Browsing by Author "Lo, Yu-Ping"

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Giant photothermal nonlinearity in a single silicon nanostructure
(2020-08-14)
Duh, Yi-Shiou
;
Nagasaki, Yusuke
;
Tang, Yu-Lung
;
Wu, Pang-Han
;
Cheng, Hao-Yu
Silicon photonics have attracted significant interest because of their potential in integrated photonics components and all-dielectric meta-optics elements. One major challenge is to achieve active control via strong photon-photon interactions, i.e. optical nonlinearity, which is intrinsically weak in silicon. To boost the nonlinear response, practical applications rely on resonant structures such as microring resonators or photonic crystals. Nevertheless, their typical footprints are larger than 10 mu m. Here, we show that 100nm silicon nano-resonators exhibit a giant photothermal nonlinearity, yielding 90% reversible and repeatable modulation from linear scattering response at low excitation intensities. The equivalent nonlinear index is five-orders larger compared with bulk, based on Mie resonance enhanced absorption and high-efficiency heating in thermally isolated nanostructures. Furthermore, the nanoscale thermal relaxation time reaches nanosecond. This large and fast nonlinearity leads to potential applications for GHz all-optical control at the nanoscale and super-resolution imaging of silicon.
Narrow-Band Thermal Emitter with Titanium Nitride Thin Film Demonstrating High Temperature Stability
(1970-01-01)
Yang, Zih-Ying
;
Ishii, Satoshi
;
Doan, Anh Tung
;
Shinde, Satish Laxman
;
Dao, Thang Duy
A refractory wavelength selective thermal emitter is experimentally realized by the excitation of Tamm plasmon polaritons (TPPs) between a titanium nitride (TiN) thin film and a distributed Bragg reflector (DBR). The absorptance reaches nearly unity at approximate to 3.73 mu m with the bandwidth of 0.36 mu m in the experiment. High temperature stabilities are confirmed up to 500 and 1000 degrees C in ambient and in vacuum, respectively. When the TiN TPP structure is compared to the TiN-insulator-TiN (TiN-metal-insulator-metal (MIM)) structure, the former shows higher Q-factor, which indicates the advantage of choosing the TiN TTP structure against the MIM structure. The proposed refractory TiN TPP structure is lithography-free and scalable, which paves a way for large scale thermal emitters in practical usage.