title: Wide-passband, temperature-insensitive, and compact pi-phase-shifted long-period gratings in endlessly single-mode photonic crystal fiber.
abstract: We demonstrate what is believed to be the first fabrication of a wide-passband, temperature-insensitive, and compact spectral filter based on a pi-phase-shifted long-period grating in an endless single-mode photonic crystal fiber. By introducing a pi-phase shift in the middle of a 12-period long-period grating, two symmetrical rejection bands at wavelengths of 1252.65 and 1418.7 nm are obtained with isolation higher than 18 dB and a passband bandwidth of 84.15 nm. The pi-phase-shifted long-period gratings are inscribed by the relaxation of mechanical stress with the focused pulses of a CO2 laser and a point-by-point technique without geometric deformation. The length of the spectral filter is approximately 6.6 mm with a sensitivity of 8 pm/ degrees C at a medium temperature range of 23-190 degrees C.
authors.affiliation: Network Technology Research Center, Nanyang Technological University, 50 Nanyang Drive, Research TechnoPlaza, Singapore 637553. eynzhu@ntu.edu.sg
authors.forename: Yinian
authors.initials: Y
authors.lastname: Zhu
authors.forename: Ping
authors.initials: P
authors.lastname: Shum
authors.forename: Hui-Wen
authors.initials: HW
authors.lastname: Bay
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Chen
authors.forename: Ching-Hwee
authors.initials: CH
authors.lastname: Tan
authors.forename: Chao
authors.initials: C
authors.lastname: Lu