Ultrahigh-temperature regenerated gratings in boron-codoped germanosilicate optical fiber using 193 nm

Abstract

Regenerated gratings seeded by type I gratings in boron-codoped germanosilicate optical fiber written with 193 nm are shown to withstand temperatures beyond 1000 degrees C.

Regenerated Fibre Bragg Gratings

“…This chirp is an exaggerated copy of the seed grating quadratic chirp so the complex profile of the seed grating was preserved. When tension is removed during regeneration, B is the same between seed and regenerated grating, also consistent with our previously reported observations [Bandyopadhyay et al 2008;Canning et al 2008b]. Fig.…”

“…In practice, we have confirmed that the stronger the seed grating, the stronger the final regenerated grating. For this case, a conventional Bragg grating inscribed into hydrogen loaded (24hrs, 200atm, 70°C) relatively highly germanium doped step index fibre with no boron (r core ~ 2μm, [GeO 2 ~ 10.5mol%], Δn co/cl = 0.012), using the 244nm output from a frequency doubled Ar + laser (P ~ 50W/cm 2 , f cumulative ~ (6-12)kJ/cm 2 , the same as that reported in Bandyopadhyay et al 2008 andCanning et al 2008b). Figure 6 shows the transmission and reflection of a very strong type I Bragg grating, readily exceeding the noise floor in transmission of our tunable laser and power meter setup (res: 1pm).…”

“…We soon recognized a more general implication of this result -rather than rely on a diffusive interpretation and subsequent polarisability change as the basis for writing gratings, an alternative approach to engineering the index change based on glass structural transformation arising from relaxation of high internal pressures and high temperature processing was proposed. Whilst much work remains to verify details of this approach, it implicitly did not rely on the fibre glass dopants at all (other than maximizing the seed grating strength) and directly led to the development of regenerated gratings in standard photosensitive fibres with transmission rejection >10%/cm and which can tolerate temperatures as high as 1295°C [Bandyopadhyay et al 2008;Canning et al 2008b]. The use of hydrogen was important, but not necessarily essential, to obtain index modulation of useful magnitude for very high temperature operation, since it permitted enhanced localisation of the pressure differences between processed and unprocessed regions.…”

“…The options available, within certain limitations, are numerous. They include type 1n (type IIa) and type Ip (type Ia) gratings that can operate between 500-800 °C depending on preparation [Canning 2008a and refs therein]; type II damage gratings ] produced by irradiation above the damage threshold of the glass using UV lasers or multiphoton excitation with longer wavelengths and more recent regenerated gratings that are based on glass structural change achieved using type I seed gratings as a template [Bandyopadhyay et al 2008;Canning et al 2008b]. The problem with these various methods is that the gratings produced often compromise the ideal properties offered by type I gratings.…”

“…Using a processing procedure identical to that optimised in Bandyopadhyay et al 2008 andCanning et al 2008b, ultra strong seed gratings were thermally processed sequentially with a standard recipe. At 950°C the onset of regeneration is observed, and over time as the seed grating disappears completely, the regenerated grating appears.…”