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1. Nonreciprocal Fabry-Perot effect and performance enhancement in a magneto-optical InSb-based Faraday terahertz isolator

   https://doi.org/10.1364/OE.411581  

   Keshock, Elise; Peng, Peisong; Zhou, Jiangfeng; Talbayev, Diyar (December 2020, Optics Express)

   The Faraday effect due to the cyclotron resonance of conduction electrons in semiconductor InSb allows for nonreciprocity of transmitted light in our Faraday THz isolator operating in the presence of a small magnetic field. We select InSb as an efficient medium for our isolator due to its high electron mobility, low electron effective mass, and narrow band gap. Experimental measurements of the isolator performance indicate a maximum achieved isolation power of 18.8 dB with an insertion loss of −12.6 dB. Our optical analysis of the device points to a remarkablenonreciprocalFabry-Perot effect in the magneto-optical InSb layer as the origin of the multi-fold isolation enhancement. This nonreciprocity occurs as the Fabry-Perot reflections in the forward direction add constructively and enhance the transmittance at certain frequencies, while the Fabry-Perot reflections in the backward direction add destructively and suppress the transmittance at the same frequencies. 

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2. Optical and electrical properties of proton-implanted p-GaSb for electrical isolation

   https://doi.org/10.35848/1882-0786/ad9377  

   Nikor, Sk_Shafaat_Saud; Sumon, Md_Saiful_Islam; Sankar, Shrivatch; Ma, Like; Patel, Victor_J; Hawkins, Samuel_D; Addamane, Sadhvikas_J; Arafin, Shamsul (December 2024, Applied Physics Express)

   Abstract The effect of proton implantation as isolation implant and subsequent annealing on the optical absorption and electrical resistivity of low-bandgapp-GaSb is reported. The measured transmittance spectra indicates that implantation creates a distribution of energy levels extending into the bandgap. Electrical measurements show that the average sheet resistance of the implanted layer increases only by an order of magnitude from its pre-implantation value at a proton dose of ∼10¹³cm⁻²followed by 200 °C annealing. It is also shown that annealing reduces the implantation-induced optical absorption while still retaining a high electrical resistivity. 

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3. Visible-telecom tunable dual-band optical isolator based on dynamic modulation in thin-film lithium niobate

   https://doi.org/10.1364/OL.482635  

   Shah, Manav; Briggs, Ian; Chen, Pao-Kang; Hou, Songyan; Fan, Linran (April 2023, Optics Letters)

   Optical isolators are an essential component of photonic systems. Current integrated optical isolators have limited bandwidths due to stringent phase-matching conditions, resonant structures, or material absorption. Here, we demonstrate a wideband integrated optical isolator in thin-film lithium niobate photonics. We use dynamic standing-wave modulation in a tandem configuration to break Lorentz reciprocity and achieve isolation. We measure an isolation ratio of 15 dB and insertion loss below 0.5 dB for a continuous wave laser input at 1550 nm. In addition, we experimentally show that this isolator can simultaneously operate at visible and telecom wavelengths with comparable performance. Isolation bandwidths up to ∼100 nm can be achieved simultaneously at both visible and telecom wavelengths, limited only by the modulation bandwidth. Our device’s dual-band isolation, high flexibility, and real-time tunability can enable novel non-reciprocal functionality on integrated photonic platforms. 

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4. Fluctuating reproductive isolation and stable ancestry structure in a fine-scaled mosaic of hybridizing Mimulus monkeyflowers

   https://doi.org/10.1371/journal.pgen.1011624  

   Farnitano, Matthew C; Karoly, Keith; Sweigart, Andrea L (March 2025, PLOS Genetics)

   Lasky, Jesse (Ed.)

   Hybridization among taxa impacts a variety of evolutionary processes from adaptation to extinction. We seek to understand both patterns of hybridization across taxa and the evolutionary and ecological forces driving those patterns. To this end, we use whole-genome low-coverage sequencing of 458 wild-grown and 1565 offspring individuals to characterize the structure, stability, and mating dynamics of admixed populations ofMimulus guttatusandMimulus nasutusacross a decade of sampling. In three streams, admixed genomes are common and aM. nasutusorganellar haplotype is fixed inM. guttatus,but new hybridization events are rare. Admixture is strongly unidirectional, but each stream has a unique distribution of ancestry proportions. In one stream, three distinct cohorts of admixed ancestry are spatially structured at ~20-50m resolution and stable across years. Mating system provides almost complete isolation ofM. nasutusfrom bothM. guttatusand admixed cohorts,and is a partial barrier between admixed andM. guttatuscohorts. Isolation due to phenology is near-complete betweenM. guttatusandM. nasutus.Phenological isolation is a strong barrier in some years between admixed andM. guttatuscohorts, but a much weaker barrier in other years, providing a potential bridge for gene flow. These fluctuations are associated with differences in water availability across years, supporting a role for climate in mediating the strength of reproductive isolation. Together, mating system and phenology accurately predict fluctuations in assortative mating across years, which we estimate directly using paired maternal and offspring genotypes. Climate-driven fluctuations in reproductive isolation may promote the longer-term stability of a complex mosaic of hybrid ancestry, preventing either complete isolation or complete collapse of species barriers. 

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5. Multilayer protection-at-lightpath for reliable slicing with isolation in optical metro-aggregation networks

   https://doi.org/10.1364/JOCN.444522  

   Marotta, A.; Cassioli, D.; Tornatore, M.; Hirota, Y.; Awaji, Y.; Mukherjee, B. (March 2022, Journal of Optical Communications and Networking)

   The high reliability required by many future-generation network services can be enforced by proper resource assignments by means of logical partitions, i.e., network slices, applied in optical metro-aggregation networks. Different strategies can be applied to deploy the virtual network functions (VNFs) composing the slices over physical nodes, while providing different levels of resource isolation (among slices) and protection against failures, based on several available techniques. Considering that, in optical metro-aggregation networks, protection can be ensured at different layers, and the slice protection with traffic grooming calls for evolved multilayer protection approaches. In this paper, we investigate the problem of reliable slicing with protection at the lightpath layer for different levels of slice isolation and different VNF deployment strategies. We model the problem through an integer linear program (ILP), and we devise a heuristic for joint optimization of VNF placement and ligthpath selection. The heuristic maps nodes and links over the physical network in a coordinated manner and provides an effective placement of radio access network functions and the routing and wavelength assignment for the optical layer. The effectiveness of the proposed heuristic is validated by comparison with the optimal solution provided by the ILP. Our illustrative numerical results compare the impact of different levels of isolation, showing that higher levels of network and VNF isolation are characterized by higher costs in terms of optical and computation resources. 

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