Since its introduction, the edge-emitting laser (EEL) technology has continued to set new records for power conversion efficiency (PCE), reaching an all-time high of 85% at -50°C in 2006. Subsequently, in 2007, EEL also achieved a high efficiency of 76% at room temperature. However, in the 15 years that followed, no one set a new efficiency record, and these achievements have been the pinnacle of semiconductor lasers.
In contrast, the efficiency of vertical-cavity surface-emitting lasers (VCSELs) has been slower. There has been no major breakthrough since 2009, when the highest PCE of 62% was reported, highlighting the apparent performance gap between VCSELs and EELS. As a microcavity laser, achieving efficient conversion in the field of photonics has always been a challenge for VCSELs.
Application prospect of high-efficiency VCSEL in green energy photonics
Due to the lower power and efficiency, the early applications of VCSELs were mainly focused on the field of small, low-power consumer electronics and short-range communications in data centers. In recent years, with the development of intelligent technology, low-power VCSELs have become the key core light source chips of intelligent sensing systems, and have been widely used in the fields of face recognition and short-range sensing, and have achieved remarkable results.
Recently, the rapid development of advanced AI technologies has revealed the great potential of VCSELs in areas such as sensing, communications, atomic clocks, optical/quantum computing, topological lasers, and medical diagnostics. In particular, the need for long-range sensing technology for autonomous driving, the need for AI computing power in high-speed data processing centers, and the development of VCSELs in the field of intelligence and quantum technology applications all highlight the importance of energy consumption as a core issue.
The energy efficiency of VCSELs has a significant impact on the energy consumption of mobile devices and data centers. Therefore, the development of ultra-energy-efficient VCSELs is essential to support the development of terminal devices in the future intelligent era and play an important role in advancing the development of photonics for green energy.
In a new paper published in Light: Science & Applications, a research team led by Professor Jun Wang from the School of Electronic Information at Sichuan University and Changguang Huaxin has achieved a breakthrough in VCSEL efficiency using multi-junction cascaded active region technology.
Principle of multi-junction cascaded vertical cavity surface-emitting lasers
By using a reverse tunnel junction to cascade the active region, the gain volume is increased. This design strategy allows the carriers to undergo multiple stimulated emission processes, which not only improves the differential quantum efficiency of the device, but also keeps the threshold current low.
As a result, in recent years, a large number of researchers have achieved exponential power gains using multi-junction VCSELs, making VCSELs a viable laser source for LiDAR for autonomous vehicles. However, the biggest potential advantage of multi-junction VCSELs should be their significant efficiency gains.
Therefore, we conducted a systematic study combining theoretical simulations and experiments to explore the advantages of multi-junction VCSELs in terms of wall-plug conversion efficiency.
The research team simulated the scaling characteristics of a multi-junction VCSEL and compared it with the scaling characteristics of a single-junction VCSEL. Numerical simulations show that the wall-plug conversion efficiency of 20-junction VCSELs can exceed 88% at ambient temperature.
In the experiment, the 15-junction VCSEL has an electro-optical conversion efficiency of 74% and a slope efficiency of 15.6W/A at room temperature, which is equivalent to a differential quantum efficiency of more than 1100%. According to the researchers, this wall-plug efficiency is the highest ever reported in the VCSEL field, and this differential quantum efficiency is also the highest reported in the field of semiconductor lasers.
Summary of the wall-plug conversion efficiency of semiconductor lasers
As the reviewer put it, "This is indeed a major breakthrough in an area that has been stagnant for a long time." ”
"In the future, we also plan to explore and expand the application of high-efficiency, high-power multi-junction VCSELs in the field of communications," the study's authors wrote. This study not only provides a valuable theoretical and experimental basis for the further optimization and application of VCSELs, but also provides a valuable reference for the further development and application of high-PCE semiconductor lasers. It is expected to have a significant impact on green energy photonics and laser physics. ”
The above content is from the world of light
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