A study led by researchers from the Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, has successfully demonstrated the potential of metal apertures in enhancing mode control within Vertical-Cavity Surface-Emitting Lasers (VCSELs). Published in Sensors, the research paper titled "Simulation of Modal Control of Metal Mode-Filtered Vertical-Cavity Surface-Emitting Laser" details a novel metal-dielectric film mode filter structure that can flexibly regulate transverse modes in VCSELs.

The study addresses the challenges of achieving single-mode output in VCSELs, which are crucial for applications such as optical storage, laser printing, and 3D sensing. Traditional oxide-confined VCSELs often struggle with increased series resistances and low output power when operating in single mode. To overcome these limitations, researchers proposed using metal apertures as an effective mode filtering technique.

The research team developed a finite element simulation model of a metal mode-filtered VCSEL (MMF-VCSEL) using COMSOL software. The simulations revealed that the modal control performance of the MMF-VCSEL is significantly influenced by the number of P-Distributed Bragg Reflector (P-DBR) pairs, metal aperture size, and oxide aperture size.

Key findings indicate that when the metal aperture is smaller than the oxide aperture, the optical scattering effect is intensified as the distance between the two apertures decreases. This results in increased mode discrimination and modal loss, facilitating better single-mode stability. The simulations also showed that the transverse optical field is strongly confined within the metal aperture when the number of P-DBRs is low, but the confinement weakens as the number of P-DBRs increases.

The study introduces a new parameter, optical gain, which characterizes the change in threshold gain of different transverse modes due to optical scattering by the structure. By balancing the optical gain difference between modes and the optical gain of the fundamental mode, researchers identified optimal structural parameters that enhance both single-mode stability and slope efficiency of the MMF-VCSEL.

Moreover, the study found that when the metal aperture exceeds the oxide aperture, the optical mode in the VCSEL is primarily controlled by the oxide aperture. This finding highlights the complex interplay between metal and oxide apertures in determining optical field confinement and mode discrimination.

The development of this metal mode-filtered VCSEL structure represents an important advancement in optical mode control. By flexibly modulating the transverse mode, researchers have demonstrated the potential for high-power, single-mode VCSELs with improved performance characteristics. The study's theoretical basis and simulation methods provide a valuable reference for future research and applications in VCSEL technology.

In conclusion, the research underscores the critical role of metal apertures in enhancing mode control in VCSELs. By optimizing key structural parameters, researchers have opened up new avenues for developing high-performance VCSELs with applications spanning various industries. The study's findings hold important real-world implications, contributing to the advancement of optoelectronic devices and technologies.