Abstract-We have investigated experimentally the pulse train (mode beating) stability of a monolithic mode-locked multi-section quantum-dot laser with an added passive auxiliary optical fiber cavity. Addition of the weakly coupled ( 24 dB) cavity reduces the current-induced shift of the principal peak in the RF spectrum (the effective pulse repetition frequency) by more than an order of magnitude, from 39 5 to 2 3 kHz/mA. The rms timing jitter of the pulse train is simultaneously reduced from 1.4 to 0.9 ps.
We present calculations for the band structure of bulk and confined quantum well and quantum wire GaInNAs structures. To treat this non-randomly alloyed material system we follow previous approaches in using an Anderson impurity model where the nitrogen localized states interact with the GaInAs conduction band states. We solve this model using Matsubara Green's functions and the associated self-energies which produce a complex band structure where both the real and imaginary components depend on the concentration of nitrogen. In particular this approach gives a definite nitrogen dependent lifetime broadening and is different from previous work in that no artificial input parameters are used. The density of states of the conduction band, derived from these functions, is strongly altered by interaction with the nitrogen states. The density of states is required for further optical and transport investigations involving this system.
We present theoretical results on steady state characteristics in bulk GaAs1−xNx alloys (x ≤ 0.2) using the single electron Monte-Carlo method. Two approaches have been used; the first assumes a GaAs band with a strong nitrogen scattering resonance and the second uses the band anti-crossing model, in which the localized N level interacts with the GaAs band strongly perturbing the conduction band. In the first model we observe two negative differential velocity peaks, the lower one associated with nitrogen scattering while the higher one with polar optical phonon emission accounting for the nonparabolicity effect. In the second model one negative differential velocity peak is observed associated with polar optical phonon emission. Good agreement with experimental low field mobility is obtained from the first model. We also comment on the results from both Models when the intervalley Г → L transfer is accounted for.
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