STED Simulation and Analysis
is shaped by a SPP element (VL) into a donut-shaped spot. In this case, we chose a Torlabs objective as an off-the-shelf cat- alog part, as it has a published Black Box available for download that we could use. Some of the other objective manufacturers and sellers offer to supply a Black Box upon request. Te parameters used in the model are summarized in Table 1. Table 2 contains a screenshot of the
Zemax Lens Data Editor, in which each line represents an optical surface. An indepen- dent optical path for each laser is defined by the multiple configurations shown in Table 3. Surface types 1 and 2 (Table 2) pro-
Figure 3: Design task challenges involved in the construction of a STED optical system and the pro- posed solution for each.
or its alternatives is expected. Te project begins with a general description of the optical setup (Figure 1): Te system consists of two single-mode Gaussian lasers of different wavelengths, positioned on the same optical path. Both sources are focused by the same achromatic objective. Te depletion laser effect
Table 1: Technical parameters of the modeled optical system: Input Parameters Excitation Wavelength [nm] 532 10
Beam size at exp(-2) [mm]
Objective
VL topological charge – “m”
Depletion 640 10
TL10X-2P EFL 20 mm, CA 20mm –
VL-209-P-Y-A (m=1)
Table 2: Zemax Lens Data Editor Layout of STED system.
vide an optimized scattering effect to cre- ate a realistic spot size individually for each wavelength. In short, this method converts a geometrical point into a spot with physi- cal dimensions, like a real light source [1]. Te method is especially useful to simu- late single-mode and multimode lasers within complex systems in both sequential and non-sequential modes, where other
methods either completely fail or take a very long time to sim- ulate. Te correct scattering ratio should be defined according to the method described in [1] to achieve a realistic spot size. Surfaces 3 and 4 (Table 2) refer to the VL element manu-
factured on a fused silica window. Surface 4 is a user-defined type of surface used to generate an ideal spiral phase. It is defined by sign for clockwise or counterclockwise azimuthal phase direction and topological charge “m” (number of accu- mulated 2-pi radians in 360o
). Te value of the topological
charge for this surface does not have to be equal to the actual one and can be fractions of an integer (m-1.1, for example). Te important thing is the physical correctness and consis- tency of the model. One must fine-tune the number around the real value and observe the resulting ring until a correct ratio of hole to ring that mirrors the SPP theoretical behavior is achieved.
62
www.microscopy-today.com • 2021 May
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92
