Two-Photon Absorption Properties Of Cuprous Oxide

In 1983,researchers at the Huges Institute in the USA,Jain R K and Lind R C,first discovered that CdS_1-xSe_x semiconductor microcrystalline-doped optical filter glass has a fast time response and a large third-order nonlinear effect.Then with the development of ultrashort pulsed lasers,the nonlinear optical properties of semiconductor materials have attracted more and more attention from researchers.In the past few years,the emergence of all-optical switching based on the two-photon absorption made all-optical switching speed did not limited by the effective carrier lifetime,which has attracted attention of researchers.Cuprous oxide?Cu₂O?is a material with remarkable optical nonlinear effects,large third order nonlinear susceptibility,ultra-fast time response,excellent chemical and thermal stability.As an excellent candidate material for all-optical switching and cross-phase modulation,cuprous oxide has attracted more and more attention from researchers.In this paper,we first introduce the concept of two-photon absorption,and enumerates the application examples of two-photon absorption in micro-nano fabrication,optical limiting,and photodynamic therapy.Then we introduce the concept of nondegenerate two-photon absorption,and list the applications of nondegenerate two-photon absorption in optical sampling,infrared detection,and all-optical switching.Finally,we briefly introduced the basic properties,preparation methods and application fields of cuprous oxide,and described the research progress Preparation and characterization of Cu₂O thin film:We prepared a pure phase Cu₂O thin film using radio-frequency?RF?magnetron sputtering,and the structure and crystallinity of Cu₂O was characterized by X-ray diffraction.The thickness was characterized by an ellipsometer,and the linear transmission spectrum was performed by a dual beam spectrophotometer.The optical bandgap of Cu₂O thin film was obtained by linear extrapolation method.The wavelength range of nondegenerate and degenerate two-photon absorption experiments were selected according the lineartransmission spectra.of nonlinear optical properties of cuprous oxide.The specific content of the paper is as follows:1.Study on nondegenerate two-photon absorption properties of Cu₂O thin film:By performing the pump-probe technique,nondegenerate two-photon absorption coefficients of the Cu₂O thin film at several different excitation wavelengths were experimentally determined.The nondegenerate two-photon absorption coefficient shows a maximum value ofb_ND=87.60±1.05 cm/GW.This study indicates that the cuprous oxide could be a promising candidate material for all-optical switching that use nondegenrate two-photon absorption as working principle,profiting from due to its large nondegenerate two-photon absorption coefficient.2.Study on degenerate two-photon absorption properties of Cu₂O thin film:By performing the Z-scan technique,degenerate two-photon absorption coefficients of the Cu₂O thin film at several different excitation wavelengths were experimentally determined.The nondegenerate two-photon absorption coefficient shows a maximum value ofb_D=26.63±0.64 cm/GW.The nondegenerate two-photon absorption coefficient always exhibits larger value than corresponding degenerate two-photon absorption coefficient,which is attributed to the effect of intermediate state resonance enhancement.In addition,due to the quantum effect,the degenerate two-photon absorption coefficient of Cu₂O thin film always exhibits larger value than the Cu₂O bulk in the literature.The large nondegenerate two-photon absorption coefficient suggests that Cu₂O would be a promising candidate material for ultrafast nonlinear photonic applications such as all-optical switching that use nondegenerate two-photon absorption as working principle.3.Study on nondegenerate two-photon absorption of Cu₂O nanoparticles:Different sizes of cuprous oxide cubic nanoparticles were prepared by water bath method,and their surface morphology was characterized by SEM.The femtosecond laser pump-probe technology was used to measure nondegenerate two-photon absorption coefficient of different sizes of cuprous oxide cubic nanoparticles.It is found that the non-degenerate two-photon absorption coefficient of cuprous oxide nanoparticles is small,which is attributed to the lower concentration and the poor dispersion.Therefore,the preparation conditions need to be optimized and we can further investigate the nondegenerate two-photon absorption properties of Cu₂O nanoparticles with different morphologies.