Significant advances are needed to improve the speed and efficiency of future communication and computing systems. Photonic interconnect components are the only solution to offer both high speed and low power consumption. Micro-lasers (i.e. vertical-cavity surface-emitting lasers, VCSELs) have been widely deployed as optical interconnects in the last two decades. This technology has been very successful and demonstrated exponential growth in recent years mainly for 3D sensing applications, which is very different from its traditional use. However, the processing approach of this technology has been proven to be particularly challenging for miniaturization, it reduces the reliability for small devices and its high thermal resistance substantially degrades the device performance. Besides, this technology is based on a non-planar structure that is inconvenient for array fabrication as it limits the density of arrays needed for high brightness.
To address these bottlenecks and realize high-performance semiconductor light sources with CW operated current injection at room temperature, flexible and precise control of photonic confinement with a high Q-factor cavity is essential. For this purpose, lithographically defined laser diodes are introduced in which the vertical-cavity, transverse optical confinement, and electrical confinement were enabled by epitaxial growth and lithography. The objectives of this project were based on using a lithographically defined laser concept to develop a novel growth and fabrication process for GaAs-based nanoscale vertical emitting lasers (NOVEL). NOVEL employed a buried electrical- and optical-confinement method to scale the transverse cavity size down to 500 nm diameter. We have designed laser epitaxial structures, developed fabrication and characterization methods for NOVEL devices. Additionally, we established NOVEL array architectures to obtain significantly increased laser beam quality and brightness for applications in 3D sensing and LiDARs.
The fundamental optical properties and versatile advantages of NOVEL cavity structures were analyzed using numerical modeling techniques. Using this cavity approach, we investigated the effect of size on the quality factor (Q-factor) for both micro-scale and sub-wavelength sizes. The limits of emission wavelength tuning with lateral size control were analyzed. We extended the modeling study to large sizes to explore the large emission apertures in order to obtain a high-power single-mode operation.
The results are expected to have a strong impact in academia, industry, and society as it opens a way for a completely new approach enabling novel photonic technologies. The NOVEL devices, with their fundamentally new capabilities, hold special promise in a wide range of multi-disciplinary areas such as optical communication, computer science, on-chip nanophotonics, and LiDARs.
