Half-percent terahertz generation efficiency from cryogenically cooled   lithium niobate pumped by Ti:sapphire laser pulses
  We obtained an optical-to-terahertz (THz) energy conversion efficiency of 0.5% using the tilted-pulse-front technique in lithium niobate at a cryogenically cooled temperature of 100 K pumped by amplified Ti:sapphire laser pulses with ~150 fs pulse duration at 800 nm wavelength. Compared with the optimized conversion efficiency of 0.18% achieved at room temperature, we achieved more than 2.5 times enhancement in conversion efficiency upon cryogenically cooling the crystal due to reduction of THz absorption. Further improvements to the conversion efficiency can be made by optimizing the out-coupling of the THz radiation, transportation of pump energy and by further decreasing the THz absorption in the lithium niobate crystal. 
Xiaojun Wu, Koustuban Ravi, Wenqian Ronny Huang, Chun Zhou, Peter   Zalden, Giulio M. Rossi, Giovanni Cirmi, Oliver D. Mueck...
physics.optics