Gain spectra measured by HakkiPaoli method

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Gain spectra measured by Hakki-Paoli method

• Literature introduction
• 2007-3-27
• Shu-man Liu

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Gpeak superlinearly
Net mode gain
Electronic mode gain ?Ge
(? mode loss)

• I ?, G at fixed ? linearly ?, Gpeak blueshift

• Above Ith, G at long ? decrease G at short ?
  still increase, due todifferent change of n with
  I for ?.

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Net modal gain
Modal group index
1.The accuracy near the peak was checked by
extrapolating the net peak gain vs current to
zero. Comparing this I to Ith indicates 1cm-1 .
Block emission from substrate
2.No step-like gain no hh and lh
transitionsimplies lifetime broadening due to
rapid intrabandscattering.
Flat tail efficient spatial andangular
filtering
3.Nonlinear of g-I affectspassive
modelockingand self-pulsation
4.ng 3.87 (1.455 eV)?ng/ ?? -3.44 ?m-1
(GaAs -2.9 -20 ) Applications optical
amplification or modelocking
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Limited gainin 1 QW
Range of 5cm-1
1 QW ?EF gtgt lowest states When EF penetrate the
band, gain is limited by step-like DOS, thus
flattens, larger N imply broad gain curve and
peak gain shift. Other mechanisms such as
thermally activated losses, carrier recom at
higher levels, or leakage are negligible.
Gain flattening
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Relation between net gain and ASE
P1 single pass ASE intensity gnet g - ?Is
spontaneous emission rate per volume A cross
section
C0 and C1 can be obtained through the linear
relationshipof p(E) and q(E).
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