Observation of a push force on the end face of a nm fiber taper exerted by outgoing light

TL;DR

This paper reports a direct experimental observation of the inward push force exerted by outgoing light on a nanometer fiber taper's end face, providing evidence supporting Abraham's momentum formulation of light in a dielectric.

Contribution

It presents the first direct measurement of the inward push force on a fiber taper's end face, clarifying the long-standing debate on light momentum in dielectrics and supporting Abraham's theory.

Findings

Supports Abraham momentum over Minkowski's theory

Demonstrates inward surface pressure from incident light

Potential applications in laser-induced inertially-confined fusion

Abstract

There are two different proposals for the momentum of light in a transparent dielectric of refractive index n: Minkowski's version nE/c and Abrahm's version E/(nc), where E and c are the energy and vacuum speed of light, respectively. Despite many tests and debates over nearly a century, momentum of light in a transparent dielectric remains controversial. In this Letter, we report a direct observation of the inward push force on the end face of a free nm fiber taper exerted by the outgoing light. Our results clearly support Abraham momentum. Our experiment also indicates an inward surface pressure on a dielectric exerted by the incident light, different from the commonly recognized pressure due to the specular reflection. Such an inward surface pressure by the incident light may be useful for precise design of the laser-induced inertially-confined fusion.