Study of the photosensitivity at 193 nm and comparison with photosensitivity at 240 nm influence of fiber tension: type IIa aging

Riant, I.; Haller, F.B.

doi:10.1109/50.618378

Cited by 50 publications

(14 citation statements)

References 16 publications

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“…With further UV exposure the type I grating growth saturates, and formation of the so-called type IIA grating commences. 2 The observed ref lectivity decreases almost to zero before increasing again and, eventually, saturating; the central refractive wavelength decreases during this stage of the exposure, indicating a negative induced index change. Type IIA gratings are usually inscribed at a wavelength of 193 nm, 2 -4 and, although the underlying mechanism is still not wholly clarif ied, links to stress and defect concentrations have been identif ied.…”

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confidence: 99%

Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

et al. 2002

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We report the observation of abnormal spectral evolution in regenerated fiber Bragg gratings in hydrogenated B -Ge-codoped and standard telecom fiber with UV overexposure. The behavior of this new type of regenerated grating, which we have designated type IA, contrasts with that of the previously reported type IIA grating in nonhydrogenated fiber by exhibiting a large redshift in Bragg wavelength with increasing exposure of as much as 18 nm from a strong (16-dB) In all observations reported to date, the type IIA gratings were formed in nonhydrogenated fibers. However, the introduction of hydrogen into the fiber to increase photosensitivity is a commonly adopted procedure. In seeking to clarify FBG growth with UV overexposure in hydrogenated standard telecom and B-Ge-codoped f ibers we have observed, for the f irst time to our knowledge, regenerated grating growth with an abnormal, i.e., contrary to the behavior expected on the basis of previously reported observation, spectral evolution that is quite distinct from that of type IIA. We have designated this new grating type IA and found it to exhibit less temperature sensitivity than the type I grating.We inscribed the FBGs reported here by two-beam holographic exposure, using a cw 244-nm laser with 8-mm beam width and 60-mW power. For reference, we produced a type I FBG in nonhydrogenated B-Ge-codoped fiber: a maximum 2.2-dB ref lectivity was obtained in ϳ2 min of UV exposure, as shown in Fig. 1(a); the ref lectivity decreased with subsequent exposure and fell to zero after 7 min. A maximum redshift of ϳ2.0 nm in the Bragg wavelength was recorded. As the UV exposure was maintained, the grating ref lectivity increased from zero, accompanied by a blueshift in the Bragg wavelength that is characteristic of the type IIA grating and a negative induced refractive-index change. Limited by the UV wavelength and power, the type IIA grating attained 8.7-dB ref lectivity and 0.66-nm blueshift after 37-min exposure. Subsequent annealing of the grating for 12 h at 70 ± C induced a further blueshift of 0.55 nm owing to relaxation of the photoinduced positive index change; the ref lectivity remained unchanged, indicating good thermal stability, as shown in Fig. 1(b).This fabrication procedure was repeated with a hydrogenated sample of the same fiber. Type I grating formation and complete erasure were again observed; however, with continued UV exposure a quite different behavior emerged that included formation of an

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Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

et al. 2002

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“…The physical basis for a linear response is the existence of only one growth process-the reason why this growth should be characterized by essentially an exponential dependence on fluence is itself extremely important. [29][30][31] This reversal of change is also observed in the optical density measured for exposed photochromic films and glasses 18 and is the origin of solarization ͑where a decrease in the measurand takes place͒ in these media. How-ever, most observations are that the growth curve can be characterized by one, usually more, exponentials providing evidence that the induced change is not directly dependent on absorption alone but is mostly a consequence of relaxation after photoexcitation.…”

Section: The Characteristic Curvementioning

confidence: 80%

The characteristic curve and site-selective laser excitation of local relaxation in glass

Canning

2004

The Journal of Chemical Physics

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The so-called characteristic curve describing photosensitivity change is elaborated and shown to be a powerful tool for understanding and characterizing photosensitive growth both at a fundamental and practical level. It has been used successfully to diagnose when optimal hypersensitization has been achieved and the physical basis for this is explained. By way of example, previous results using 355 nm hypersensitization are re-examined. Evidence of single site-selective glass relaxation through direct laser excitation offers a new approach to accessing and studying induced relaxations.

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“…Photo-induced index variation of 1 O can be reached without treatment when the fiber is irradiated at 193 nm [6][7]. The absorption band at 193 nm is related to the Germanium defect GeE'.…”

Section: Germanosilicate Fibers and Waveguidesmentioning

confidence: 99%

Laser induced index change and its applications to optical devices

Riant¹

2003

Fourth International Symposium on Laser Precision Microfabrication

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Isabe1le. Riant(a,alcatelfi The impressing growth of Wavelength Division Multiplexing (WDM) transmissions has pushed the development of photo-induced Bragg gratings in optical fibers. Numerous studies on the photosensitivity of germanosilicate fibers have then been carried out since its discovery in 1978, to understand, stabilize and enhance the effect. Some of those studies are presented here together with some illustrating applications.

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Study of the photosensitivity at 193 nm and comparison with photosensitivity at 240 nm influence of fiber tension: type IIa aging

Cited by 50 publications

References 16 publications

Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

Abnormal spectral evolution of fiber Bragg gratings in hydrogenated fibers

The characteristic curve and site-selective laser excitation of local relaxation in glass

Laser induced index change and its applications to optical devices

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