Averaged Stokes polarimetry applied to evaluate retardance and flicker in PA-LCoS devices

Recently we proposed a novel polarimetric method, based on Stokes polarimetry, enabling the characterization of the linear retardance and its flicker amplitude in electro-optic devices behaving as variable linear retarders. In this work we apply extensively the technique to parallel-aligned liquid crystal on silicon devices (PA-LCoS) under the most typical working conditions. As a previous step we provide some experimental analysis to delimitate the robustness of the technique dealing with its repeatability and its reproducibility. Then we analyze the dependencies of retardance and flicker for different digital sequence formats and for a wide variety of working geometries.Work supported by Ministerio de Trabajo y Competitividad of Spain (projects FIS2011- 29803-C02-01 and FIS2011-29803-C02-02), by Generalitat Valenciana of Spain (projects PROMETEO/2011/021 and ISIC/2012/013), and by Univ. de Alicante (project GRE12-14)

Generation and characterization of polarization scrambled optical signals

Controlling the state of polarization of a light beam of an optical fiber is of crucial importance. Non-Linear Polarization Pulling (NLPP) is an all-optical way to control the state of polarization of signals which has been proposed in recent years. Polarization attraction effect enables to align a generic input State of Polarization (SOP) towards a fixed one. NLPP can be induced by various nonlinear effects occurring in optical fibers, in particular by the Stimulated Raman Scattering (SRS). This Thesis is propaedeutic for experiments investigating NLPP. In fact, any experiment on SRS polarization pulling needs a proper polarimeter which can analyze the signals in the wavelength range from 1550 nm to 1640 nm. It is therefore necessary to employ a suitable polarimetric technique which should also give information on the spectral composition of the signals, mainly to estimate the Amplified Spontaneous Emission (ASE) due to the SRS. This polarimeter is tested and characterized in experimental tests performed during this Thesis. Moreover, there is also the necessity to generate depolarized signals to verify the repolarization capability of the NLPP effect. To meet this need, two different polarization scramblers have been employed and systematically tested to characterize the generated polarization scrambled signal

Error Analysis of a Rotating Quarter-Wave Plate Stokes' Polarimeter

NRC publication: Ye

Analysis and application of nonlinear amplification effects in single-mode optical fibers

This thesis focuses on all-optical signal generation and processing through nonlinear amplification phenomena in single-mode fibers. Three different nonlinear fiber optical oscillators are investigated and experimentally demonstrated. A continuous-wave pump for fiber Raman amplifiers, developed with the goal of achieving high degree of polarization, tunability and suppression of stimulated Brillouin scattering, is presented, discussed and used to achieve nonlinear polarization attraction. A fast and widely tunable fiber optical oscillator based on stimulated Raman scattering and on broad- and narrow-band fiber optical parametric amplification, and exploiting the time-dispersion-tuning technique, is demonstrated and characterized. Each nonlinear effect dominates in a different spectral region, so that the fiber optical oscillator achieves a tuning range of 160 nm. Through the same time-dispersion-tuning method, a fast tunable optical frequency comb, based on cascaded four-wave mixing, is obtained by using a single pump, avoiding the limitations in spectral purity and frequency and phase stability given by double pump systems. Finally, the control of the state of polarization and of the degree of polarization through nonlinear polarization attraction in counter-propagating fiber Raman amplifiers in standard, randomly birefringent, single-mode fibers is studied, analyzed and characterized. The analysis, including the effects of pump depletion, nonlinear polarization rotation and orthogonal Raman gain, shows that counter-propagating fiber Raman amplifiers are effective in attracting the signal toward a predetermined state of polarization settled by the pump input state of polarization. Moreover, the importance of the role of pump depletion in achieving signal repolarization in fibers with moderately-high polarization-mode dispersion is discussed. The performances and the limits of repolarization efficiency are determined, leading to a quantitative relationship between the degree of polarization and the gain of the fiber Raman amplifier, which is then confirmed to represent an upper bound on the maximum achievable degree of polarization