HW5 solutions

HW5 solutions - 4.12 Laser diode efficiency a There are...

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Unformatted text preview: 4.12 Laser diode efficiency a There are several laser diode efficiency definitions as follows: The external quantum efficiency η EQE , of a laser diode is defined as η EQE = Number of output photons from the diode per unit second ( ) Number of injected electrons into diode per unit second ( ) The external differential quantum efficiency , η EDQE , of a laser diode is defined as η EDQE = Increase in number of output photons from diode per unit second ( ) Increase in number of injected electrons into diode per unit second ( ) Th e external power efficiency, η EPE , of the laser diode is defined by η EPE = Optical output power Electical input power If P o is the emitted optical power, show that η EQE = eP o E g I η EDQE = e E g dP o dI η EPE = η EQE E g eV b A commercial laser diode with an emission wavelength of 670 nm (red) has the following characteristics. The threshold current at 25 ° C is 76 mA. At I = 80 mA, the output optical power is 2 mW and the voltage across the diode is 2.3 V. If the diode current is increased to 82 mA, the optical output power increases to 3 mW. Calculate the external QE, external differential QE and the external power efficiency of the laser diode. c Consider an InGaAsP laser diode operating at λ = 1310 nm for optical communications. At I = 40 mA, the output optical power is 3 mW and the voltage across the diode is 1.4 V. If the diode current is increased to 45 mA, the optical output power increases to 4 mW. Calculate external quantum efficiency (QE), external differential QE, external power efficiency of the laser diode. Solution a The external quantum efficiency η EQE , of a laser diode is defined as η EQE = Number of output photons from the diode per unit second ( ) Number of injected electrons into diode per unit second ( ) ∴ η EQE = Optical Power / h υ Diode Current / e = P o / E g I / e = eP o IE g The external differential quantum efficiency , η EDQE , of a laser diode is defined as η EDQE = Increase in number of output photons from diode per unit second ( ) Number of injected electrons into diode per unit second ( ) ∴ η EDQE = (Change in Optical Power) / h υ (Change Diode Current) / e = Δ P o / E g Δ I / e = e E g dP o dI The...
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HW5 solutions - 4.12 Laser diode efficiency a There are...

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