Lead-free double-perovskite Cs4CuSb2Cl12 as an efficient saturable absorber for Q-switched mode-locking fiber lasers

Abstract

Perovskites have emerged as a new family member of saturable absorbers (SAs) to generate high energy and ultrashort laser pulses due to their unique optoelectronic properties, structural and chemical diversity. However, the toxicity of lead-based perovskites as well as their chemical instability constrains the practical implementations of the materials. In this work, we created one alternative lead-free and stable “elpasolite” double perovskite of Cs₄CuSb₂Cl₁₂, which demonstrated highly saturated absorption extending to the near-infrared (NIR) spectral region with a large β_eff value of −6.8 × 10⁻⁷ m W⁻¹ at 1064 nm superior to previously reported perovskite materials. Femtosecond transient absorption spectroscopy provides an overall picture of charge carrier dynamics of the perovskite crystals accounting for their strong nonlinear saturation absorption. The as-prepared Cs₄CuSb₂Cl₁₂ crystal acted as an efficient saturable absorber for Q-switched mode-locking an Yb-doped fiber laser. The ∼1 μm NIR laser modulation with high pulse-energy operation and low saturation power demonstrates the great potential of the new perovskite for integration into lasers, modulators and other photonic devices.