Illustration of the conditions of the strongly subluminal regime of optical-to-terahertz conversion. The intersection point of with defines the phase-matched frequency . The spectrum of the optical intensity envelope is negligible at . Parameters are taken for GaP pumped at 800 nm by a Gaussian pulse with .
Schematics of the problem: a Ti:sapphire laser pulse focused in the -direction by a cylindrical lens propagates through a slab of GaP with a group velocity .
The free-(open circles) and forced-wave (filled squares) pulses and the total terahertz field (solid line) in GaP plotted on the basis of Eq. (8) for successive moments of time. The laser pulse duration is and the peak laser intensity is .
Terahertz waveforms emitted from a slab of GaP of different thicknesses (shown in millimeter near the corresponding curves) for (a) and (b) . The peak laser intensity is .
Snapshots of at successive moments of time (numerated in order) for (a) and (b) . The laser pulse duration is and the peak laser intensity is (a) and (b) . The crystal thickness is and the crystal boundaries are shown by the dashed lines. In vacuum, a magnetic field of 1 G corresponds to an electric field of 0.3 kV/cm.
Terahertz waveforms emitted from the slab of GaP at the angles of 0° and 45° (shown near the corresponding curves) to the -axis after propagating a 2 mm distance in vacuum (in far field). Parameters are the same as in Fig. 5(b).
The distributions , , and for (a) GaP and (b) ZnTe crystals excited with Ti:sapphire laser . The crystal thickness is 2 mm. The dashed curves show the normalized profile of optical intensity.
The normalized distributions for GaP (solid) and ZnTe (dashed) crystals of a 2 mm thickness excited with Ti:sapphire laser . The dotted curve is for GaP. The shaded area shows the normalized profile of optical intensity.
The transverse size of the terahertz near field (at ) as a function of plotted on the basis of Eq. (7) for (solid). The dashed straight line is shown for reference.
The limiting (at ) spatial distribution of the near field calculated on the basis of Eq. (7) for and the laser pulse energy of . The transverse (at ) and longitudinal (at ) profiles of the field are plotted on the basis of Eq. (7) (solid line) and Eq. (16) (open circles).
The normalized limiting (at ) distributions (solid and dashed, respectively) on the opposite sides of the exit boundary of GaP for .
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