Plasmon-enhanced ultrabroadband optical limiting performance of colloidal and thin film silver nanowires

Date

2026-05-01

Author

YILDIZ, ELİF
Unal, Nur
Cakir, Onuralp
PEPE, YASEMİN
COŞKUN, ŞAHİN
KARATAY, AHMET
Ünalan, Hüsnü Emrah
ELMALI, AYHAN

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Optical limiting materials are essential for the innovation of optoelectronic devices and human eyes in defense industry. The two most important parameters for an ideal optical limiter are the optical limiting spectral range and a low optical limiting threshold value. Herein, silver nanowires (Ag NWs) were examined in both colloidal dispersion and as thin films embedded within a polymethyl methacrylate (PMMA) matrix to evaluate their optical limiting performance across an ultrabroad wavelength range. PMMA polymer, which does not exhibit nonlinear absorption, was used to reveal the nonlinear optical property of Ag NWs. For this purpose, the nonlinear optical response of colloidal and thin film Ag NWs was investigated using the open aperture Z-scan technique, under varying excitation wavelengths and input intensities using a femtosecond pulsed laser system. To gain deeper insight into the underlying mechanism of nonlinear optical behavior, ultrafast pump–probe spectroscopy measurements were conducted. Open aperture Z-scan experiments revealed that both colloidal and thin-film AgNWs exhibit similar nonlinear optical behavior under excitation wavelengths ranging from 400 to 800 nm with increments of 100 nm. Moreover, to analyze nonlinear absorption properties in near infrared region, experiments were also carried out using pulsed laser excitation at 1200 and 1600 nm. Among the excitation wavelengths studied, 1600 nm located in the longitudinal mode of surface plasmon resonance of Ag NWs produced the highest βeff value. This enhancement was attributed to multiphoton absorption and plasmon-enhanced excited-state absorption (ESA) processes. Under 1200 and 1600 nm excitation, the colloidal Ag NW dispersion exhibited reverse saturable absorption (RSA) signals superimposed on saturable absorption (SA) behavior, in contrast to the thin-film form, where only RSA was observed. Across the ultrabroadband excitation range of 400-1600 nm, the optical limiting performance exhibited threshold values ranging from 0.02 to 0.33 J/cm2, indicating wavelength-dependent nonlinear absorption behavior. This work is among the first to systematically investigate Ag NW based optical limiters over an ultrabroad excitation range extending from the visible to the near-infrared (400–1600 nm). Overall, Ag NWs in both colloidal and thin-film forms exhibited ultrabroadband optical limiting responses, highlighting their potential for photonic and optoelectronic applications.

Subject Keywords

Optical limiting, Plasmonics, Silver nanowires, Thin film, Ultrafast pump–probe spectroscopy

URI

https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=105027729805&origin=inward
https://hdl.handle.net/11511/118522

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Department of Metallurgical and Materials Engineering, Article