Wide-passband, temperature-insensitive, and compact pi-phase-shifted long-period gratings in endlessly single-mode photonic crystal fiber.

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.

[1]  T A Birks,et al.  Structural long-period gratings in photonic crystal fibers. , 2002, Optics letters.

[2]  M. Shigehara,et al.  Gain-flattening filter using long-period fiber gratings , 2002 .

[3]  S. Vasiliev,et al.  Bandpass filters based on pi-shifted long-period fiber gratings for actively mode-locked erbium fiber lasers. , 2001, Optics letters.

[4]  Anders Bjarklev,et al.  Investigation of microdeformation-induced attenuation spectra in a photonic crystal fiber. , 2003, Optics letters.

[5]  K. Chiang,et al.  Analysis of phase-shifted long-period fiber gratings , 1998, IEEE Photonics Technology Letters.

[6]  U. Paek,et al.  Residual stress relaxation in the core of optical fiber by CO(2) laser irradiation. , 2001, Optics letters.

[7]  Georges Humbert,et al.  Characterizations at high temperatures of long-period gratings written in germanium-free air-silica microstructure fiber. , 2004, Optics letters.

[8]  Dug Young Kim,et al.  Effect of CO2 laser irradiation on the refractive-index change in optical fibers. , 2002, Applied optics.

[9]  Fumiaki Hanawa,et al.  Drawing-induced residual stress effects on optical characteristics in pure-silica-core single-mode fibers , 1989 .

[10]  G. Humbert,et al.  High performance bandpass filters based on electric arc-induced /spl pi/-shifted long-period fibre gratings , 2003 .

[11]  Chao Lu,et al.  Deep-notch, ultracompact long-period grating in a large-mode-area photonic crystal fiber. , 2003, Optics letters.

[12]  John E. Sipe,et al.  Long-period fiber gratings as band-rejection filters , 1995 .

[13]  B. Lee,et al.  Tunable fiber gratings fabricated in photonic crystal fiber by use of mechanical pressure. , 2004, Optics letters.

[14]  D. M. Atkin,et al.  All-silica single-mode optical fiber with photonic crystal cladding. , 1996, Optics letters.