Question

Question 1
A Fabry-Perot etalon consists of a 1 cm thick block of glass, refractive index 1.5, with parallel
faces. The faces are coated so their reflectivity is 0.95. At 500 nm, calculate the following
parameters:
(i) Separation in nm of the transmission peaks at normal incidence.
Half-width of these transmission peaks.
Resolving power of the etalon.

Answer 1

ginen thickness, d=1cm referactive index, n = 1.5 reflectivity, r=0.95=R wandlength, n = 500mm I Separtion of transmission peaks at normal incidance is known as free spectral range & ad F SR.) GREGR = 2 = m (500) 2x10-18 2X 1 x 10-2 = 25 x 10-12 m = 12.5 x 10-12 m = 125x10-m = (1.25X102) *10-9m = 1.25x10-2 nm. » Half adth of thansmission peaks (of) 8 = 4 fein1 (/2) Finonest, F L 3 = Toyo = 1520 I 8=4 sint ( 2 ) = 4 din 1(- 025) =(5-73) Radian 1) Resolving power of etalon- Y= 2 &* a 1520 MIJE IVF x 24 TIX 1920 x 10-2 500x10-9 = 24.5 X105