Study of refractive index of GeO_2:SiO_2 mixtures using deposited-thin-film optical waveguides

Huang, Agnes S.; Arie, Y.; Neil, C. C.; Hammer, Jacob

doi:10.1364/ao.24.004404

Cited by 9 publications

(4 citation statements)

References 8 publications

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“…Given the refractive index data of pure silica, germanosilicate, and pure germanium oxide [6,7], the radius and Ge concentration of the step-indexed fiber core can be derived from the NA and the cutoff wavelength of the fiber (Table 1). These properties are sufficient to calculate the effective refractive index of the core mode ( n e co ) and the v th-order cladding mode ( n e v ) at a given wavelength λ along with their electromagnetic fields, using a three-layer model with the ambient air as the outer layer [5].…”

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confidence: 99%

Emergence of self-organized long-period fiber gratings in supercontinuum-generating optical fibers

Lü

Marks

et al. 2009

Opt. Lett.

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A localized long-period fiber grating emerges in a silica optical fiber transmitting femtosecond pulseinduced supercontinuum. Simultaneously, a specific higher-order fiber cladding mode associated with the grating gains amplification at the expense of the fiber core mode. The grating has a period dependent on the dielectric structure of the fiber and is therefore classified as a self-organized structure.Despite the increasing popularity of the supercontinuum (SC) generated from optical fibers [1], the long-term stability and optical effects of such source remain relatively unknown. Here we observe that SC-generating optical fibers tend to induce long-period fiber gratings (LPFGs) that upon formation will modify the incident light field and the SC output. While this effect may be undesirable for fiber-based SC applications, it offers a novel method to fabricate the LPFGs useful for applications such as fiber sensing [2].Our experiments involved pumping UHNA3 fiber (Nufern, East Granby, Conn.) with 80 MHz, 820 nm femtosecond pulses for SC generation [3]. The entrance end of an irradiated fiber (~1 m) developed a ~10 mm long waveguide exhibiting the expected 15-70% transmission loss across the 700-925 nm range [4]. The fiber was then reversed so that its cleaved exiting end was used for light coupling, while the end containing the waveguide became the exit (Fig. 1). Such rearrangement aimed to examine the cladding mode(s) into which the waveguide scatters away the core mode [4]. The cladding mode(s) should mostly exit from the reversed fiber without the loss occurring to the original arrangement. Indeed, the coupling efficiency (CE) of cw probe light (produced by the cw operation of the writing laser) for the reversed irradiated fiber was maximized at about 80% across the 700-925 nm range, just like a pristine (control) UHNA3 fiber (~1 m), which has no waveguide in its cleaved exit end (Fig. 1). The CE was measured to be the ratio of the maximized power exiting from the fiber to the power incident on the aspheric lens (Fig. 1). However, the far-field pattern of the exiting beam at a visible probe wavelength of 710 nm differed dramatically between the two. While the Gaussian-like pattern of the core mode is observed for the control fiber, a strong circular ring emerged from the pattern (shown as the weak background) for the irradiated fiber (Fig. 2), suggesting the presence of a higher-order cladding mode. The far-field ring was also observed at probe wavelengths across 710-860 nm. The divergence angle θ of the ring (Fig. 1) as a function of probe wavelength was measured [ Fig. 3(b) Femtosecond pulses at 820 nm have also written waveguides in a UHNA1 fiber (~1 m) (Nufern, East Granby, Conn.). The measurements on this fiber yield qualitatively similar results. Quantitatively, the θ of the far-field ring is smaller [ Fig. 3 Given the refractive index data of pure silica, germanosilicate, and pure germanium oxide [6,7], the radius and Ge concentration of the step-indexed fiber core can be derived from the NA an...

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confidence: 99%

Emergence of self-organized long-period fiber gratings in supercontinuum-generating optical fibers

Lü

Marks

et al. 2009

Opt. Lett.

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“…UHNA3 and LMA-8 have NAs of 0.35 and 0.10 and mode field diameters of 2.0 and 6.0 µm (at 825 nm), respectively. UHNA3 has a step-index-type germanosilicate core, allowing Ge concentration to be estimated as 29 mol% [14]. The 120 fs 80 MHz pulses from a tunable Ti:sapphire laser (Mai Tai HP, Spectra-Physics, Mountain View, California) served as the pumping and probing source with ~10 nm bandwidth.…”

Section: Methodsmentioning

confidence: 99%

Localized waveguide formation in germanosilicate fiber transmitting femtosecond IR pulses

Tu¹,

Koh²,

Marks³

et al. 2008

J. Opt. Soc. Am. B

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Transmission of intense femtosecond 825 nm pulses progressively produces a waveguide at the entrance of a heavily Ge-doped silicate fiber. The waveguide behaves as a multimillimeter long-fiber bandpass filter that scatters away light with wavelengths shorter or longer than 850 nm. This phenomenon has been correlated with the ~800 nm photosensitivity producing type I-IR fiber Bragg gratings in side-written lightly Ge-doped silicate fibers and low-loss waveguides in pure silica bulk glass. A model incorporating color center formation is proposed to understand the underlying mechanism.

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“…For these calculations, the silica refractive index, n lo � n SiO 2 , was obtained using its Sellmeier equation [22], and the refractive index of the rods, n hi , was assumed to be uniform and calculated through [23]:…”

Section: Fiber Characteristics and Transmission Spectramentioning

confidence: 99%

Temperature response of an all-solid photonic bandgap fiber for sensing applications

et al. 2013

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The spectral shift due to temperature in the photonic bandgap (PBG) of an all-solid PBG fiber is investigated, aiming at discrete and distributed temperature sensing. A temperature rise induces a red shift in the bandgap spectra, which can be easily and precisely monitored by measuring the fiber transmission near one of the band edges. Two different situations that are potentially compatible with distributed and quasi-distributed sensing were investigated: heating a 2 m section of a longer (~10 m) fiber, and heating the whole extension of a fiber that is tens of centimeters in length and was spliced to conventional fibers on both sides. The latter setup yielded bandgap spectral shifts up to ~35 pm/°C. Aiming at discrete sensing, a short (~50 mm) fiber section was subjected to a tight bend so as to exhibit increased temperature sensitivity. Choosing the position of the bend allows for reconfiguration, on demand, of the sensor. A semi-analytical method to identify the spectral position of bandgaps was used to model the fiber transmission, as well as the bandgap shift with temperature, with consistent results.

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Study of refractive index of GeO_2:SiO_2 mixtures using deposited-thin-film optical waveguides

Cited by 9 publications

References 8 publications

Emergence of self-organized long-period fiber gratings in supercontinuum-generating optical fibers

Emergence of self-organized long-period fiber gratings in supercontinuum-generating optical fibers

Localized waveguide formation in germanosilicate fiber transmitting femtosecond IR pulses

Temperature response of an all-solid photonic bandgap fiber for sensing applications

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