![]() The field amplitudes of these modes inside the resonator are given by a S ±. In the forward and reverse operation direction shown in panels (b) and (c), the system is probed by the external fields a S ± ( in ) (solid blue and cyan arrows). The field amplitude a P + corresponds to the large intensity pump mode inside the resonator. In both forward and reverse configurations, the resonator can be pumped in the CCW direction by an external field a P + ( in ) (thick red arrow). The ring resonator case is recovered by setting t S = 1 and k S = 0. The dashed green (orange) rectangles indicate directional couplers coupling the ring resonator to the bus waveguides (S-shaped element), with transmission and coupling amplitudes t w ( t S) and i k w ( i k S), respectively. General scheme of a ring or TJR operated in (b) forward and (c) reverse directions. This allows us to set the CCW (CW) modes as the forward (reverse) operation direction of our optical isolator. While FWM (symbolized by the gray arrows) can effectively couple CCW-propagating pump, signal, and idler modes, it cannot couple the pump P + with the signal S − because the resulting idler would completely fall out of resonance. The green dashed lines are the dispersion relations for CCW ( ℓ > 0) and CW ( ℓ < 0) modes including the curvature given by Eq. ( 3). (a) Dispersion relation of the resonant frequencies ω ℓ ( 0 ) of a ring or Taiji (TJR) resonator as a function of the angular momentum ℓ of the mode. A few most relevant setups realizing our proposal are specifically investigated, such as a coherently illuminated passive ring resonator and unidirectionally lasing ring or Taiji resonators. ![]() Taking advantage of a close analogy with fluids of light, our proposed isolation mechanism is physically understood in terms of the Bogoliubov dispersion of collective excitations on top of the strong pump beam. The mechanism underlying optical isolation is based on the breaking of optical reciprocity induced by the asymmetric action of four-wave mixing processes coupling a strong propagating pump field with copropagating signal and idler modes but not with reverse-propagating ones. Such devices can be straightforwardly realized in state-of-the-art integrated photonics platforms. ![]() It pressures the magnetic element of a Faraday rotator, which is usually a rod designed with a magnetic crystal beneath the strong magnetic field through Faraday Effect.In this work we propose and theoretically characterize optical isolators consisting of an all-dielectric and nonmagnetic resonator featuring an intensity-dependent refractive index and a strong coherent field propagating in a single direction. This type of isolator is also named as the polarized optical-isolator in a new face. This is an independent polarized type optical-isolator, which can be used in EDFA optical amplifier which includes different components like wavelength-division multiplexer (WDM), erbium-doped fiber, pumping diode laser, etc. The latter is more complicated and often used in EDFA optical amplifier. Also, there are dependent and independent polarized optical-isolators. It allows light to transmit in forwarding direction, however, prohibits every light beam to transmit back. This isolator uses the polarization axis to keep light transmit in one direction. Optoisolators are classified into three types which include Polarized, Composite, and Magnetic optical-isolator Polarized Type Optical-Isolator Thus, the light beam will be either absorbed or reflected. After that, the 90° polarization light turns into vertical toward the i/p polarizer & cannot depart the isolator. When it transmits throughout the Faraday rotator, rotates continuously for another 45° in a similar path. Similarly in backward mode, initially the light enters into the o/p polarizer with a 45°. Therefore, finally, the light leaves from the o/p polarizer at 45°. Once the light beam arrives at the Faraday rotator, then the rod of the Faraday rotator will turn with 45°. In forward mode, the light enters into the input polarizer then becomes linearly polarized. The operation modes of this isolator are classified into two types based on the different directions of light such as forward mode & backward mode. The working of this is like when light passes through the i/p polarizer in the forward direction & turn into polarized within the vertical plane. The block diagram representation is shown below. An optical isolator includes three main components namely a Faraday rotator, i/p polarizer, & an o/p polarizer.
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