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International audience; In this letter, we experimentally demonstrate a 4-dB increase of the stimulated Brillouin scattering threshold in a microstructured optical fiber. This result is obtained by periodically varying the size of the air-hole structure by only 7% amplitude, while keeping a low attenuation coefficient. The efficiency of this passive technique is verified by use of the Brillouin echoes-distributed sensing technique where the Brillouin frequency-shift oscillation is clearly observed.

We investigate experimentally the MI process in a dispersion oscillating fiber. An important number of unstable frequencies over 10 THz are generated that then lead to a new degree of freedom for tailoring nonlinear effects.

A simple analytical model is developed to analyze and explain the complex dynamics of the multi-peak modulation instability spectrum observed in dispersion oscillating optical fibers [M. Droques et al., 37, 4832-4834 Opt. Lett., (2012)]. We provide a simple expression for the local parametric gain which shows that each of the multiple spectral components grows thanks to a quasi-phase-matching mechanism due to the periodicity of the waveguide parameters, in good agreement with numerical simulations and experiments. This simplified model is also successfully used to tailor the multi-peak modulation instability spectrum shape. These theoretical predictions are confirmed by experiments., Comment: 18 pages, 6 figures. arXiv admin note: substantial text overlap with arXiv:1207.4667

We report, through numerical simulations and experimental data, the first successful fabrication of a polarization maintaining single-mode fiber delivering a flat top intensity profile at 1.05 µm. A high quality flat mode was obtained and single-mode behavior was checked by shifting the injection and by S² imaging method. Numerical investigations were performed to show that it would be possible to increase further the 0.6x10⁻⁴ experimental group birefringence.

International audience; Solid-core photonic crystal fibers with the core derived from non-doped or Erbium-doped sol-gel silica rods are fabricated. The results demonstrate that the direct polymeric sol-gel route constitutes a promising method to prepare large high quality glass pieces that can be integrated into microstructured optical fibers suitable for passive and active optical fiber applications.

Supercontinuum generation in the long pulse regime in optical fibers is first initiated by modulation instability, which is highly sensitive to noise and gives rise to a large variety of solitonic pulses in terms of width and peak power. The most intense of them experience most efficient Raman self-frequency shift which induces important pulse-to-pulse energy fluctuations at the long-wavelength spectrum edge [1]. We propose here a passive method based on the use of a solid-core photonic bandgap (PBG) fiber, allowing a strong reduction of the long-wavelength edge fluctuations, thanks to a cancellation of the soliton self-frequency shift.

We report an experimental study of the nonlinear propagation of femtosecond pulses in solid-core photonic bandgap fibers. An extreme deceleration of the soliton self-frequency shift accompanied by a spectral compression is observed near the photonic bandgap edge. In practice, this extreme deceleration is equivalent to a suppression of the soliton self-frequency shift and so to a stabilization of the soliton frequency. The physical origin of this phenomenon is discussed with the help of numerical simulations. Finally, a simple model is proposed to identify the main physical mechanism responsible for the extreme deceleration of soliton self-frequency shift. In the case of our fiber design, it is mainly due to the strong third-order dispersion experienced by the soliton as it approaches the photonic bandgap edge.

International audience; In this paper we investigate the effect of microstructure irregularities and applied strain on backward Brillouin scattering by comparing two photonic crystal fibers drawn with different parameters in order to minimize diameter and microstructure fluctuations. We fully characterize their Brillouin properties including the gain spectrum and the critical power. Using Brillouin echoes distributed sensing with a high spatial resolution of 30 cm we are able to map the Brillouin frequency shift along the fiber and get an accurate estimation of the microstructure longitudinal fluctuations. Our results reveal a clear-cut difference of longitudinal homogeneity between the two fibers.

International audience; We show that the infrared edge of supercontinua generated in solid core photonic bandgap fibers is characterized by a very different temporal behavior than the one obtained in standard fibers. In particular, pulse-to-pulse spectral power fluctuations are significantly reduced near the bandgap edge, and the statistical distribution is quasi-gaussian. The spectral dynamics of this process and statistical properties are investigated experimentally and confirmed by numerical simulations. The reduction of power fluctuations originates from the cancellation of the soliton self-frequency shift near the bandgap edge.

We demonstrate a source of photon pairs with widely separated wavelengths, 810 nm and 1548 nm, generated through spontaneous four-wave mixing in a microstructured fiber. The second-order auto-correlation function g^{(2)}(0) was measured to confirm the non-classical nature of a heralded single photon source constructed from the fiber. The microstructured fiber presented herein has the interesting property of generating photon pairs with wavelengths suitable for a quantum repeater able to link free-space channels with fiber channels, as well as for a high quality telecommunication wavelength heralded single photon source. It also has the advantage of straightforward coupling into optical fiber. These reasons make this photon pair source particularly interesting for long distance quantum communication., 3 pages, 3 figures. Published version

We achieved a 0.2nm linewidth output at 1178nm with powers up to 6.4W in a linear 80m Bismuth-doped fiber cavity pumped by a 55W Yb fibre laser. The potential of frequency doubling of the non-polarized output at 1178nm in MgO doped periodically poled lithium niobate was demonstrated and resulted in 125mW average power at 589nm. The approach can be extended to a linearly-polarized large mode area format with under 0.1nm linewidth capable of scaling to Watts level in the 560-620nm range.

We report on the development of hollow-core photonic bandgap fibers for the delivery of high energy pulses for precision micro-machining applications. Short pulses of (65ns pulse width) and energies of the order of 0.37mJ have been delivered in a single spatial mode through hollow-core photonic bandgap fibers at 1064nm using a high repetition rate (15kHz) Nd:YAG laser. The ultimate laser-induced damage threshold and practical limitations of current hollow-core fibers for the delivery of short optical pulses are discussed.

We describe a hollow-core photonic bandgap fiber designed for use in the 850 nm wavelength region. The fiber has a minimum attenuation of 180dB/km at 847nm wavelength. The low-loss mode has a quasi- Gaussian intensity profile. The group-velocity dispersion of this mode passes through zero around 830nm, and is anomalous for longer wavelengths. The polarization beat length varies from 4 mm to 13 mm across the band gap. We expect this fiber to be useful for delivery of high-energy ultrashort optical pulses.

International audience; We report on the fabrication and the characterization of a design of highly birefringent solid-core photonic bandgap fibers. A form birefringence is obtained by keeping open all interstitial air holes but two diametrically opposite and close to the fiber core. Group birefringence as high as 0.57×10-3 and 0.47×10-3 at 1.1 and 1.55 μm, respectively, are demonstrated in the first bandgap.

Fibers used for high power delivery are designed to ensure single-mode operation (in order to guarantee good output beam quality), large effective areas (A eff ) and resistance to bend-induced distortions (in order to avoid non-linear effects). For simple step index fibers, the maximum Aeff of the fundamental mode that can practically be achieved at 1.06μm is ~350μm 2 . All-solid-silica Bragg fibers with large cores were proposed as an alternative solution for high power delivery through their fundamental core mode. These fibers consist of a low-refractive index core surrounded by a multilayer cladding that acts as a Bragg mirror. The loss spectrum of such fibers consists of a concatenation of several transmission windows separated by high-loss peaks. Here, we simultaneously study, for the first time (at our knowledge), the bending impact on Bragg fibers for the three critical properties required for high power delivery: large A eff , single-mode propagation and low bend losses for the fundamental mode. Thanks to their specific guiding mechanism, A eff as large as ~500μm 2 at 1.06μm can be achieved in Bragg fibers, while maintaining single-mode operation and bend losses lower than 0.1dB/m. Our numerical results are validated by experimental measurements on a PCVD Bragg fiber with a 40μm diameter core.

International audience; Fiber Bragg Gratings with reflectivity up to 25 dB have been photo-written in the core of a 2D all-solid Photonic Bandgap Fiber without modification of the guiding properties of the fiber. This result is obtained by combining an appropriate glass composition for the high index inclusions constituting the micro-structured cladding and a photosensitive low index core. Couplings of the fundamental core guided mode with cladding modes are investigated and compared to theoretical predictions.

International audience; We experimentally investigate the nonlinear propagation of subnanosecond pulses in solid-core photonic bandgap fibers. By launching pulses with a few kilowatts peak power, a flat supercontinuum is generated. The long-wavelength edge of the supercontinuum can be controlled thanks to the original linear properties inherent to solid-core photonic bandgap fibers. This allows one to tailor the generated supercontinuum radiation and to keep it over a given spectral range of interest without any significant power loss

We report on a possible phase matching between two fundamental modes guided in an appropriately designed photonic crystal fiber. The phase index matching condition can be perfectly fulfilled for second or third harmonic generation and for wavelengths over a large spectral range, simply by tuning the lattice pitch. This can be achieved in such a structure thanks to the coexistence of total internal reflection and photonic bandgap guidance, leading to two different dispersive behaviours for the fundamental and the harmonic waves.

We study the effect of bends on the transmission window of the first PCVD large-mode-area Bragg fibre. The origin and the consequences of this effect are also presented.

Several strong narrowband resonances are observed in the transmission spectra of fiber Bragg gratings photo-written in photonic crystal fiber that has a refractive index-neutral germanium/fluorine co-doped core. Experimental results for the strain, temperature and refractive index sensitivities of these mode resonances are reported and compared to those of conventional single mode fiber. In particular, we identify three kinds of resonances whose relative sensitivities to strain, temperature and refractive index are markedly different and present numerical simulations to explain these properties. Potential multiparameter optical sensor applications of these mode resonances are briefly discussed.

Fiber Bragg gratings with strong resonance peaks for both Bragg and cladding modes are made in photonic crystal fiber modified with a germanium doped core. Experimental results for strain, temperature and refractive index sensitivities of fiber Bragg gratings are reported. We show the existence of an inner cladding mode that has the largest coupling from the core mode and that is insensitive to surrounding index changes. The core mode, inner cladding mode and outer cladding modes all have the same temperature sensitivity. By tracking the cladding mode resonances shifts relative to the core mode, a temperature and index insensitive strain sensor can be made.

We report the generation of a broadband super- continuum with a CW Yb fiber laser and a PCF. The spectrum extends toward short wavelengths through efficient dispersive wave generation.

We present recent progress in the field of solid-core photonic bandgaps fibers in terms of designs, losses and their possible applications (laser sources, second or third harmonic generation...)

We demonstrate that our previous loss results [1] in an all-solid photonic bandgap fiber were in fact limited by bend loss. A new design, based on the addition of an extra ring of air holes on the outside of the all solid photonic bandgap structure, is then proposed, realized and characterized. We demonstrate that it significantly reduces both the fiber diameter and its sensitivity to bend loss.

We investigate both experimentally and numerically confinement and bend losses in solid-core photonic bandgap fibers. We proposed two designs, based on the addition of air regions in the cladding, allowing these losses to be reduced significantly while keeping the optical properties of bandgap fibers. We also present and discuss numerical results on the impact of transversal defects on the fiber confinement loss in the case of a realistic low loss fiber.

We report the fabrication, characterization and modeling of a solid-core photonic bandgap fiber with interstitial air holes between the cladding rods. The presence of these interstitial air holes leads to a great improvement of optical properties for this kind of fiber. Particularly, we demonstrate that confinement losses and bend sensitivity are substantially reduced. Our experimental results for this new solution are well supported by numerical results.

We numerically investigate the impact of transversal defects on the minimum confinement loss value in the case of a solid-core photonic-bandgap fiber with parabolic germanium-doped inclusions. We show that a standard deviation of only 5% of either the diameter, the refractive-index contrast, or the position of the high-index inclusions could double the minimal value-as a function of frequency-of losses. Moreover, we demonstrate that, in our case, accurately controlling the position of the doped inclusions along the first ring around the core is more important than having an accurate control on their diameter and index contrast. Oddly enough, we also point out that the defects could lead to a decrease of the minimum loss value. Furthermore, we demonstrate that a structure made of inclusions of two different refractive indices could have lower loss than both structures made of only one of these two types of inclusion.

International audience; A laser based on a ribbon multicore ytterbium doped fiber where different cores amplified different spectral bands, has been mode-locked with a single saturable absorber mirror. Tunable dual wavelength synchronized picosecond pulses were obtained. Compensation of differential cavity roundtrip times was achieved in the fiber.

International audience; Active coherent beam combination using a 7-non-coupled core,polarization maintaining, air-clad, Yb-doped fiber is demonstrated as amonolithic and compact power-scaling concept for ultrafast fiber lasers. Amicrolens array matched to the multicore fiber and an active phasecontroller composed of a spatial light modulator applying a stochasticparallel gradient descent algorithm are utilized to perform coherentcombining in the tiled aperture geometry. The mitigation of nonlineareffects at a pulse energy of 8.9 μJ and duration of 860 fs is experimentallyverified at a repetition rate of 100 kHz. The experimental combiningefficiency results in a far field central lobe carrying 49% of the total power,compared to an ideal value of 76%. This efficiency is primarily limited bygroup delay differences between cores which is identified as the maindrawback of the system. Minimizing these group delay issues, e.g. by usingshort and straight rod-type multicore fibers, should allow a practical powerscaling solution for femtosecond fiber systems.

SC-PBG fibers were realized and characterized from 0.5 ?m to 1.7?m. Fiber losses were measured equal to 6 dB/km. Scatterring and bending losses were measured. Band gap modifications were realized using OH floodding.

Bending losses are investigated experimentally and numerically in a solid-core bandgap fiber with parabolic refractive index inclusions. Previous record of 20 dB/km is reduced to 6 dB/km by increasing the fiber bend radius.

Stable microwave oscillators are realized based on high quality factor resonators, which in turn are realized using acoustic, electromagnetic, and optical technologies. Since a large quality factor could be achieved using small and long fiber delay lines, optical techniques are particularly attractive. Among various techniques, opto-electronic oscillators (OEOs) have demonstrated the lowest close-to-carrier phase noise compared to all other techniques. Nevertheless, the temperature sensitivity of OEOs is of concern due to changes in the index of refraction of optical fibers. This paper provides results regarding the performance of an OEO at 10 GHz and performance comparison is made in using both standard (SMF-28) and solid-core photonic crystal fiber (SC-PCF). The OEO using SC-PCF fiber delay lines exhibits a factor of three reductions in its temperature sensitivity over SMF-28 based OEO.

High power Er/Yb lasers at 1.55 /spl mu/m are attractive for a number of applications, for example sensors, spectroscopy and free space telecommunications. In this paper, we report a double-clad fiber, which has an Er/Yb doped core and an inner cladding waveguide suspended in air by very thin silica bridges. The massive acceptance angles, numerical aperture larger than 0.8, and the laser output power demonstrated during the course of this work clearly indicate the potential of this technology for high power fiber lasers.

Despite the fact that laser scanning confocal microscopy (LSCM) has become an important tool in modern biological laboratories, it is bulky, inflexible and has limited field of view, thus limiting its applications. To overcome these drawbacks, we report the development of a compact dual-clad photonic-crystal-fiber (DCPCF) based multiphoton scanning microscope. In this novel microscope, beam-scanning is achieved by directly scanning an optical fiber, in contrast to conventional beam scanning achieved by varying the incident angle of a laser beam at an objective entrance pupil. The fiber delivers femtosecond laser pulses for two-photon excitation and collects fluorescence back through the same fiber. Conventional fibers, either single-mode fiber (SMF) or multimode fiber (MMF), are not suitable for this detection configuration because of the low collection efficiency for a SMF and low excitation rate for a MMF. Our newly invented DCPCF allows one to optimize collection and excitation efficiency at the same time. In addition, when a gradient-index (GRIN) lens is used to focus the fiber output to a tight spot, the fluorescence signal collected back through the GRIN lens forms a large spot at the fiber tip because of the chromatic aberrations of the GRIN lens. This problem prevents a standard fiber from being applicable, but is completely overcome by the DCPCF. We demonstrate that this next generation scanning confocal microscope has an extremely simple structure and a number of unique features owing to its fundamentally different scanning mechanism: high flexibility, arbitrarily large scan range, aberration-free imaging, and low cost.

We report the development of a novel double-clad photonic-crystal-fiber based multiphoton scanning microscope, which has a number of advantages over conventional scanning microscopes.

Fluorescence is a powerful tool for biosensing, but conventional fluorescence measurements are limited because solid tumors are highly scattering media. To obtain quantitative in vivo fluorescence information from tumors, we have developed a two-photon optical fiber fluorescence (TPOFF) probe where excitation light is delivered and the two-photon fluorescence (TPF) excited at the tip of the fiber is collected back through the same fiber. In order to determine whether this system can provide quantitative information, we measured the fluorescence from a variety of systems including mouse tumors (both ex vivo and in vivo ) which were transfected with the gene to express varying amounts of green fluorescence protein (GFP), and tumors which were labeled with targeted dendrimer-based drug delivery agents. The TPOFF technique showed results quantitatively in agreement with those from flow cytometry and confocal microscopy. In order to improve the sensitivity of our fiber probe, we developed a dual-clad photonic-crystal fiber which allowed single-mode excitation and multimode (high numerical aperture) collection of TPF. These experiments indicate that the TPOFF technique is highly promising for real-time, in vivo , quantitative fluorescence measurements.

We report on the generation of pure rotational stimulated Raman scattering in a hydrogen gas hollow-core photonic crystal fiber. Using the special properties of this low-loss fiber, the normally dominant vibrational stimulated Raman scattering is suppressed, permitting pure conversion to the rotational Stokes frequency in a single-pass configuration pumped by a microchip laser. We report 92% quantum conversion efficiency (40 nJ pulses in 2.9 m fiber) and threshold energies (3 nJ in 35 m) more than 1 x 10(6) times lower than previously reported. The control of the output spectral components by varying only the pump polarization is also shown. The results point to a new generation of highly engineerable and compact laser sources.

Air-silica microstructured fibers are designed and fabricated to yield numerical aperture (NA) greater than 0.9. A model is presented which accurately predicts the structural parameters required in order to realize high NAs. Such fibers have application in lasers and laser-induced-fluorescence systems.

Conventional silica fiber optics cannot currently deliver the high beam quality, high peak power pulses required for micro-machining applications due to damage limitations. Recently developed photonic bandgap (PBG) fibers have the potential to overcome this limitation as the power is mostly contained within an air-core, with guidance arising from the periodic nature of the cladding. We report the delivery of high energy nanosecond pulses from a high repetition rate (up to 100 kHz) Q-switched Nd:YAG laser through the fundamental mode of a PBG fiber at 1064 nm. The damage limitations of the PBG silica structure are investigated, together with its application to precision micro-machining. We present an optimized fiber design to reduce the light-in-glass fraction and hence maximize the power handling capability. Short pulses (around 60 ns pulse width) and energies of the order of 0.5 mJ were delivered in a single spatial mode through the hollow-core fiber providing the pulse energy and high beam quality required for micro-machining of metals. Practical micro-machining of metal sheet is also presented.Conventional silica fiber optics cannot currently deliver the high beam quality, high peak power pulses required for micro-machining applications due to damage limitations. Recently developed photonic bandgap (PBG) fibers have the potential to overcome this limitation as the power is mostly contained within an air-core, with guidance arising from the periodic nature of the cladding. We report the delivery of high energy nanosecond pulses from a high repetition rate (up to 100 kHz) Q-switched Nd:YAG laser through the fundamental mode of a PBG fiber at 1064 nm. The damage limitations of the PBG silica structure are investigated, together with its application to precision micro-machining. We present an optimized fiber design to reduce the light-in-glass fraction and hence maximize the power handling capability. Short pulses (around 60 ns pulse width) and energies of the order of 0.5 mJ were delivered in a single spatial mode through the hollow-core fiber providing the pulse energy and high beam quality requi...

In this letter it is demonstrated that the sol–gel route combined with fiber fabrication by the stack and draw method can be used to realize efficient fiber lasers. More precisely, a pure silica ytterbium-doped photonic crystal fiber with a core obtained by the sol–gel polymeric technique is studied, and a laser efficiency of more than 73% is achieved for a laser emission around 1034 nm. The optical and spectroscopic properties of the monolith and fiber are investigated, together with the sensitivity of the fiber to photodarkening. The dimensions of the ytterbium-doped monolith combined with the uniform doping and refractive index that are reported make this technique particularly interesting for the realization of large-mode area fibers.

International audience; We report the fabrication and characterization of a photonic crystal fiber (PCF) having a sol-gel core doped with ionic copper. Optical measurements demonstrate that the ionic copper is preserved in the silica glass all along the preparation steps up to fiber drawing. The photoluminescence results clearly show that such an ionic copper-doped fiber constitutes a potential candidate for UV-C (200-280 nm) radiation dosimetry. Indeed, the Cu+-related visible photoluminescence of the fiber shows a linear response to 244 nm light excitation measured for an irradiation power up to 2.7 mW at least on the Cu-doped PCF core. Moreover, this response was found to be fully reversible within the measurement accuracy of this study ( ± 1%), underlying the remarkable stability of copper in the Cu+ oxidation state within the pure silica core prepared by a sol-gel route. This reversibility offers possibilities for the achievement of reusable real-time optical fiber UV-C dosimeters.

Observation of sub-picosecond pulses from a single section Fabry Perot InAs/GaAs edge emitting quantum dot (QD) based laser at 1.3 μm under continuous wave operation is reported. After group delay dispersion compensation, pulse durations as short as 770 fs in a 45 GHz repetition rate device have been measured, with 1.9 W of peak power and a narrow radio frequency spectrum of only a few kHz linewidth. The experiments show evidence of an unexplored mode locking regime in the InAs/GaAs quantum dot material system, which still needs theoretical modelling and further analysis.

We report the experimental demonstration of a modulation instability (MI) process assisted by a periodic dispersion modulation in an optical fiber. We observe the spontaneous growth of more than 10 pairs of MI sidebands spanning over more than 10 THz thanks to a quasi-phase-matched process.

One watt of laser power at 1535 nm has been generated from an Er:Yb codoped double-clad fiber structure, in which the inner cladding was suspended in air by a large number of thin silica webs. The acceptance numerical aperture (NA) of the inner cladding has been measured over a range of wavelengths, for lengths from 1 up to 100 m. For fiber lengths of ∼40 m, the NA at the pump diode wavelength was 0.88.

All-optical-fiber Fabry-Perot interferometers (FPIs) with microcavities of different shapes were investigated. It was found that the size and shape of the cavity plays an important role on the performance of these interferometers. To corroborate the analysis, FPIs with spheroidal cavities were fabricated by splicing a photonic crystal fiber (PCF) with large voids and a conventional single mode fiber (SMF), using an ad hoc splicing program. It was found that the strain sensitivity of FPIs with spheroidal cavities can be controlled through the dimensions of the spheroid. For example, a FPI whose cavity had a size of ~10x60 μm exhibited strain sensitivity of ~10.3 pm/με and fringe contrast of ~38 dB. Such strain sensitivity is ~10 times larger than that of the popular fiber Bragg gratings (~1.2 pm/με) and higher than that of most low-finesse FPIs. The thermal sensitivity of our FPIs is extremely low (~1pm/°C) due to the air cavities. Thus, a number of temperature-independent ultra-sensitive microscopic sensors can be devised with the interferometers here proposed since many parameters can be converted to strain. To this end, simple vibration sensors are demonstrated.

Thanks to an all solid core photonic crystal fiber (PCF) used as a multicore fiber, we propose and experimentally demonstrate what is to our knowledge a new optical detection scheme for the spontaneous emission collection of cold atoms. A Magneto-Optical Trap (MOT) is placed in front of a polished PCF end-face. As they display a higher optical index than the surrounding cladding silica, the 108 rods (equivalent to a 108 pixels camera) of this PCF are light guiding and behave like an array of detectors. Both global and local properties of the trapped atoms are probed. A MOT lifetime is reported. We also take advantage of the multi-core geometry for a real time detection of the center-of-mass motion of the atomic cloud.

We report on a microscopic Fabry-Perot interferometer whose cavity is a bubble trapped inside an optical fiber. The microcavity is formed by pressuring a photonic crystal fiber (PCF) with large voids during fusion splicing with a conventional single-mode fiber. The technique allows achieving high repeatability and full control over the cavity size and shape. It was found that the size of the PCF voids contributes to control the cavity size independently of the pressure in the PCF. Our devices exhibit a record fringe contrast of 30 dB (visibility of 0.999) due to the ellipsoidal cavity whose surfaces compensate for the diffraction of the reflected beam. The strain sensitivity of the interferometers is higher when the cavities are ellipsoidal than when they are spherical.

The concept of photonic crystal fibers (PCFs) has opened the route to a new family of optical fibers available for a wide range of applications in nonlinear optics. The nonlinear performances are based both on the easy chromatic dispersion management possible with PCFs and on the increased fiber nonlinearity, thanks to the small effective mode areas accessible with these fibers. Hence, even if necessary, the intrinsic nonlinearity of the material used to realize the fiber generally plays a secondary role. This is true for most of the realizations which are based on pure silica glass, a matrix with modest nonlinear coefficients. However, various glass matrices are known to offer larger nonlinear coefficients and could be useful to further improve the performances of systems based on highly nonlinear fibers. Among these, conventional glasses containing dopants presenting nonlinear properties, like gold nanoparticles (Au NPs), appear as promising candidates [1]. However, realization of glasses doped by Au NPs is mainly limited to films and bulk materials and there are only two reports of insertion of such systems in the core of a conventional optical fiber, mainly due to the difficulty induced by the high temperatures commonly used to synthesize optical fibers (typically 1500–2000°C) as compared to the gold melting point [2,3].

Optical properties of a Bismuth-doped pure silica sol-gel core photonic crystal fiber (PCF) were investigated. We report on the absorption, CW luminescence and time resolved luminescence spectra at different excitation wavelengths at room temperature. Complex structure of the energy levels of Bismuth-connected centers in pure silica glass is put in evidence.