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In this paper, performance of monolithic quantum dot passively mode-locked lasers over broad temperature excursions is characterized. It is shown that there is a linear dependence between absorber to gain length ratio and the characteristic temperature that a device transitions from ground-state to excited-state lasing when the saturable absorber is grounded. The pulse shape and optical spectrum characteristics are examined in detail around these transition regimes. Experimental operational maps have also been constructed showing the range of biasing conditions that produce stable mode-locking across a wide range of temperatures. A comparison is made between regions of mode-locking stability for two devices having the same absorber to gain length ratio, with varying ridge waveguide widths. Finally, gain and absorption characteristics are derived from measurements of amplified spontaneous emission, and a correlation between reduced values of unsaturated absorption and reduced time-bandwidth product is shown. Key features in the experimental operational maps and their respective significance on the operation and design of future devices is discussed.

In this paper, we investigate the dynamics of a nonlinear delay differential equation model for passive mode-locking in semiconductor lasers, when the delay model is seeded with parameters extracted from the gain and loss spectra of a quantum dot laser. The approach used relies on narrowing the parameter space of the model by constraining the values of most of the model parameters to values extracted from gain and loss measurements at threshold. The impact of the free parameters, namely, the linewidth enhancement factors that are not available from the gain and loss measurements, on the device output is then analyzed using the results of direct integration of the delay model. In addition to predicting experimentally observed trends such as pulse trimming with applied absorber bias, the simulation results offer insight into the range of values of the linewidth enhancement factors in the gain and absorber sections permissible for stable mode-locking near threshold. Further, the simulations show that this range of permissible values progressively decreases with increasing bias voltage on the absorber section. This is important for telecomm and datacom applications where such devices are sought as pulsed sources, as well as in military RF photonic applications, where mode-locked diode lasers are used as low noise clocks for sampling.

This paper examines and models the effect of temperature on the mode-locking stability of monolithic two-section InAs/GaAs quantum dot passively mode-locked lasers. A set of equations based on an analytic net-gain modulation phasor approach is used to model the observed mode-locking stability of these devices over temperature. The equations used rely solely on static device parameters, measured on the actual device itself, namely, the modal gain and loss characteristics and describe the hard limit where mode-locking exists. Employment of the measured gain and loss characteristics of the gain material over temperature, wavelength and current injection in the model provides a physical insight as to why the mode-locking shuts at elevated temperatures. Moreover, the model enables a temperature-dependent prediction of the range of cavity geometries (absorber to gain length ratios) where mode-locking exists. Excellent agreement between the measured and the modeled mode-locking stability over a wide temperature range is achieved for an 8-stack InAs/GaAs mode-locked laser. This is an extremely attractive tool to guide the design of monolithic passively mode-locked lasers for applications requiring broad temperature operation.