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Paradigm Shift of On-Chip Interconnects from Electrical to Optical
Published in Thomas Noulis, Noise Coupling in System-on-Chip, 2018
Swati Joshi, Amit Kumar, Brajesh Kumar Kaushik
Modulators are essential components in photonics circuits. They control the characteristics of light through the circuits according to an external modulating signal. There are stringent requirements for optical modulators to meet complex future demands, such as high speed, low energy per bit, compact design, low loss, large optical bandwidth, modulation depth, low-temperature sensitivity, CMOS compatible process flow, and low drive voltage. The thermo-optic effect, electro-optic effect, and microelectromechanical systems (MEMS) are some of the current optical modulation schemes. In an electro-optic modulator, the electro-optic effect is used to modulate a beam of light. The modulation can be in terms of change of intensity, phase, or polarization of the output beam. MEMS and thermal effects find less application in current devices due to their slow speed. An optical modulation scheme is shown in Figure 14.27.
THz Photonics
Published in Chi H. Lee, Microwave Photonics, 2017
Albert Redo-Sanchez, X.-C. Zhang
Optical rectification is based on the inverse process of the electro-optic effect [7]. The electro-optic effect is the change in the optical properties of a material as a result of applying an electric field with a lower frequency than the frequency of light. The most important electro-optic effects are the Pockels effect and the Kerr effect, in which birefringence is induced or modified by the electric field applied onto the material. The Pockels effect is a change in the refractive index or birefringence that depends linearly with the field. The Kerr effect is a change in the index or birefringence that is quadratic with the field and generally is weaker than the Pockels effect. All materials display the Kerr effect but only certain crystalline solids show the Pockels effect because the Pockels effect requires the crystal to have no inversion symmetry.
Electro-Optical and Acousto-Optical Devices
Published in Daniel Malacara-Hernández, Brian J. Thompson, Advanced Optical Instruments and Techniques, 2017
In an electro-optic crystal, such as those mentioned in the last section, the change in the index of refraction n along a crystal axis may be expressed in series form as Δ1n2=pE+kE2+..., where E is the electric field, p is the linear electro-optic coefficient, and k is the quadratic electro-optic coefficient. In useful crystal, either the linear electro-optic effect (referred to as the Pockels effect) or the quadratic electro-optic effect (referred to as the Kerr effect) is predominant. In either case, the index of refraction will change at the modulation rate of the electric field. The effect allows a means of controlling the intensity or phase of the propagating beam of light. A Pockels cell uses the linear effect in crystals, whereas a Kerr cell uses the second-order electro-optic effect in various liquids and ferroelectrics; however, the former requires far less power than the latter to achieve the same amount of rotation and thus is used more widely. The Pockels effect, in particular, depends on the polarity of the applied electric field.
Accurate second Kerr virial coefficient of rare gases from the state-of-the-art ab initio potentials and (hyper)polarizabilities
Published in Molecular Physics, 2020
The Kerr effect, discovered by John Kerr in 1878 [1], describes the refractive-index change of a material when an electric field is applied. The Kerr electro-optic effect has a fast response to the change of an external electric field and is the basis for electronic controlled optical switches. The Kerr optical effect means that the change of refractive index is proportional to the intensity of light. Its most well-known application nowadays is Kerr-lens modelocking. For an ideal gas, Buckingham et al. [2,3] found that the Kerr constant Km is linearly proportional to the gas density ρ: where the coefficient AK (also called the first Kerr virial coefficient) depends on the atomic second hyperpolarizability γ0. With increasing pressures or densities, the deviations from Eq. (1) can be observed and the terms quadratic, cubic and higher in density contribute to Km(ρ): where BK(T) and CK(T) are the second and third Kerr virial coefficients, respectively and T is the temperature.
Uniform asymptotics of solutions of the wave operator with meromorphic coefficients
Published in Applicable Analysis, 2023
Maria V. Korovina, Hovik A. Matevossian, Ilya N. Smirnov
In this paper the problem of wave propagation in the medium whose velocity characteristics change under an external impact in three-dimensional case is considered. We study the problem of constructing the asymptotics of solutions for a wave equation with a variable coefficient that depends on time at the Laplacian and is a meromorphic function in a neighborhood of infinity. For the first time, a physical interpretation of such a problem was considered in [1], in which the phenomenon of light self-focusing was studied. This phenomenon is one of the effects of self-action of light and manifests itself in the concentration of the light-beam energy in the nonlinear medium with a refractive index that increases with increasing light intensity. It was also shown there that the ionizing, thermal, and separating effect of the beam of intensive radiation on the medium can be so strong that it leads to a drastic difference between the medium properties in the beam and outside it, which results in the waveguide propagation of the beam and eliminates its geometrical and diffraction divergence; this interesting phenomenon can be called the self-focusing of the electromagnetic beam. Later, the foundations of a mathematically rigorous theoretical description of this phenomenon were laid in [2]. However, still in 1875, J. Kerr discovered the Kerr effect, or the quadratic electro-optic effect – the phenomenon of a change in the value of refractive index of an optical material caused by an applied electric field and being proportional to the square of the electric field strength. The Kerr effect can be observed in all media, however, for some liquids, it is more pronounced than for other substances.
Ferroelectric, Piezoelectric Mechanism and Applications
Published in Journal of Asian Ceramic Societies, 2022
Arun Singh, Shagun Monga, Neeraj Sharma, K Sreenivas, Ram S. Katiyar
The electro-optic effect can be employed in optical modulators and display systems. A thin film, electro-optic light modulators is shown in Figure 13 (c) [33]. The light is coupled with the film by using a prism coupling (not shown in the figure). The small separation between electrodes across the optical wave guide enables the application of large electric fields at relatively low voltages. The change in polarization depends on the applied field and the length of the waveguide. An applied ac signal can produce intensity variations in a polarized light beam when seen through an analyzer.