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 (|alpha|>or=1) must have a length scale lambda<66 microm, agreeing well with the latest result of the E?t-wash group. Our result sets a unification energy scale of M*>or=2.8 TeV/c2 for the two compactified extra space dimensions with the same size R*<47 microm.