Analysis of power enhancement of terahertz waves in periodically inverted GaP pumped at 1.55 mm

Abstract We have generated terahertz (THz) waves by difference frequency generation (DFG) with a 1.55 μm pump laser. 1.55 μm pump beams were effectively converted to 1 THz waves through a periodically χ⁽²⁾‐inverted GaP stack fabricated by direct wafer bonding. The output efficiency was an order of magnitude larger than that of typical χ⁽²⁾ materials such as lithium niobate employing a similar DFG method. To investigate the increase in output power due to quasi‐phase matching including optical losses, we measured its dependence on stack length. From the measured data, we analyze the conditions for effective power enhancement and show that it takes place if the pump‐beam loss, α, is much smaller than that of the THz waves, α₃ (or the pump‐beam attenuation length, 1/α, is much longer than that of the THz waves, 1/α₃), which is achieved by improving the bonding quality of the stack. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)