M. Andrés - Academia.edu (original) (raw)

Papers by M. Andrés

Optics Letters

Wideband tuning of strong bands generated through polarization modulation instability (PMI) in mi... more Wideband tuning of strong bands generated through polarization modulation instability (PMI) in microstructured optical fibers (MOFs) is reported. Tunability is achieved by exploiting the dependence of the phase-matching condition on the fiber's chromatic dispersion and birefringence, which is particularly sensitive when the fiber is pumped near the zerodispersion wavelength. MOFs designed to accomplish PMI phase-matching when they are infiltrated with ethanol and pumped at 1064 nm were designed and fabricated. Taking advantage of the large thermo-optic coefficient of ethanol, both chromatic dispersion and birefringence were varied through temperature. Wavelength shifts from 937 nm to 863 nm (anti-Stokes) and from 1231 nm to 1387 nm (Stokes) is demonstrated. Such a tuning range corresponds to a frequency shift between the pump and a PMI sideband ranging from 1274 cm-1 to 2189 cm-1 .

Optics Letters

We propose the implementation of fiber Bragg gratings in tapered few-modes, and multimode fibers ... more We propose the implementation of fiber Bragg gratings in tapered few-modes, and multimode fibers to accomplish single-mode operation by reducing the core diameter while preserving the core-cladding structure. Gratings present a single reflection band and the device show low insertion losses after the taper fabrication and the fiber Bragg gratings inscription. The excitation of high order odd-modes in the core of the fiber has been identified as the main loss mechanism; it can be prevented by means of symmetric illumination of the fibers. We also demonstrate the excitation of high order cladding modes (cladding-air modes) along the taper transitions; these modes can be removed without a significant increment of the insertion loss.

Laser Physics

Q-switched and mode-locked (QML) pulse generation from an all-fiber ring laser based on intermoda... more Q-switched and mode-locked (QML) pulse generation from an all-fiber ring laser based on intermodal acousto-optic bandpass modulation is reported. The modulator relies on full-acoustooptic mode re-coupling cycle induced by a standing flexural acoustic wave, with a transmission response that is controlled by amplitude modulation of the acoustic wave signal. The Q factor of the cavity is controlled by a rectangular pulse wave with variable frequency and duty cycle, whereas mode locking is achieved by amplitude modulation derived from a standing flexural acoustic wave. The best QML pulses were obtained at 0.5 kHz repetition rate, with a pump power of 549.2 mW, at the optical wavelength of 1568.2 nm. A maximum overall energy of 2.14 J at an average output power of 1.07 mW was achieved, corresponding to a burst of mode-locked sub-pulses of 100 ps pulse duration within a QML envelope of 3.5 s.

Laser Physics Letters

Active mode-locking of an all-fiber ring laser by transmittance modulation of an in-fiber acousto... more Active mode-locking of an all-fiber ring laser by transmittance modulation of an in-fiber acousto-optic tunable bandpass filter (AOTBF) is reported. Cavity loss modulation is achieved by full acousto-optic mode re-coupling cycle induced by standing flexural acoustic waves. The modulator permits the implementation of 28 dB of nonresonant light suppression, 1.4 nm of modulation bandwidth, 74% of modulation depth and 4.11 dB of optical loss in a 72.5 cm-long all-fiber configuration. The effects of the modulated AOTBF on the laser performance are investigated. Transform-limited optical pulses of 8.8 ps temporal width and 6.0 W peak power were obtained at 4.87 MHz repetition rate.

Optics Express

Acousto-optic coupling in polyimide-coated single-mode optical fibers using flexural elastic wave... more Acousto-optic coupling in polyimide-coated single-mode optical fibers using flexural elastic waves is demonstrated. The effect of the polyimide coating on the acoustooptic interaction process is analyzed in detailed. Theoretical and experimental results are in good agreement. Although the elastic attenuation is significant, we show that acousto-optic coupling can be produced with a reasonably good efficiency. To our knowledge, it is the first experimental demonstration of acousto-optic coupling in optical fibers with robust protective coating.

Optics letters, Jan 15, 2016

We measured the instantaneous frequency profile of two different dissipative soliton resonant (DS... more We measured the instantaneous frequency profile of two different dissipative soliton resonant (DSR) light pulses, the usual flat-top and less-common trapezoid-shaped light pulses. The DSR light pulses were provided by an ytterbium-doped polarization-maintaining fiber ring passively mode-locked laser using the adequately selected amount of net-normal dispersion. We confirmed that the DSR light pulses have a (moderately) low linear chirp across the pulse, except at the edges, where the chirp changes exponentially. This unique instantaneous frequency behavior can be succinctly resumed by the following parameters: linear chirp slope and leading and trailing chirp lifetimes. As the pump power increases, the linear chirp slope decreases, whereas the leading and trailing chirp lifetimes do not show an appreciable change. The results are compared with previous theoretical works.

Optics express, Jan 2, 2016

We investigated the dissipative solitons resonance in an ytterbium-doped fiber ring laser in whic... more We investigated the dissipative solitons resonance in an ytterbium-doped fiber ring laser in which all the elements are polarization maintaining (PM). A semiconductor saturable absorber mirror was used as a mode-locker. The cavity included a normal dispersion single-mode fiber (SMF) and an anomalous dispersion photonic crystal fiber. The change of the length of the PM SMF allows the variation of the net-normal dispersion of the cavity in the range from 0.022 ps² to 0.262 ps². As the absolute value of the net-normal dispersion increases from 0.022 ps² to 0.21 ps², a square-shaped single pulse transformed to a single right-angle trapezoid-shaped pulse, and, at the dispersion of 0.262 ps², to multiple right-angle trapezoid-shaped pulses, per round-trip.

Fiber Lasers XIII: Technology, Systems, and Applications, 2016

A polarization asymmetrical nonlinear optical loop mirror (NOLM) is investigated to perform pedes... more A polarization asymmetrical nonlinear optical loop mirror (NOLM) is investigated to perform pedestal-free optical pulses in a figure-eight laser (F8L). The results demonstrate that in the low-power regime the NOLM operates as a halfwave plate and the output polarization is orthogonal to the input one. However, at higher power level the polarization component parallel to the input appears, with a transmission that always begins from zero at low power, allowing the rejection of low-intensity components. Experimental results demonstrate that by employing this configuration we can obtain a contrast between the peak and continuous background higher that 40 dB.

AIP Conference Proceedings, 2008

We give the details of the fabrication approach that we follow to prepare Erbium-doped photonic c... more We give the details of the fabrication approach that we follow to prepare Erbium-doped photonic crystal fibers and the basic characterization of these fibers. The fibers were fabricated using the conventional stack-and-draw technique. The preforms were prepared combining pure silica capillaries to form a hexagonal lattice and an Erbium doped wire to define the core. Fibers with different pitch, air

Optical Sensors 2015, 2015

In this work an optical fiber laser with loop configuration was developed for magnetic field meas... more In this work an optical fiber laser with loop configuration was developed for magnetic field measurement. The transducer element is an FBG written in a HiBi fiber whose wavelength is modified using a magnetostrictive material that applies deformation in the presence of the magnetic field. The laser has a bandwidth of 450 MHz and operates in single polarization. A shift of 258.5 pm was observed in the laser operating wavelength for a magnetic field of 17.85 mT. Moreover, a maximum sensitivity of 14.72 pm/mT in the linear regime operation was achieved when increasing the magnetic field. The system provides a narrow emission line that is dependent on the magnetic field magnitude enabling high resolution interferometric measurement schemes. The laser response to AC magnetic fields was also characterized using a passive interferometer with higher sensitivity in the range of 8.32 to 17.93 mTRMS.

Optics Express, 2015

The time-resolved acousto-optic technique demonstrated recently to be a very useful method for th... more The time-resolved acousto-optic technique demonstrated recently to be a very useful method for the analysis of fiber axial non-uniformities, able to detect variations of fiber diameter in the nanometric scale with a spatial resolution of few cm. An edge interrogation approach is proposed to improve further the performance of this technique. The detection of subnanometer fiber diameter changes or sub-ppm changes of the core refractive index is demonstrated.

Laser Physics, 2014

The dynamic response after pump switch-on of a 980 nm pumped-ring laser based on an active photon... more The dynamic response after pump switch-on of a 980 nm pumped-ring laser based on an active photonic crystal fiber with an Er3+ ion concentration of ≈1020 ions cm−3 was registered. Then a numerical fitting procedure of a theoretical model was followed to the experimental values of the relaxation oscillation parameters as a function of the input pump power. Non-radiative energy-transfer mechanisms’ coefficients: homogeneous upconversion coefficient (Cup) and critical radii for upconversion (Ru) and migration (Rm) were determined. The calculated best-fit coefficients (Cup = 1.3 × 10−24 m3 s−1, Ru = 9 × 10−10 m, Rm = 13 × 10−10 m) were compared to those obtained with other steady-state and dynamic characterization techniques.

Optics letters, 2015

In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C ... more In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C band in a single-mode ytterbium-doped optical fiber under 980 nm pumping. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. The electronic contribution to the refractive index change is quantified from the wavelength shift. Using a time-resolved acousto-optic method, we investigate the distribution of pump absorption, and the resulting refractive index change profile, along sections of ytterbium-doped fiber exceeding 1 m long under different pump power levels.

23rd International Conference on Optical Fibre Sensors, 2014

In-fiber acousto-optic interaction is used to investigate the refractive index changes generated ... more In-fiber acousto-optic interaction is used to investigate the refractive index changes generated along an Yb-doped fiber by a 976 nm pump. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. Thermal and electronic contributions of the refractive index change are analyzed from the wavelength shift. Additionally, the non-uniform distribution of pump absorption along the fiber length is investigated by a time-resolved acousto-optic technique.

22nd Congress of the International Commission for Optics: Light for the Development of the World, 2011

ABSTRACT In this paper a simple theoretical model is presented where the energy conservation prin... more ABSTRACT In this paper a simple theoretical model is presented where the energy conservation principle is used. The model is based on semi-analytical equations describing the behaviour of an erbium-doped photonic crystal fibre (PCF) inside a ring laser. These semi-analytical equations allow the characterisation of the erbium-doped PCF. Spectral absorption and emission coefficients can be determined through the measurement of the gain in the PCF as a function of pump power attenuation for several fibre lengths by means of a linear fitting. These coefficients are proportional to the erbium concentration and to the corresponding absorption or emission cross section. So if the concentration is known the erbium cross sections can be immediately determined. The model was successfully checked by means of two different home-made erbium doped PCFs. Once the fibres were characterised the values of the spectral absorption and emission coefficients were used to simulate the behaviour of a back propagating ring laser made of each fibre. Passive losses of the components in the cavity were previously calibrated. A good agreement was found between simulated and experimental values of efficiency, pump power threshold and output laser power for a wide set of experimental situations (several values of the input pump power, output coupling factor, laser wavelength and fibre length).

SPIE Proceedings, 2009

Supercontinuum generation in a highly Ge-doped core Y-shaped microstructured optical fiber using ... more Supercontinuum generation in a highly Ge-doped core Y-shaped microstructured optical fiber using long pump pulses of 9 ns duration at 1064 nm is reported. The generation of nonlinear effects takes advantage of the large nonlinear refractive index and Raman gain of the Ge-doped core, as well as the air hole structure that surrounds the core. The fiber is easy to fabricate due to its simple structure and shows good compatibility with standard fibers. Although the fiber was pumped in normal dispersion far from the zero dispersion wavelength, flat and smooth supercontinuum in the fundamental mode from 550 nm to beyond 1750 nm was generated with a value of fiber length and pump peak power product of 11.7 kW•m.

Optical Sensors 2009, 2009

In this work we describe the development of a compact all-fiber pulsed light source composed by a... more In this work we describe the development of a compact all-fiber pulsed light source composed by a fiber-Bragg-grating-based distributed-feedback fiber laser. We demonstrate that the temporal and spectral characteristics of this fiber laser are suitable as light source for Brillouin back-scattering sensors. Using a 10 km fiber spool, we have measured the Stokes and anti-Stokes processes at different pump powers and they were clearly discernible around the central (Rayleigh backscattering) peak at the appropriate wavelength shift (88 pm at room temperature). Our results indicate that this compact all-fiber source is a good alternative for Brillouin sensor applications.

Optics letters, Jan 15, 2011

We present a fiber laser made in a single piece of conventional doped-core fiber that operates by... more We present a fiber laser made in a single piece of conventional doped-core fiber that operates by combined feedback of the fundamental core mode LP((0,1)) and the high-order cladding mode LP((0,10)). The laser is an all-fiber structure that uses two fiber Bragg gratings and a long-period grating to select the modes circulating in the cavity; the laser emits at the coupling wavelength between the core mode LP((0,1)) and the counterpropagating cladding mode LP((0,10)) in the Bragg gratings. This work demonstrates the feasibility of high-order mode fiber lasers assisted by long-period gratings.

Optics letters, 2011

We show that whispering-gallery modes (WGMs) in optical microresonators can be excited and detect... more We show that whispering-gallery modes (WGMs) in optical microresonators can be excited and detected using a fused-tapered fiber tip (FTFT). The fabrication of FTFTs is simple and inexpensive; they are robust and allow the excitation and interrogation of the resonances with a single fiber. Excitation of high-Q WGMs in silica microcylinders and microspheres is demonstrated.

Optics letters, 2014

The temperature sensitivity of whispering-gallery mode resonances of an optical fiber is exploite... more The temperature sensitivity of whispering-gallery mode resonances of an optical fiber is exploited to measure thermal effects induced by an optical signal of moderate power along a fiber Bragg gating (FBG). The UV inscription technique used for the fabrication of FBG introduces a permanent change in the absorption coefficient of the fiber; thus, thermal effects are expected. The resonance wavelength shift of whispering-gallery modes provides information about the temperature change in the fiber, point to point. We present the experimental characterization of the thermal effects in FBG as a function of the wavelength and the power of the launched optical signal through the grating.

Optics Letters

Wideband tuning of strong bands generated through polarization modulation instability (PMI) in mi... more Wideband tuning of strong bands generated through polarization modulation instability (PMI) in microstructured optical fibers (MOFs) is reported. Tunability is achieved by exploiting the dependence of the phase-matching condition on the fiber's chromatic dispersion and birefringence, which is particularly sensitive when the fiber is pumped near the zerodispersion wavelength. MOFs designed to accomplish PMI phase-matching when they are infiltrated with ethanol and pumped at 1064 nm were designed and fabricated. Taking advantage of the large thermo-optic coefficient of ethanol, both chromatic dispersion and birefringence were varied through temperature. Wavelength shifts from 937 nm to 863 nm (anti-Stokes) and from 1231 nm to 1387 nm (Stokes) is demonstrated. Such a tuning range corresponds to a frequency shift between the pump and a PMI sideband ranging from 1274 cm-1 to 2189 cm-1 .

Optics Letters

We propose the implementation of fiber Bragg gratings in tapered few-modes, and multimode fibers ... more We propose the implementation of fiber Bragg gratings in tapered few-modes, and multimode fibers to accomplish single-mode operation by reducing the core diameter while preserving the core-cladding structure. Gratings present a single reflection band and the device show low insertion losses after the taper fabrication and the fiber Bragg gratings inscription. The excitation of high order odd-modes in the core of the fiber has been identified as the main loss mechanism; it can be prevented by means of symmetric illumination of the fibers. We also demonstrate the excitation of high order cladding modes (cladding-air modes) along the taper transitions; these modes can be removed without a significant increment of the insertion loss.

Laser Physics

Q-switched and mode-locked (QML) pulse generation from an all-fiber ring laser based on intermoda... more Q-switched and mode-locked (QML) pulse generation from an all-fiber ring laser based on intermodal acousto-optic bandpass modulation is reported. The modulator relies on full-acoustooptic mode re-coupling cycle induced by a standing flexural acoustic wave, with a transmission response that is controlled by amplitude modulation of the acoustic wave signal. The Q factor of the cavity is controlled by a rectangular pulse wave with variable frequency and duty cycle, whereas mode locking is achieved by amplitude modulation derived from a standing flexural acoustic wave. The best QML pulses were obtained at 0.5 kHz repetition rate, with a pump power of 549.2 mW, at the optical wavelength of 1568.2 nm. A maximum overall energy of 2.14 J at an average output power of 1.07 mW was achieved, corresponding to a burst of mode-locked sub-pulses of 100 ps pulse duration within a QML envelope of 3.5 s.

Laser Physics Letters

Active mode-locking of an all-fiber ring laser by transmittance modulation of an in-fiber acousto... more Active mode-locking of an all-fiber ring laser by transmittance modulation of an in-fiber acousto-optic tunable bandpass filter (AOTBF) is reported. Cavity loss modulation is achieved by full acousto-optic mode re-coupling cycle induced by standing flexural acoustic waves. The modulator permits the implementation of 28 dB of nonresonant light suppression, 1.4 nm of modulation bandwidth, 74% of modulation depth and 4.11 dB of optical loss in a 72.5 cm-long all-fiber configuration. The effects of the modulated AOTBF on the laser performance are investigated. Transform-limited optical pulses of 8.8 ps temporal width and 6.0 W peak power were obtained at 4.87 MHz repetition rate.

Optics Express

Acousto-optic coupling in polyimide-coated single-mode optical fibers using flexural elastic wave... more Acousto-optic coupling in polyimide-coated single-mode optical fibers using flexural elastic waves is demonstrated. The effect of the polyimide coating on the acoustooptic interaction process is analyzed in detailed. Theoretical and experimental results are in good agreement. Although the elastic attenuation is significant, we show that acousto-optic coupling can be produced with a reasonably good efficiency. To our knowledge, it is the first experimental demonstration of acousto-optic coupling in optical fibers with robust protective coating.

Optics letters, Jan 15, 2016

We measured the instantaneous frequency profile of two different dissipative soliton resonant (DS... more We measured the instantaneous frequency profile of two different dissipative soliton resonant (DSR) light pulses, the usual flat-top and less-common trapezoid-shaped light pulses. The DSR light pulses were provided by an ytterbium-doped polarization-maintaining fiber ring passively mode-locked laser using the adequately selected amount of net-normal dispersion. We confirmed that the DSR light pulses have a (moderately) low linear chirp across the pulse, except at the edges, where the chirp changes exponentially. This unique instantaneous frequency behavior can be succinctly resumed by the following parameters: linear chirp slope and leading and trailing chirp lifetimes. As the pump power increases, the linear chirp slope decreases, whereas the leading and trailing chirp lifetimes do not show an appreciable change. The results are compared with previous theoretical works.

Optics express, Jan 2, 2016

We investigated the dissipative solitons resonance in an ytterbium-doped fiber ring laser in whic... more We investigated the dissipative solitons resonance in an ytterbium-doped fiber ring laser in which all the elements are polarization maintaining (PM). A semiconductor saturable absorber mirror was used as a mode-locker. The cavity included a normal dispersion single-mode fiber (SMF) and an anomalous dispersion photonic crystal fiber. The change of the length of the PM SMF allows the variation of the net-normal dispersion of the cavity in the range from 0.022 ps² to 0.262 ps². As the absolute value of the net-normal dispersion increases from 0.022 ps² to 0.21 ps², a square-shaped single pulse transformed to a single right-angle trapezoid-shaped pulse, and, at the dispersion of 0.262 ps², to multiple right-angle trapezoid-shaped pulses, per round-trip.

Fiber Lasers XIII: Technology, Systems, and Applications, 2016

A polarization asymmetrical nonlinear optical loop mirror (NOLM) is investigated to perform pedes... more A polarization asymmetrical nonlinear optical loop mirror (NOLM) is investigated to perform pedestal-free optical pulses in a figure-eight laser (F8L). The results demonstrate that in the low-power regime the NOLM operates as a halfwave plate and the output polarization is orthogonal to the input one. However, at higher power level the polarization component parallel to the input appears, with a transmission that always begins from zero at low power, allowing the rejection of low-intensity components. Experimental results demonstrate that by employing this configuration we can obtain a contrast between the peak and continuous background higher that 40 dB.

AIP Conference Proceedings, 2008

We give the details of the fabrication approach that we follow to prepare Erbium-doped photonic c... more We give the details of the fabrication approach that we follow to prepare Erbium-doped photonic crystal fibers and the basic characterization of these fibers. The fibers were fabricated using the conventional stack-and-draw technique. The preforms were prepared combining pure silica capillaries to form a hexagonal lattice and an Erbium doped wire to define the core. Fibers with different pitch, air

Optical Sensors 2015, 2015

In this work an optical fiber laser with loop configuration was developed for magnetic field meas... more In this work an optical fiber laser with loop configuration was developed for magnetic field measurement. The transducer element is an FBG written in a HiBi fiber whose wavelength is modified using a magnetostrictive material that applies deformation in the presence of the magnetic field. The laser has a bandwidth of 450 MHz and operates in single polarization. A shift of 258.5 pm was observed in the laser operating wavelength for a magnetic field of 17.85 mT. Moreover, a maximum sensitivity of 14.72 pm/mT in the linear regime operation was achieved when increasing the magnetic field. The system provides a narrow emission line that is dependent on the magnetic field magnitude enabling high resolution interferometric measurement schemes. The laser response to AC magnetic fields was also characterized using a passive interferometer with higher sensitivity in the range of 8.32 to 17.93 mTRMS.

Optics Express, 2015

The time-resolved acousto-optic technique demonstrated recently to be a very useful method for th... more The time-resolved acousto-optic technique demonstrated recently to be a very useful method for the analysis of fiber axial non-uniformities, able to detect variations of fiber diameter in the nanometric scale with a spatial resolution of few cm. An edge interrogation approach is proposed to improve further the performance of this technique. The detection of subnanometer fiber diameter changes or sub-ppm changes of the core refractive index is demonstrated.

Laser Physics, 2014

The dynamic response after pump switch-on of a 980 nm pumped-ring laser based on an active photon... more The dynamic response after pump switch-on of a 980 nm pumped-ring laser based on an active photonic crystal fiber with an Er3+ ion concentration of ≈1020 ions cm−3 was registered. Then a numerical fitting procedure of a theoretical model was followed to the experimental values of the relaxation oscillation parameters as a function of the input pump power. Non-radiative energy-transfer mechanisms’ coefficients: homogeneous upconversion coefficient (Cup) and critical radii for upconversion (Ru) and migration (Rm) were determined. The calculated best-fit coefficients (Cup = 1.3 × 10−24 m3 s−1, Ru = 9 × 10−10 m, Rm = 13 × 10−10 m) were compared to those obtained with other steady-state and dynamic characterization techniques.

Optics letters, 2015

In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C ... more In-fiber acousto-optic interaction is used to characterize the refractive index changes at the C band in a single-mode ytterbium-doped optical fiber under 980 nm pumping. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. The electronic contribution to the refractive index change is quantified from the wavelength shift. Using a time-resolved acousto-optic method, we investigate the distribution of pump absorption, and the resulting refractive index change profile, along sections of ytterbium-doped fiber exceeding 1 m long under different pump power levels.

23rd International Conference on Optical Fibre Sensors, 2014

In-fiber acousto-optic interaction is used to investigate the refractive index changes generated ... more In-fiber acousto-optic interaction is used to investigate the refractive index changes generated along an Yb-doped fiber by a 976 nm pump. The transmission notch created by the acoustic-induced coupling between the core mode and a cladding mode shifts to longer wavelengths when the pump is delivered to the fiber. Thermal and electronic contributions of the refractive index change are analyzed from the wavelength shift. Additionally, the non-uniform distribution of pump absorption along the fiber length is investigated by a time-resolved acousto-optic technique.

22nd Congress of the International Commission for Optics: Light for the Development of the World, 2011

ABSTRACT In this paper a simple theoretical model is presented where the energy conservation prin... more ABSTRACT In this paper a simple theoretical model is presented where the energy conservation principle is used. The model is based on semi-analytical equations describing the behaviour of an erbium-doped photonic crystal fibre (PCF) inside a ring laser. These semi-analytical equations allow the characterisation of the erbium-doped PCF. Spectral absorption and emission coefficients can be determined through the measurement of the gain in the PCF as a function of pump power attenuation for several fibre lengths by means of a linear fitting. These coefficients are proportional to the erbium concentration and to the corresponding absorption or emission cross section. So if the concentration is known the erbium cross sections can be immediately determined. The model was successfully checked by means of two different home-made erbium doped PCFs. Once the fibres were characterised the values of the spectral absorption and emission coefficients were used to simulate the behaviour of a back propagating ring laser made of each fibre. Passive losses of the components in the cavity were previously calibrated. A good agreement was found between simulated and experimental values of efficiency, pump power threshold and output laser power for a wide set of experimental situations (several values of the input pump power, output coupling factor, laser wavelength and fibre length).

SPIE Proceedings, 2009

Supercontinuum generation in a highly Ge-doped core Y-shaped microstructured optical fiber using ... more Supercontinuum generation in a highly Ge-doped core Y-shaped microstructured optical fiber using long pump pulses of 9 ns duration at 1064 nm is reported. The generation of nonlinear effects takes advantage of the large nonlinear refractive index and Raman gain of the Ge-doped core, as well as the air hole structure that surrounds the core. The fiber is easy to fabricate due to its simple structure and shows good compatibility with standard fibers. Although the fiber was pumped in normal dispersion far from the zero dispersion wavelength, flat and smooth supercontinuum in the fundamental mode from 550 nm to beyond 1750 nm was generated with a value of fiber length and pump peak power product of 11.7 kW•m.

Optical Sensors 2009, 2009

In this work we describe the development of a compact all-fiber pulsed light source composed by a... more In this work we describe the development of a compact all-fiber pulsed light source composed by a fiber-Bragg-grating-based distributed-feedback fiber laser. We demonstrate that the temporal and spectral characteristics of this fiber laser are suitable as light source for Brillouin back-scattering sensors. Using a 10 km fiber spool, we have measured the Stokes and anti-Stokes processes at different pump powers and they were clearly discernible around the central (Rayleigh backscattering) peak at the appropriate wavelength shift (88 pm at room temperature). Our results indicate that this compact all-fiber source is a good alternative for Brillouin sensor applications.

Optics letters, Jan 15, 2011

We present a fiber laser made in a single piece of conventional doped-core fiber that operates by... more We present a fiber laser made in a single piece of conventional doped-core fiber that operates by combined feedback of the fundamental core mode LP((0,1)) and the high-order cladding mode LP((0,10)). The laser is an all-fiber structure that uses two fiber Bragg gratings and a long-period grating to select the modes circulating in the cavity; the laser emits at the coupling wavelength between the core mode LP((0,1)) and the counterpropagating cladding mode LP((0,10)) in the Bragg gratings. This work demonstrates the feasibility of high-order mode fiber lasers assisted by long-period gratings.

Optics letters, 2011

We show that whispering-gallery modes (WGMs) in optical microresonators can be excited and detect... more We show that whispering-gallery modes (WGMs) in optical microresonators can be excited and detected using a fused-tapered fiber tip (FTFT). The fabrication of FTFTs is simple and inexpensive; they are robust and allow the excitation and interrogation of the resonances with a single fiber. Excitation of high-Q WGMs in silica microcylinders and microspheres is demonstrated.

Optics letters, 2014

The temperature sensitivity of whispering-gallery mode resonances of an optical fiber is exploite... more The temperature sensitivity of whispering-gallery mode resonances of an optical fiber is exploited to measure thermal effects induced by an optical signal of moderate power along a fiber Bragg gating (FBG). The UV inscription technique used for the fabrication of FBG introduces a permanent change in the absorption coefficient of the fiber; thus, thermal effects are expected. The resonance wavelength shift of whispering-gallery modes provides information about the temperature change in the fiber, point to point. We present the experimental characterization of the thermal effects in FBG as a function of the wavelength and the power of the launched optical signal through the grating.