Long-period fiber grating inscription under high-intensity 352 nm femtosecond irradiation: Three-photon absorption and energy deposition in cladding

Slattery, Stephen A.; Nikogosyan, David N.

doi:10.1016/j.optcom.2005.06.011

Cited by 15 publications

(20 citation statements)

References 29 publications

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“…In previous reports, the spectral characteristics of LPGs are assessed ether with an OSA [7], [9], [13], [27] or with an interrogator [26]. For our first tests were run with the setup depicted in Fig.…”

Section: Materials and Experimentsmentioning

confidence: 99%

“…As compared to FBGs, LPGs have a length of the order of centimeters against few mm in the case of FBGs, and a larger pitch of the modulation profile, in the order of hundreds of m as compared to FBGs which exhibit a period G 750 nm [3], [4]. Various techniques were used to fabricate LPGs: CO 2 lasers [2], [4], [5]; UV radiation [6]- [8]; visible [3] or UV fs laser radiation [3], [9], [10]; IR fs laser radiation [11]; electric arc discharge [8], [12], [13]; LPGs were inscribed in pure-silica-core fibers/ F-doped silica cladding [13]; SMF-28 Gedoped SiO 2 [2]- [4], [7], [9], [11], [14]; B co-doped fiber [8]; N-doped silica fibers [14]; microstructured PMMA optical fiber [6]; special optical fibers for radiation environments [15]; FORC or Fujikura telecommunication optical fiber [3]; pure fused silica photonic crystal fiber [10]; H2loaded SMF-28 [10]; Al 3þ -doped and Er 3þ =Al 3þ -codoped fibers [12]; solid-core PCFs or air-core PBFs [5]. The writing methods were either a step-by-step process [1], [2], [4], [6], [9]- [11] or amplitude mask [1], [7].…”

Section: Introductionmentioning

confidence: 99%

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Online Tests of an Optical Fiber Long-Period Grating Subjected to Gamma Irradiation

et al. 2014

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This paper reports the outcomes of the tests that we conducted as online measurements for the evaluation of one optical fiber long-period grating produced by a fusion technique in a single-mode radiation-hardened optical fiber, and subjected to gamma irradiation. During the irradiation, the grating temperature was monitored. Before the irradiation, the temperature sensitivity of the grating was 27.7 pm= C, while the value of this parameter postirradiation was found to be 29.3 pm= C. The spectral characteristics of the grating were measured (i) in the laboratory with an ANDO AQ6317C optical spectrum analyzer and (ii) online, for the first time, with a LUNA OBR 4600 backscatter reflectometer, operating in the frequency acquisition mode. Such online measurement enables the study of recovery effects during the irradiation. The wavelength dip of the grating shifted under gamma irradiation, with 16 pm/kGy for the maximum total dose of 45 kGy. At room temperature, the recovery of the irradiation-induced shift of the wavelength dip was almost complete in about 120 h, at a rate of 6.7 pm/h. Postirradiation heating of the sensor produced the reversing of the recovery effect. The investigation indicated that, up to 45 kGy, the grating is more sensitive to radiation than other optical fiber sensors.

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Section: Materials and Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Online Tests of an Optical Fiber Long-Period Grating Subjected to Gamma Irradiation

et al. 2014

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“…When applying high-intensity (200-500 GW/cm ) light at either 264 or 211 nm (fourth and fifth harmonics of our femtosecond Nd : glass laser system), two-photon excitation (via a virtual state) takes place [8], [9]. By irradiating the telecom fiber with 352-nm femtosecond pulses (third harmonic of our femtosecond Nd : glass laser system) at an intensity of about 1000 GW/cm , we realize three-photon excitation [10]. It should be mentioned that the energy bandgap for a standard Corning telecom fiber with 3-mol.% Ge-doping is higher than 7.1 eV (the only literature value given is for 5-mol.% Ge-doped fused silica [11]), but it should be lower than that of pure fused silica (cladding), which is about 9.3 eV [12].…”

Section: Introductionmentioning

confidence: 99%

“…But as geometrically the fiber consists mainly of the cladding and as the inscribing UV radiation entering the fiber first propagates through the cladding, most of the absorbed energy will be deposited there. It was shown [10] that in a standard telecom fiber single-mode fiber (SMF-28), the fraction of incident fluence absorbed in the cladding increases from 74.7% at 264 nm to 95.5% at 211 nm and further to 98.1% at 352 nm. It follows that LPFGs recorded at high-intensity femtosecond UV irradiation are very asymmetric relative to the fiber axis and, like nonphotochemical LPFGs, should possess noticeable polarization properties.…”

Section: Introductionmentioning

confidence: 99%

Polarization properties of long-period gratings prepared by high-intensity femtosecond 352-nm pulses

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Fotiadi

Mégret

et al. 2005

IEEE Photon. Technol. Lett.

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We inscribed long-period gratings in a hydrogenated single-mode fiber (SMF-28) by high-intensity femtosecond near-ultraviolet pulses via a three-photon absorption mechanism. Due to energy deposition in the fiber cladding, such gratings are similar to those fabricated by CO 2 laser induced heating, mechanical pressure, or electric arc. We found that these gratings exhibit significant polarization properties.

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“…% Ge-doped fused silica samples irradiated with high-intensity (up to 2000 GW/ cm 2 ) 352 nm femtosecond pulses, the three-photon absorption mechanism was confirmed and the three-photon absorption coefficients were measured. 15 In the literature there is only one mention of LPFG inscription by cw near-UV ͑333-364 nm͒ light: A weak 3 dB long-period grating with a period of 200 m and 4 cm length was recorded in an unloaded 10 mol. % Ge-doped fiber.…”

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confidence: 99%

Strong long-period fiber gratings recorded at 352?nm

et al. 2005

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We describe long-period grating inscription in hydrogenated telecom fibers by use of high-intensity femtosecond 352 nm laser pulses. We show that this technique allows us to fabricate high-quality 30 dB gratings of 300 m period and 2 cm length by use of a three-photon absorption mechanism. © Long-period fiber gratings (LPFGs, also known as transmission gratings) have existed since the mid-1990s. 1 They were originally fabricated photochemically by UV laser light at wavelengths coinciding with the maximum of the absorption band of defects in germanosilicate glass, and this is the most frequently used way of LPFG fabrication. For this purpose, KrF excimer laser radiation (248 nm; Ref. 2) or the second-harmonic radiation of a cw argon-ion laser (244 nm; Ref. 3) is usually used. Such a conventional low-intensity UV approach leads to a refractive-index change in the Ge-doped fiber core by means of single-quantum photochemical reactions. Recently we used high-intensity 264 nm femtosecond pulses (the fourth harmonic of our Nd:glass laser system 4 ) for recording LPFGs in single-mode telecom fibers. Under these experimental conditions, the inscription proceeds by means of a two-photon mechanism. 5In this report, we applied 352 nm radiation for LPFG inscription in the hydrogenated single-mode telecommunication fibers SMF-28 and SMF-28e. A schematic of the experimental setup is given in Fig. 1. For inscription of LPFGs we used the thirdharmonic radiation of a commercial femtosecond Nd-:glass laser (Twinkle; Light Conversion, Ltd., Lithuania), which was generated in a 2 mm long KDP crystal cut for type I interaction ( = 47.6°, = 45°). The method of frequency tripling was similar to that described in Ref. 6. The pulse duration of the resultant 352 nm pulses was 250 fs (FWHM), the beam diameter was 0.27 cm (FWHM), the repetition rate was 27 Hz, and the pulse energy was as much as 150 J. The femtosecond UV pulses were focused by a CaF 2 spherical lens, with a 48.6 cm focal distance, through a slit of width 150 m and onto a fiber (with the acrylate coating removed) that was placed behind the slit at a distance of ϳ100 m. The movement of the fiber and the control of the light's fluence were accomplished according to the method described in Ref. 5. For LPFG inscription we used the standard telecom fiber SMF-28 (supplied by Elliot Scientific) and the enhanced telecom fiber SMF-28e (supplied by Corning), both with a core diameter of 8.2 m, a cladding diameter of 125 m, and a numerical aperture of 0.14. The fibers were sensitized in a hydrogen atmosphere at 160 bars ͑120 kTorr͒ at 80°C for 90 h.Figures 2(a) and 2(b) present the experimental transmission loss spectra for two recorded gratings in SMF-28 and SMF-28e fibers, respectively. These gratings were fabricated with a 300 m period, and they were 2 cm in length.First we want to emphasize that our LPFGs, inscribed by high-intensity 352 nm pulses, are stronger than those produced by other photochemical methods. This statement refers to gratings of the same length and the sam...

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Long-period fiber grating inscription under high-intensity 352 nm femtosecond irradiation: Three-photon absorption and energy deposition in cladding

Cited by 15 publications

References 29 publications

Online Tests of an Optical Fiber Long-Period Grating Subjected to Gamma Irradiation

Online Tests of an Optical Fiber Long-Period Grating Subjected to Gamma Irradiation

Polarization properties of long-period gratings prepared by high-intensity femtosecond 352-nm pulses

Strong long-period fiber gratings recorded at 352?nm

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