Imaging with ultrashort exposure times is generally achieved with acrossed-beam geometry. In the usual arrangement, an off-axis gating pulseinduces birefringence in a medium exhibiting a strong Kerr response (commonlycarbon disulfide) which is followed by a polarizer aligned to fully attenuatethe on-axis imaging beam. By properly timing the gate pulse, imaging lightexperiences a polarization change allowing time-dependent transmission throughthe polarizer to form an ultrashort image. The crossed-beam system is effectivein generating short gate times, however, signal transmission through the systemis complicated by the crossing angle of the gate and imaging beams. This workpresents a robust ultrafast time-gated imaging scheme based on a combination oftype-I frequency doubling and a collinear optical arrangement in carbondisulfide. We discuss spatial effects arising from crossed-beam Kerr gating,and examine the imaging spatial resolution and transmission timing affected bycollinear activation of the Kerr medium, which eliminates crossing anglespatial effects and produces gate times on the order of 1 ps. In addition, thecollinear, two-color system is applied to image structure in an optical fiberand a gasoline fuel spray, in order to demonstrate image formation utilizingballistic or refracted light, selected on the basis of its transmission time.
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