Exceptional Three-Level Switching Behaviors of Quadratic Nonlinear Optical Properties in a Tristable Molecule-Based Dielectric

Significant
progress on a new brilliant scheme for the solid phase
transition has opened up new possibilities of highly efficiently switching
the quadratic nonlinear optical (NLO) properties. However, the NLO
switching capacities of previously reported solid-state materials
were restrictively modulated between the conventional bistable states.
Exploring NLO tristability is strongly required for multistep operations
in multilevel memory elements and optoelectronic devices. Here, we
first report a tristable molecule-based dielectric, dipropylammonium
trichloroacetate (DPA-TCA), which shows an exceptional three-level
switching of quadratic NLO effects (i.e., NLO-off, low-NLO, and high-NLO
states). This unprecedented three-level switching of the NLO effect
originates from the stepwise ordering of the dynamic molecular components
in DPA-TCA, associated with the tristability of dielectric phase transitions
at 142 and 228 K. It is believed that this finding will shed light
on the further design of new multilevel NLO switching materials and
promote their prospective device applications.

针对固相相变的新型高效方案已取得重大进展，为高效调控二次非线性光学（quadratic nonlinear optical, NLO）特性开辟了全新可能。然而，此前报道的固态材料的NLO开关性能仅能在传统双稳态之间进行受限调控。针对多级存储单元与光电器件的多步操作需求，亟需探索NLO三稳态特性。本文首次报道了一种具备三稳态特性的分子基电介质——二丙基三氯乙酸铵（DPA-TCA），其展现出优异的二次NLO效应三级开关特性（涵盖NLO关闭态、低NLO态与高NLO态）。这种前所未有的NLO效应三级开关特性源于DPA-TCA中动态分子组分的逐步有序化过程，与142 K和228 K下发生的电介质相变三稳态密切相关。我们相信，本研究成果将为新型多级NLO开关材料的后续设计提供重要思路，并推动其在实际器件中的应用转化。