# Dual-Color Laser Induced Terahertz Generation in Strong Field Approximation

## TL;DR

This paper presents a theoretical study of terahertz wave generation in dual-color laser fields using strong field approximation, identifying continuum-continuum transitions as the core mechanism and linking quantum and classical models.

## Contribution

It introduces a SFA-based analytic model for THz generation, emphasizing continuum-continuum transitions, and validates it with experimental data.

## Key findings

- Continuum-continuum transitions are the main mechanism of THz generation.
- The SFA-based model aligns with classical photoelectric current theory.
- Experimental THz yields depend on parametric variations and harmonic measurements.

## Abstract

The mechanism of the terahertz (THz) wave generation (TWG) in dual-color fields is elucidated within the theoretical framework of single-atom based strong field approximation (SFA). Evaluating the transition dipole moment, the continuum-continuum (CC) transition, rather than the continuum-bound recombination for the high-order harmonic generation, is confirmed to be the core mechanism of the TWG. The analytic form of the SFA-based CC description is consistent with the classical photoelectric current model, establishing the quantum-classical correspondence for the TWG. The theory is supported by parametric dependence of experimental THz yields calibrated by the joint measurement of the third-order harmonics. Present studies leave open the possibility of probing the ultrafast dynamics of continuum electron.