Increased THz emitter efficiency by coherent superposition in a high repetition rate resonator

Summary form only given. The wide range of attractive applications of time domain THz sensing is strongly hampered by the low conversion efficiency of optically excited THz emitters. Conversion efficiencies for most coherent THz emitters are extremely low, typically on the order of 10/sup -5/. Considerable interest is therefore directed towards possible ways of increasing the THz emitter efficiency. We follow the approach of exposing the emitter to a coherent phase-matched THz background field during the emission process in order to radiate more energy before dephasing occurs, thereby amplifying the amount of coherently emitted THz radiation (Martini et al, 1998). In this presentation, we discuss recent experiments where an InGaAs surface field emitter is placed in a high repetition rate THz resonator. By synchronously pumping the emitter with a high repetition rate (1 GHz) Ti:sapphire laser source (Bartels et al, 1999), a net efficiency increase is demonstrated for the first time.