RESUMO
We present a design to generate structurally propagation invariant light beams carrying non-integer orbital angular momentum (OAM) using Hermite-Laguerre-Gaussian (HLG) modes. Different from previous techniques, the symmetry axes of our beams are fixed when varying the OAM; this simplifies the calibration technique for beam positional measurement using a quadrant detector. We have also demonstrated analytically and experimentally that both the OAM value and the HLG mode orientation play an important role in the quadrant detector response. The assumption that a quadrant detector is most sensitive at the beam center does not always hold for anisotropic beam profiles, such as HLG beams.
Assuntos
Luz , Modelos Teóricos , Óptica e Fotônica/métodos , Refratometria/métodos , Calibragem , Desenho de Equipamento , Interferometria/instrumentação , Interferometria/métodos , Lasers de Gás , Lentes , Óptica e Fotônica/instrumentação , Refratometria/instrumentação , Espalhamento de RadiaçãoRESUMO
Under appropriate laser exposure, a thin film of InSb exhibits a sub-wavelength thermally modified area that can be used to focus light beyond the diffraction limit. This technique, called Super-Resolution Near-Field Structure, is a potential candidate for ultrahigh density optical data storage and many other high-resolution applications. We combined near field microscopy, confocal microscopy and time resolved pump-probe technique to directly measure the induced sub-diffraction limited spot in the near-field regime. The measured spot size was found to be dependent on the laser power and a decrease of 25% (100 nm) was observed. Experimental evidences that support a threshold-like simulation model to describe the effect are also provided. The experimental data are in excellent agreement with rigorous simulations obtained with a three dimensional Finite Element Method code.
Assuntos
Antimônio/química , Antimônio/efeitos da radiação , Índio/química , Índio/efeitos da radiação , Lasers , Lentes , Desenho de Equipamento , Análise de Falha de EquipamentoRESUMO
We report the first measurement of the spin Hall effect of light (SHEL) on an air-metal interface. The SHEL is a polarization-dependent out-of-plane shift on the reflected beam. For the case of metallic reflection with a linearly polarized incident light, both the spatial and angular variants of the shift are observed and are maximum for -45°/45° polarization, but zero for pure s and p polarization. For an incoming beam with circular polarization states however, only the spatial out-of-plane shift is present.
