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Electromagnetic Waves and Lasers
Published in Hitendra K. Malik, Laser-Matter Interaction for Radiation and Energy, 2021
Many applications require polarized light in a specific state or direction, so it becomes mandatory to segregate the states of polarization of light. Many optical applications depend on good polarization control systems. These include laser materials processing, liquid crystal device characterization and manufacturing, fluorescence polarization assays and imaging, polarization diversity detection in communications and range-finding, polarized Raman spectroscopy, second harmonic-generation imaging and many other laser applications based on holography, interferometry and so forth. There are so many polarizers available, but not every problem is solved using one or the other. Thus, the number of important applications are lacking due to the lack of ideal polarization component. An ideal polarizer gives 100% transmission of the required polarization components and eliminates the unwanted components. The most significant parameter that governs an ideal polarizer is the ‘contrast ratio’. The contrast ratio is defined as the ratio of the transmissions through a pair of polarizers when they are aligned parallel and when they are crossed. This ratio varies from about 102:1 to as large as 104:1. Another parameter known as the ‘extinction ratio’ is the inverse of the contrast ratio.
Tilted Dielectric Coatings
Published in H. Angus Macleod, Thin-Film Optical Filters, 2017
The extinction ratio, that is, the ratio of the irradiance of the undesired mode of polarization to that of the desired (although extinction ratio is sometimes defined as the reciprocal), is a guide to the performance of a polarizer, but the extinction ratio takes no account of the level of throughput of the device, and so we must supplement it by some measure of efficiency, usually the transmittance, or the reflectance if appropriate. Another older, and rather less useful, performance parameter is polarizing efficiency defined as (Idesired ‑ Iunwanted)/(Idesired + Iunwanted) and usually expressed as a percentage.
All-fiber spectral modulating device based on microfiber interferometer grown with tungsten disulfide
Published in Instrumentation Science & Technology, 2020
Meng Luo, Xinghua Yang, Pingping Teng, Depeng Kong, Zhihai Liu, Danheng Gao, Zhanao Li, Xingyue Wen, Libo Yuan, Kang Li, Nigel Copner
Meanwhile, with the increase of the control light power, the normalized intensity at the selected wavelength was monotonically increased. Here, the transmission extinction ratio is defined to be equal to Ex = [(I0 − Ip)/I0] × 100% where I0 is the intensity for the control light power of zero and Ip is the intensity for the control light power. In the experimental measurements, the value of Ip is the maximum control light power value equal to 656 mw. The maximum extinction ratios of 8.4, 16.9, 18.1 and 15% were obtained for the signal radiation values equal to 1554.5, 1553.5, 1552.5 and 1551.5 nm, respectively. Experimentally, the ideal extinction rate may be higher. However, the pump light intensity is limited. In general, this tungsten disulfide microfiber phase shifter has been demonstrated to be capable of adjusting the output light amplitude.
Dynamic O-band to C-band wideband wavelength converter for integrated VCSEL-based optical interconnects
Published in Journal of Modern Optics, 2019
G. M. Isoe, D. K. Boiyo, T. B. Gibbon
Figure 2 shows the bias characteristic performance of the considered 1550 and 1310 nm VCSEL carriers. The bias current of each VCSEL was individually varied from 0.2 to 9.8 mA, as the respective output optical power was monitored using an optical power meter. Both VCSEL carriers were noted to have a current threshold of less than 1.5 mA, while the current roll over point remained above 8.6 mA as shown in Figure 2. The considered VCSELs were also noted to operate optimally for drive currents below 10 mA. This good energy efficiency of VCSELs makes them ideal candidate for large-scale deployment in densely packed optical interconnects. Both the 1550 nm and 1310 nm VCSELs were biased at their respective linear regions for bias currents between 5.52 and 5.56 mA. This was to ensure best extinction ratio for optimum direct modulation data signals.
Fabrication of polarization colour filter device via direct Au film imprinting
Published in Journal of Modern Optics, 2021
The probe light was polarized with polarizers. The TM transmittance was found to be approximately 30% at the wavelength of 1000 nm, and a large dip was observed at the 690 nm wavelength. In contrast, the transmittance of TE polarization was lower than that of TM polarization; it was below 1% over the wavelength of 900 nm. The extinction ratio of 14.5 dB was obtained at the wavelength of 1000 nm. Here, the extinction ratio was defined as 10log(TTM/TTE) [dB], where TTM and TTE denote the transmittances for the TM-polarized and TE-polarized light, respectively. In addition, a transmission peak of over 5% at a wavelength of approximately 510 nm was observed.