The interaction of nonresonant intense periodic optical field shifts the ground state excitonic position which can be understood by Floquet manipulation in Jaynes–Cummings model. The induced shift can be manifested by the optical Stark effect (OSE) and Bloch-Siegert effect (BSE) via controlling the light helicity. It is noteworthy that the energy shift is proportional to field intensity and inversely to the detuning at nearly resonant excitation which understood by rotating wave approximation. Recently, OSE and BSE have observed simultaneously with very large detuning (infrared excitation) for CsPbI3 quantum dots. However, observing the BSE at near resonance with small detuning is difficult due to the dominance shift by OSE. Here, we have chosen Cu-doped CsPbI3 nanocrystals and incorporated a helicity-resolved transient absorption spectroscopic technique. Moreover, the dynamical excitonic effect in a small percentage of Cu-doping reduced the binding energy and blueshifted the continuum band without changing the excitonic position. Interestingly we observe blueshift in excitonic position for co (σ+σ+)- and cross(σ+σ-)-polarization of pump and probe at small detuning. We observed a huge BSE shift ~ 122 meV with the ratios of shifts (i.e., ΔBSE/ΔOSE) are 0.74 at the lowest detuning, 193 meV Cu-doped CsPbI3, respectively. Thus, our study advances high-field Floquet engineering with a doping mechanism and can be potentially exploited in strong-field device applications as well as a quantum information process.
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