Electro-optic Modulator System Research Articles

High sensitivity ultraviolet graphene-metamaterial integrated electro-optic modulator enhanced by superlubricity

Abstract Ultraviolet (UV) electro-optic modulation system based on graphene-plasmonic metamaterials nanomechanical system (NEMS) with superlubricity is investigated. Due to the strong optical absorption intensity of graphene in the UV region and the combination of metamaterial structure based on surface plasmons, the modulation depth of the UV NEMS electro-optic modulator approaches as high as 8.5 times compared to the counterpart modulator in visible light region. Meanwhile, the superlubricity significantly reduces the power consumption of the UV electro-optic modulation system due to its extremely low friction coefficient. It also significantly increases the response speed of the modulator, with response time down to nanoseconds. The modulation voltage can be equal to or less than 150 mV. The proposed electro-optic modulation system has a simple structure and high sensitivity, which is supposed to have important applications in UV optoelectronic devices and systems.

Measurement of the Quadratic Electro-Optic Coefficient of KTN Crystal with an Electro-Optic Modulation System in the Presence of Polar Nano-Regions

An electro-optic modulation system was adopted for measuring the quadratic electro-optic coefficient of KTN crystal. Theoretical analysis and experimental results verified the feasibility of this method. The quadratic electro-optic coefficient of a KTN crystal chip, which has a Curie temperature of 0 °C, was measured using this system in the temperature range of 2 °C to 18 °C (Tc = 0 °C). The influences of temperature, AC voltage and frequency on the quadratic electro-optic coefficient were discussed. It was found that the relaxation effect of PNRs (polar nano-regions) played an important role in the determination of the quadratic electro-optic coefficient of KTN crystal.

Narrow-linewidth and highly stable optical frequency comb realized with a simple electro-optic modulator system in a mode-locked Er:fiber laser

We demonstrate a mode-locked Er:fiber laser with a compact fiber-pigtailed optical bench containing a free-space electro-optic modulator for high-speed feedback control. The achieved servo bandwidth of the beat frequency between a given comb component and a reference laser is approximately 850 kHz. The realization of a narrow-linewidth and highly stable frequency comb is confirmed by measuring both in-loop and out-of-loop beat frequencies. We also demonstrate the frequency measurement of two iodine-stabilized Nd:YAG lasers through the narrow-linewidth comb without stability degradation. The developed optical frequency comb can work continuously for weeks without maintenance.

Characterization of Chaotic Electro Optic Modulator with the Helpof Lyapunov Exponent and Bifurcation Analysis Technique.

Chaos is a fundamental property that comes out of nonlinearity and a sensitive dependence on initial condition. A nonlinear dynamic system that displays a chaotic steady state behaviour is purely deterministic, but its long-term behaviour cannot be predicted because of the property of sensitivity to initial conditions. One of the most promising applications of chaos theory, which exploits both the deterministic and unpredictable aspects of chaotic behaviour, is chaos-based secure communications. The sensitivity to initial condition is quantified with the help of the entropy named Lyapunov Exponent. Generation of chaos from nonlinear optical devices have been explored from several years. In this paper an EO modulator system of cos2 type of nonlinearity is selected as chaos producing device and characterized with the help of Lyapunov Exponent. The Lyapunov Exponent is computed here to determine the dependence of a chaotic signal on the initial conditions and also on the system parameters. The period doubling behaviour in this Electro optic modulator system have also been studied here. The transition from periodic to chaotic behaviours in this one-dimensional discrete dynamical system have been controlled through variation of a single parameter out of different system parameters. With the help of Lyapunov Exponent and bifurcation analysis technique an estimation of the system parameters has been carried out to predict the nature of the output generated at the terminal of the EO cell.

Large scale calculation for holography using SSD

Computer based holography such as electro-holography and digital holography advances because the resolution of an imaging display and a sensing device such as a liquid crystal display (LCD) and a charge coupled device (CCD) becomes higher. A higher resolution of imaging device requires the more powerful computing system. On the other hand, a solid state drive (SSD) develops as a storage device of computers. We studied the effectiveness of SSD for a large-scale digital holography calculation. When the calculation data scale exceeds the main memory capacity, the SSD system showed better performance compared with the hard disk drive (HDD) system at computational speed and stability. Full Text: PDF References M. Stanley et al., 100-megapixel computer-generated holographic images from Active Tiling: a dynamic and scalable electro-optic modulator system, Proc. SPIE 5005, Practical Holography XVII and Holographic Materials IX, 247 (2003) CrossRef H. Sasaki, K. Yamamoto, Y. Ichihashi, T. Senoh, Large size three-dimensional video by electronic holography using multiple spatial light modulators, Scientific Reports 4, Article number 04000 (2014) CrossRef T. Kozacki, G. Finke, P. Garbat, W. Zaperty, M. Kujawinska, Wide angle holographic display system with spatiotemporal multiplexing, Opt. Express 20, 27473-27481 (2012) CrossRef T. Shimobaba et al., In-line digital holographic microscopy using a consumer scanner, Scientific Reports 3, Article number 02664 (2013). CrossRef S.O.Isikman, A.Greenbaum, W.Luo,A.F.Coskun, A.Ozcan, Giga-Pixel Lensfree Holographic Microscopy and Tomography Using Color Image Sensors, PloS one, 7(9), e45044 (2012) CrossRef T. Shimobaba et al., Computational wave optics library for C++: CWO++ library, Comput. Phys. Commun. 183, 1124-1138 (2012) CrossRef

Improving detection sensitivity for partial discharge monitoring of high voltage equipment

Partial discharge (PD) measurements are an important technique for assessing the health of power apparatus. Previous published research by the authors has shown that an electro-optic system can be used for PD measurement of oil-filled power transformers. A PD signal generated within an oil-filled power transformer may reach a winding and then travel along the winding to the bushing core bar. The bushing, acting like a capacitor, can transfer the high frequency components of the partial discharge signal to its earthed tap point. Therefore, an effective PD current measurement can be implemented at the bushing tap by using a radio frequency current transducer around the bushing-tap earth connection. In addition, the use of an optical transmission technique not only improves the electrical noise immunity and provides the possibility of remote measurement but also realizes electrical isolation and enhances safety for operators. However, the bushing core bar can act as an aerial and in addition noise induced by the electro-optic modulation system may influence overall measurement sensitivity. This paper reports on a machine learning technique, namely the use of a support vector machine (SVM), to improve the detection sensitivity of the system. Comparison between the signal extraction performances of a passive hardware filter and the SVM technique has been assessed. The results obtained from the laboratory-based experiment have been analysed and indicate that the SVM approach provides better performance than the passive hardware filter and it can reliably detect discharge signals with apparent charge greater than 30 pC.

A frequency doubling electro-optic modulation system for Pockels effect measurements: Application in LiNbO3

A novel system is presented which is capable of measuring with high accuracy the linear (Pockels) electro-optic effect by means of a new dynamic (ac) method. This method is based on the observation of the photodetected output obtained from a Senarmont-type ellipsometric system with an ac (modulating) voltage being applied onto the electro-optic sample under test. This observation is made on a high sensitivity oscilloscope and allows us to determine accurately the null point of the system by locating the position of the analyzer that produces in the output a characteristic and abrupt doubling of the (modulation) frequency. By locating this frequency doubling position without and with electric field one can finally determine the corresponding electro-optic coefficients. Theoretical analysis and considerations of practical interest are presented in the article and show that the system in question can ensure reduced errors and increased sensitivity. Also, experimental evidence in support of the expected performance is obtained by implementing and applying the system for the measurement of the composite electro-optic coefficient rc of LiNbO3 for various temperatures in the range of 17–20 °C.