Radiation from Wavepackets

We use laser high-order harmonics and a polarization-ratio-reflectance technique to determine the optical constants of copper and oxidized copper in the wavelength range 10-35 nm. This measurement resolves previously conflicting data sets, where disagreement on optical constants of copper in the extreme ultraviolet most likely arises from inadvertent oxidation of samples before measurement. (C) 2009 Optical Society of America

We discuss the inevitable dissipation of energy that must accompany the creation of a pulse-medium excitation state in a passive dielectric. We show that there is a minimum amount of energy that an optical pulse must deposit in the medium to create a given pulse-medium state and that energy deposited beyond this minimum value must be dissipated in the medium. We compare this notion of dissipation to a related concept found by determining the fraction of energy stored in a medium that is irrecoverable by future fields. These two notions of dissipation are model-independent and form upper and lower bounds for real-time loss. Any model-dependent notion of loss that falls outside these bounds has serious conceptual difficulties. We show that a traditional notion of real-time loss based on a multiple-Lorentz oscillator model fails to give reasonable results in classes of passive linear media near EIT, while the notions of loss we introduce give sensible results for all passive media.

We demonstrate a technique for determining optical constants of materials in the extreme UV from the ratio of p-polarized to s-polarized reflectance. The measurements are based on laser-generated high-order harmonics, which have easily rotatable linear polarization but that are prone to brightness fluctuations and systematic drifts during measurement. Rather than measure the absolute reflectance, we extract the optical constants of a material from the ratio of p-polarized to s-polarized reflectance at multiple incident angles. This has the advantage of dividing out long-term fluctuations and possible systematic errors. We show that the reflectance ratio is as sensitive as the absolute reflectance to material optical properties. (C) 2009 Optical Society of America