Research On Super-resolution Optical Field Detection Based On Optical Nonlinearity Of Graphene Oxide

Micro-nanotechnology has imperceptibly penetrated into various fields of scientific research and life,with the development of science and technology increasingly miniaturization,integrated direction,the structure and size of various types of functional devices gradually move to the nanometer scale,gave people great convenience,also spawned a series of measurement problems.As a common technique for detecting micro-nano structures,micro-nano optical detection technology has been favored by researchers for a long time because of its characteristics of non-contact measurement,no damage,wide measurement range and fast speed.However,due to the existence of the diffraction limit of the optical eigenvalue,the further improvement of its measurement accuracy is restrained,and it is difficult to satisfy the increasingly sophisticated needs of the micro-nano structure detection device.In this paper,a method for super-resolution detection with cleverly bypassed diffraction limit was proposed.Based on the traditional micro-nano optical detection technology,the nonlinear saturation absorption characteristic of graphene oxide(GO)film was used to further reduce the size of the focused light field.Finally,a super-resolution light field was generated theoretically and experimentally.The super-resolution light field has great application value not only in the field of micro-nano optical detection and super-resolution imaging,but also can be widely used in high density data storage,particle manipulation,micro-nano processing,optical recording and other fields.In this paper,the GO film was prepared by vacuum filtration method,and its microscopic morphology and linear optical parameters were analyzed.The third-order optical nonlinearity coefficients of GO films were measured by Z-scan detection technique under the excitation of femtosecond laser with wavelength 532 nm and pulse width 350 fs,and the theoretical and experimental data were fitted.By adjusting the energy of the femtosecond laser pulses used,a continuous and flexible adjustment of the nonlinear saturation absorption capability of the GO film was achieved.In this paper,the function of GO film was equivalent to a unique amplitude filter,which regulates the amplitude distribution of the light field by its nonlinear saturated absorption property.And the GO film was put in the focal position of the incident femtosecond beam,which can make the low loss of high intensity laser pass,and the low intensity laser was absorbed.The light field amplitude distribution was flexibly applied to achieve spot cutting.In this paper,a multi-layer system model for analyzing the interaction between light field and thin film materials was proposed.The model was used to calculate and simulate the light intensity distribution in the process of incident film with incident depth.At the same time,the absorption distribution of GO film was demonstrated,and the change of the beam inside the GO film and the mechanism of the whole process were also explored.Finally,the resolution of full width at half maximum less than λ/3 was realized by optimizing parameter condition,and the diffraction limit is exceeded.In addition,we modulated and detected the polarization state distribution of the light field and generated radial polarized light.By used the tight focus characteristic of the radial polarized light combined with the nonlinear effect of the GO film to cut the spot,the full width at half maximum of the focused spot was further approached to λ/5,thus achieved higher resolution,and theoretically analyzed the mechanism of the super-resolution light field generated by the vector beam.