Plasmon‐Assisted Broadband All‐Optical Control of Highly Intense Femtosecond Laser by Weak Continuous‐Wave Laser

Abstract Dynamically manipulating highly intense ultrafast pulses by optical modulators is extremely useful for strong‐field physics. However, the manipulation has been severely restricted by the fundamental drawbacks of most modulators such as the low laser damage threshold and high energy consumption. Here, the implementation of an all‐optical modulator on femtosecond lasers up to 10 11 W cm −2 covering wavelengths from 1.6 to 2.3 µm is demonstrated; the modulator is controlled by a weak continuous‐wave laser (≈10 3 W cm −2 ) based on the prominent plasmon‐assisted thermo‐optic nonlinearity of suspended antimonene quantum dots (AQDs). The strong localization of the surface plasmon of the AQDs contributes a tremendous effective nonlinear refractive index ( n 2 ≈ 10 −5 cm 2 W −1 ) under weak light excitation, modulating the optical phase of copropagating intense lasers, and realizing robust “ON/OFF” alterations. It is also verified that the thermo‐optical effect occurs at a fast speed of ≈240 ps in this nanomaterial system. The findings provide new insight for exploiting the potential of plasmonic nonlinearities of nanomaterials, which offers a pragmatic and extensible solution to the urgent demand for manipulating and optical limiting of strong field physics in further nanophotonic platforms.