High-power and high-efficiency 4.3 μm ZGP-OPO

In this paper,a high-power and high-efficiency 4.3μm mid-infrared(MIR)optical parametric oscillator(OPO)based on ZnGeP_(2)(ZGP)crystal is demonstrated.An acousto-optically Q-switched Ho Y_(3)Al_(5)O_(12) laser operating at 2.1μm with a maximum average output power of 35 W and pulse width of 38 ns at a repetition rate of 15 kHz is established and employed as the pump source.A doubly resonant OPO is designed and realized with the total MIR output power of 13.27 W,including the signal and idler output power of 2.65 W at 4.07μm and 10.62 W at 4.3μm.The corresponding total optical-to-optical and slope efficiencies are 37.9%and 67.1%,respectively.The shortest pulse width,beam quality factor,and output power instability are measured to be 36 ns,M_(x)^(2)=1.8,M_(y)^(2)=2.0,and RMS<1.9%at 8 h,respectively.Our results pave a way for designing high-power and high-efficiency 4–5μm MIR laser sources.

Nonlinear optical absorption properties of InP nanowires and applications as a saturable absorber

Indium phosphide(InP)nanowires(NWs)have attracted significant attention due to their exotic properties that are different from the bulk counterparts,and have been widely used for light generation,amplification,detection,modulation,and switching,etc.Here,high-quality InP NWs were directly grown on a quartz substrate by the Au-nanoparticle assisted vapor-liquid-solid method.We thoroughly studied their nonlinear optical absorption properties at 1.06μm by the open-aperture Z-scan method.Interestingly,a transition phenomenon from satu-rable absorption(SA)to reverse saturable absorption(RSA)was observed with the increase of the incident laser intensity.In the analysis,we found that the effective nonlinear absorption cofficient(βeff-10^2 cm/MW)under the SA process was 3 orders of magnitude larger than that during the RSA processes.Furthermore,the SA proper-ties of InP NWs were experimentally verified by using them as a saturable absorber for a passively Q-switched Nd:YVO4 solid-state laser at 1.06μm,where the shortest pulse width of 462 ns and largest single pulse energy of 1.32μJ were obtained.Moreover,the ultrafast carrier relaxation dynamics were basically studied,and the intraband and inter-band ultrafast carrier relaxation times of 8.1 and 63.8 ps,respectively,were measured by a degenerate pump-probe method with the probe laser of 800 nm.These results well demonstrate the nonlinear optical absorption properties,which show the excellent light manipulating capabilities of InP NWs and pave a way for their applications in ultrafast nanophotonic devices.

Ta_(2)NiSe_(5) nanosheets as a novel broadband saturable absorber for solid-state pulse laser generation

Two-dimensional(2D)ternary chalcogenides have attracted great attentions because of their novel chemical and physical properties arising from the synergistic effect and stoichiometric variation with the additional third element compared with their binary counterparts.Here,high-quality 2D tantalum nickel selenide(Ta_(2)NiSe_(5))nanosheets are successfully fabricated by a liquid-phase exfoliation(LPE)method.The ultrafast excited carrier relaxation time and nonlinear optical absorption response are investigated and reveal that the prepared 2D Ta_(2)NiSe_(5)nanosheets have excellent broadband saturable absorption properties,which are further illustrated by three passively Q-switched(PQS)allsolid-state lasers operating at 1.0,2.0 and 2.8μm with the Ta_(2)NiSe_(5)nanosheet-based saturable absorber(SA).Furthermore,mode-locked laser operation with the pulse width as short as 356 fs is also realized at 1.0μm.This work not only demonstrates the excellent nonlinear optical proprieties and optical modulation performance of Ta_(2)NiSe_(5),but also paves the way for exploring the photonic and optoelectronic proprieties of ternary chalcogenide materials.