A Novel Metal-Dielectric Film Mode Filter for Enhanced VCSEL Performance

Researchers from the Changchun Institute of Optics, Fine Mechanics and Physics at the Chinese Academy of Sciences have discovered a novel metal-dielectric film mode filter structure that can flexibly regulate transverse modes in vertical-cavity surface-emitting lasers (VCSELs). This study demonstrates the potential of using metal apertures to enhance mode control within VCSELs. The research was published in the journal Sensors.

Traditional oxide-confined VCSELs often encounter challenges such as increased series resistance and reduced output power during single-mode operation. To overcome these limitations, researchers have introduced an effective mode filtering technique using metal apertures.

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

Specifically, when the number of P-DBRs was low, the transverse optical field was strongly confined within the metal aperture. However, as the number of P-DBRs increased, this confinement weakened, affecting the laser's mode control.

The optical scattering effect intensified as the distance between the metal and oxide apertures decreased, particularly when the metal aperture was smaller than the oxide aperture. This led to better single-mode stability due to increased mode discrimination and higher modal loss. Conversely, when the metal aperture was larger than the oxide aperture, the oxide aperture predominantly controlled the optical mode, highlighting the complex interaction between the two apertures in determining mode discrimination and optical field confinement.

The researchers introduced a new concept, optical gain, to describe how optical scattering within the structure affects the threshold gain of different transverse modes. By optimizing the balance between the optical gain differential across modes and the optical gain of the fundamental mode, they identified structural parameters that significantly enhanced the MMF-VCSEL's single-mode stability and slope efficiency.

The VCSEL structure with a metal mode filter represents a significant advancement in optical mode control. Researchers have demonstrated the potential for high-power, single-mode VCSELs with enhanced performance by dynamically adjusting the transverse mode.

This study highlights the critical role metal apertures play in improving VCSEL mode control, opening up new possibilities for the development of high-performance VCSELs with a wide range of applications.

Journal Reference:

Mu, J., et al. (2024) Simulation of Modal Control of Metal Mode-Filtered Vertical-Cavity Surface-Emitting Laser. Sensors. doi.org/10.3390/s24144700.