Generation of strong short coherent Terahertz pulses in gases and solids using quantum coherence
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We have shown that coherently driven atomic, molecular, and solid media can potentially produce strong controllable short pulses of THz radiation. The high efficiency of the technique is based on excitation of maximal quantum coherence by applying resonant optical pulses to the medium. The excited coherence in the medium is either directly connected to macroscopic polarization leading to THz emission, or is used to efficiently scatter infrared into THz radiation. We have performed detailed simulations by solving the coupled density matrix and Maxwell equations. By using a variety of simple energy schemes (, V, ladder, etc.), we have demonstrated that the energy of generated THz pulses ranges from nJ to hundreds J for gases and from hundreds of pJ to nJ at room temperature and J at liquid helium temperature in solids, with pulse durations from tens fs to ns for gases, and from ps to tens ns for solids. We have also suggested a coherent ruby source that lases on two optical wavelengths and simultaneously generates THz radiation. We discussed also possibilities of extension of the technique to different atomic, molecular, and solid-state materials. Copyright 2007 American Scientific Publishers All rights reserved.
