overcomes two fundamental problems associated with the low-frequency cutoff of this mode, the group velocity dispersion and the spectral filtering, which have prevented the use of this mode for THz wave guiding in the past. We also observe a remarkable counter-intuitive property of the TE1 mode: its attenuation decreases with increasing frequency. This phenomenon has not been observed with any other THz waveguide to date, and can enable extremely low-loss propagation. In addition, we find that it is possible to achieve almost 100% coupling to the TE1 mode from an input Gaussian beam. These results favor the use of the TE1 mode for the efficient guiding of THz pulses.

Thermally induced mode instability in high power fiber amplifiers

Abstract: We present a physical model that may describe the observed phenomenon of modal instability in high power fiber amplifiers. In the power range of several hundred watts, large-mode-area, cladding-pumped, Yb 3+ -doped fiber amplifiers (both step-index and photonic crystal fibers), exhibit a sudden transition in the output beam profile from the fundamental mode to a higher order mode. We show how this behavior can be caused by a thermally induced mode coupling that leads to exponential gain of the higher order mode, and we implement a numerical model that quantitatively predicts the instability threshold for any large-mode-area step index fiber amplifier.