Highly polarization-dependent periodic coupling in mechanically induced long period grating over air-silica fibers

Abstract

A very flexible and versatile tunable mechanical grating platform is introduced, with which highly polarization-dependent mode coupling is observed for three types of air-silica microstructured fibers: hollow core fiber, hexagonal-boundary holey fiber (HHF), and circular-boundary holey fiber. The resonances of gratings showed highly polarization-dependent broadband coupling compared with conventional single-mode fibers due to their unique beat-length dispersions between the core and the cladding modes, which could find applications in wideband polarization-dependent loss compensation. We further present significance of the spatial symmetry of HHF in distinct mode coupling for different rotation angles around the fiber axis.

Long period gratings in air-core photonic bandgap fibers

“…1(b)] caused by the changes and collapses of air holes, which induces large birefringence and asymmetrical mode field profile. Strong PDLs were also observed in mechanically induced LPGs on hollow fibers with a ring core, and hexagonal-and circular-boundary holey fibers [25].…”

Long Period Gratings in New Generation Optical Fibers

“…13 shows the measured relation between the resonant wavelength (the resonant dip A) and the grating pitch. Mechanical pressure has provided another direct and flexible means for LPG inscription in PCF (Lim et al, 2004, D. Lee et al, 2006, Parka et al, 2006. Pressure on the fiber surface with a periodic grooved plate induces periodic index changes in the fiber.…”

“…LPGs with proper lengths and periods have to be selected such that mode coupling occurs at the predetermined wavelength. However, the coupling was found to be highly polarizationdependent and dependent on the angular position where stress was applied (D. Lee et al, 2006). The highly polarization-dependent broadband coupling was observed due to the unique beat-length dispersion between the core-mode and cladding-mode, which could find potential applications in wide-band polarization dependent loss (PDL) compensation.…”

Long period gratings in photonic crystal fibers

“…Therefore, non-photochemical inscription techniques are commonly used. These may include CO 2 laser irradiation [4][5][6][7][8][9][10], electrical arc discharge [11][12][13], applying mechanical pressure [14][15][16], and acousto-optic interaction [17][18][19][20]. It was until 2007 that photochemical recording of LPG in PCF by using a high-intensity femtosecond UV radiation was reported [21].…”

“…Mechanical pressure has provided another direct and flexible means for LPG inscription in PCF [14][15][16]. The strength and wavelength of the resonant peak can be tuned simply by adjusting the grating period and the pressure applied on the PCF.…”