  We report enhanced broadband Terahertz (THz) generation and detailed
characterization from the interaction of femtosecond two colour laser pulses
with thin transparent dielectric tape target in ambient air. The proposed
source is easy to implement, exhibits excellent scalability with laser energy.
Spectral characterization using Fourier transform spectrometer reveals yield
enhancement of more than 150 % in the THz region of 0.1 - 10 THz with respect
to conventional two-colour laser plasma source in ambient air. Further, the
source spectrum extends up to 40 THz with an enhancement of flux > 30 %.
Experimental results, well supported with two-dimensional particle-in-cell
simulations establishes that the transient photo-current produced by the
asymmetric laser pulse interaction with air plasma as well as near solid
density plasma formed on the tape surface is responsible for the enhanced
terahertz generation. The source will be useful for the multidisciplinary
activities and ongoing applications of the laboratory-based terahertz sources.
