Wu Zhixin, Liu Guowei, Li Boyao, Huang Junjie, Sun Jinghua
Opt Express. 2024 Jun 3;32(12):20638-20653. doi: 10.1364/OE.524681.
Gallium nitride (GaN) nanowire, as a type of wide bandgap nanomaterial, has attracted considerable interest because of its outstanding physicochemical properties and applications in energy storage and photoelectric devices. In this study, we prepared GaN nanowires via a facile chemical vapor deposition method and investigated their nonlinear absorption responses ranging from ultraviolet to near-infrared in the z-scan technology under irradiation by picosecond laser pulses. The experiment revealed that GaN nanowires exhibit remarkable nonlinear absorption characteristics attributed to their wide bandgap and nanostructure, including saturable absorption and reverse saturable absorption. When compared to bulk GaN crystals, the nanowires provide a richer and more potent set of nonlinear optical effects. Furthermore, we conducted an analysis of the corresponding electronic transition processes associated with photon absorption. Under high peak power density laser excitation, two-photon absorption or three-photon absorption dominate, with maximum modulation depths of 73.6%, 74.9%, 63.1% and 64.3% at 266 nm, 355 nm, 532 nm, and 1064 nm, respectively, corresponding to absorption coefficients of 0.22 cm/GW, 0.28 cm/GW, 0.08 cm/GW, and 2.82 ×10 cm/GW. At lower peak energy densities, GaN nanowires demonstrate rare and excellent saturation absorption characteristics at wavelength of 355 nm due to interband transitions, while saturable absorption is also observed at 532 nm and 1064 nm due to band tail absorption. The modulation depths are 85.2%, 41.9%, and 13.7% for 355 nm, 532 nm, and 1064 nm, corresponding to saturation intensities of 3.39 GW/cm, 5.58 GW/cm and 14.13 GW/cm. This indicates that GaN nanowires can be utilized as broadband optical limiters and high-performance pulse laser modulating devices, particularly for scarce ultraviolet optical limiters, and saturable absorbers for ultraviolet and visible lasers. Furthermore, our study demonstrates the application potential of wide bandgap nanomaterials in nonlinear optical devices.
氮化镓（GaN）纳米线作为一种宽带隙纳米材料，因其优异的物理化学性质以及在储能和光电器件中的应用而备受关注。在本研究中，我们通过简便的化学气相沉积法制备了GaN纳米线，并利用皮秒激光脉冲辐照，在z扫描技术中研究了它们从紫外到近红外的非线性吸收响应。实验表明，由于其宽带隙和纳米结构，GaN纳米线表现出显著的非线性吸收特性，包括饱和吸收和反饱和吸收。与块状GaN晶体相比，纳米线呈现出更丰富、更强大的非线性光学效应。此外，我们对与光子吸收相关的相应电子跃迁过程进行了分析。在高峰值功率密度激光激发下，双光子吸收或三光子吸收起主导作用，在266 nm、355 nm、532 nm和1064 nm处的最大调制深度分别为73.6%、74.9%、63.1%和64.3%，对应的吸收系数分别为0.22 cm/GW、0.28 cm/GW、0.08 cm/GW和2.82×10 cm/GW。在较低的峰值能量密度下，由于带间跃迁，GaN纳米线在355 nm波长处表现出罕见且优异的饱和吸收特性，而在532 nm和1064 nm处由于带尾吸收也观察到饱和吸收。355 nm、532 nm和1064 nm处的调制深度分别为85.2%、41.9%和13.7%，对应的饱和强度分别为3.39 GW/cm²、5.58 GW/cm²和14.13 GW/cm²。这表明GaN纳米线可作为宽带光学限幅器和高性能脉冲激光调制器件，特别是对于稀缺的紫外光学限幅器，以及紫外和可见激光的饱和吸收体。此外，我们的研究展示了宽带隙纳米材料在非线性光学器件中的应用潜力。
