Abstract

Intensity- and concentration-dependent nonlinear absorption of Cu-doped (\(\gamma \) and \(\beta )\)-\(\hbox {BaB}_{2}\hbox {O}_{4}\) nanostructures was measured by a standard open aperture Z-scan setup under nanopulsed (9 ns, 10 Hz) laser excitation (532 nm) at various peak intensities (1.26–2.52 GW/\(\hbox {cm}^{2})\). Intensity-dependent 2PA coefficient exposes the involvement of accumulative 2PA process rather than genuine 2PA. From ground state absorption studies, existence of new energy states due to Cu incorporation has availed a near-resonant state favoring excited state absorption leading to sequential 2PA. Among the samples, 0.05 M Cu-doped \(\gamma \)-\(\hbox {BaB}_{2}\) \(\hbox {O}_{4}\) \((2.6\times 10^{-10}\) m/W, \(0.78\times 10^{12}\) \(\hbox {W}/\hbox {m}^{2})\) and 0.03 M Cu-doped \(\beta \)-\(\hbox {BaB}_{2} \hbox {O}_{4}\) \((2.5\times 10^{-10}\) m/W, \(1.21\times 10^{12}\hbox {W}/\hbox {m}^{2})\) exhibit higher 2PA coefficient and lower onset limiting threshold. The presence of CT and intragap states of \(\hbox {Cu}^{2+}\) ions-induced strain in visible region transformed genuine 2PA in pristine (\(\gamma \) and \(\beta )\)-\(\hbox {BaB}_{2}\) \(\hbox {O}_{4}\) nanorods into sequential 2PA (1PA\(+\)2PA) in Cu-doped (\(\gamma \) and \(\beta )\)-\(\hbox {BaB}_{2}\) \(\hbox {O}_{4}\). By simple hydrothermal process, concentration-dependent Cu-doped (\(\gamma \) and \(\beta )\)-\(\hbox {BaB}_{2}\) \(\hbox {O}_{4}\) nanostructures were prepared and their structural and optical properties were studied. Thus, Cu-doped (\(\gamma \) and \(\beta )\)-\(\hbox {BaB}_{2}\) \(\hbox {O}_{4}\) exhibit sequential 2PA (1PA\(+\)ESA)-based optical limiting with enhanced 2PA coefficient than its pristine (\(\gamma \) and \(\beta )\)-\(\hbox {BaB}_{2}\) \(\hbox {O}_{4}\) nanorods.

Graphic Abstract

中文翻译：

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纳米脉冲激光激发下Cu掺杂硼酸钡纳米结构的激发态吸收

摘要

掺杂铜（\（\ gamma \）和\（\ beta）\） - \（\ hbox {BaB} _ {2} \ hbox {O} _ {4} \）的强度和浓度依赖的非线性吸收纳米结构是通过标准的开孔Z扫描装置在各种峰值强度（1.26-2.52 GW / \（\ hbox {cm} ^ {2}）\}下在纳米脉冲（9 ns，10 Hz）激光激发（532 nm）下测量的。 ）。强度相关的2PA系数揭示了累积2PA过程而不是真实2PA的参与。从基态吸收研究来看，由于铜的结合而存在的新能量态已经利用了近共振态，有利于激发态吸收，从而导致了连续2PA。在这些样本中，有0.05 M的Cu掺杂\（\ gamma \） - \（\ hbox {BaB} _ {2} \） \（\ hbox {O} _ {4} \） \（（2.6 \ times 10 ^ {-10} \） m / W，\（0.78 \ times 10 ^ {12} \） \（\ hbox {W} / \ hbox {m} ^ {2}）\）和0.03 M掺杂Cu的\（\ beta \） - \（\ hbox {BaB} _ {2} \ hbox {O} _ {4} \） \（ （2.5 \ times 10 ^ {-10} \） m / W，\（1.21 \ times 10 ^ {12} \ hbox {W} / \ hbox {m} ^ {2}）\）表现出更高的2PA系数和更低的2PA系数发作极限阈值。可见区中\（\ hbox {Cu} ^ {2 +} \）离子诱导的应变的CT和能隙状态的存在转化了原始的真正2PA（\（\ gamma \）和\（\ beta）\） - \（\ hbox {BaB} _ {2} \） \（\ hbox {O} _ {4} \）纳米棒分成连续的2PA（1PA \（+ \）2PA）在Cu掺杂的（\（\ gamma \）和\（\ beta）\） - \（\ hbox {BaB} _ {2} \） \（\ hbox {O} _ {4} \）中。通过简单的水热过程，浓度依赖于铜的掺杂（\（\ gamma \）和\（\ beta）\） - \（\ hbox {BaB} _ {2} \） \（\ hbox {O} _ {4 } \）纳米结构的制备，并对其结构和光学性质进行了研究。因此，Cu掺杂（\（\ gamma \）和\（\ beta）\） - \（\ hbox {BaB} _ {2} \） \（\ hbox {O} _ {4} \）表现出连续的2PA基于（1PA \（+ \） ESA）的光学限制，其原始2PA系数（\（\ gamma \）和\（\ beta）\） - \（\ hbox {BaB} _ {2} \） \（\ hbox {O} _ {4} \）纳米棒。

图形摘要