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

Abstract Herein 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 SnS 2 nanosheets. All ion‐intercalated samples exhibit remarkably enhanced optical nonlinearity compared with an untreated sample, and Li‐intercalated SnS 2 (Li 0.952 Sn II 0.398 Sn IV 0.563 S 2 ) possesses optimized strong NLO performance. Li 0.952 Sn II 0.398 Sn IV 0.563 S 2 exhibits strong saturable absorption, and the corresponding nonlinear absorption coefficient (β eff ) is ‐1.7 × 10 4 cm GW –1 for the laser excitation at 515 nm. Li 0.952 Sn II 0.398 Sn IV 0.563 S 2 shows prominent reverse saturable absorption with the laser excitation at 800 nm (β eff : 2.8 × 10 4 cm GW –1 ) and 1030 nm (β eff : 1.4 × 10 4 cm GW –1 ). All β eff values are larger than most of the reported inorganic NLO materials at corresponding wavelengths. The optical limiting threshold of Li 0.952 Sn II 0.398 Sn IV 0.563 S 2 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.