Optical nanoantennas possess great potential for controlling the spatial distribution of light in the linear regime as well as for frequency conversion of the incoming light in the nonlinear regime. However, the usually used plasmonic nanostructures are highly restricted by Ohmic losses and heat resistance. Dielectric nanoparticles like silicon and germanium can overcome these constrains [1,2], however second harmonic signal cannot be generated in these materials due to their centrosymmetric nature. GaAs-based III-V semiconductors, with non-centrosymmetric crystallinity, can produce second harmonic generation (SHG) . Unfortunately, generating and studying SHG by AlGaAs nanocrystals in both backward and forward directions is very challenging due to difficulties to fabricate III-V semiconductors on low-refractive index substrate, like glass. Here, for the first time to our knowledge, we designed and fabricated AlGaAs nanoantennas on a glass substrate. This novel design allows the excitation, control and detection of backwards and forwards SHG nonlinear signals. Different complex spatial distribution in the SHG signal, including radial and azimuthal polarization originated from the excitation of electric and magnetic multipoles were observed. We have demonstrated an unprecedented SHG conversion efficiency of 10-4; a breakthrough that can open new opportunities for enhancing the performance of light emission and sensing .
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Maria del Rocio Camacho Morales, Mohsen Rahmani, Sergey S. Kruk, Lei Wang, Lei Xu, Daria A. Smirnova, Alexander S. Solntsev, Andrey E. Miroshnichenko, Hoe Tan, Fouad Karouta, Shagufta Naureen, Kaushal D. Vora, Luca Carletti, Costantino De Angelis, Chennupati Jagadish, Yuri S. Kivshar, and Dragomir N. Neshev, "Directional second harmonic generation from AlGaAs nanoantennas (Conference Presentation)," Proc. SPIE 10343, Metamaterials, Metadevices, and Metasystems 2017, 103430J (Presented at SPIE Nanoscience + Engineering: August 06, 2017; Published: 21 September 2017); https://doi.org/10.1117/12.2273553.5583319732001.
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