![]() In this work, the large magnetic field limited the practical applications of the device. In 2016, an isolator based on the magneto-optical Kerr effect of graphene was experimentally demonstrated with an isolation ratio of ~20 dB and an insertion loss of ~7.5 dB, which was suitable for circularly polarized terahertz signals under room temperature and a magnetic field of 7 T 15. Recently, experiments with great performances for space transmission have been demonstrated to exhibit the isolation function 14, 15, 16, 17, 26. When we take the performances of reported devices into consideration, terahertz isolators which possess high isolation ratios and small insertion losses are still the main research target 10, 13, 15, 16. To achieve integrated, compact, and high-efficiency terahertz systems 9, 32, there is an urgent need for the realization of on-chip terahertz isolators, which has not yet been reported. However, the schemes above strongly rely on the adjustment of the polarization or the control of the terahertz signal incident angle, therefore, these methods are more suitable for demonstrating terahertz isolators in the process of space transmission. The other kind of method is based on the unidirectional absorption 26, 27 and reflection 16, 28, which results from the nonreciprocal directional dichroism 26, 27, 29, 30, 31 and nonreciprocal reflection loss of the magnetic materials in specific directions 16, 28. High-mobility semiconductors (InSb 18, 19, 20, 21, HgTe 22), graphene 23, 24, ferrofluid 25, and magnetic materials 14 are candidates that can be utilized to generate polarization rotation of terahertz waves. Schemes based on Faraday effect 14, 17 and magneto-optical Kerr effect 15 are introduced to design isolators with the help of polarization-converting elements. Traditional terahertz isolators are realized with magnetic-optical materials, which are mostly considered in the following schemes. Recently, researches on terahertz isolators have attracted widespread attention. With nonreciprocity, these devices can constitute terahertz isolators (analogous to diodes) and circulators 13, 14, 15, 16, which has great significance in protecting terahertz sources, mitigating multipath interference, and suppressing undesired signal routing 10, 13. Among these components, nonreciprocal terahertz devices hold the possibility of breaking the time-reversal symmetry, consequently realizing the function of irreversible terahertz propagation 10, 11, 12, 13. Although recent advances in terahertz frequencies provide both opportunities and challenges, the lack of high-efficiency terahertz sources, high-sensitivity detectors, and functional devices is still the main blocking element hindering the progress of terahertz technology 3, 4, 9. Users should refer to the original published version of the material for the full abstract.Terahertz science and technology have witnessed unprecedentedly rapid development during the past decade and therefore have grown into a disruptive interdisciplinary subject 1, 2, 3, which possesses compelling prospects in fundamental science 3, wireless communications 4, 5, 6, imaging 7, 8, and sensing 3. No warranty is given about the accuracy of the copy. However, users may print, download, or email articles for individual use. Copyright of Applied Physics B: Lasers & Optics is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission.It was used as a basis for a new scheme of Faraday isolator with external compensation of thermally induced birefringence. A method of compensating thermally induced birefringence without reciprocal polarization rotator was described theoretically and demonstrated in experiments for the first time. Simultaneous reduction of thermally induced depolarization and thermal lens in the Faraday isolator based on a TGG crystal was demonstrated experimentally for the first time using an Sm:CaF crystal. Abstract: A Faraday isolator system with external compensation of thermally induced birefringence was investigated for the case when optical components of the Faraday isolator and the compensator are made of different materials.
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