ABSTRACT
The recombination of photoinduced carriers in photocatalysts is considered one of the biggest barriers to the increase of photocatalytic efficiency. Piezoelectric photocatalysts open a new route to realize rapid carrier separation by mechanically distorting the lattice of piezoelectric nanocrystals to form a piezoelectric potential within the nanocrystals, generally requiring external force (e.g., ultrasonic radiation, mechanical stirring, and ball milling). In this study, a low-power UV pulsed laser (PL) (3 W, 355 nm) as a UV light source can trigger piezoelectric photocatalytic CO2 reduction of tetragonal BaTiO3 (BTO-T) in the absence of an applied force. The tremendous transient light pressure (5.7 × 107 Pa, 2.7 W) of 355 nm PL not only bends the energy band of BTO-T, thus allowing reactions that cannot theoretically occur to take place, but also induces a pulsed built-in electric field to determine an efficient photoinduced carrier separation. On that basis, the PL-triggered piezoelectric photocatalytic CO2 reduction realizes the highest reported performance, reaching a millimole level CO yield of 52.9 mmol g-1 h-1 and achieving efficient photocatalytic CO2 reduction in the continuous catalytic system. The method in this study is promising to contribute to the design of efficient piezoelectric photocatalytic reactions.
ABSTRACT
Stable picosecond dissipative soliton pulses were observed in an ytterbium-doped fiber laser employing a high-quality mixture of BP/SnSe2-PVA saturable absorber (SA). The modulation depth, saturation intensity, and non-saturable loss of the mixture of BP/SnSe2-PVA SA were measured with values of 5.98%, 18.37 MW/cm2, and 33%, respectively. Within the pump power range of 150-270 mW, stable dissipative soliton pulses were obtained with an output power of 1.68-4 mW. When the minimum pulse duration is 1.28 ps, a repetition rate of 0.903 MHz, center wavelength of 1064.38 nm and 3 dB bandwidth of 2 nm were obtained. The maximum pulse energy of 4.43 nJ and the signal-to-noise ratio up to 72 dB were achieved at pump power of 270 mW. The results suggest that the BP/SnSe2-PVA mixture SA has outstanding nonlinear saturable absorption characteristics and broad ultrafast laser applications.
ABSTRACT
Based on an as-prepared high-quality WS2 film and an electro-optic modulator (EOM), a dual-loss-modulated low repetition rate mode-locking laser at 0.53 µm with high peak power is presented for the first time. The laser characteristics versus the pump power are investigated experimentally and theoretically. At a pump power of 10.67 W, the shortest pulse duration of 305 ps can be measured, corresponding to the highest peak power of 931 kW, which is much higher than those of the single passive modulated lasers with WS2-SA. A simple rate equation simulation was used to describe this dual-loss-modulated mode-locking green laser based on WS2 and EOM. The results of the numerical simulation are basically in accordance with the experimental values.
