Collinear, two-color optical Kerr effect shutter for ultrafast time-resolved imaging

TL;DR

This paper introduces a collinear, two-color optical Kerr effect shutter that simplifies ultrafast time-resolved imaging by eliminating crossing angle effects, achieving approximately 1 ps gate times and enabling imaging of dynamic structures.

Contribution

It presents a novel collinear, two-color Kerr gating system that improves spatial resolution and simplifies setup for ultrafast imaging compared to traditional crossed-beam methods.

Findings

Achieved gate times on the order of 1 ps.

Eliminated crossing angle spatial effects.

Successfully imaged optical fiber and fuel spray structures.

Abstract

Imaging with ultrashort exposure times is generally achieved with a crossed-beam geometry. In the usual arrangement, an off-axis gating pulse induces birefringence in a medium exhibiting a strong Kerr response (commonly carbon disulfide) which is followed by a polarizer aligned to fully attenuate the on-axis imaging beam. By properly timing the gate pulse, imaging light experiences a polarization change allowing time-dependent transmission through the polarizer to form an ultrashort image. The crossed-beam system is effective in generating short gate times, however, signal transmission through the system is complicated by the crossing angle of the gate and imaging beams. This work presents a robust ultrafast time-gated imaging scheme based on a combination of type-I frequency doubling and a collinear optical arrangement in carbon disulfide. We discuss spatial effects arising from crossed-beam Kerr gating, and examine the imaging spatial resolution and transmission timing affected by collinear activation of the Kerr medium, which eliminates crossing angle spatial effects and produces gate times on the order of 1 ps. In addition, the collinear, two-color system is applied to image structure in an optical fiber and a gasoline fuel spray, in order to demonstrate image formation utilizing ballistic or refracted light, selected on the basis of its transmission time.