Sun Yanhui, Li Hui, Hou Ruipeng, Diao Mengjuan, Liang Ying, Huang Zhipeng, Humphrey Mark G, Zhang Chi
School of Chemical Science and Engineering, Tongji University, Shanghai 200092, PR China.
Research School of Chemistry, Australian National University, Canberra, ACT 2601, Australia.
ACS Appl Mater Interfaces. 2020 Oct 28;12(43):48982-48990. doi: 10.1021/acsami.0c14447. Epub 2020 Oct 19.
Electrical tuning of the nonlinear absorption of materials has promising application potential, while studies remain rare. In this work, we show that the third-order nonlinear absorption of poly(3,4-ethylenedioxythiophene) chemically doped with poly(styrene sulfonic acid) [PEDOT:PSS] can be effectively modulated by external voltage. The nonlinear absorption of the film can be varied between reverse saturable absorption (RSA) and saturable absorption (SA) via voltage control with laser excitation at 800 nm, and the corresponding nonlinear absorption coefficient can be tuned in the range -1606 ± 73 to 521 ± 9 cm GW. The doping level and energy structure of PEDOT are modulated with different voltages. The undoped film affords two-photon absorption and accordingly the RSA response. A moderately doped sample has two polaron levels, and Pauli blocking associated with these two polaron levels results in SA. The bipolaron level in heavily doped PEDOT leads to excited-state absorption and therefore RSA behavior. The approach reported here can be applied to other semiconductors and is a convenient, effective, and promising method for the electrical tuning of the optical nonlinearity.
材料非线性吸收的电调谐具有广阔的应用潜力，但相关研究仍然较少。在这项工作中，我们表明，用聚（苯乙烯磺酸）[PEDOT:PSS]化学掺杂的聚（3,4-乙撑二氧噻吩）的三阶非线性吸收可以通过外部电压有效地调制。通过在800 nm激光激发下的电压控制，薄膜的非线性吸收可以在反饱和吸收（RSA）和饱和吸收（SA）之间变化，相应的非线性吸收系数可以在-1606±73至521±9 cm GW范围内调节。PEDOT的掺杂水平和能量结构通过不同的电压进行调制。未掺杂的薄膜呈现双光子吸收并因此产生RSA响应。适度掺杂的样品有两个极化子能级，与这两个极化子能级相关的泡利阻塞导致SA。重掺杂PEDOT中的双极化子能级导致激发态吸收，因此呈现RSA行为。这里报道的方法可以应用于其他半导体，是一种用于光学非线性电调谐的方便、有效且有前景的方法。
