Extinction ratio

About: Extinction ratio is a research topic. Over the lifetime, 8541 publications have been published within this topic receiving 111908 citations.

Single- and dual-wavelength switchable erbium-doped fiber ring laser based on intracavity polarization selective tilted fiber gratings.

Abstract: We propose and demonstrate a single- and dual-wavelength switchable erbium-doped fiber laser (EDFL) by utilizing intracavity polarization selective filters based on tilted fiber gratings (TFGs). In the cavity, one 45° TFG functions as an in-fiber polarizer and the other 77° TFG is used as a fiber polarization dependent loss (PDL) filter. The combined polarization effect from these two TFGs enables the laser to switch between the single- and the dual-wavelength operation with a single-polarization state at room temperature. The laser output at each wavelength shows an optical signal-to-noise ratio (OSNR) of >60 dB, a side mode suppression ratio (SMSR) of >50 dB, and a polarization extinction ratio of ~35 dB. The proposed EDFL can give stable output under laboratory conditions.

Highly polarization-sensitive, visible-blind and self-powered ultraviolet photodetection based on two-dimensional wide bandgap semiconductors: a theoretical prediction

Abstract: Two-dimensional wide bandgap (2D-WBG) semiconductors have attracted extensive research interest in ultraviolet (UV) photodetection because of their excellent performances including ultrafast response, high responsivity and low dark current. Using quantum transport simulations, we proposed here a kind of self-powered, visible-blind and UV-polarized photodetector driven by the photogalvanic effect (PGE) based on several 2D-WBG (3.0–7.41 eV) semiconductors and their heterostructures. Such 2D-WBG semiconductors show sharp optical absorption peaks ranging from 4 eV to 8 eV, which is suitable for a variety of application fields in UV photodetection. We also designed a vertical van der Waals heterostructure (vdWh) with a type-II energy band alignment composed of 2D monolayer MgBr2 and CdCl2. Robust PGEs can be induced in the photodetectors based on this vdWh and also on monolayer ZrNY (Y = Cl and Br) due to the C3v symmetry under the illumination of both linearly and elliptically polarized light. The broadband and highly polarization-sensitive photocurrent is therefore generated at zero bias voltage, which exhibits a remarkably high extinction ratio of up to 280. These results suggest a promising mechanism for polarization-sensitive and visible-blind UV photodetection with low power consumption.

Polarization characteristics of a wire-grid polarizer in a rotating platform.

Abstract: I explore the polarization characteristics of a wire-grid polarizer operating in a rotating platform using well-established rigorous coupled-wave analysis. The results show that the performance of a wire-grid polarizer evaluated in transmittance and extinction ratio is substantially degraded with rotation, although it is still more robust than that of a perfect polarizer. The performance may further deteriorate with inclined incidence due to an increased negative effect of a Rayleigh anomaly. Either a finer or a deeper grating reduces the adverse effect of rotation. Although implementation of such a grating is difficult, the rotation characteristics can be enhanced by means of pixelating the wire grids of various orientations and capturing the input images with a sufficiently high sampling rate.

Broad-band optical directional couplers and polarization splitters

Abstract: A method is described for designing broadband optical directional couplers. The basic idea is to determine an optimum distance between the waveguides where wavelength dependence of the coupling coefficient vanishes at a given wavelength. The method is applied to design directional coupler polarization splitters. As an example the computer design of a polarization splitter made of single-mode twin-core optical fiber is presented. The extinction ratio obtained for waves with undesired direction of polarization is better than -20 dB within a wavelength range of 80 nm. The sensitivity of the design to variations of the main parameters caused by the production process is discussed for characteristic examples. >

A Photonic Crystal Fiber Polarized Filter at 1.55 μm Based on Surface Plasmon Resonance

Abstract: A single-polarization photonic crystal fiber (PCF) based on surface plasmon resonance (SPR) is proposed. Finite element method is employed in simulating the PCF with gold-coated. The resonance wavelength can be modulated by changing the thickness of gold layer. At the resonance wavelength 1.55 μm, the loss of y-polarized mode is much larger than the loss of x-polarized mode. When the fiber length is set to 2 mm, the value of extinction ratio reaches to −118.7 dB, the y-polarized mode is suppressed and only x-polarized mode can be guided. The fiber is applicable in the production of single-polarization filter. The PCF has a simple structure and a big error tolerance, it has a good practicability.