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In this work, we present an enhanced nano-optical tweezers based on the new triple-nanoaperture structure for trapping nanoparticles using low power laser. Different structures with a single, double and triple-nanoaperture with nanometer gap created in 65 nm gold film, are examined. The results show there is a several times enhancement in transmission coefficient for proposed triple-nanoaperture based design. Considering this structure, the geometrical parameters like radius (R), center-to-center distance (D) and configuration of aperture have been manipulated to achieve optimum design. Using optimized parameters both transmission and optical force calculated and compared with the original structure which uses a single aperture. The results show total optical force inserted to 30 nm nanoparticle, enhanced up to 20 times as compared with the original structure. This structure and related results can be used to design new enhanced nano-optical tweezers with high accuracy for different applications.

In this paper, we proposed a new design of infrared photodetector structure based on ring-shaped multiple quantum wells for long-infrared and far-infrared (FIR) regimes. The absorption coefficient of the proposed photodetector that consists of GaAs/Al_0.25Ga_0.75As quantum wells with a thickness of 4 nm and a barrier of 40 nm has been calculated, from which a dominant peak of 50 um locates in the FIR regime. The proposed device has a planar structure with small thickness compared with ordinary rectangular multiple quantum well photodetectors. Also, there is 100% enhancement in typical IR absorption versus these ordinary photodetectors. Electronic states and wave functions calculated through solving the Schrödinger equation and then the effect of quantum well number on important parameters of photodetectors, such as gain mode and dark current, are investigated. According to the results, dark current decreases 1 order of magnitude when the number of quantum wells increases from 3 to 4. Also, absorption has redshift and simultaneously increases.