Using air as an emitting medium to generate terahertz wave has attracted attention because of its potential applications for remote distance THz wave sensing and imaging. Yet, the cutting edge energy conversion efficiency of THz wave generation with optical method is extremely low. Researchers at Rensselaer have developed a method for generating amplified terahertz radiation that includes inducing a first volume of a gas to produce a seed plasma and emit pulsed seed terahertz radiation by focusing an optical seed beam in the first volume. The seed terahertz radiation is then amplified by focusing an optical gain beam to produce a gain plasma in a second volume overlapping with the pulsed seed terahertz radiation remote from the seed plasma. The method may be implemented in a system for detecting and analyzing a remotely-located object such as an explosive material, a biological agent, andor a chemical agent.