Improvement for Testing the Gravitational Inverse-Square Law at the Submillimeter Range

We improve the test of the gravitational inverse-square law at the submillimeter range by suppressing the vibration of the electrostatic shielding membrane to reduce the disturbance coupled from the residual surface potential. The result shows that, at a 95% confidence level, the gravitational inverse-square law holds (vertical bar a vertical bar <= 1) down to a length scale lambda = 48 mu m. This work establishes the strongest bound on the magnitude alpha of the Yukawa violation in the range of 40-350 mu m, and improves the previous bounds by up to a factor of 3 at the length scale lambda approximate to 70 mu m. Furthermore, the constraints on the power-law potentials are improved by about a factor of 2 for k = 4 and 5.