Abstract by Clayton Moss
Chemistry and Biochemistry
COHERENT TERAHERTZ RADIATION GENERATED FROM THREE INCOMMENSURATE COLOR ULTRAFAST LASER PULSES
Coherent pulses of terahertz (THz) radiation are a uniquely powerful tool to study nonlinear effects in delicate samples. Laser-induced plasma generation of THz pulses is becoming a more common technique, having the advantage of minimal dependence on expensive crystalline materials. It has been established that mixing a fundamental wavelength with its (commensurate wavelength) second harmonic in a plasma generates THz efficiently. We investigate THz emission of plasma generated by mixing two IR light pulses of orthogonal polarization tuned from ~1200-2000 nm with a pulse of 800 nm light. We show that these incommensurate pulses from our carrier-envelope phase unstable laser generate coherent THz when all three pulses are present. Additionally, we demonstrate the polarization and frequency dependencies of the generated THz in relation to the plasma pump pulses. This newly discovered mechanism of THz generation may provide additional insight into currently proposed models of plasma THz emission.