We present an experimental investigation on the period-one dynamics of an optically injected InAs/GaAs quantum dot laser as a photonic microwave source. It is shown that the microwave frequency of the quantum dot laser's period-one oscillation is continuously tunable through the adjustment of the frequency detuning. The microwave power is enhanced by increasing the injection strength providing that the operation is away from the Hopf bifurcation, whereas the second-harmonic distortion of the electrical signal is well reduced by increasing the detuning frequency. Both strong optical injection and high detuning frequency are favorable for obtaining a single sideband optical signal. In addition, particular period-one oscillation points of low sensitivity to the frequency detuning are found close to the Hopf bifurcation line.

By optically injecting a quantum dash laser and simultaneously producing a significant lowering of the device threshold, a large enhancement in the differential gain is realized. This effect is observed by way of a dramatic reduction in the linewidth enhancement factor and a large increase in the 3-dB modulation bandwidth, especially as the injection wavelength is blue-shifted. Compared to its free-running value, a 50X improvement in the laser's differential gain is found.

International audienceA dual-mode laser operating in the excited states (ESs) of a quantum dot is realized by combining asymmetric pumping and external optical feedback stabilization. In generating two single-mode emission peaks, a mode separation ranging from 1.3-THz to 3.6-THz is demonstrated over temperature. This effect is attributed to the unique carrier dynamics of the quantum-dot gain medium via the excited state inhomogeneous linewidth coupled with a proper external control. These results are particularly important towards the development of future THz optoelectronic sources with compact size, low fabrication cost, and high performance

The timing jitter performance of a 5 GHz quantum dot passively mode-locked laser is investigated at different harmonics in the RF spectrum. The necessity of measuring the phase noise at relatively large harmonic numbers is motivated experimentally in the context of determining the corner frequency, its correlation to the RF linewidth, and the related white noise plateau level. The single-sideband phase noise with an integrated timing jitter of 211 fs (4-80 MHz) is reported. An all-microwave technique has been used to determine a pulse-to-pulse rms timing jitter of 96 fs/cycle. This low timing jitter value makes the chip-scale quantum dot mode-locked laser an attractive source for low noise applications such as optical clocking and sampling.

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Simultaneous generation of microwave and millimeter-wave (mm-wave) signals is demonstrated experimentally using a 1310-nm Quantum Dot (QD) Distributed-Feedback (DFB) Laser. The reported technique is based on the period-1 dynamics and dualmode lasing induced in the laser device under external optical injection. Tunability of the generated microwave and mm-wave signals is obtained. Furthermore, abrupt switching between different frequency regimes in the microwave and mm-wave bands is also observed. These novel frequency switching mechanisms added to the tuning capability of the system offers exciting prospects for novel uses of QD lasers in ultra-high frequency applications. Our approach also benefits from a simple experimental configuration using basic optical fibre components making our technique totally compatible with optical telecommunication networks.

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Articles you may be interested inTuning the external optical feedback-sensitivity of a passively mode-locked quantum dot laser Appl. Phys. Lett. 105, 041112 (2014); 10.1063/1.4891576Effect of the number of quantum dot layers and dual state emission on the performance of InAs/InGaAs passively mode-locked lasers