azu_td_1349475_sip1_... - Arizona Campus Repository

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A m = e-^sinci^j^t
ij = 0
3.17
and the diffraction efficiency of the m th order is defined as
T]=A mA m 3.18
Solving Equation 3.18, the diffraction efficiency of the m th order of an N phase
level element becomes,
Vm = sin(jjm-0))
i* 1 )
sin^m-ipo))
2
3.19
The primary focus of the diffractive lens occurs in the first order and is the case
of interest. For m=1, ^0=1, Equation 3.19 reduces to the familiar expression
T|=sinc 2 (l/N) 320
Figure 3-9 is a histogram of "H as a function of N which shows that as N
increases, the diffraction efficiency of multilevel element approaches 100%.
3.5 Fabrication
The zone boundaries for the desired N level diffractive lens are
calculated for M masks using Equation 3.9. This data is then converted into a
format that can be read by an electron beam writing machine. The electron
beam writer approximates the circular zones of the diffractive lens by using
chains of multi-sided polygons" 2 and creates a set of binary amplitude masks