Plasmonic nanoparticles embedded in single crystals synthesized by gold ion implantation for enhanced optical nonlinearity and efficient Q-switched lasing

Abstract

We report on the synthesis of embedded gold (Au) nanoparticles (NPs) in Nd:YAG single crystals using ion implantation and subsequent thermal annealing. Both linear and nonlinear absorption of the Nd:YAG crystals have been enhanced significantly due to the embedded Au NPs, which is induced by the surface plasmon resonance (SPR) effect in the visible light wavelength band. Particularly, through a typical Z-scan system excited by a femtosecond laser at 515 nm within the SPR band, the nonlinear absorption coefficients of crystals with Au NPs have been observed to be nearly 5 orders of magnitude larger than that without Au NPs. This giant enhancement of nonlinear absorption properties is correlated with the saturable absorption (SA) effect, which is the basis of passive Q-switching or mode-locking for pulsed laser generation. In addition, the linear and nonlinear absorption enhancement could be tailored by varying the fluence of implanted Au ions, corresponding to the NP size and concentration modulation. Finally, the Nd:YAG wafer with embedded Au NPs has been applied as a saturable absorber in a Pr:LuLiF crystal laser cavity, and efficient pulsed laser generation at 639 nm has been realized, which presents superior performance to the MoS saturable absorber based system. This work opens an avenue to enhance and modulate the nonlinearities of dielectrics by embedding plasmonic Au NPs for efficient pulsed laser operation.

Visible-wavelength pulsed lasers with low-dimensional saturable absorbers

“…The linear optical absorption spectrum of SWCNT films has been measured from the visible to the mid-infrared region, as shown in Figure 3C, revealing a broad absorption spectrum and relatively high absorption in visible spectral range. Additionally, noble metal NPs/ NRs have attracted intense research attention in the last decade due to their wide applications in the fields of biomedicine, optics, plasma science, and catalysis [145,146]. mainly due to localized surface plasmon resonance (SPR), which arises from the strong coupling between the free electrons in the conduction band and an external electromagnetic field [102].…”

“…At 635 nm wavelength, the corresponding results were 20.1%, 0.66 GW cm −2 , and 14.1% (see Figure 6D). In addition, Nie et al, in 2018, studied the nonlinear saturable absorption properties of embedded Au NPs in Nd: YAG single crystals with a femtosecond laser at 515 nm [145]. Linear and nonlinear optical properties of these lowdimensional nanomaterials prove their feasibility as SAs.…”

“…Based on this, the prepared Au NPs have been used as SAs to obtain pulsed operation of solid-state crystal lasers in visible wavelengths since 2015 [164]. By using Au NRs as SA, passive Q-switching was demonstrated at 605, 639, and 721 nm with the pulse energy of 81, 64, and 51 nJ, respectively [145].…”

Plasmonic Nanoparticles in Dielectrics Synthesized by Ion Beams: Optical Properties and Photonic Applications

“…[ 1–5 ] To date, a number of applications have been achieved based on the embedded metallic NPs in a wide range of fields, including photonics, biology, chemistry, energy, and information science. [ 6–10 ] The tailoring of LSPR effect in nanocomposites is of vital importance to the emergence of novel mechanisms and the improvement of device performance. In theory, it is closely associated with the NP species, shapes, sizes, dielectric environment, etc.…”

“…In photonics, the synergistic effect between NPs and functional dielectric crystals shows significant potential for material modification with unprecedented optical phenomena, e.g., electron transfer mechanism, high‐order nonlinearity enhancement, modulation, and so on. [ 6,8,25,27 ] To promote the interaction effect between NPs and dielectrics, some well‐developed techniques have been proposed to embed NPs into the matrix for designed nanocomposite systems, such as ion beam implantation/irradiation, ion exchange, and femtosecond laser processing. [ 27–29 ]…”