Abstract
Up to now, full tunability of waveforms was possible only in electronics, up to radio-frequencies. Here we propose a new concept of producing few-cycle terahertz (THz) pulses with widely tunable waveforms. It is based on control of the phase delay between different parts of the THz wavefront using linear diffractive optical elements. Suitable subcycle THz wavefronts can be generated via coherent excitation of nonlinear low-frequency oscillators by few-cycle optical pulses. Using this approach it is possible to shape the electric field rather than the slow pulse envelope, obtaining, for instance, rectangular or triangular waveforms in the THz range. The method is upscalable to the optical range if the attosecond pump pulses are used.
Highlights
Generation of few-cycle pulses in terahertz (THz) (0.1–10 THz) range is a subject of intensive research[1,2,3,4,5]
Most of the methods of THz pulse generation proposed up to now are based on a nonlinear conversion of optical pulses in nonlinear media[1,2] using optical rectification in different media such as lithium niobate[8,9], semiconductors[10,11] and organic crystals[12,13], or the ionization-based nonlinearity which leads to creation of plasma currents in gases[15,16,17,18] or semiconductors[1,2]
There is a big interest in half-cycle pulses at various wavelengths[20,21,22,23,24] since they are important in ultrafast spectroscopy[23,25], as well as in attosecond science[26,27]
Summary
The idea of the proposed method is to generate subcycle THz waveforms in a thin nonlinear layer (see Fig. 1) and phase-shape the partial waves on the way to the detector. It is seen that the pulse after the filter has the shape of a half-sine wave of the duration T0/2 = 3.14 · 10−13 s−1 surrounded by weak long tails, which fully compensate the electric area of the central part, giving zero value of the dc-component It can be shown (see Appendix III) that taking into account these long tails results just in a minor modification of the amplitude of the pulse after an arbitrary DOE without changing the main part of its waveform.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
