This study presents a photo-driven micro-lever fabricated to multiply optical forces using the two-photon polymerization 3D-microfabrication technique. The micro-lever is a second class lever comprising an optical trapping sphere, a beam, and a pivot. A micro-spring is placed between the short and long arms to characterize the induced force. This design enables precise manipulation of the micro-lever by optical tweezers at the micron scale. Under optical dragging, the sphere placed on the lever beam moves, resulting in torque that induces related force on the spring. The optical force applied at the sphere is approximately 100 to 300 pN, with a laser power of 100 to 300 mW. In this study, the optical tweezers drives the micro-lever successfully. The relationship between the optical force and the spring constant can be determined by using the principle of leverage. The arm ratio design developed in this study multiplies the applied optical force by 9. The experimental results are in good agreement with the simulation of spring property.
A thin film comprising parallel tilted nanorods was deposited by directing silver vapor obliquely towards a plane substrate. The reflection and transmission coefficients of the thin film were measured at three wavelengths in the visible regime for normal-illumination conditions, using ellipsometry and walk-off interferometry. The thin film was found to display a negative real refractive index. Since vapor deposition is a well-established industrial technique to deposit thin films, this finding is promising for large-scale production of negatively refracting metamaterials.
Refraction of light from an isotropic dielectric medium to an anisotropic dielectric material is a complicated phenomenon that can have several different characteristics not usually discussed in electromagnetics textbooks for undergraduate students. With a simple problem wherein the refracting material is uniaxial with its optic axis normal to the interface plane, the phenomena of (i) negative/positive refraction, (ii) negative/positive phase velocity, (iii) counterposition of the phase velocity and the time-averaged Poynting vector, and (iv) 'negative refraction' of the energy flux density can be examined. The last-named phenomenon is really negative deflection by refraction.
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