Laboratory limit on the charge of photons by electric field deflection

TL;DR

This paper reports a laboratory experiment that uses electric field deflection of a laser beam to set an upper limit on the photon charge, achieving a bound of less than 10^{-14} times the elementary charge.

Contribution

It introduces a practical experimental method for measuring photon charge using phase-sensitive detection in a modulated electric field.

Findings

Photon charge upper limit of 10^{-14}e established

Experimental technique suitable for educational settings

Demonstrates precision measurement methods in optics

Abstract

The deflection of a laser beam traveling through a modulated electric field is measured using phase-sensitive detection to place an upper bound on photon charge. An upper limit of $10^{-14}e$ is obtained. The experiment involves a number of experimental techniques that are commonly encountered in modern precision measurements and is suitable for both advanced undergraduate and beginning graduate students in physical science as a laboratory exercise.