Analysis of short-term Polarization Stability using Allan Variance

The use of Allan variance to characterize the stability of optical signals affected by stochastic polarization fluctuations and the identification of the underlying power law noise processes is explored. Allan variance can ease the comparison in terms of polarization stability of optical systems affected by polarization fluctuations and define a near-optimum integration interval to reveal trends. Experiments with different optical sources show that white noise and random walk terms can be observed. This information can easily be used to systematically define, in real time, the denoising strategy in polarization-based sensing and for the optimization of polarization sensitive optical systems instead of the conventional approach relying on heuristics or information criteria

Broadband photonic microwave noise sources

[EN] The generation of wideband microwave white noise based on optical technology is investigated. It is shown that strong broadband noise in the microwave band can be generated using amplified spontaneous noise (ASE). Measurements show wideband operation (0-20 GHz) and very large tunable excess noise ratio (ENR) up to 62 dB. Photonics offer an alternative implementation of noise sources for system characterization over very broad bandwidths and potential to be employed in the millimeter and submillimeter-wave bands where conventional noise sources are complex or inexistentThis work was supported in part by the European Union's Horizon 2020 Research and Innovation Programme (ULTRAWAVE-Project), under Grant 762119.Vidal Rodriguez, B. (2020). Broadband photonic microwave noise sources. IEEE Photonics Technology Letters. 32(10):592-594. https://doi.org/10.1109/LPT.2020.2986739S592594321

Brillouin wavelength-selective all-optical polarization conversion

[EN] The manipulation of the polarization properties of light in guided media is crucial in many classical and quantum optical systems. However, the capability of current technology to finely define the state of polarization of particular wavelengths is far from the level of maturity in amplitude control. Here, we introduce a light-by-light polarization control mechanism with wavelength selectivity based on the change of the phase retardance by means of stimulated Brillouin scattering. Experiments show that any point on the Poincare sphere can be reached from an arbitrary input state of polarization with little variation of the signal amplitude (<2.5 dB). Unlike other Brillouin processing schemes, the degradation of the noise figure is small (1.5 dB for a full 2 pi rotation). This all-optical polarization controller can forge the development of new polarization-based techniques in optical communication, laser engineering, sensing, quantum systems, and light-based probing of chemical and biological systems. (C) 2020 Chinese Laser PressMinisterio de Ciencia, Innovacion y Universidades (TEC2016-80906-R).Samaniego, D.; Vidal Rodriguez, B. (2020). Brillouin wavelength-selective all-optical polarization conversion. Photonics Research. 8(4):440-447. https://doi.org/10.1364/PRJ.371513S44044784Wang, X.-L., Luo, Y.-H., Huang, H.-L., Chen, M.-C., Su, Z.-E., Liu, C., … Pan, J.-W. (2018). 18-Qubit Entanglement with Six Photons’ Three Degrees of Freedom. Physical Review Letters, 120(26). doi:10.1103/physrevlett.120.260502Preece, D., Keen, S., Botvinick, E., Bowman, R., Padgett, M., & Leach, J. (2008). Independent polarisation control of multiple optical traps. Optics Express, 16(20), 15897. doi:10.1364/oe.16.015897Heismann, F., & Whalen, M. S. (1991). Broadband reset-free automatic polarisation controller. Electronics Letters, 27(4), 377. doi:10.1049/el:19910237Koch, B., Noé, R., Sandel, D., & Mirvoda, V. (2011). 100 krad/s endless polarisation tracking with miniaturised module card. Electronics Letters, 47(14), 813-814. doi:10.1049/el.2011.1522Shmilovitch, Z., Primerov, N., Zadok, A., Eyal, A., Chin, S., Thevenaz, L., & Tur, M. (2011). Dual-pump push-pull polarization control using stimulated Brillouin scattering. Optics Express, 19(27), 25873. doi:10.1364/oe.19.025873Vidal, B. (2012). Photonic millimeter-wave frequency multiplication based on cascaded four-wave mixing and polarization pulling. Optics Letters, 37(24), 5055. doi:10.1364/ol.37.005055Stiller, B., Morin, P., Nguyen, D. M., Fatome, J., Pitois, S., Lantz, E., … Sylvestre, T. (2012). Demonstration of polarization pulling using a fiber-optic parametric amplifier. Optics Express, 20(24), 27248. doi:10.1364/oe.20.027248Heebner, J. E., Bennink, R. S., Boyd, R. W., & Fisher, R. A. (2000). Conversion of unpolarized light to polarized light with greater than 50% efficiency by photorefractive two-beam coupling. Optics Letters, 25(4), 257. doi:10.1364/ol.25.000257Kozlov, V. V., Nuño, J., & Wabnitz, S. (2011). Theory of lossless polarization attraction in telecommunication fibers: erratum. Journal of the Optical Society of America B, 29(1), 153. doi:10.1364/josab.29.000153Pitois, S., Millot, G., & Wabnitz, S. (2001). Nonlinear polarization dynamics of counterpropagating waves in an isotropic optical fiber: theory and experiments. Journal of the Optical Society of America B, 18(4), 432. doi:10.1364/josab.18.000432Fatome, J., Pitois, S., Morin, P., & Millot, G. (2010). Observation of light-by-light polarization control and stabilization in optical fibre for telecommunication applications. Optics Express, 18(15), 15311. doi:10.1364/oe.18.015311Kozlov, V. V., Barozzi, M., Vannucci, A., & Wabnitz, S. (2013). Lossless polarization attraction of copropagating beams in telecom fibers. Journal of the Optical Society of America B, 30(3), 530. doi:10.1364/josab.30.000530DeLong, A., Astar, W., Mahmood, T., & Carter, G. M. (2017). Polarization attraction of 10-Gb/s NRZ-BPSK signal in a highly nonlinear fiber. Optics Express, 25(21), 25625. doi:10.1364/oe.25.025625Loayssa, A., & Lahoz, F. J. (2006). Broad-band RF photonic phase shifter based on stimulated Brillouin scattering and single-sideband modulation. IEEE Photonics Technology Letters, 18(1), 208-210. doi:10.1109/lpt.2005.861307Pagani, M., Marpaung, D., Choi, D.-Y., Madden, S. J., Luther-Davies, B., & Eggleton, B. J. (2014). Tunable wideband microwave photonic phase shifter using on-chip stimulated Brillouin scattering. Optics Express, 22(23), 28810. doi:10.1364/oe.22.028810Galtarossa, A., Palmieri, L., Santagiustina, M., Schenato, L., & Ursini, L. (2008). Polarized Brillouin Amplification in Randomly Birefringent and Unidirectionally Spun Fibers. IEEE Photonics Technology Letters, 20(16), 1420-1422. doi:10.1109/lpt.2008.927884Liao, M., Chaudhari, C., Qin, G., Yan, X., Kito, C., Suzuki, T., … Misumi, T. (2009). Fabrication and characterization of a chalcogenide-tellurite composite microstructure fiber with high nonlinearity. Optics Express, 17(24), 21608. doi:10.1364/oe.17.021608Morrison, B., Casas-Bedoya, A., Ren, G., Vu, K., Liu, Y., Zarifi, A., … Eggleton, B. J. (2017). Compact Brillouin devices through hybrid integration on silicon. Optica, 4(8), 847. doi:10.1364/optica.4.000847Chen, L., & Bao, X. (1998). Analytical and numerical solutions for steady state stimulated Brillouin scattering in a single-mode fiber. Optics Communications, 152(1-3), 65-70. doi:10.1016/s0030-4018(98)00147-

Brillouin Microwave Filter with enhanced Skirt Selectivity using a Birefringent Fiber

© 2019 IEEE. Personal use of this material is permitted. Permissíon from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertisíng or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.[EN] A technique to enhance the slope of a photonic microwave filter based on the stimulated Brillouin scattering is proposed. It relies on exploiting the polarization dependence of Brillouin gain in birefringent fibers. The presence of two orthogonal Brillouin gains/loss in birefringent fibers results in two filter responses that can be subtracted in a balanced photodetector to remove the slow Lorentzian decay of the natural Brillouin gain response. The experimental results show that a filter slope of 8.3 dB/oct can be obtained.The work of D. Samaniego was supported by SENESCYT "Convocatoria Abierta 2012" under Grant AR2Q-4233.Samaniego, D.; Vidal Rodriguez, B. (2019). Brillouin Microwave Filter with enhanced Skirt Selectivity using a Birefringent Fiber. IEEE Photonics Technology Letters. 31(6):431-434. https://doi.org/10.1109/LPT.2019.2897398S43143431

Photonic Microwave Filter With Steep Skirt Selectivity Based on Stimulated Brillouin Scattering

A method to enhance the filter slope of Brillouin-based photonic microwave filters is presented. This improvement is achieved by the combination of Brillouin gain and loss responses over phase-modulated signals. The experimental results show passband responses exhibiting a slope of 16.7 dB per octave, which corresponds with a threefold improvement in comparison to the natural Lorentzian response for the same gain.This work was supported in part by the Spanish Ministry of Economy and Competitiveness through TEC2016-80906-R project and by the European Union through TWEETHER project.Samaniego-Riera, D.; Vidal Rodriguez, B. (2016). Photonic Microwave Filter With Steep Skirt Selectivity Based on Stimulated Brillouin Scattering. IEEE Photonics Journal. 8(6). https://doi.org/10.1109/JPHOT.2016.2634782S8

Dynamic Tuning of Mean Carrier Momentum Relaxation Time in InGaAs InAlAs THz Photoconductive Switches

The carrier transport in InGaAs InAlAs multilayer heterostructures used for the implementation of terahertz (THz) photoconductive antennas is investigated under the injection of a continuous optical wave. By varying the amplitude level of the continuous optical wave in the transmitter or receiver antennas used in a conventional pulsed THz time-domain spectrometer, the amplitude of the detected photocurrent can be controlled without affecting its bandwidth. Unlike increasing the optical power of the pulsed signal, it is shown that raising the continuous optical power results in a reduction of the measured photocurrent. This lowering of the conductivity can be explained by changes in the instantaneous carrier momentum relaxation time in the material rather than variations of the free carrier density level. This behavior affects in systems showing optical continuous-wave components, as, for example, fiber-based THz time-domain spectrometers including optical amplifiers.This work was supported in part by the Spanish Ministry of Economy and Competitiveness through Project TEC2012-35797 and FPU Grant 12/02847.Bockelt, AS.; Vidal Rodriguez, B. (2017). Dynamic Tuning of Mean Carrier Momentum Relaxation Time in InGaAs InAlAs THz Photoconductive Switches. IEEE Transactions on Terahertz Science &amp; Technology. 7(1):107-113. https://doi.org/10.1109/TTHZ.2016.2636742S1071137

Chroma Key wthout Color Restrictions based on Asynchronous Amplitude Modulation of Background Illumination on Retroreflective Screens

A simple technique to avoid color limitations in image capture systems based on chroma key video composition using retroreflective screens and light-emitting diodes (LED) rings is proposed and demonstrated. The combination of an asynchronous temporal modulation onto the background illumination and simple image processing removes the usual restrictions on foreground colors in the scene. The technique removes technical constraints in stage composition, allowing its design to be purely based on artistic grounds. Since it only requires adding a very simple electronic circuit to widely used chroma keying hardware based on retroreflective screens, the technique is easily applicable to TV and filming studios.Vidal Rodriguez, B.; Lafuente, JA. (2016). Chroma Key wthout Color Restrictions based on Asynchronous Amplitude Modulation of Background Illumination on Retroreflective Screens. Journal of Electronic Imaging. 25(2):230091-230095. doi:10.1117/1.JEI.25.2.023009S23009123009525

Particle Size Inversion from Spectrally Resolved Full-Field Forward Scattering

[EN] Ensemble particle sizing has traditionally relied on inversion of extinction measurements for the characterization of the particle size distribution (PSD) in particulate media. However, particulate media induce complex phase changes that contain valuable information about their structure. Here, we propose the use of coherent detection to derive particle size distributions in inhomogeneous samples from light scattering. This is achieved by exploiting THz waves, which allow for both extinction and refractive index information to be directly retrieved. A modified version of the iterative Twomey method is presented in order to take into account this information. Additionally, by using a forward model based on the Waterman-Truell formula for the complex refractive index, samples with absorption in both the matrix medium and the particulate phase can be measured. The inversion needs neither a priori assumptions nor constraints regarding the PSD shape. Numerical simulations show that this full-field approach reduces the error of the inversion process potentially up to 65% compared with inversion using only extinction data. Experimental validation of the technique is provided by measuring calibrated spherical glass particles inside a PTFE matrix and retrieving the PSD in the case of monodisperse and polydisperse samples showing an enhancement of up to 32% in comparison to inversion from extinction data.This work was supported in part by the Spanish Ministerio de Ciencia e Innovacion-Agencia Estatal de Investigacion under project PID2019-111339GBI00.Báez-Chorro, MÁ.; Vidal Rodriguez, B. (2023). Particle Size Inversion from Spectrally Resolved Full-Field Forward Scattering. Analytical Chemistry. 95(43):15994-16003. https://doi.org/10.1021/acs.analchem.3c031781599416003954

Analysis of the THz response of a simple periodic graphite-based structure

We report the observation of the dichroism effect in simple wire grid structures made of graphite on a paper substrate, i.e. we investigate the feasibility of drawing polarizers for the THz band using conventional graphite-based lead pencils. The displacement of the maximum frequency of the selective absorption phenomenon by varying the wire pitch hints at a polarizing behavior. Measurements of the maximum and minimum of transmission efficiency, extinction ratio and degree of polarization are carried out with a transmission fiber THz-TDS setup. Experimental results show a 9 dB extinction ratio for an inexpensive (<1$) home-made component. (C) 2014 Optical Society of AmericaSpanish Ministry of Economy and Competitiveness, project TEC2012-35797.Colleoni, MPM.; Vidal Rodriguez, B. (2014). Analysis of the THz response of a simple periodic graphite-based structure. Optics Express. 22(24):30156-30160. doi:10.1364/OE.22.030156S3015630160222