Near‐Infrared Broadband Polymer‐Dot Modulator with High Optical Nonlinearity for Ultrafast Pulsed Lasers

Abstract

Optical modulators hold great promise for nonlinear optical and photonic devices. However, current optical modulators are exclusively based on inorganic saturable absorbers such as semiconductor thin films, 2D materials, and plasmonic nanocrystals. Here, nonlinear optical modulation is demonstrated by designing a series of organic semiconducting polymer dots (Pdots) for passive Q‐switching and mode‐locking lasers in the near‐infrared (NIR) region. Combining density functional theory and judicious polymer design, Pdots with large extinction coefficient and broadband absorption are developed which span the entire spectrum from ultraviolet (UV) to NIR region (300 to 2500 nm). The Pdots exhibit strong saturable absorption (β = −1.2 × 10−3 cm W−1) and optical nonlinearity (Imχ(3) = −8.4 × 10−7 esu), which are of orders higher than other nonlinear optical materials such as carbon‐based materials, plasmonic metal nanoparticle, and semiconductor nanocrystals. The Pdot modulators are integrated into the fiber laser systems, and demonstrate passively mode‐locked lasers at 1036, 1038, 1945, 1950 nm and Q‐switched lasers at wavelengths of 1559 and 1957 nm, highlighting the potential of Pdots for advanced nonlinear optical and photonic applications.

Large optical nonlinearity enhancement under electronic strong coupling

“…T hird-order optical nonlinear effects are intrinsic characteristics of a material. Because many significant optical nonlinear phenomena, such as four wave mixing, optical modulation, self-focusing and stimulated Raman scattering, are caused by the third-order optical nonlinear susceptibility 1 , they have been explored extensively in various materials ranging from metals 2 , semiconductors [3][4][5] , 2D materials 6,7 , topological insulators 8 to organic materials [9][10][11][12][13] . An ideal nonlinear optical material should possess large refractive index change at low optical power.…”

Silver Nanowires with Ultrabroadband Plasmon Response for Ultrashort Pulse Fiber Lasers

“…As shown in Figure 3e-h, the wavelength dependence of saturable absorption properties of AgNWs have been determined at 1064, 1560, 1930, and 2800 nm. By fitting the following equation [33]…”

Highly Efficient and Robust Broadband Nano‐VO2(M) Saturable Absorber for Nonlinear Optics and Ultrafast Photonics

“…The obtained data was exhibited in the Figure 2a, and a model described in the Supporting Information was used to match the data. [49,50] The α s , I S , and α ns represented modulation depth, saturable intensity, and nonsaturable loss. The corresponding values were calculated to be 15.1%, 9.5 MW cm −2 , and 27.5%, respectively.…”