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(a) Schematic diagram of a DFB TL with native oxide confinement and a surface grating over the active region having a width . The total device length is . (b) SEM image of the front facet of the device showing the edge oxide confinement layer (2) and the grating etched into the upper emitter AlGaAs cladding layer (1). The grating region is backfilled with benzocyclobutene (BCB) dielectric to facilitate emitter contact formation.
Collector characteristics of the DFB TL of Fig. 1 ( emitter) operated at . Threshold occurs at base current and current gain , the compression typical of a TL. The inset plot of vs with collector-base bias shows a reduction in gain from 3.2 to 2.9 at threshold.
Comparison of the CW operation optical emission intensity as a function of base current from a single-facet of the DFB-TL (black lines) and a FP TL (gray lines) operating at with . Bias points (a) and (b) correspond to the data of Fig. 4. The dotted lines are a plot of single-facet output slope efficiency for each device. Both devices have dimensions of .
(a) CW operation recombination radiation spectra corresponding to the characteristics of the DFB-TL of Fig. 2 at a base current of and collector to emitter bias of . Plot (b) shows the multimode spectrum of the FP TL of Fig. 3 operated at and .
CW stimulated emission spectra for various base bias currents (, 19, and 25 mA) above laser threshold for the DFB-TL of Fig. 2. The total wavelength shift in the peak output is 0.24 nm .
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