Detection of out-of-plane pitch rotation of an asymmetric particle analyzing emission in the backscattered direction

Determination of out-of-plane rotations has been an interesting subject to explore. However, it is generally performed with the forward scattered light, which remains inaccessible in some cases. Here, we show an alternative technique to detect the out-of-plane pitch rotation using a hexagonal up-converting particle. We simultaneously trap and excite the particle with the wavelength of 975 nm and analyze the visible emission with video-microscopy to estimate the rotational motion. In addition, we carry out lumerical FDTD simulation to obtain qualitative relation between the change of interference pattern with rotation angle using the reflected light. This new approach offers a potential strategy for situations where detection in the forward scattering direction is difficult and challenging to probe.