Effect of electric field on one-quantum photodecay of oxygen-deficient centers in germanosilicate fibers

Abstract

The effect of a strong electric field ͑up to 10 6 V/cm͒ on one-quantum UV photoexcitation and photodecomposition of germanium oxygen deficient centers ͑GODC͒ in twin-hole germanosilicate fibers with internal wire electrodes is reported. The fiber has been irradiated with the UV light of a deuterium lamp and triplet photoluminescence of GODC has been used to monitor the kinetics of its photodecay. Applying such an electric field did not affect the spectral characteristics of GODC but increased the rate of their one-quantum photodecomposition, while direct photoionization and charge separation did not take place. We have also shown that this effect is caused by the suppression of secondary photoinduced recombination processes of intermediates, rather than by acceleration of primary photodecomposition of GODC. © 2000 American Institute of Physics. ͓S0003-6951͑00͒01437-6͔The effect of UV photosensitivity of Ge-doped silica glass is widely used for effective photoinscription of fiber and planar microstructures.1 This effect is recognized to be associated with structural phototransformation of germanium oxygen-deficient centers ͑GODC͒ and local density alteration in a Ge-doped glass network. Exposure of GODC to UV light is produced mostly in 242 nm singlet absorption band (S 0 -S 1 electron transition͒ and also in weak triplet absorption 330 nm band (S 0 -T 1 electron transition͒.2 Singlet photoexcitation of GODC results in the appearance of two luminescence bands-singlet band centered at about 300 nm (S 1 -S 0 transition͒ and triplet band at about 400 nm (T 1 -S 0 transition͒. To increase the photosensitivity of germanosilicate glass the ''chemical'' pathways of UV energy relaxation in GODC should be accelerated.3-5 The mechanisms of GODC chemical phototransformation are very complicated, and they are far from being completely understood. Different parameters of glass such as concentration of Ge 5,6 and other dopants 7 and impregnated molecular species ͑like hydrogen 5,8 ͒, can be critical for these mechanisms. It should be noticed that the mechanism of charge ͑elec-tron or hole͒ displacement has always been considered as an initial step of GODC phototransformation. This is why one of the possible approaches to control GODC phototransformation calls for the application of a strong electric field. 9-11It is important that depending on UV light intensity, both one-quantum and two-quantum GODC photodecomposition may occur. 9,12 It was shown directly in Ref. 8, that UV photoexcitation of GODC with intense pulses of KrF laser ( ϭ248 nm, ⌽Ͼ10 Ϫ2 J/cm 2 ͒ in an electric field results in efficient two-quantum ionization of GODC and generation of photocurrent pulses. It has been observed in similar cases that the effects of a strong electric field on acceleration of both GODC decomposition 10 and formation of Bragg gratings 11 can be quite naturally attributed to the increase of displacement of charge carriers from ionized GODC and, as a result, to the suppression of recombination processes. The effects of a strong electric f...

Medium-range ordering in glass structures as a background of photosensitivity in silica fibers

“…The defects of this type are an oxygen vacancy with a trapped charge (the E 0 -center) and a relaxed diamagnetic oxygen vacancy suggested as a model for ODC. The effect of UV photosensitivity of a Ge-doped silica glass fiber is recognized to be associated with a structural phototransformation of germanium-oxygen-deficient centers (GODCs) and local density alteration in a Ge-doped glass network [28]. Earlier, a direct correlation was reported between the SHG efficiency and the appearance of an induced UV absorption band in Ge-doped silica fibers [29].…”

Spectroscopic characterization of silica-based fibers using picosecond SRS technique

“…Defects of this type are an oxygen vacancy with a trapped charge (the E΄-center) and the relaxed diamagnetic oxygen vacancy, suggested as a model for ODC. The effect of UV photosensitivity of a Ge-doped silica glass fiber is recognized to be associated with structural phototransformation of germanium-oxygen-deficient centers (GODCs) and local density alteration in a Ge-doped glass network 17 . Earlier, a direct correlation was reported between the SHG efficiency and the appearance of an induced UV absorption band in Ge-doped silica fibers 18 .…”

ITO electrode-embedded double-cladding single-crystal LiNbO_3 optical fiber

“…In contrast, fiber modulators may resolve those concerns to some extent if a practically useable fiber modulator becomes available. Modulators with different EO materials in fiber form have been studied [9][10][11][12]. However, many challenges remain, including (1) how to obtain a material with high enough EO coefficient and acceptable optical/environmental stability, (2) how to fabricate the EO material into a core-cladding optical fiber with singlemode (or few-mode) characteristics and low loss, and (3) how to implant electrical paths (electrodes) with low resistivity in a robust process.…”

“…However, many challenges remain, including (1) how to obtain a material with high enough EO coefficient and acceptable optical/environmental stability, (2) how to fabricate the EO material into a core-cladding optical fiber with singlemode (or few-mode) characteristics and low loss, and (3) how to implant electrical paths (electrodes) with low resistivity in a robust process. From literature [9][10][11][12], there are mainly four techniques used to incorporate electrical paths along the fiber: (1) liquid metal perfusion [9], (2) sheet metal join [10], (3) metal wire insertion [11], and (4) metal wire introduction during the fiber drawing process [12]. Although those methods have their own advantages, they commonly suffer from the complicated multiple-step postprocess of electrode implementation.…”