TWO-STATE LASING in INJECTION MICRODISK LASERS with INAS/GAAS QUANTUM DOT ACTIVE REGION

This paper is dedicated to the investigation and analysis of the characteristics of two-state lasing in microdisk lasers with InAs/GaAs and InAs/InGaAs quantum dots (QD). The first demonstration of the two-state lasing phenomena in injection microdisk lasers with InAs/GaAs quantum dots is presented. The dependence of lasing threshold currents on the diameter of the disk resonator is investigated. It is revealed that the InAs/GaAs QD structure exhibits low threshold currents for two-state lasing. The temperature evolution of the lasing threshold characteristics is studied, showing that threshold current densities increase with temperature for both ground-state and excited-state transitions, distinguishing InAs/GaAs from InAs/InGaAs quantum dots. High-temperature stability is demonstrated in InAs/GaAs microdisk lasers, with lasing observed up to 90°C for 24 µm microdisks and up to 110°C and 120°C for 12 µm and 32 µm microdisks, respectively. The ability to control two-state lasing threshold currents by varying the area of the top electrical contact is shown for the first time. Using focused ion beam etching, the upper contact of InAs/InGaAs microdisk lasers was segmented into sections with different area ratios and etch depths of 500, 1000, 1500, and 2000 nm. It is shown that reducing the section areas for 24 µm and 28 µm microdisk lasers results in decreased threshold current values for excited-state lasing and slight increases in threshold currents for ground-state lasing. The temperature evolution of lasing in a microdisk laser with a separated upper electrical contact is investigated. It is shown that critical temperature at which two-state lasing disappears is similar for small and large sections of a single microdisk with shallow etching depths. The influence of etching depth on the dependence of diode series resistance on the area of the upper split contact section is examined. A nearly 100 mA reduction in two-state lasing threshold current is demonstrated for a 28 µm microdisk laser with a section area ratio of 1:2 and an etching depth of 1500 nm. Pumping different sections within one microlaser also results in different lasing modes.