Waveguide structures for quantum well (QW) lasers are analyzed numerically by a straightforward 2×2 matrix approach. It is shown that this approach is capable of analyzing separate-confinement heterostructure (SCH) waveguides, having any arbitrarily graded-index (GRIN) profile in the waveguide layers and any number of QWs in the active layer, to any desired level of accuracy. Using this waveguide analysis, general GRIN-SCH waveguide structures of QW lasers can be optimized for maximum confinement factors. It is estimated that the laser threshold current density can be reduced typically by 10% as a result of this waveguide optimization.
We propose and demonstrate a photonic integrated tunable receiver which cascades a traveling-wave optical preamplifier, a passive tunable grating-assisted codirectional coupler filter, and a waveguide photodetector. The devices contain three strained InGaAs quantum wells and operate around λ=0.98 μm. The spectral responses have been measured using the broadband spontaneous emission from the integrated amplifier. Optical filters ∼4-nm wide, ∼10-nm apart with grating pitches ranging from 7.4 to 10.6 μm were observed. Wavelength selective photodetection of a channel ∼3-nm wide, tunable over 4.3 nm with a reverse bias is in relatively good agreement with theory.
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