Comparison of different theories for focusing through a plane interface

Abstract

Phase conjugation of optical dipole fields is considered in a static holographic scheme with totally internally reflected reference and reconstruction waves. It is shown that as the distance between the dipole object and the recording medium decreases from the far-to the near-field region, the intensity distribution of the reconstructed dipole field changes from a diffraction-limited light spot to a subwavelength-sized light spot that is brightest at the surface of the hologram. The influence of the thickness of the recording medium, the angle of incidence of the reconstruction wave, and the polarization configuration on the reconstructed intensity distribution are also discussed.

Optical trap stiffness in the presence and absence of spherical aberrations

“…A more accurate approximation is in principle possible, 27,28 but the difference between the results is below our experimental error margin. Additionally, we ignored the fact that not only the position of the focus but also the position of the potential minimum for trapping is changed by spherical aberrations because the balance between scattering and gradient forces changes.…”

Femtosecond laser induced structural changes in fluorozirconate glass

“…Furthermore, these glasses feature a low nonlinearity, that limits unwanted nonlinear pulse propagation effects during the fs laser direct-write process. They also exhibit a relatively low refractive index (≈ 1.5), thereby reducing the refractive index mismatch and as such the associated spherical aberrations when focusing the writing beam into the glass [24].…”

Focusing properties of aberration-free electromagnetic waves in thin dielectric slabs

“…We let the phase φ(x , y ) be determined from geometrical optics so as to cancel the aberrations introduced on refraction through the front interface of the slab. Figure 1 shows that the requirement of equal phase at the focal point (0, 0, z f ) inside the slab for fields along all geometrical rays from different source points (x , y , 0) via different refraction points (x 00 , y 00 , z 0 ) at the interface z = z 0 is given by (12) where D 11 is the distance from a source point (x , y , 0) in the aperture plane to the corresponding refraction point (x 00 , y 00 , z 00 ) at the first interface, and D 22 is the distance from (x 00 , y 00 , z 00 ) to the focal point (0, 0, z f ), i.e. (see Figure 2)…”

“…Optimization and shaping of the focused intensity distribution are of paramount importance in these applications. Since the first paper on focusing of electromagnetic waves from air through a plane interface was published by Ling and Lee [1], a number of papers related to this topic have appeared [2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Flagello et al [2] considered high numerical aperture (NA) imaging in thin-film stacks employing a scalar approach, while Kant [14] examined the vector diffraction problem of focusing in a multilayered medium.…”

“…Török et al [3][4][5][6] considered essentially the same problem as in [1], but based on the Debye approximation, implying that their results were valid only at sufficiently high Fresnel numbers. Wiersma and co-workers [10][11][12] used the so-called m-theory to obtain the field in the second medium by means of a vectorial approach. The main disadvantage of the Debye approximation is that it will not provide valuable information about focal shifts, which are predicted theoretically [15][16][17][18][19][20][21][22][23][24][25] and observed experimentally [26][27][28] for low Fresnel number systems.…”