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Unformatted text preview: Tuning an Interference Filter A “one half wavelength” thick interference ﬁlter is speciﬁed to pass green light
from an argon laser of freespace wavelength 514.5 nm at normal incidence. It is com-
posed of parallel layers of refractive indices 1.5 and 1.6 as shown in the ﬁgure. By rotat-
ing this interference ﬁlter it is tuned to pass violet light from an argon laser of freespace
wavelength 488.0 nm. It is now desired to tune the ﬁlter to select the violet light of the V argon laser of freespace wavelength 476.5 nm. Calculate, showing all work, the required angular rotation, Aa, in degrees that
is required to tune from 488.0 nm to 476.5 nm. Express your answer accurately to four signiﬁcant ﬁgures. Put your answer in the space provided. Aa= ° Tuning an Interference Filter
The angular tuning is described by ‘ 2ndcos,6 = mA For one half wavelength ﬁlters at normal incidence
2nd 2 A" and so 2nd = 514.5nm = An For tuning to A1 = 488.0 nm 003,61 2: :1 and so [31 = 18.4692° Parallel glass plates do not affect the ray direction in air. Thus from Snell’s law
1.0 sinal = 1.5 sinﬂl and so a1 = 28.3720°.
For tuning to A2 = 476.5 nm
/\ cosﬁg = A—2- and so ,82 = 22.1588°
n 1.03ina2 = 1.53inﬂ2 and so (12 = 34.4553°. A0: = (IQ-“C21 = ...
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This note was uploaded on 04/29/2008 for the course ECE 4500 taught by Professor Gaylord during the Spring '08 term at Georgia Institute of Technology.
- Spring '08