Dynamic performance and reflection sensitivity of quantum dot distributed feedback lasers with large optical mismatch

This work reports on a high-efficiency In As/Ga As distributed feedback quantum dot laser.The large optical wavelength detuning at room temperature between the lasing peak and the gain peak causes the static,dynamic,and nonlinear intrinsic properties to all improve with temperature,including the lasing efficiency,the modulation dynamics,the linewidth enhancement factor,and consequently the reflection insensitivity.Results reported show an optimum operating temperature at 75°C,highlighting the potential of the large optical mismatch assisted single-frequency laser for the development of uncooled and isolator-free high-speed photonic integrated circuits.

Quantum dot mode-locked frequency comb with ultra-stable 25.5 GHz spacing between 20℃ and 120℃

Semiconductor mode-locked lasers(MLLs)are promising frequency comb sources for dense wavelength-divisionmultiplexing(DWDM)data communications.Practical data communication requires a frequency-stable comb source in a temperature-varying environment and a minimum tone spacing of 25 GHz to support high-speed DWDM transmissions.To the best of our knowledge,however,to date,there have been no demonstrations of comb sources that simultaneously offer a high repetition rate and stable mode spacing over an ultrawide temperature range.Here,we report a frequency comb source based on a quantum dot(QD)MLL that generates a frequency comb with stable mode spacing over an ultrabroad temperature range of 20–120℃.The two-section passively mode-locked In As QD MLL comb source produces an ultra-stable fundamental repetition rate of 25.5 GHz(corresponding to a 25.5 GHz spacing between adjacent tones in the frequency domain)with a variation of 0.07 GHz in the tone spacing over the tested temperature range.By keeping the saturable absorber reversely biased at-2 V,stable mode-locking over the whole temperature range can be achieved by tuning the current of the gain section only,providing easy control of the device.At an elevated temperature of 100℃,the device shows a 6 d B comb bandwidth of 4.81 nm and 31 tones with>36 d B optical signal-to-noise ratio.The corresponding relative intensity noise,averaged between 0.5 GHz and 10 GHz,is-146 d Bc∕Hz.Our results show the viability of the In As QD MLLs as ultra-stable,uncooled frequency comb sources for low-cost,large-bandwidth,and low-energy-consumption optical data communications.