Atomic-scale time and space resolution of terahertz frequency acoustic waves.

Using molecular dynamics simulations and analytics, we find that strain waves of terahertz frequencies can coherently generate radiation when they propagate past an interface between materials with different piezoelectric coefficients. By considering AlN/GaN heterostructures, we show that the radiation is of detectable amplitude and contains sufficient information to determine the time dependence of the strain wave with potentially subpicosecond, nearly atomic time and space resolution. We demonstrate this phenomenon within the context of high amplitude terahertz frequency strain waves that spontaneously form at the front of shock waves in GaN crystals.

Measurements of terahertz electrical conductivity of intense laser-heated dense aluminum plasmas.

We report the electrical conductivity of laser-produced warm dense aluminum plasmas measured using single-shot ultrafast terahertz (THz) frequency spectroscopy. In contrast with experiments performed at optical frequencies, measurements based upon THz probe reflectivity directly determine a quasi-dc electrical conductivity, and therefore the analysis does not require a free-electron Drude model based extrapolation to recover the near zero frequency conductivity. In fact, our experimental results indicate that the Drude model breaks down for warm (>0.

Single-shot terahertz pulse characterization via two-dimensional electro-optic imaging with dual echelons.

A single-shot measurement of terahertz electromagnetic pulses is implemented using two-dimensional electro-optic imaging with dual echelon optics. The reported embodiment produces sequentially delayed multiprobe beamlets, routinely providing a time window of >10 ps with ~25 fs temporal step sizes. Because of its simplicity and robustness, the technique is ideally suited for real-time ultrashort relativistic electron bunch characterization.

Comment on "Temporally resolved electro-optic effect".

We comment on the recent Letter by S. P. Jamison et al.

Terahertz emission from ultrafast ionizing air in symmetry-broken laser fields.

A transient photocurrent model is developed to explain coherent terahertz emission from air irradiated by a symmetry-broken laser field composed of the fundamental and its second harmonic laser pulses. When the total laser field is asymmetric across individual optical cycles, a nonvanishing electron current surge can arise during optical field ionization of air, emitting a terahertz electromagnetic pulse. Terahertz power scalability is also investigated, and with optical pump energy of tens of millijoules per pulse, peak terahertz field strengths in excess of 150 kV/cm are routinely produced.

Details of electro-optic terahertz detection with a chirped probe pulse.

By revisiting the theory of terahertz pulse detection schemes employing a chirped optical probe pulse, we address and resolve a conflict that exists in literature. In this report, we show that the equation governing the detected field depends upon the experimental scheme, and in the limit of small bandwidth, that this expression differs from the conventionally used equation through a phase factor. We experimentally verify this equation using a spectral in-line interferometry approach.

Subpicosecond time-resolved infrared spectral photography.

An apparatus for recording broadband infrared absorption spectra from 2.2 to 2.7 microm with subpicosecond time resolution is described.