Fabrication and Resonance Wavelengths of Long-Period Gratings Written in a Pure-Silica Photonic Crystal Fiber by the Glass Structure Change

Long-period gratings based on Photonics crystal fibers and applications

“…4 shows the calculated resonance wavelength as a function of the period of PCF-LPG. It is clear that the resonance wavelength of PCF-LPG decreases with increasing LPG period, which is consistent with other experimental observations [27,33,34]. This is in contrast to LPGs written in conventional SMFs and is because of the highly dispersive property of the cladding mode due to the existence of the air-holes.…”

Modelling of Long Period Gratings in Photonic Crystal Fibres and Sensors Based on Them

“…It confirms the experimental observation that an increase in the grating period causes blue shift in the resonant wavelength. In the given wavelength range such behaviour is characteristic of PCFs and has been explained in (Morishita & Miyake, 2004). Resonant wavelengths of the first order grating are found at intersections of these curves with the line Λ=L, where L is the grating period.…”

“…3b), features two pronounced attenuation bands at 1402nm and 1239nm. Increase in the grating period causes a blue shift in the wavelength spectrum, in contrast to LPG behaviour in conventional single mode fibre, but similar to other LPGs in PCFs (Morishita & Miyake, 2004). Since neither the grating spectrum nor the bending sensitivity indicated any birefringence, the original hexagonal symmetry of the fibre was considered unaffected by the electric arc.…”

“…Whereas gratings written in step-index fibres usually consist of the change in the refractive index of the photosensitive core, gratings written in PCFs are slightly more complicated. They comprise change in the refractive index across the fibre cross-section and the change in the geometry of the PCF, for example squeezing of holes induced by the strong electric-arc (Morishita & Miyake, 2004). As the waveguiding principle of PCF lifts the requirement for the photosensitive core, all parts of the fibre can be made of the same material (usually silica) which makes them equally sensitive to the writing technique.…”

Characterisation of femtosecond laser inscribed long period gratings in photonic crystal fibre

“…One of the major problems to date is the inscription of the LPG into the PCF due to the fact that the majority of PCFs are made from pure fused-silica, which is not photosensitive to UV and thus traditional UV inscription techniques are not applicable. Several other inscription approaches have been used such as the electric-arc method [15], CO 2 lasers [16] and femtosecond lasers [17] to overcome this problem with the femtosecond laser technique being recognised as possibly the most versatile. With the increasing usage of femtosecond lasers to fabricate LPGs in PCF, we feel it important to study the temporal spectral stability of such fibre devices, and have discovered that all the LPGs we produced exhibited post-fabrication spectral evolution at room temperature as well as at higher temperatures along with polarisation dependence, all of which seem to be related to the inscription power used.…”