Measuring the complete force field of an optical trap

摘要: The use of optical traps to measure or apply forces on the molecular level requires a precise knowledge trapping force field. Close trap center, this field is typically approximated as linear in displacement trapped microsphere. However, applications demanding high at low laser intensities can probe light-microsphere interaction beyond regime. Here, we measured full nonlinear and response an two dimensions using dual-beam setup with back-focal-plane photodetection. We observed substantial stiffening regime that depends microsphere size, agreement Mie theory calculations. Surprisingly, found detection range for exceeds one by far. Our approach allows complete calibration trap.