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Unformatted text preview: Gallium Arsenide Slab Waveguide - Parameters A heterostructure semiconductor slab waveguide is fabricated by molecular beam
epitaxial growth of layers of the ternary alloy semiconductor AlzGa1_1As. The wave-
guide structure consists of a 1.000 pm thick layer of GaAs surrounded by a 500 pm thick
cover of Alo,40Ga0.60As and a 500 um thick substrate of AloaoGaOJO/is. The GaAs ‘ layer acts as the “ﬁlm” of the slab waveguide and has a refractive index of TL}: 2 3.4210.
The waveguide guides light in the GaAs layer. The Al0,4oGa0.60As layer has a refractive
index of no 2 3.2617. The Alo.3oGa0.70As layer has a refractive index of n5 : 3.2998.
Since the thicknesses of the cover and substrate are very large compared to the wave-
length of the light, these regions may be treated as if they are semi—inﬁnite in thickness. Both TE and TM modes can be excited in the waveguide. For the TED mode and the TMO mode in this waveguide, calculate, showing all
work, the asymmetry parameters (arm;0 and aTMo), the normalized cut—off frequencies
(VTE0 and VT M0), and the cut-off wavelengths (ATEo and ATMO). Express cut-off wave-
lengths in nm. Express all answers accurately to six signiﬁcant ﬁgures. Put your ﬁnal answers in the spaces provided below. aTEo :
VTEO = VTM0 = ATMO = _____________ nm Gallium Arsenide Slab Waveguide - Parameters nc = 3.2617 nf = 3.4210 72.5 = 3.2998 h=1.000,um
2_ 2 arm; 2 n; "g = 0.306905
“4 2_ 2 am: -§ “3 “g = 0.371399
nc nf—na VTE0 = tan-1 GTE 0.505902 I VTMO = tan‘lvaTM = 0.547321 A 27mm; ~ 7291’” 2” (“3" “91/2 11209223
TEo " T “ W— ‘W — ' W 27rh (n2 — n2)”2 27rh ('n2 —— n2)”2
A z __f____s_ = ___f—3_ : 10.360950
TMo VIIMO tan—1 IaTM Hm ...
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- Spring '08
- Wavelength, Gallium arsenide, molecular beam epitaxy, Gallium nitride, Thin film