Transient spectroscopy has almost universally used planar light, but helical light bearing orbital angular momentum may access new states that have not been previously resolved, and chemical dynamics associated with these states. This “twisted light” deposits its angular momentum to the sample upon absorption, but theoretical work has far outpaced experimental results to describe the resulting dynamics. While planar light induces a polarization in most systems, twisted light can also induce an additional magnetization, complicating the excited state dynamics. Furthermore, this effect will depend on how much orbital angular momentum is embedded into the light. Unlike spin, light’s orbital angular momentum can span all integers in principle, and even fractional values. We perform twisted pump/planar probe transient spectroscopy on bulk GaAs cooled by liquid helium to obtain “helical chirality” signals, which emphasize the signals derived from the magnetization by comparing the signals obtained from left- and right-oriented twisted light. Segregating the portion of the signal generated by the twist within the beam reveals how the orbital angular momentum is carried in the system and how long-lived its contributions may be, which is an important step in understanding what contributions this light may have in future applications.

Electronic dynamics in bulk GaAs induced by light with orbital angular momentum

253rd National Meeting (2017)

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