A physical model is presented to understand and calculate trapping force exerted on a dielectric micro-particle under focused evanescent wave illumination. This model is based on our recent vectorial diffraction model by a high numerical aperture objective operating under the total internal condition. As a result, trapping force in a focused evanescent spot generated by both plane wave (TEM00) and doughnut beam (TEM*01) illumination is calculated, showing an agreement with the measured results. It is also revealed by this model that unlike optical trapping in the far-field region, optical axial trapping force in an evanescent focal spot increases linearly with the size of a trapped particle. This prediction shows that it is possible to overcome the force of gravity to lift a polystyrene particle of up to 800 nm in radius with a laser beam of power 10 microW.

In this letter we present a physical model, both theoretically and experimentally, which describes the mechanism for the conversion of evanescent photons into propagating photons detectable by an imaging system. The conversion mechanism consists of two physical processes, near-field Mie scattering enhanced by morphology dependant resonance and vectorial diffraction. For dielectric probe particles, these two processes lead to the formation of an interference-like pattern in the far-field of a collecting objective. The detailed knowledge of the far-field structure of converted evanescent photons is extremely important for designing novel detection systems. This model should find broad applications in near-field imaging, optical nanometry and near-field metrology.

A sinfisiodese pubica juvenil (SPj), e o fechamento precoce induzido por cirurgia da sinfise pubica com intuito de alterar o crescimento da pelve. O estudo da sinfisiodese pubica, em dez Porquinhos da India, avaliou a rotacao acetabular e o desenvolvimento da pelve, pelo uso de um eletrocauterio bipolar por um tempo de 10 segundos com 10w de potencia, atravessando a sinfise pubica e destruindo desta forma a placa germinativa, promoveu uma significativa rotacao do acetabulo, entretanto, essa rotacao foi acompanhada de estreitamento do aspecto caudal da pelve.