Fused Silica with Embedded 2D‐Like Ag Nanoparticle Monolayer: Tunable Saturable Absorbers by Interparticle Spacing Manipulation

Abstract

Saturable absorbers are key elements for generation of ultrafast laser pulses. The commercially available semiconductor saturable absorber mirrors are wavelength sensitive and with complex fabrication process and high cost. Fused silica is one of the basic materials for various optical applications. Plasmonic nanoparticles can be used to efficiently modulate the optical properties of dielectric materials owing to the enhanced field effects based on localized surface plasmonic resonance. Ion implantation is a direct technique to synthesize plasmonic nanoparticles inside dielectric materials, which can simultaneously tailor the optical nonlinearity of substrates significantly. In this work, Ag ion implantation into fused silica with tunable interparticle spacing is used to generate broadband optical nonlinearities and to endow silica with ultrafast saturable absorption property. This ion implantation forms a 2D‐like Ag nanoparticle monolayer buried inside fused silica wafer. The fused silica with embedded 2D‐like Ag nanoparticle monolayer is further applied as a new saturable absorber to generate ultrafast laser pulses with pulse duration of 27 ps and repetition rate of 6.5 GHz through the passive mode‐locking process. This work opens up a new route to develop low‐cost, highly stable saturable absorbers, and offers the possibility to build novel silica‐based photonic systems through nanoparticle spacing manipulation.

Near‐Infrared All‐Optical Switching Based on Nano/Micro Optical Structures in YVO4 Matrix: Embedded Plasmonic Nanoparticles and Laser‐Written Waveguides

“…Table 1 shows the third‐order typical embedded material systems. Notably, the modulation depth in this work is much higher than previous embedded systems (e.g., 1.1% of Ag:SiO 2 and 2.7% of Ag:YAG) at the same wavelength, [ 24,25 ] which indicates that Ag:YVO 4 sample can be used as a promising new nonlinear absorption material for light modulation. Overall, the observed ultrafast relaxation and superior saturable absorption response (e.g., high modulation depth and low saturation intensity) endow Ag:YVO 4 with a great potential for modulating the intracavity losses toward all‐optical switching applications.…”

“…To gain further knowledge of the nonlinear absorption properties, an open‐aperture Z‐scan technique is utilized with an infrared femtosecond laser (1030 nm, 340 fs, and 100 Hz) excitation (see the Experimental Section for more details). [ 24,42,43 ] As shown in Figure 4c, there are negligible nonlinear absorption effects for the pristine YVO 4 matrix. In contrast, for Ag:YVO 4 nanocomposite, an obvious nonlinear saturable absorption effect is observed as shown in the positive response in the nonlinear transmission during the laser focus ( Z = 0), which indicates its potential as a Q‐switch in the pulsed laser generation.…”

“…The dependence of pulse energy and peak power is shown in Figure 5g, and the maximum pulse energy and peak power of a single pulse can reach 6.27 nJ and 298 mW. Most of the previous works only achieved a mixed state of Q‐switched and mode‐locking, [ 23–25,44 ] which is typically considered as not stable. The high modulation depth and low saturation intensity of Ag:YVO 4 endow the realization of all‐optical switching functionalities instead of the insufficient mixed state of Q‐switched mode‐locking operation in an optical waveguide.…”

“…For example, Au NPs have been used to tailor the nonlinear response of LiNbO 3 , [ 23 ] and Ag NPs have been used to enhance the third‐order optical nonlinearity of SiO 2 (fused silica) and YAG matrix. [ 24,25 ] Yttrium vanadate (YVO 4 ) crystal is a widely used optical component with wide transparency range and large birefringence, as well as an ideal host for solid‐state lasers. [ 26 ] The successful fabrication of embedded plasmonic NPs and an understanding of its optical properties within these systems will facilitate the future development of integrated photonics circuits.…”

Plasmonic Saturable Absorbers

“…For practical applications, these noble metal‐based nanostructures have to be stabilized by dispersion in the solid matrix with high laser damage threshold. [ 102,103 ] Recently, Chen et al used ion‐implantation method to inject Ag ions into a quartz glass‐based waveguide. The implanted Ag ions formed clusters and NPs, and the spacing of NPs can be adjusted artificially by the implantation condition.…”