Abstract: Nonlinear absorption of a sub-picosecond laser pulse is used to generate one or more spatially elongated heated gas volumes. Transient density variations caused by the spatially elongated heated gas volumes provide a refractive index profile capable of guiding electromagnetic radiation through the gas. The waveguide structure in the gas is disposed between the spatially elongated heated gas volumes and results from interaction between acoustic waves generated by the spatially elongated heated gas volumes or from a non-uniform thermal gas profile caused by the spatially elongated heated gas volumes. The nonlinear absorption can be repeated at regular intervals in time and space to renew the waveguide in the gas, thereby allowing for the guiding of high average power radiation (e.g., megawatts) that is well below self-focusing or stimulated Raman scattering thresholds.

Abstract: A terahertz generation system that emits pulsed THz radiation and incorporates a rapidly oscillating, high voltage bias across electrodes insulated from a photoconductive material. The system includes an ultrafast optical pulse source configured to generate an optical pulse having a duration between about ten picoseconds and ten femtoseconds, the pulse further having a repetition rate of about one megahertz or higher. The system further includes a photoconductor configured to receive the optical pulse from the ultrafast optical pulse source and to generate a terahertz frequency pulse, the photoconductor having insulated electrodes. The system still further includes a radio frequency generator configured to apply an electric field to the photoconductor via the insulated electrodes.

Abstract: A terahertz generation system that emits pulsed THz radiation and incorporates a rapidly oscillating, high voltage bias across electrodes insulated from a photoconductive material. The system includes an ultrafast optical pulse source configured to generate an optical pulse having a duration between about ten picoseconds and ten femtoseconds, the pulse further having a repetition rate of about one megahertz or higher. The system further includes a photoconductor configured to receive the optical pulse from the ultrafast optical pulse source and to generate a terahertz frequency pulse, the photoconductor having insulated electrodes. The system still further includes a radio frequency generator configured to apply an electric field to the photoconductor via the insulated electrodes.