Giant Nonlinear Optical Absorption of Ion‐Intercalated Tin Disulfide Associated with Abundant In‐Gap Defects

Abstract

AbstractHerein it is reported that electrochemical ion‐intercalation is a convenient and effective strategy toward materials with giant nonlinear optical (NLO) absorption. Alkali‐metal ions (i.e., Li+, Na+, K+) are electrochemically intercalated into SnS2 nanosheets. All ion‐intercalated samples exhibit remarkably enhanced optical nonlinearity compared with an untreated sample, and Li‐intercalated SnS2 (Li0.952SnII0.398SnIV0.563S2) possesses optimized strong NLO performance. Li0.952SnII0.398SnIV0.563S2 exhibits strong saturable absorption, and the corresponding nonlinear absorption coefficient (βeff) is ‐1.7 × 104 cm GW–1 for the laser excitation at 515 nm. Li0.952SnII0.398SnIV0.563S2 shows prominent reverse saturable absorption with the laser excitation at 800 nm (βeff: 2.8 × 104 cm GW–1) and 1030 nm (βeff: 1.4 × 104 cm GW–1). All βeff values are larger than most of the reported inorganic NLO materials at corresponding wavelengths. The optical limiting threshold of Li0.952SnII0.398SnIV0.563S2 is 8 × 10–4 J cm–2, two orders of magnitude smaller (better) than the bench‐mark composite (e.g., SWNT‐NH‐TPP). Ion intercalation introduces abundant in‐gap defects. The excitation of electrons in in‐gap states to conduction band intensifies the Pauli‐blocking effect and therefore promotes the saturable absorption under the 515 nm laser excitation, while the in‐gap defect states acting as effective excitation pathway facilitate excited‐state absorption for 800 and 1030 nm laser.