Spectral purity and sources of noise in femtosecond-demodulationterahertz sources driven by Ti:sapphire mode-locked lasers

摘要

Direct measurements of the spectral purity in terahertznfemtosecond-demodulation sources are reported and compared to theory.nBecause these sources operate at very high harmonicsn(~102-104) of the mode-lock frequency, a high spectral puritynsource is very dependent on a low-jitter femtosecond laser. Conversely,nthe spectral content of the terahertz sources provides detailedninformation about timing jitter and stringent tests of models used tondescribe the jitter. We find that both the behavior of the central core,nand the noise skirts of the power spectrum of our sources, can benquantitatively related to measured ripple and continuum amplitude noisenon the Ar+ pump laser by use of modulation theory