LECTURE 22 NOTICE: RECITATION WILL START AT 8 (NOT 9:30) FOR THE REST OF THE TERM (2 MORE WKS) MODES/RESONANCES Fabry-Perot mλ = 2L neff DFB λ = 2Λ neff 2 kλ = 2π 2π 2neff kλ = 2π 2π 2neff With 1/4 segment included λ/4 d = 2λ GENERALIZED COMPARISON OF IPL's + VCSEL's IPL's High Power (Watts) Tunable, mode-locked Not to demanding Difficult to test, package Asymmetrical beam VCSEL's Low power (a few mW) Not to demanding Easy to test, package Symmetrical beam VCSEL ISSUES Active Region QW's are necessary Top 3QW layers (2-3) Series Resistance Lateral Cavity Definition i) Ion implantation ii) High mesa oxidation → Al2O3 No good Imp/Etch due to low aspect ratio Mirror Stack Best: DBR/DBR No good Imp/Etch due to low aspect ratio Achieved are distributed dielectric stacks MATERIALS FOR SPECIFIC RANGES SHORT UV & VISIBLE: GaAlN [II-VI → ZnSeTe] LONG λ VISIBLE: InGaA/InGaA/InGaP InGaP/GaP 0.8-1.0 μm: AlGaAs/GaAs QWs/GaAs InGaAsP/InP 1.3, 1.55 μm: InGaAsP/InP InGaAsP/InP 2-5 μm: AlGaAsSb/GaSb [Pb-Salt] [Pb-Salt] QUANTUM CASCADE 10-30 μm: QUANTUM CASCADE FREQ RESP. OF LASER DIODES dn/dt = G(n-n_th) - S n ds/dt = ΓG(n-n_th)S - S/τ n = n_th [α(t) + βR]

6.772 Lecture 22 Notes

Related Documents

Recommended Documents

Description

Related Documents

Free up your schedule!

Take 5 seconds to unlock