Study On Nonlinear Optical Property Of A Bi-doped GaAs Semiconductor Saturable Absorber

With the development of laser technology and nonlinear optical theory,many nonlinear optical materials continue to mount.Nonlinear optical materials have potential applications in many fields.They can be used in optical logic devices,optical modulators,optical storage,optional switches and some other electronic functional devices.The properties of these instruments are directly related to the nonlinear optical properties of the selected material.For solid-state lasers,saturable absorbers should have fast response,low loss,large broadband performance as while as high modulation depth.In order to break through the bottleneck of the technology and promote and develop the mode-locked laser technology,one of the key tasks is to find excellent saturable absorber materials.The saturable absorption effect of the optical material is classified into a third-order nonlinear optical range.Therefore,the preparation of lasers with short pulse and high energy,and the exploration-of saturable absorbers having excellent nonlinear optical absorption characteristics are the focus of nonlinear optics study.In this paper,we analyze the nonlinear absorption characteristics of Bi-doped GaAs prepared in different ion implantation conditions.By constructing passively.Q-switched solid state lasers and performing open-aperture Z-scan technique,we compare the laser output characteristics and Z-scan measurements of various materials,and then study the differences between Bi:GaAs and pure GaAs.Specific work contents are as follows:(a)We introduce the applications of GaAs in passively Q-switched laser at 1?m wavelength.After that,we present the performance of 1?m Nd:YVO4 laser with Bi-doped GaAs or undoped GaAs as saturable absorber.We measure and compare the laser output characteristics experimentally.At the same condition,the output parameters generated by Bi-doped GaAs as a saturable absorber can produce higher output power,shorter pulses,higher single pulse energy and higher peak power.The enhancements of saturable absorption response of GaAs with different ion implantation conditions are verified.At the same ion implantation depth,the Bi:GaAs has a better saturable absorption response with a higher doping concentration.At the same doping concentration,the Bi:GaAs has a better saturable absorption response with a higher ion implantation depth.(b)We explain the experimental principle of Open-Aperture Z-scan technique.The nonlinear optical properties of GaAs and Bi-doped GaAs,including the saturable absorption property and reverse saturable absorption property are systematically measured and analyzed directly in detail by using an Open-Aperture Z-scan technique with both femtosecond and nanosecond laser pulses at 1064nm.Key optical nonlinear parameters of SA in the GaAs and Bi-doped GaAs have been determined,including TPA coefficient and saturable intensity.Compared to pure GaAs,Bi-doped GaAs has a lower saturation intensity,wider saturable absorption energy region,lower two-photon absorption coefficient,better saturable absorption response and stronger optical limiting response.The results suggest that the incorporation of Bismuth in GaAs is an effective way of improving the nonlinear optical properties of GaAs,which provide crucial experimental evidence for that the characteristics of the passively Q-switched laser with Bi-doped GaAs saturable absorber is better than pure GaAs,and the large modulation depth of the Bi-doped GaAs under the femtosecond laser indicates that it is an excellent optical limiting material in the infrared band.