Stark-shift-chirped rapid-adiabatic-passage technique in tripod systems

We show that the technique of Stark-chirped rapid adiabatic passage (SCRAP), can be implemented in tripod quantum systems. We propose a scheme for coherent superposition among two ground states via Stark-shiftchirped rapid adiabatic passage technique in a tripod system. Tripod-SCRAP uses four laser pulses: an intense far-off-resonance Stark laser pulse modifies the transition frequency between the states by Stark shifting their energies and three nearly resonant pump, Stokes, and control laser pulses that fractionally transfer the population between the ground states via adiabatic passage. In our scheme, the pulse duration of the pump pulse must be larger than the pulse duration of the Stokes and control pulses, although with a smaller amplitude, and the atom encounters with the pump, Stokes, control, and Stark laser pulses with counterintuitive order (Stokes pulse arrives before the rest of the pulses). This technique can be applied to one-photon as well as multiphoton transitions and it is not necessary to vanish the pulses (pump and Stokes) simultaneously and it is a powerful alternative tool for f-STIRAP and tripod-STIRAP techniques at least when inhomogeneous broadenings are included. inhomogeneous broadening. This technique is robust against moderate variations in the intensities of the laser pulses,in detunings, and in delays between the pulses.

Injection-Seeded Terahertz Parametric Oscillator with a Ring-Cavity Configuration

This paper reports the characteristics of an injection-seeded terahertz parametric oscillator (TPO) with a ring-cavity configuration based on the MgO:LiNbO3 crystal. The ring cavity is constituted of three mirrors and the THz wave output surface where the pump and Stokes beams are totally reflected. The THz pulse energies and the Stokes pulse energies as functions of the pump pulse energy for different seed powers of 47.5 mW, 150.7 mW, and 312.8 mW were investigated. The experimental results showed that the injection-seeded ring cavity TPO exhibited the benefits of lower pump thresholds and higher output energies for the Stokes and THz waves. The smaller the pump pulse energy, the more obvious the effect of the seed injection. The reasons for the laser performance improvement were analyzed.