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CHAPTER 4 46 EXPERIMENTAL FABRICATION PROCEDURE In this chapter, the experimental procedure developed for fabricating diffractive lenses via photolithography is presented. While photolithography is not the only method employed to fabricate diffractive lenses, it is a commonly used method and the one employed in this thesis. Each part of the fabrication process is individually discussed. The final results of the combined processes are then discussed at the end of the chapter. 4.1 Mask Generation The first step in fabricating a diffractive lens by photolithography is to generate a mask set that physically describes the lens. Two, four level diffractive lens designs were produced. One set of lenses was designed to operate at a wavelength of 670 nm and the other to operate at a wavelength of 780 nm. Since the lenses were designed to contain four phase levels, each mask set consisted of two masks with alignment marks which were necessary to achieve proper registration between successive masks. Several different alignment marks were examined for use (Figure 4-1). A common element to each configuration is the use of symmetry ( Since the human eye is very sensitive to detecting asymmetry in a high contrast pattern). 44 Detection of asymmetry in the overlying alignment marks indicates misalignment between successive substrate exposures.
47 B Q B mosiac aligned misaligned aligned misaligned square within a square • • • • • vernier aligned misaligned Figure 4-1 Three different alignment marks. The left column contains the alignment mark pairs. The center column shows the marks when they are aligned with each other. The right column illustrates when the marks are misaligned with respect to each other.
Page 1: INFORMATION TO USERS This manuscrip
Page 5 and 6: DIFFRACTIVE MICROLENSES FOR FIBER O
Page 7 and 8: ACKNOWLEDGEMENTS 3 I would like to
Page 9 and 10: 5 Page 4.3 Photoresist Deposition 4
Page 11 and 12: 7 Page 4-2 Exposure test results fr
Page 13 and 14: ABSTRACT 9 The design, fabrication,
Page 15 and 16: 11 architectures. 3,4 5 8 In all of
Page 17 and 18: 13 microlenses have been presented
Page 19 and 20: 15 element acts as an interface bet
Page 21 and 22: CHAPTER 2 17 LENS PARAMETERS FOR FI
Page 23 and 24: 19 power coupling efficiency, T, be
Page 25 and 26: lens is, 21 NAflber = ^=m^. R R . 2
Page 27 and 28: 2.3 Chromatic Aberration 23 Despite
Page 29 and 30: 25 JL 0.985 0.99 0.995 .005 .015 >r
Page 31 and 32: 27 Propagation Distance (mm) Figure
Page 33 and 34: 29 spherical wave emitted from a po
Page 35 and 36: 31 zones is used, the light from ev
Page 37 and 38: 33 OPD=Jrl+f 2 3 3 The incident pla
Page 39 and 40: 3.3 Multi-level Diffractive Lenses
Page 41 and 42: 37 four level approximation. As the
Page 43 and 44: 39 a) T/N b) t(x) T/N ej2ro|> - I-*
Page 45 and 46: 41 A m = e-^sinci^j^t ij = 0 3.17 a
Page 47 and 48: 43 defining the structure of the le
Page 49: 45 where n is the index of the subs
Page 53 and 54: 49 4.3 Photoresist Deposition Shipl
Page 55 and 56: 51 Kfl A) 0 . . t .. .'i'S'l'lTtj
Page 57 and 58: 53 A. Substrate Preparation: 1. Soa
Page 59 and 60: 55 modulation is calculated using E
Page 61 and 62: Figure 4-5 Photographs from a scann
Page 63 and 64: 59 was taken as the distance the kn
Page 65 and 66: 61 SAMPLE 1 t IMAX=40.37% SAMPLE 2
Page 67 and 68: 63 670 nm Laser diode Microlens Arr
Page 69 and 70: 65 1 Experimental data n Ideal Gaus
Page 71 and 72: 67 /OwQ\ xCX /TK X~X Fiber Figure 5
Page 73 and 74: 5.4 Conclusions 69 The design, fabr
Page 75 and 76: Appendix A: MATLAB PROGRAM
Page 77 and 78: theta=4*lammm/pi/dmm; z=0:100; dg=d
Page 79 and 80: 75 4" MASK 1" SQUARE CENTER I NOTES
Page 81 and 82: TWP67 V=2mm H=5mm, 77 TWD671 BL1 AM
Page 83 and 84: 15 J.Jahns and A. Huang, "Planar in
Page 85: "J.L. Vossen and W. Kem, Thin Film

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