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Interferometric Fiber-Optic Sensors
Published in Krzysztof Iniewski, Ginu Rajan, Krzysztof Iniewski, Optical Fiber Sensors, 2017
Sara Tofighi, Abolfazl Bahrampour, Nafiseh Pishbin, Ali Reza Bahrampour
The strong and weak grating limits are defined as ΔnL≫λB and ΔnL≪λB, respectively, where Δn = n − n0 is an index modulation and L is the FBG length. For the strong and weak FBGs, the reflection bandwidth is proportional to Δn and 1/L, respectively [38]. The FBG bandwidth is typically below one nanometer. In the polarization rotator, a mode with a given polarization is coupled to another mode with a different polarization. The conservation laws of energy and momentum can be employed to obtain the governing equations of FBG interferometer. The period of FBG depends on its application and can vary systematically or randomly along the optical fiber core. In a chirped FBG, the period varies monotonically along the optical fiber and has many applications in sensors and optical fiber networks [39].
Sources, Detectors, and Recording Media
Published in Rajpal S. Sirohi, Introduction to OPTICAL METROLOGY, 2017
As is obvious, the direction of optic axis is along the x-axis inside the first plate. At any plane z, the optic axis lies in x–y plane but makes an angle θ with the x-axis. In order to study the propagation of polarized beam in the liquid crystal medium, we divide the medium into thin layers perpendicular to the axis of twist. Each of these layers acts as a uniaxial crystal, with optic axis rotating slowly in a helical fashion. Each layer of thickness Δz rotates the plane of polarization by αΔz and also introduces a phase difference βΔz, where β = 2π(μe – μ0)/λ0 and λ0 is the vacuum wavelength. The cumulative effect of these layers on the transmitted wave is then determined considering both these factors. Let us consider a case in which the incident wave is linearly polarized along x-direction at z = 0 plane, which is the inner face of the first plate. It may be noted that β ≫ α, hence the linearly polarized wave maintains its linearly polarized state but the plane of polarization rotates in alignment with the molecular twist. The NLC cell in a configuration shown in Figure 3.11 rotates the plane of polarization by π/2. In other words, it acts as a polarization rotator.
Optical Methods in Solid Mechanics
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
In the above polariscope, there is a need to manually rotate the analyzer, which makes it difficult to achieve high stability and repeatability. A new method based on a liquid crystal polarization rotator to get full-field sub-fringe stress distribution is proposed. By changing the applied voltage to the liquid crystal phase plate, the phase-shift images are recorded and processed to get the stress distribution. Figure 23.8 is the schematic of the proposed polariscope using the liquid crystal (LC) polarization rotator as the phase-shifting element. The LC polarization rotator, a key component of the proposed polariscope system, consists of an LC phase plate inserted between two crossed QWPs. The extraordinary (fast) axis of the first QWP is parallel to the x-axis. The extraordinary axis of the LC phase plate is oriented at 45°, and the extraordinary axis of the second QWP is oriented parallel to the y-axis. An LED light source illuminates the object with circularly polarized light and the transmitted light goes through LC polarization rotator before impinging on the analyzer whose orientation is set parallel to the x-axis (α = 0°).
Design for the reconfigurable polarization rotator by inhibiting Fano resonance with graphene-metal grating structures
Published in Waves in Random and Complex Media, 2022
Yuan-Zhe Sun, Cheng-Jing Gao, Zi-Han Guo, Dan Zhang, Hai-Feng Zhang
The current level and the trend of the PCR collaboratively manifest that the interference of the dark mode (the dual-L resonator) at a higher operating band is efficiently inhibited, reversing the main resonant of the bright mode. (the 8SR), which plays a decisive role in widening the PCR band. The previous narrow-band region of the PCR fades into the ineffective sate (comparing the PCR responses in Figure 20(a) and Figure 10(b)), which can be likewise interpreted as the red-shift of the high-frequency resonance peak compensating for the original transmission drop. In general, the Fano linear shape is successfully suppressed via adjusting the resonant peak ω2 (i.e. a = 25 µm), corresponding to the DDSOM. The stable ultrabroadband integrated polarization rotator is gradually polished and theoretically accomplished guided by the new-proposed DDSOM.
Dual-polarization operating hybrid plasmonic 2×2 multimode interferometer with mode converter for SOI platform
Published in Journal of Modern Optics, 2020
J. Wang, J. J. Wang, X. Xu, N. N. Ning, Q. F. Liu, Y.Q. Lu
To reduce the footprint of the optical device and further improve the integration level of PICs, a hybrid plasmonic waveguide (HPW) has been proposed, whose light confinement ability is not limited by diffraction and leads to much smaller device sizes [9,10]. Recently, the plasmonic polarizer [11,12], the polarization rotator [13], the polarization beam-splitter [14] and the optical hybrid [15] have been proposed. Especially, with the same waveguide width, a multimode HPW can support more guided modes than a dielectric multimode waveguide [16]. Moreover, HPW is compatible with silicon photonic technology and can be integrated on the SOI platform. However, because the plasmonic modes of HPW are mostly concentrated near the interface between the metal and dielectric layers, the dual-polarization operation condition of HPW-MMI would be much strict and harsh. Also, because the HPW modes still undergo the Ohmic loss in the metal, the little high propagation loss limits the utilization of the HPW devices in a large chip scale.
Rome teleportation experiment analysed in the Wigner representation: the role of the zeropoint fluctuations in complete one-photon polarization-momentum Bell-state analysis
Published in Journal of Modern Optics, 2018
A. Casado, S. Guerra, J. Plácido
The analyser at Alice's station includes two PBSs, PBS3 and PBS4, which operate in opposite ways. PBS3 (PBS4) is placed in the path of beam () and transmits the vertical (horizontal) polarization. A polarization rotator of is located at each of the outgoing channels and . After some easy algebra, we obtain the following expression for the field amplitudes after considering the action of the PBSs, the polarization rotators, and the mirrors and : where and represent the zeropoint beams entering the polarizing beam-splitters PBS3 and PBS4, respectively (see Figure 1). These two inputs of noise introduce four ZPF sets of modes which contribute to the measurement of the four one-photon polarization-momentum Bell states.