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Unidirectional photonic circuit with a phase-change Fano resonator
摘要： We demonstrate that the integration of a phase-change material (PCM) in one of the two microresonators of a photonic circuit, coupled to a bus waveguide, can lead to unidirectional Fano resonances and to the emergence of a unidirectional transmission window. The phase change is caused by light-induced heating and is accompanied by an abrupt increase in the extinction coefficient of the PCM resonator. Due to the photonic circuit asymmetry, the critical value of the input light intensity triggering the phase change is strongly dependent on the input light direction. The latter determines the unidirectional nature of the emerging transmission window. This effect can be utilized in on-chip magnetic-free isolators and Q switches.
关键词： optical isolators,phase-change material,photonic circuit,unidirectional transmission,Fano resonances
更新于2025-09-23 15:21:01
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Nonreciprocity and zero reflection in nonlinear cavities with tailored loss
摘要： We demonstrate how to tailor the losses of nonlinear cavities in order to suppress their re?ection and enhance their nonreciprocal transmission. We derive analytical expressions predicting the existence of zero-re?ection channels in single and coupled nonlinear cavities, depending on the driving frequency and loss rates. While suppressing the re?ection from a single cavity imposes a stringent condition on the input-output leakage rates, we demonstrate that this condition can be signi?cantly relaxed in systems of coupled cavities. In particular, zero-re?ection and nonreciprocity can be achieved across a range of driving frequencies in coupled cavities by tuning the output leakage rate alone. Numerical calculations based on the driven-dissipative Gross-Pitaevskii equation, usually employed to describe microcavity polaritons, reveal the spatial phenomenology associated with zero-re?ection states and provide design guidelines for the construction of nonlinear optical isolators.
关键词： optical isolators,nonreciprocity,nonlinear cavities,tailored loss,zero re?ection
更新于2025-09-19 17:15:36
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Characterization of the Verdet Constant of Dy <sub/>2</sub> O <sub/>3</sub> Ceramics in the Two-Micron Spectral Range
摘要： High-power solid-state mid-IR lasers are being actively developed, as they possess the key properties for a vast number of technological applications [1] (e. g. lidar, gas sensing, or pump sources optical parametric oscillators) and are in a high demand for basic research as well [2]. These potentialities have recently led to intensive investigations of new mid-IR laser gain media [3,4] and other optical elements. One of the key components under investigation is an optical isolator (OI), a magneto-optical device enabling safe operation of a laser by preventing harmful back-reflections into the laser cavity. The development of high-power OIs is particularly challenging due to the severe thermal effects which arise because of the relatively high absorption of the currently available magneto-optical elements. Therefore, a lot of scientific effort is being put into the research of novel magneto-optical materials with the desired properties: high Verdet constant, low absorption and excellent thermal properties. All of these properties enable a reduction of the heat generated in the magneto-optical element. A large number of new magneto-optical materials for high-power OIs have been reported in the recent years. The vast majority of these reports targeted materials suitable for the wavelengths around 1 μm (corresponding to the neodymium and ytterbium doped gain media) in the task to find a better alternative to the most commonly used magneto-optical material for this spectral range – the terbium gallium garnet (TGG) [5]. In this manner, materials based on highly magnetically active rare-earth ions (e. g. Ce3+ [6], Tb3+ [7] or Ho3+ [8]) have been established as a possible next generation of magneto-optical materials for the visible and near-IR OIs. Some of these materials possess local transparency windows in the mid-IR as well, however, reports dealing with their magneto-optical characteristics in this region (or reports of any other suitable materials) were so far very rare. Nevertheless, Verdet constants of CeF3 crystal [9], DyxY0.95-xLa0.05O3 ceramics (with variable doping X = 0.7 – 0.9) [10] and EuF2 crystal [11] have been recently reported at the wavelength of ~1.94 μm, having ~7, ~10 - 14, and ~12 rad/Tm respectfully. We present broadband experimental characterizations of the Verdet constant of three novel material samples of Dy2O3-based ceramics in a broad spectral range 0.6 – 2.4 μm with the relative error of the measurement ~5%. An analytical approximation of the data is a challenging task due to the multiple resonances and absorption bands of Dy3+ ions within the measured range and is currently under investigation. The obtained values for the Verdet constant at 1.94 μm were 17.8, 22.2 and 26.8 rad/Tm predicting a high potential for Dy2O3 ceramics utilization in a high-power mid-IR OIs. The measured transmittances of our samples at 1.94 μm were equal to 54%, 72% and 76%.
关键词： mid-IR lasers,optical isolators,magneto-optical materials,Dy2O3 ceramics,Verdet constant
更新于2025-09-12 10:27:22