Enhanced resolution in two-photon imaging using a TM_01 laser beam at a dielectric interface

Abstract

We have experimentally demonstrated that the resolution of a commercial two-photon microscope is improved using a TM(01) laser beam. With a water immersion objective having a 1.2 NA, the measured point- spread function has an area of 0.15lambda(2). We used a plane interface between dielectrics instead of an annular aperture to increase the relative contribution of the longitudinal field of the TM(01) laser beam. The results are in agreement with the vectorial diffraction theory established by Richards and Wolf [Proc. R. Soc. Lond. A253, 358 (1959)]. The TM(01) laser beam was produced with a quadrant of half-wave plates. We have also used the same mode converter to generate a TE(01) laser beam with a zero at the beam center.

Light Microscopy with Doughnut Modes: A Concept to Detect, Characterize, and Manipulate Individual Nanoobjects

“…Additionally, theoretic simulations suggest that even third harmonic generation (THG) from a bulk sample under defined conditions should be detectable 99. Moreover, RPDMs are important to improve the resolution in two‐photon microscopy 100. Accordingly, also in THG microscopy, a better spatial resolution is expected 99…”

Creation of a 50,000λ long needle-like field with 036λ width

“…A strong axial component appears at the focal region of a tightly focused radial polarized light [1,[6][7][8][9][10][11][12]. Besides being of academic interest, this unusual axial field has many attractive applications, such as particle acceleration [12][13][14][15][16], fluorescent imaging [17,18], nanolithography [19], second-harmonic generation [20,21], Raman spectroscopy [22], high-density optical data storage [23], microscope [24,25], and optical trapping [26]. However, to create a slim, uniform, and pure axial field is still a big challenge.…”

Vector-Field Nonlinear Microscopy of Nanostructures

“…This has been achieved through the enhancement of the longitudinal fields of RP at dielectric-air interfaces, which resulted in the reduction of the spot size at the focal plane of a TPEF microscope by a factor of 1.7 (Figure 8a). 259 In another study, by taking the difference of the TPEF images that were acquired by a bright (linear polarization) and a dark (AP) beam, the spatial resolution was shown to improve by a factor of 2 (Figure 8b). 260 In a separate application, AP was used as a robust depletion beam in a fiber-optical TPEF stimulated emission depletion (STED) endoscope.…”

“…Resolution enhancement can be achieved by minimizing the excitation volume in TPEF, which has the additional benefit that it reduces the invasiveness of the method arising from the excitation of the fluorophores. This has been achieved through the enhancement of the longitudinal fields of RP at dielectric-air interfaces, which resulted in the reduction of the spot size at the focal plane of a TPEF microscope by a factor of 1.7 (Figure a) . In another study, by taking the difference of the TPEF images that were acquired by a bright (linear polarization) and a dark (AP) beam, the spatial resolution was shown to improve by a factor of 2 (Figure b) .…”