Abstract
Gold nanobipyramids (Au-NBPs) were successfully fabricated using the seed-mediated growth method. The saturable absorption performance of the Au-NBPs at a 2-μm band wavelength was characterized. Using excellent-quality, mature Ho:YLF crystals, a doubly Q-switched (DQS) laser joining an acousto-optic modulator (AOM) with an Au-NBP saturable absorber (SA) was achieved. When the modulation rate of the AOM was 1 kHz, the shortest pulse width (54 ns) was attained, corresponding to the highest peak power (3.87 kW). This was compared with a singly Q-switched laser joining an AOM with an Au-NBP SA, whereby the maximum pulse width compression ratio was 15.2 and the highest peak power enhancement factor was 541.3. Our study has shown that Au-NBPs are a potential saturable absorption nanomaterial, and the DQS laser has the benefit of compressing the pulse width and increasing the peak power at a wavelength of 2.1 μm.
Highlights
Au-NBPs are a potential saturable absorption nanomaterial, and the doubly Q-switched (DQS) laser has the benefit of compressing the pulse width and increasing the peak power at a wavelength of 2.1 μm
Q-switching is an effective method for deriving a short pulse mode, and includes two well-known traditional techniques—active Q-switching (AQS) and passive Q-switching (PQS) [7,8]
The third-order optical nonlinear effect is the most prominent, which enables them to act as saturable absorber (SA) for all-optical switching and for the modulation of light
Summary
Ho-doped pulsed lasers, with a narrow pulse width, high repetition rate, and good symmetry, have wide applicability in the fields of micro-machining, ranging, remote sensing, microsurgery, etc. [1,2,3]. A doubly Q-switched (DQS) laser with an acousto-optic modulator (AOM) and SA can simultaneously compress the pulse width, improve the pulse symmetry, and enhance the peak power. This kind of pulsed laser has multiple functions in different applications. Reported on a DQS Tm:Ca(Gd,Lu)AlO4 laser using an AOM with a WS2 SA, through which the shortest pulse width of 91 ns and the highest peak power of 1.2 kW were obtained [37]. There are, as yet, no reports on DQS operation in a Ho-doped laser using an AOM and a nanomaterial SA at a wavelength of 2.1 μm. In comparison with the singly Q-switched operation, the DQS laser achieved a shorter pulse width and a higher peak power
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