azu_td_1349475_sip1_... - Arizona Campus Repository

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modulation is calculated using Equation 3.22,
du = —^—
2>-l). 4-1
In this case, M equals one since only one mask is necessary to produce a
binary lens. The index of refraction of Shipley 1811 photoresist at 670 nm is
approximately equal to 1.64* Thus the necessary photoresist thickness is 0.52
|im for a wavelength of 670 nm and a thickness of 0.61 |im for a wavelength of
780 nm. The photoresist thickness was tailored to be close to these thickness
values using the spinning parameters discussed in section 4.4.
A portion of one of the resulting lens arrays produced is shown in Figure
4-4. The ring structure of the binary photoresist lenses from this 4x4 array is
clearly evident. Each lens in the array has 500 nm diameter, 59 zones, and a f-
number of 3.5. More detailed information on the lens structure obtained from a
scanning electron microscope is provided in Figure 4-5. The optical
performance of these binary lenses will be discussed in chapter five.