All III-Arsenide Low Threshold InAs Quantum Dot Lasers on InP(001)
Jinkwan Kwoen, Natalia Morais, Wenbo Zhan, Satoshi Iwamoto and Yasuhiko Arakawa
This study investigates the development of InAs quantum dot (QD) lasers on a InP(001) substrate, utilizing only III-arsenide layers. This approach avoids the issues associated with the use of phosphorus compounds, which are evident in the crystal growth of conventional C/L-band QD lasers, making the manufacturing process safer, simpler, and more cost-effective. The threshold current density of the fabricated QD laser was 633 A/cm2, which is the lowest value for QD lasers in the 1.6 μm-wavelength region. This result suggests a high cost-effectiveness and paved the way toward a large-scale production technology for high-performing C/L/U-band QD lasers.
Introduction: Conventional-band (C-band) and long-band (L-band) lasers used in optical communications are prevalent for long-distance communication due to their minimal loss within optical fibers. These lasers play a crucial role in enabling high-speed data transmission over long distances [1, 2]. The potential applications of lasers extend beyond traditional optical communications. Advancements in laser technology have opened new possibilities, such as their use as gain media for silicon photonics and as nonlinear optical components for quantum computing[3, 4]. These emerging fields require lasers with specific properties and capabilities. Quantum dot (QD) lasers have attracted considerable interest in recent years due to their unique characteristics. They exhibit features such as low threshold current density, high-temperature stability, and exceptional emission efficiency [5–7]. These attributes make them promising candidates for various applications. InAs QDs on InP substrates have been extensively researched for C/L-band QD lasers [8–10]. The combination of InAs quantum dots and InP substrates has shown great potential for achieving efficient lasing in the C and L wavelength bands.
However, it is generally standard to concurrently use group V materials, arsenic and phosphorus, in the crystalline growth of C/L-band quantum dot lasers via molecular beam epitaxy. The use of indium materials in fabrication presents several challenges. The production of white phosphorus, which is both spontaneously combustible and toxic, complicates the manufacturing process and poses safety risks. Further, the need for additional phosphorus supply equipment such as cells, pumps, and safety traps increase both cost and process complexity. Moreover, there is a need for precise control over the phosphorus and arsenic mix during crystal growth. These issues can be mitigated by using only Group III-Arsenide (III-As) materials. Without using phosphorus, the manufacturing process becomes safer, simpler, and cost-effective.