Precise calibration of few-cycle laser pulses with atomic hydrogen

Interaction of atoms and molecules with strong electric fields is a fundamental process in many fields of research, particularly in the emerging held of attosecond science. Therefore, understanding the physics underpinning those interactions is of significant interest to the scientific community. One crucial step in this understanding is accurate knowledge of the few-cycle laser held driving the process. Atomic hydrogen (H), the simplest of all atomic species, plays a key role in benchmarking strong-held processes. Its wide-spread use as a testbed for theoretical calculations allows the comparison of approximate theoretical models against nearly-perfect numerical solutions of the three-dimensional time-dependent Schrodinger equation. Until recently, relatively little experimental data in atomic H was available for comparison to these models, and was due mostly due to the difficulty in the construction and use of atomic H sources. Here, we review our most recent experimental results from atomic H interaction with few-cycle laser pulses and how they have been used to calibrate important laser pulse parameters such as peak intensity and the carrier-envelope phase (CEP). Quantitative agreement between experimental data and theoretical predictions for atomic H has been obtained at the 10% uncertainty level, allowing for accurate laser calibration intensity at the 1% level. Using this calibration in atomic H, both accurate CEP data and an intensity calibration standard have been obtained Ar, Kr, and Xe; such gases are in common use for strong-held experiments. This calibration standard can be used by any laboratory using few-cycle pulses in the 10(14) W cm(-2) intensity regime centered at 800 nm wavelength to accurately calibrate their peak laser intensity to within few-percent precision.