Passively Q-switched mid-infrared laser pulse generation with gold nanospheres as a saturable absorber

Abstract

High-quality gold (Au) nanospheres (Au-NPs) with a diameter of 52 nm were prepared by the seeded growth method. The mid-infrared (MIR) nonlinear saturable absorption properties were measured by a balanced twin-detector measurement technique. With the as-prepared Au-NPs saturable absorber (SA), an efficient passively Q-switched laser was realized at 2.95 μm for the first time, to the best of our knowledge. Under an absorbed pump power of 4.0 W, a maximum output power of 268 mW was obtained with the shortest pulse width of 734 ns and repetition rate of 91 kHz, corresponding to the pulse energy up to 2.95 μJ. The results indicate that Au-NPs are promising candidates as SAs for MIR laser pulse generation.

Recent Progress of Two-Dimensional Materials for Ultrafast Photonics

“…The emergence of low dimensional nanomaterials, including 2D and 3D materials, offers reliable options for SAs. 3D materials, such as Dirac semimetal Cd As , metal nanosphere, and nanoscale charcoal powder, have been investigated in the past few years [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Cd As showed significant saturable absorption properties in the near- and mid-infrared regions [ 31 ].…”

“…Cd As showed significant saturable absorption properties in the near- and mid-infrared regions [ 31 ]. Metal nanospheres have the advantages of wideband adjustability and an ultrafast response time [ 29 ]. In addition, nanoscale charcoal powder has a higher modulation depth of 26% and transmittance of 0.91 that benefits from the decrease of size [ 36 ].…”

“…Three-dimensional (3D) materials, such as Dirac semimetal cadmium arsenide (Cd As ), metal nanospheres, and nanoscale charcoal powder, can also be used as SAs. However, most 3D materials do not possess the saturable absorption property, and the large insertion loss limits further applications in ultrafast pulsed lasers [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 ]. Compared with artificial SAs, CNTs, and 3D materials, 2D materials are extensively used in ultrafast pulsed lasers as superior SAs owing to the excellent saturable absorption properties, tunable modulation depths, and broadband responses.…”

Two-dimensional Au & Ag hybrid plasmonic nanoparticle network: broadband nonlinear optical response and applications for pulsed laser generation

“…of plasmonic NPs have been designed and fabricated for specific scientific researches and applications [6,[14][15][16][17][18][19][20]. In particular, the excellent third-order NLO properties in terms of a large third-order nonlinear susceptibility, an ultrafast relaxation time, the suitable modulation depth, and saturation intensity, make metallic NPs to be an excellent saturable absorber (SA), which is the key element of the passively Q-switched (PQS) or modelocked pulsed lasers [21][22][23][24][25]. In noble metal NPs, Au and Ag are the two most frequently and widely studied plasmonic materials due to the advantages including but are not limited to the following: First, easy fabrication makes it possible to synthesize Au NPs and Ag NPs with different shapes, sizes, as well as external factors, leading to the ability of manipulating the plasmonic functionalities and applications [26,27]; Second, the LSPR of Au NPs and Ag NPs can be tuned throughout the visible, infrared and even mid-infrared (MIR) regions [21,28]; Third, they have large nonlinear saturable absorption coefficient and third-order nonlinear susceptibilities, which are comparable to that of the novel two-dimensional (2D) materials [29,30]; Fourth, the ultrafast response on the time scale of femtoseconds or picoseconds makes Au NPs and Ag NPs to exhibit great potential in ultrafast optical signal processing [21,31].…”

A Tale of Two Tantalum Borides as Potential Saturable Absorbers for Q-Switched Fiber Lasers

“…Transition metal dichalcogenides have been applied to different laser systems [29]- [34] from 635 nm to 3000 nm, with pulse durations from 500 ns to more than 2000 ns. Finally metal nano-particles (e.g., silver and gold) have also been used as saturable absorbers in fiber lasers [35], [36].…”