Quantum Coherent Control of Giant Injection Photocurrent from Destructive Interference of Second‐Order Nonlinear Optical Responses

ABSTRACT

Quantum interference (QI) under dual‐wavelength excitation in semiconductors is crucial for applications in quantum computation and quantum sensing. Recently, coherently controlled terahertz (THz) emission spectroscopy has emerged as a powerful tool to investigate the injection photocurrent generated from QI under dual‐wavelength excitation. However, second‐order nonlinear optical effects under single‐wavelength excitation constructively interfere and inevitably contribute to the THz emission, thereby veiling the injection photocurrent derived from the third‐order nonlinear optical effect from a macroscopic perspective. Herein, we reveal a giant injection photocurrent in antimony selenide (Sb ₂ Se ₃ ) via destructive interference of second‐order nonlinear optical effects. This destructive interference is theoretically attributed to the opposite signs of the real part of the second‐order nonlinear susceptibility (which dominates the displacement photocurrent) and the second‐order nonlinear conductivity (which dominates the shift photocurrent), as evidenced by the opposite THz waveforms observed in experiments. Notably, the THz emission efficiency from the unveiled injection photocurrent exceeds that of many reported layered and bulk materials. This work provides a distinctive method to unveil the giant injection photocurrent by THz technique, which would open an avenue for developing ultrafast quantum photonic devices.