Characteristics of Passively Mode-Locked Quantum Dot Lasers from 20 to 120 ℃

摘要

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