Room temperature optical constants of plastic materials have been measured over the 50–350-cm−1 spectral range. The materials reported include high density polyethylene, TPX, Aclar, Kapton, Surlyn, and Mylar. All except TPX are available in sheet form and exhibit birefringence as a consequence of Stretching during the manufacturing process. Only the average of the two sets of optical constants is reported for each material. The refractive index was calculated from the channeled spectrum as observed in reflection from the sample, while the absorption coefficient was determined, in all cases but polyethylene, from a transmission measurement.
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The refractive index is constant to within the experimental uncertainty of 0.1%. The uncertainty in the absorption coefficient is substantially larger, about 10%.
There is indication of an additional absorption peak below 50 cm−1, which was not observed in either work. Our absorption curve rises below 85 cm−1, but the peak apparently lies outside our region of observation.
Uncertainty in index is 0.3% (systematic) resulting from a similar accuracy in the thickness of the sample. Uncertainty in the absorption coefficient is 5%.
Estimated uncertainty in refractive index is 0.1%, in absorption coefficient 5%.
Table VII
Optical Constants of Mylar (Polyethylene Terephthalate)a
Wave-number (cm−1)
Refractive indices
Absorption coefficients
σ
n1
n2
α1
α2
50
1.717
1.752
13
13
60
1.715
1.756
28
21
70
1.712
1.762
36
27
80
1.710
1.761
45
40
90
1.703
1.750
55
50
100
1.694
1.744
52
45
110
1.692
1.746
46
42
120
1.697
1.750
47
48
125
1.753
51
55
130
1.696
1.754
57
68
135
1.741
63
84
140
1.688
1.727
67
123
145
1.720
60
83
150
1.682
1.716
55
75
160
1.684
1.721
49
59
170
1.688
1.727
52
58
180
1.688
1.728
60
65
190
1.687
1.729
64
69
200
1.688
1.729
62
66
210
1.691
1.732
65
64
220
1.693
1.736
75
68
230
1.691
1.737
91
77
240
1.686
1.736
95
87
250
1.686
1.736
91
87
260
1.688
1.737
95
90
270
1.688
1.740
106
99
280
1.688
1.742
120
110
290
1.688
1.742
122
118
300
1.691
1.744
122
109
310
1.697
1.747
127
112
320
1.705
1.750
133
119
330
1.713
1.752
138
132
340
1.721
1.753
144
151
Estimated uncertainty in the index is 0.1%, in absorption coefficient 3%. These data are shown graphically in Figs. 8 and 9 of Ref. 1. In this case both accessible optical constants are tabulated to maintain consistency with the illustrations.
The refractive index is constant to within the experimental uncertainty of 0.1%. The uncertainty in the absorption coefficient is substantially larger, about 10%.
There is indication of an additional absorption peak below 50 cm−1, which was not observed in either work. Our absorption curve rises below 85 cm−1, but the peak apparently lies outside our region of observation.
Uncertainty in index is 0.3% (systematic) resulting from a similar accuracy in the thickness of the sample. Uncertainty in the absorption coefficient is 5%.
Estimated uncertainty in refractive index is 0.1%, in absorption coefficient 5%.
Table VII
Optical Constants of Mylar (Polyethylene Terephthalate)a
Wave-number (cm−1)
Refractive indices
Absorption coefficients
σ
n1
n2
α1
α2
50
1.717
1.752
13
13
60
1.715
1.756
28
21
70
1.712
1.762
36
27
80
1.710
1.761
45
40
90
1.703
1.750
55
50
100
1.694
1.744
52
45
110
1.692
1.746
46
42
120
1.697
1.750
47
48
125
1.753
51
55
130
1.696
1.754
57
68
135
1.741
63
84
140
1.688
1.727
67
123
145
1.720
60
83
150
1.682
1.716
55
75
160
1.684
1.721
49
59
170
1.688
1.727
52
58
180
1.688
1.728
60
65
190
1.687
1.729
64
69
200
1.688
1.729
62
66
210
1.691
1.732
65
64
220
1.693
1.736
75
68
230
1.691
1.737
91
77
240
1.686
1.736
95
87
250
1.686
1.736
91
87
260
1.688
1.737
95
90
270
1.688
1.740
106
99
280
1.688
1.742
120
110
290
1.688
1.742
122
118
300
1.691
1.744
122
109
310
1.697
1.747
127
112
320
1.705
1.750
133
119
330
1.713
1.752
138
132
340
1.721
1.753
144
151
Estimated uncertainty in the index is 0.1%, in absorption coefficient 3%. These data are shown graphically in Figs. 8 and 9 of Ref. 1. In this case both accessible optical constants are tabulated to maintain consistency with the illustrations.