Understanding bend loss in single-ring hollow-core photonic crystal fibers(PCFs)is becoming of increasing importance as the fibers enter practical applications.While purely numerical approaches are useful,there is a n...Understanding bend loss in single-ring hollow-core photonic crystal fibers(PCFs)is becoming of increasing importance as the fibers enter practical applications.While purely numerical approaches are useful,there is a need for a simpler analytical formalism that provides physical insight and can be directly used in the design of PCFs with low bend loss.We show theoretically and experimentally that a wavelength-dependent critical bend radius exists below which the bend loss reaches a maximum,and that this can be calculated from the structural parameters of a fiber using a simple analytical formula.This allows straightforward design of single-ring PCFs that are bend-insensitive for specified ranges of bend radius and wavelength.It also can be used to derive an expression for the bend radius that yields optimal higher-order mode suppression for a given fiber structure.展开更多
Hefei Light Source （HLS） is being upgraded to HLS Ⅱ. Its emittance will be much lower than before, therefore the Touschek scattering will increase significantly and become the dominant factor of beam loss. So it is...Hefei Light Source （HLS） is being upgraded to HLS Ⅱ. Its emittance will be much lower than before, therefore the Touschek scattering will increase significantly and become the dominant factor of beam loss. So it is necessary to build a new beam loss monitoring （BLM） system that, in contrast to the old one, is able to obtain the quantity and position information of lost electrons. This information is useful in the commissioning, troubleshooting, and beam lifetime studying for HLS Ⅱ. This paper analyzes the distribution features of different kinds of lost electrons, introduces the operation parameters of the new machine and discusses how to choose proper monitoring positions. Based on these comprehensive analyses, a new BLM system for HLS Ⅱ is proposed.展开更多
An antiresonant ring （ARR） interferometer configuration is introduced for the characterization of a continuous wave （CW） Nd：YAG laser output. The output of the ARR device is precisely characterized to determine t...An antiresonant ring （ARR） interferometer configuration is introduced for the characterization of a continuous wave （CW） Nd：YAG laser output. The output of the ARR device is precisely characterized to determine the gain and loss of a laboratory CW Nd：YAG laser by using the Findlay-Clay approach. The ARR arm is then experimentally arranged inside the cavity of an arranged high power side-pumped CW Nd：YAG laser. A coated beam splitter with 50–50% re？ectivity at normal incidence is placed inside the cavity to provide a wide range of re？ectivity from 0 to 100%. This is performed by a rotatable stage and tilting the beam splitter by 10？ with the steps of 0.05. By changing the input electrical power of the laser pump the variation of the output laser power is monitored for 20 individual re？ectivity of ARR arm. Average pump threshold power of about 180 W is obtained. With the help of the derived equations and obtained threshold power, small signal gain and loss associated with the emerging beam is estimated. It is verified that the former is very dependent to the input parameters. Laser efficiency is also measures 5.6% which is quite comparable with the reported values.展开更多
文摘Understanding bend loss in single-ring hollow-core photonic crystal fibers(PCFs)is becoming of increasing importance as the fibers enter practical applications.While purely numerical approaches are useful,there is a need for a simpler analytical formalism that provides physical insight and can be directly used in the design of PCFs with low bend loss.We show theoretically and experimentally that a wavelength-dependent critical bend radius exists below which the bend loss reaches a maximum,and that this can be calculated from the structural parameters of a fiber using a simple analytical formula.This allows straightforward design of single-ring PCFs that are bend-insensitive for specified ranges of bend radius and wavelength.It also can be used to derive an expression for the bend radius that yields optimal higher-order mode suppression for a given fiber structure.
基金Supported by National Natural Science Foundation of China(11175180,11175182)
文摘Hefei Light Source （HLS） is being upgraded to HLS Ⅱ. Its emittance will be much lower than before, therefore the Touschek scattering will increase significantly and become the dominant factor of beam loss. So it is necessary to build a new beam loss monitoring （BLM） system that, in contrast to the old one, is able to obtain the quantity and position information of lost electrons. This information is useful in the commissioning, troubleshooting, and beam lifetime studying for HLS Ⅱ. This paper analyzes the distribution features of different kinds of lost electrons, introduces the operation parameters of the new machine and discusses how to choose proper monitoring positions. Based on these comprehensive analyses, a new BLM system for HLS Ⅱ is proposed.
文摘An antiresonant ring （ARR） interferometer configuration is introduced for the characterization of a continuous wave （CW） Nd：YAG laser output. The output of the ARR device is precisely characterized to determine the gain and loss of a laboratory CW Nd：YAG laser by using the Findlay-Clay approach. The ARR arm is then experimentally arranged inside the cavity of an arranged high power side-pumped CW Nd：YAG laser. A coated beam splitter with 50–50% re？ectivity at normal incidence is placed inside the cavity to provide a wide range of re？ectivity from 0 to 100%. This is performed by a rotatable stage and tilting the beam splitter by 10？ with the steps of 0.05. By changing the input electrical power of the laser pump the variation of the output laser power is monitored for 20 individual re？ectivity of ARR arm. Average pump threshold power of about 180 W is obtained. With the help of the derived equations and obtained threshold power, small signal gain and loss associated with the emerging beam is estimated. It is verified that the former is very dependent to the input parameters. Laser efficiency is also measures 5.6% which is quite comparable with the reported values.
