A computational optimization of parameters leading to maximal third harmonic conversion efficiency in the presence of a laser-induced plasma is introduced, building on previous experimental work. The model contains full spatial and temporal dynamics for nonlinear interaction and pulse dispersion. Optimization of a localized plasma for a significant further enhancement of conversion efficiencies is suggested by the modeling.
We review high-energy, broadband terahertz (THz) generation in two-color laser-produced gaseous plasma. We first describe our microscopic plasma current model for directional plasma current and far-field THz radiation generation. Experimental results for THz yield dependence on laser energy, optical phase difference, gas species, and gas pressure are presented. We also describe ultrabroadband THz generation and detection in our experiments and numerical simulations. Finally, we discuss 2-D plasma currents for THz polarization control and macroscopic phase-matched THz generation.
We discuss recent experiments and calculations of the high-intensity optical nonlinearity in gases. Spectral interferometry measurements of the nonlinear optical response of air constituents to laser intensities near the ionization threshold are performed. A calculation of the phase shift caused by a plasma grating created by interference between the pump and probe beams in a transient birefringence measurement suggests that experimental techniques measuring cross phase modulation of a probe pulse by a strong pump pulse are unreliable for studying the optical nonlinearity when the pump and probe pulses are of the same wavelength. An interferometric measurement of the electron density in a filament is also performed. The peak elec-tron density measured is consistent with a model that includes plasma defocusing, but not higher-order Kerr terms. These tech-niques promise to improve the quantitative understanding of nonlinear optics near the ionization threshold and filamentation.
Spatially confined plasmas with dimensions in the submillimeter range have been found to be stable at atmospheric pressure. These microplasmas are nonequilibrium plasmas with an electron energy distribution which contains a significant fraction of high energy electrons. This favors, in combination with the high gas density, the formation of excimers. The possibility for operating these discharges in parallel, or expanding the nonequilibrium plasma two-dimensionally on a flat cathode allows for extended area light-sources, including excimer lamps. The spectral range of these lamps reaches from the visible into the vacuum ultraviolet, down to wavelengths of 75 nm for helium excimer radiation. Highest efficiencies of 6–9% were obtained for xenon excimers when the discharge was operated dc, and 20% when operated in a nanosecond pulsed mode. Besides excimer radiation, microdischarges have also been shown to emit intense line radiation in the vacuum ultraviolet when noble gases with small admixtures of hydrogen and oxygen were used.
Continuing experiments with electric oxygen-iodine laser (ElectricOIL) technology have significantly increased laser power output by increasing the product of gain and gain-length,
We report the first comprehensive experimental analysis on the dynamics of an optically injected 1550-nm vertical-cavity surface-emitting laser (VCSEL) over a wide temperature range going from
We present measurement data of fundamental thermal noise in a 40-m fiber optic Mach–Zehnder interferometer (MZI) using 80-
High-speed direct modulation capability was investigated in 1.55-
The near-field intensity distributions of quantum-cascade lasers emitting at
A theoretical investigation into the operation of AlInN ultraviolet laser (UV) diodes on AlN substrates is presented. 2-D optoelectronic simulation of a prototypical design predicts lasing at a target wavelength of 250 nm. Simulations indicate optical gain degradation attributable to a parasitic inversion layer, which forms as a result of polarization charge associated with homogeneous electron blocking layers. Appreciable improvement in optical gain is demonstrated in designs featuring inhomogeneous electron blocking layers, by virtue of a volumetric redistribution of polarization charge. Numerical simulations inspire confidence in AlInN as a viable alternative to AlGaN technologies for UV laser-diode operation.