Search results for "fibras ópticas"
showing 10 items of 31 documents
Fabrication of long period fiber gratings of subnanometric bandwidth.
2017
This paper reports on the fabrication of long period fiber gratings having subnanometric bandwidth in the 1500 nm spectral region. Large gratings have been photo-inscribed in a high NA fiber, the grating pitch and the order of the HE cladding mode are optimized to produce gratings with a large number of periods and preventing the coupling to TE, TM or EH modes. Resonances with a FWHM of 0.83 nm and 0.68 nm have been achieved for gratings 15 and 20 cm long respectively, the free spectral range between transmission notches is 125 nm. The polarization effects and the sensitivity of the gratings to temperature and to strain variations are presented as well. © 2015 Optical Society of America Thi…
Improved All-Fiber Acousto-Optic Tunable Bandpass Filter
2017
An all-fiber acousto-optic tunable bandpass filter based on a 1.185-mm long coreless core mode blocker is reported. Experimental results demonstrate a minimal insertion loss of 1.2 dB at the optical resonant wavelength of 1527.7 nm with 3-dB optical bandwidth of 0.83 nm. The optimization of the device takes into account the attenuation of the acoustic wave and leads to an asymmetric configuration in which the coupling section is shorter than the recoupling part. Under the effect of a standing flexural wave the device can be operated as a bandpass modulator. The device exhibits a maximum modulation depth of 28%, 4 dB of insertion loss and 0.97 nm of optical bandwidth at 4.774 MHz.
Actively mode-locked all-fiber laser by 5 MHz transmittance modulation of an acousto-optic tunable bandpass filter
2018
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.
Flat supercontinuum generation pumped by amplified noise-like pulses from a figure-eight erbium-doped fiber laser
2017
The conditions to obtain noise-like pulses (NLPs) from a figure-eight fiber laser (F8L) and their application for supercontinuum (SC) generation in the anomalous dispersion regime are reported. The F8L is designed to remove the undesired low-intensity background radiation from pulse emission, generating NLPs with a 3 dB spectral bandwidth of 17.43 nm at the fundamental repetition frequency of 0.8 MHz. After amplification, NLPs reach a maximum average power of 9.2 mW and 123.32 nm spectral bandwidth. By controlling the amplifier pump power, flat SC generation is demonstrated through both a 800 m long spool of SMF-28 fiber and a piece of 5 m long highly nonlinear optical fiber. The results de…
Tunable Dual-Wavelength Thulium-Doped Fiber Laser Based on FBGs and a Hi-Bi FOLM
2017
A tunable dual-wavelength thulium doped fiber laser is demonstrated experimentally. For the first time for the 2- $\mu \text{m}$ wavelength band we propose the independent tuning of the generated laser lines based on fiber Bragg gratings and the use of a Hi-Bi fiber optic loop mirror for the fine adjustment of the cavity losses to obtain stable dual-wavelength operation. Dual-wavelength laser generation with the laser lines separation in the range from 0.3 to 6.5 nm is obtained. The laser emission exhibits an optical signal-to-noise ratio better than 56 dB. Improved stability with output power fluctuations less than 1 dB is observed in dual-wavelength generation with equal power of lines.
Propagation length enhancement of surface plasmon polaritons in gold nano-/micro-waveguides by the interference with photonic modes in the surroundin…
2017
Abstract In this work, the unique optical properties of surface plasmon polaritons (SPPs), i.e. subwavelength confinement or strong electric field concentration, are exploited to demonstrate the propagation of light signal at 600 nm along distances in the range from 17 to 150 μm for Au nanostripes 500 nm down to 100 nm wide (30 nm of height), respectively, both theoretically and experimentally. A low power laser is coupled into an optical fiber tip that is used to locally excite the photoluminescence of colloidal quantum dots (QDs) dispersed in their surroundings. Emitted light from these QDs is generating the SPPs that propagate along the metal waveguides. Then, the above-referred propagat…
MWP true time delay implemented in PbS-SU8 waveguides
2015
Es presenta un nou tipus de dispositiu de retard en temps real de microones (TTD) basat en la dispersió de punts quàntics col·loïdals PbS (QD) en el fotoresist SU8 disponible comercialment. Amb aquest propòsit, els nanocompostos PbS-SU8 s’integren en una plataforma de silici en forma de guies d’ones de cresta. Quan aquestes estructures es bomben a longituds d’ona per sota de l’interval de banda dels PbS QD, es realitza un desplaçament de fase en un senyal de microones transmès òpticament (a 1550 nm) i, per tant, es produeix un retard temporal. A més, es milloren els resultats mitjançant la implementació d’una nova guia d’ones de doble capa de cresta composta per un nanocompost PbS-SU8 i una…
Oligonucleotide-Hybridization Fiber-Optic Biosensor using a Narrow Bandwidth Long Period Grating
2017
Nanometric narrowband Long Period Gratings (LPG) are investigated for the implementation of improved fiber optic biosensors. The reduction of more than one order of magnitude in the linewidth of the LPG with respect standard LPG at 1500 nm, leads to the improvement of the resolution of the sensor. By selecting the proper fabrication parameters (high numerical aperture, relatively high order mode and large length), LPGs with a 3-dB bandwidth of 1.5 nm were fabricated. The sensitivity of the LPG as a refractometer was calculated, and experimentally characterized in detail. In particular, the LP0,17 and LP0,18 resonances were investigated, in order to select the most suitable one for the bioex…
An approach to the measurement of the nonlinear refractive index of very short lengths of optical fibers
2018
A method for the measurement of the nonlinear-refractive index coefficient in single-mode optical fibers is presented. It takes advantage of the high sensitivity of the acousto-optic interaction effect in optical fibers to the fiber properties. Direct measurement of the nonlinear-refractive index change resulting from cross-phase modulation between a probe and a pump signal is obtained from the fiber's acousto-optic interaction performance. It is a non-interferometric method in which a very short length of fiber (<0.25 m) is required.
Acousto-optic interaction in polyimide coated optical fibers with flexural waves
2017
Acousto-optic coupling in polyimide-coated single-mode optical fibers using flexural elastic waves is demonstrated. The effect of the polyimide coating on the acousto-optic 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.