Bessel beam

About: Bessel beam is a research topic. Over the lifetime, 1946 publications have been published within this topic receiving 42264 citations.

Femtosecond cellular transfection using a non diffracting light beam

Abstract: Foreign DNA introduction inside the living cell has been demonstrated using a Bessel beam. This obviates the need to locate precisely the cell membrane permitting two-photon photoporation along a line leading to successful transfection.

Discussion of methods for depth enhancement in single and multiphoton-stimulated emission microscopy

Abstract: Methods to enable enhanced tissue depth in stimulated emission imaging are discussed. To take advantage of the increased scattering length and reduced absorption in the near infrared, 2–4 photons are used for both molecular excitation and stimulated emission in stimulated fluorescence imaging. The method is called multiphoton-stimulated emission microscopy (MP-STEM). In a confocal microscope, the axial focal spot in 3-photon MP-STEM may be reduced to about ½ the wavelength of the stimulated emission beam, potentially enabling the detection of ballistic backscatter at the tissue surface. Also discussed is a microscope geometry that combines Bessel beam excitation with an orthogonal structured illumination stimulated emission beam. This geometry is called Bessel beam-stimulated emission microscopy (BB-STEM). It is shown that the axial focal spot diameter of the stimulated emission beam may be reduced to less than ½ of the stimulated emission beam wavelength for 1–3 photon stimulated emission processes, enabling dipole backscatter ballistic photons to be detected in both stimulated fluorescence and stimulated Raman processes. Dipole ballistic backscatter detection reduces emitter concentrations detection thresholds by the reduction of the detected stimulated emission beam background noise. Use of multiple time delays between the excitation and emission processes enables the use of these approaches to measure the fluorescent lifetime of species with multiple lifetimes. Also discussed are the challenges of these methods, including the required laser power, focal spot blooming, and array detectors.

Functionalization of freeform curved surfaces by shaped femtosecond laser pulses in the propagation axis.

Abstract: With ultrashort pulse durations and ultrahigh peak intensities, ultrafast lasers can create different types of micro/nano-structures to functionalize the processed surface with new properties. However, the applications of this method on freeform surfaces are still limited by the short length of a laser focusing spot and complex control of the 3D moving trajectory in the fabrication process. In this paper, we overcome this problem by shaping the on-axis intensity along the propagation axis using the spatial light modulator. By designing the phase mask, we increased the length of the stable-intensity zone (intensity fluctuation < 10%) by more than 3 times compared to that of an unshaped Bessel beam. The energy deposition was also optimized to be less than 2% fluctuation based on simulations. Using this method, we fabricated micro/nano structures on 3D surfaces at different fluences and demonstrated various properties including colorization, anti-reflection, and hydrophobicity in large height range. We demonstrated the applications of the proposed method in creating hydrophobicity on complex freeform syringe tip surfaces. This improved the minimum manipulatable volume of a liquid droplet to 2 times smaller compared with untreated syringe, thus greatly extending its performance for micro-droplet manipulation. This method offers an alternative approach for reliable and affordable freeform curved-surface processing.

Method for preparing silicon nanowire structure by utilizing electronic dynamic regulation and control

Abstract: The invention relates to a method for controllably processing a silicon nanowire structure by regulating and controlling chemical etching by utilizing electronic dynamics and assisting a double-pulse femtosecond laser Bessel beam, and belongs to the technical field of femtosecond laser application. The femtosecond laser is subjected to time-domain and space-domain shaping, and the local transient electronic dynamics (mainly free electron density distribution) of a laser action area is regulated and controlled, so that the chemical characteristics of a processed material are regulated and controlled, and preparation of the high-collimation-degree silicon nanowire structure is realized. Compared with the traditional femtosecond laser processing method, the method for controllably processing the silicon nanowire structure by regulating and controlling chemical etching by utilizing electronic dynamics and assisting the double-pulse femtosecond laser Bessel beam has the advantages that the collimation degree of the nanowire can be increased by several times and the processing structure size breaks through the optical diffraction limitation.

The vector reflector

Abstract: A linearly polarized Bessel beam, whose spatial frequencies correspond to the Brewster angle, impinging at normal incidence on a higher refractive-index interface is shown to lead to a reflected field that can be used to produce an azimuthally polarized optical vector beam.