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0Nonlinear control of coherent tunnelling by adiabatic passage in hybrid integrated waveguides
O. Borovkova1*, I. Bilenko1'2, D. Chermoshentsev1'3'4
1-Russian Quantum Center, Skolkovo Innovation Center, Bolshoy boulevard, 30, bld. 1, 121205, Moscow,
Russia
2- Faculty of Physics, Lomonosov Moscow State University, Leninskie Gory, Moscow 119991, Russia 3- Moscow Institute of Physics and Technology, 141701, Dolgoprudny, Russia 4- Skolkovo Institute of Science and Technology, Moscow 143025, Russia
* o.borovkova@rqc.ru
Integrated photonics is a perspective platform for various applications from biosensors to compact light sources, from quantum technologies to neural networks and information processing, etc. Optical waveguides and directional couplers made by CMOS-compatible technology are basic elements for integrated photonics; and advances of light routing and control in them attracts an interest of researchers. In our work we analyze the possibilities of the light routing and transfer provided by the integrated planar waveguide structure on the silicon dioxide chip based on the coherent tunnelling by adiabatic passage (CTAP) [1-3]. The CTAP is an optical analogue of the stimulated Raman adiabatic passage (a laser-based method of efficient and selective transfer of population between quantum states) well-known for atomic and molecular physics [4]. In optical CTAP scheme the waveguides adiabatically couple with each other and enable light evolution via the dark state of the three-state system (composed of two weakly-curved waveguides and one straight waveguide between them). The most interesting is the so-called counter-intuitive scheme, when coupling between idle waveguides (one of lateral waveguides and the central one) appears before the excited waveguide becomes coupled with one of them. As a result, the central waveguide is not excited via coupling, but just serves for light transfer. An advantage of such scheme is that light transfer can be effectively controlled via parameters and optical properties of the central waveguide, but there is no light transfer in it.
We consider the hybrid integrated waveguide scheme, where the lateral bent waveguides are made of silicon nitride and the central waveguide can be made of different material, e.g., from the lithium niobate, that is well-known due to its large second-order nonlinear susceptibility and greater refractive index than silicon nitride. We show that the light transfer in such waveguide scheme can be controlled by external field applied to the central waveguide. It is demonstrated that the efficiency of the light transfer in the hybrid CTAP scheme is higher than in pure silicon nitride one, and the intermediate waveguide in this case doesn't carry any signal at all. Also, we address the robustness of the CTAP scheme to the polarization state of the transferred light and revealed that both polarizations (TE and TM) possess close transmittance coefficients due to the adiabatic character of the light transfer. This aspect is especially important for practical applications. Moreover, we performed the optimization of the parameters of the considered setup to achieve the maximum transmittance of the setting.
This study was supported by Russian Science Foundation (project no. 24-22-00190).
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