Null Test of Newtonian Inverse-Square Law at Submillimeter Range with a Dual-Modulation Torsion Pendulum

A null experimental test of the Newtonian inverse-square law at submillimeter range using a torsion pendulum was presented. Under the dual modulations of both the expected signal and the gravitational torque for calibration, our data concluded with 95% confidence that no new forces were observed and any gravitational-strength Yukawa forces (||1) must have a length scale <66, agreeing well with the latest result of the E\"ot-wash group. Our result sets a unification energy scale of M^*2. 8 TeV/c^2 for the two compactified extra space dimensions with the same size R^*<47.