The periodical pulse bundles were presented in a Yb-doped double-clad distributed Bragg reflector all-fiber configuration. With a pumped power of 529.2 mW, the periodical pulse bundles is obtained. Furthermore, a single pulse bundle composes of one main pulse and two sub-pulses. The pulse width of the main pulse and the sub-pulse are 2.2 μs and 7.7 μs, respectively. The separations of between main pulse, right sub-pulse and left are 22.70 μs and 22.15 μs, respectively. The average period of the pulse bundle is approximately 75 μs with repetition rate of 13.3 kHz. The number of sub-pulses between adjacent main pulses decreases to one when the pumped power does to 450.2mW. When the pumped power increases to 594.4 mW, the number goes to three.
Germanene (Ge) has a Dirac-type electronic structure similar to that of graphene and has excellent nonlinear saturable absorption properties, which has attracted extensive research. In this paper, few-layer Ge nanosheets were prepared and characterized in detail. Its nonlinear modulation depth was measured to be 8.5%, and the saturation intensity was 0.12 GW/cm2. Ge nanosheets are used as a saturable absorber (SA) in an Er-doped fiber laser (EDFL) to obtain a stable Q-switched mode-locking (QML) pulse. As the pump power (Ppump) increases from 64.2 mW to 204 mW, the repetition frequency (RF) and pulse width of the Q-switched (QS) envelope increase from 46.2 KHz to 109 KHz and decrease from 4.4 μs to 2.25 μs, respectively. The mode-locked pulse has a RF of 30.2 MHz with a center wavelength of 1559.6 nm. The QML pulses obtain a maximum output power of 2.278 mW and a maximum pulse energy of 20.9 nJ when the Ppump is 204 mW. Our study proves that Ge, as a high-energy light pulse absorbing material, can be used in the field of ultrafast laser.
MoSe2 thin films have excellent catalytic, electrical, and optical properties and have potential applications in the fields of catalytic hydrogen precipitation, field effect transistors, sensor devices, and optoelectronic devices. In this paper, MoSe2 thin films were synthesized based on the solid-phase reaction at the interface between Se and Mo film at high temperatures, which are deposited on sapphire substrates sequentially. The structure and morphology were characterized by Raman spectroscopy, scanning electron microscopy and atomic force microscopy. The synthesis temperature and saturable absorption (SA) properties of the MoSe2 films were investigated. The results show that 400°C is close to the optimal temperature for synthesizing MoSe2 films, and the synthesized MoSe2 films exhibit multilayer structure. When it is applied as a saturable absorber in a 1064 nm solid-state laser, the maximum repetition frequency of the Q-modulated laser pulse is obtained to be 428.1kHz, which corresponds to a pulse width of 67.6 ns and a maximum modulation depth of 27.4%.
Semiconductor laser devices have the characteristic of small size, high integration and stable requirements, and TO package red semiconductor laser are widely used in laser display application market. Due to the limitations of the electro-optical conversion efficiency of laser devices, the active region will generate over 55% of Joule waste heat under normal operation, and the traditional TO9 packaging form with Aluminum Nitride heat sink is not conducive to the heat dissipation for high power laser application. Therefore, this has become a key factor restricting the stable operation of short wavelength red semiconductor laser devices. In order to improve the heat dissipation problems, this paper developed an upgraded TO packaging type of red wavelength laser device using single-crystal Silicon Carbide (SiC) heat-sink under constant temperature condition. The experimental results show that the output power of TO packaged red laser with self-developed single-crystal SiC heat-sink is significantly higher than that of AlN heat-sink packaged device at high temperatures. The maximum electro-optical conversion efficiency of TO devices contained SiC heat sink is also improved, and the thermal resistance of the package dissipation is effectively reduced.
In recent years, layered transition metal sulfides (TMDCs) exhibit excellent nonlinear saturable absorption properties in laser modulations. Nevertheless, few of them are applied to the optimization of optical parametric oscillators (OPOs). In this work, we prepared a 12.5 nm-thickness platinum disulfide (PtS2) saturable absorber (SA) by a combination of electron beam evaporation (EBE) and post-vulcanization method. The nonlinear transmittance is measured, which exhibits the SA characteristic of PtS2 film. The acousto-optic (AO) Q-switch and the prepared PtS2 SA are used to realize the operation of active and passive Q-switched OPO, and the mid-infrared idler pulse with nanosecond width is obtained. By measuring the experimental output results, the optimizations of PtS2 SA to OPO’s operation are analyzed, including the stabilization of pulse train by 240%, the compression of idler-light pulse by 59.7%, the improvement of peak power by 198%. As a result, the improvement of nonlinear conversion is attained by 16.9%. The phenomenon may be due to the excellent saturable absorption effect of PtS2 SA to the fundamental light. This paper shows the optimization effect of the prepared layered transition metal sulfide for laser intracavity modulation on the nonlinear frequency conversion process, especially for the improve of nonlinear conversion effect.
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