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<P>Broadband AR for a Cone of Light</P>
+ d4 Q# M; N. D6 i8 S<P>Here we consider a coating on glass that reflects only 0.5% of a cone of light for a range of wavelengths from 420 to 680 nm. The cone axis is normal to the glass. The cone has an F-number of 0.778, which means the half-angle is 40 degrees. An uncoated glass surface reflects 4.4% of this cone of light. We use a feature new to version 3.5: cone-angle targets. As optimization targets we use : K) Y; W2 ^6 a8 f! c
<P><BR>R < 0.5% for wavelengths 420, 425, 430,..., 680 and for a 40-degree cone
) s* b. {# J* v( ?5 A; O4 E# O<P><BR>In TFCalc, these targets are easy to enter by using the "Generate Cone Targets" command on the Options menu of the "Targets - Cone Angle" window. We use TFCalc's needle/tunneling optimization to design the coating from "scratch". That is, we begin the design process with a single thin layer of TiO2 and allow TFCalc to increase the thickness and number of layers in the design. TFCalc finds a 6-layer design in a few minutes. The performance of this design is shown below. The little circles indicate the optimization targets.
: U ~( k& X+ U$ `: M( N* q# z<P>- {) A0 @5 N2 \( w, g6 a2 n; }
<P align=center> </P>7 S1 I6 v& y$ ]/ u9 v& t
<P>Here is the design, starting with the layer closest to glass, and with thicknesses given in nm: </P>8 C5 m0 U9 L) X) C
<P><PRE>TIO2 11.04% o+ F9 G7 } w$ l( x& _
SIO2 44.43& H6 ^; r, H4 C. H& I6 m. i; F4 V
TIO2 34.99
. X- k6 V2 r: ] J, ]SIO2 28.25
. c3 Y! S- I! R9 |3 a$ [" {2 \TIO2 30.465 r0 N9 d( {, w# ?
SIO2 104.92
3 q3 l& E& h2 }$ i% p. v6 Q</PRE> |
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发表于 2005-8-23 14:28:01
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发表于 2005-9-4 22:13:38
