In this work, the transverse optical trapping of spherical particle with strong absorption is studied in geometrical optics
model by numerical simulation. In our work, the exact expressions of wave vector are used instead of traditional
approximate expressions, and the transverse optical trapping force acting on a spherical particle due to strong absorption
is calculated when the particle is illuminated by a focused Gaussian beam of TEM<sub>00</sub> mode. The calculated results show
that stable transverse optical trapping positions only exist when the center of the spherical particle is located in front of
the focus of the beam. Our results also reveal that the trapping positions are decided by the radius of the beam waist ω0.
The magnitude of transverse optical trapping force and the stiffness of optical trapping decrease with the increase in ω0.
Optical heterodyne interferometry has been widely used in precision measurements. In this paper, we develop a modified
Mach-Zehnder interferometer for measurement of light polarization state in real time by using two heterodyne frequency
reference beams. Two collinear linearly polarized reference beams with different frequency, ω<i><i><sub>p</sub></i></i> and ω<i><i><sub>s</sub></i></i>, interfere simultaneously with the measured beam with frequency ω<i><sub>0</sub></i>. The polarization directions of the two reference beams are perpendicular to each other. The light intensity of the interference fringe is monitored by a photodetector. The heterodyne signals, ω<i><sub>p</sub></i> and ω<i><sub>s</sub></i> - ω<i><sub>0</sub></i>, give the amplitudes and the phase difference of the orthogonal polarization components of the measured beam projected to the polarization directions of the reference beams. We analyze the beat frequency signals by Fourier and inverse Fourier transform and realize accurate measurement of polarization state experimentally.