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2.5 Designs for Related Problems of an ESEC LD 75
where
[E 1 E 2 t 1 t 2 (α 1 − α 2 )(t 1 + t 2 )+ E 1 E 3 t 1 t 3 (α 1 − α 3 )(t 1 +2t 2 + t 3 )
+E 1 E 4 t 1 t 4 (α 1 − α 4 )(t 1 +2t 2 +2t 3 + t 4 )
C =3∆Tl 2 +E 1 E 5 t 1 t 5 (α 1 − α 5 )(t 1 +2t 2 +2t 3 +2t 4 + t 5 )
+E 2 E 3 t 2 t 3 (α 2 − α 3 )(t 2 + t 3 )
+E 2 E 4 t 2 t 4 (α 2 − α 4 )(t 2 +2t 3 + t 4 )+ E 2 E 5 t 2 t 5 (α 2 − α 5 )
×(t 2 +2t 3 +2t 4 + t 5 )
+E 3 E 4 t 3 t 4 (α 3 − α 4 )(t 3 + t 4 )+ E 3 E 5 t 3 t 5 (α 3 − α 5 )(t 3 +2t 4 + t 5 )
+E 4 E 5 t 4 t 5 (α 4 − α 5 )(t 4 + t 5 )]
2
[E 1 E 2 t 1 t 2 (t 1 + t 2 ) + E 1 E 3 t 1 t 3 (t 1 +2t 2 + t 3 ) 2
+E 1 E 4 t 1 t 4 (t 1 +2t 2 +2t 3 + t 4 ) 2
2
D =3 +E 1 E 5 t 1 t 5 (t 1 +2t 2 +2t 3 +2t 4 + t 5 ) + E 2 E 3 t 2 t 3 (t 2 + t 3 ) 2
+E 2 E 4 t 2 t 4 (t 2 +2t 3 + t 4 ) 2
2
+E 2 E 5 t 2 t 5 (t 2 +2t 3 +2t 4 + t 5 ) + E 3 E 4 t 3 t 4 (t 3 + t 4 ) 2
2
2
+E 3 E 5 t 3 t 5 (t 3 +2t 4 + t 5 ) + E 4 E 5 t 4 t 5 (t 4 + t 5 ) ]
+(E 1 t 1 + E 2 t 2 + E 3 t 3 + E 4 t 4 + E 5 t 5 )
3
3
3
3
3
×(E 1 t + E 2 t + E 3 t + E 4 t + E 5 t )
5
4
3
1
2
Figure 2.55 shows the deflection of a bimorph MC with the antireflection
(2)
coating, and Au as a parameter. Deflection greater than λ/2 is possible
when Au (2) is thicker than 78 nm for InP (λ =1.3 µm), and thicker than 81
nm for GaAs (λ =0.83 µm) LDs. As a result, the final five-layer MC design
with antireflection and bimorph structures is shown in Table 2.2.
We derived an analytical model for a five-layer semiconductor MC to pre-
dict beam deflection that occurs due to temperature changes caused by a laser
light. We confirmed that the tip deflection of a bimorph MC (0.1-µm gold layer
and a 0.1-µmSi 3 N 4 dielectric layer) with an antireflection coatingis enhanced
by more than a half-wavelength to widen the tunable LD wavelength variation.
1000
Au (1) / Si N (1) /
3 4
Au (2) / Si N 4 (2) /InP
3
800
Deflection (nm) 600 415 (GaAs) (1) (1)
650 (InP)
Au
400
3
/ Si N
Au (2) / Si N 4 4 (2) / /GaAs
3
200
78 81
0
0 50 100 150 200
Thickness of Au (2) film (nm)
Fig. 2.55. Deflection of bimorph MCs with antireflection coating, Au (2) thickness
as a parameter