An orthogonal-transmitting double-beam optical trap system for wide-range and high-precision relative gravimetry

We propose an orthogonal-transmitting double-beam optical trap (OTDBOT) scheme for both three-dimensional capture of microspheres and relative gravitational acceleration sensing. One weak-focused vertical beam provides axial scattering force to counteract initial gravity of sensing microspheres, and one horizontal high-focused beam forms radial gradient force to provide relative gravimetry. This optical trap system can achieve a wide dynamic measurable range of up to ±1 kGal and high sensitivity in the order of μGal/Hz in high vacuum only by an optical-trapped microsphere and trapping laser with less than 1 W, theoretically. The sensing properties of this scheme with different noncoplanar offsets and non-orthogonal tilts are also calculated. Numerical simulation results show that excessive offset distance will decline the dynamic measurement range and vertical trap stiffness, but the tilt angle within 15° will almost not. Both the distance and angle will not lead to the sensing microsphere escaping from the trap.