image: Figure.1 | Tailoring VCSEL performance through cavity geometry engineering. (a) Five distinct cavity geometries—circular, square, D-shaped, mushroom, and pentagonal—enable control over the output waveform and modal properties of VCSELs. (b) Near-field emission profiles from fabricated devices highlight differences in spatial mode structure across geometries. (c) SEM image of the fabricated VCSEL array, showing precise lithographic patterning of the various cavity shapes. (d) Statistical comparison of maximum optical power across over 60 devices, showing enhanced emission from non-circular geometries, especially the pentagonal and mushroom designs. (e) Demonstration of speckle suppression using a mushroom-shaped VCSEL, leading to improved image contrast in a resolution target compared to a conventional circular VCSEL.
Credit: Boon S. Ooi et al.
Vertical-cavity surface-emitting lasers, or VCSELs, are compact and energy-efficient light sources ubiquitous in smartphones, autonomous vehicles, and optical networks. However, their performance has long been limited by their conventional symmetric circular cavity design.
Now, in a study published in Light: Science & Applications, the Photonics Lab led by Prof. Boon Ooi at King Abdullah University of Science and Technology (KAUST) has demonstrated that reshaping the geometry of VCSEL cavities into non-circular forms, such as pentagonal, mushroom, square, and D-shaped outlines, can fundamentally improve their performance by redefining the boundary condition of eigenmodes, introducing new functionalities accordingly.
“The geometry of the cavity determines how light evolves inside the laser. By breaking circular symmetry, we can unlock hidden performance potential,” explains Prof. Ooi.
Among the five designs studied, the pentagonal VCSEL stood out with over twice the power density of traditional circular VCSELs and the fastest polarization dynamics, making it promising for applications such as parallel random number generation and photonic reservoir computing. Meanwhile, the mushroom-shaped VCSEL offered both high power and low spatial coherence, perfect for speckle-free imaging. The D-shaped VCSEL achieved the best polarization stability with controlled multimode operation, suitable for low-coherence illumination and sensing.
Crucially, these enhancements were realized without altering the core VCSEL fabrication process or adding extra cost. “This makes our approach immediately compatible with existing manufacturing pipelines,” explains lead author Hang Lu.
The researchers used a 940-nm VCSEL wafer and characterized optical performance across more than 60 devices. Experimental results were further supported by simulations of optical mode dynamics and Q-factor distributions, confirming that asymmetric shapes enable broader mode access and higher energy conversion efficiency.
Moreover, they showed how cavity geometry affects beam shape, spectral width, speckle formation, and polarization behavior—key parameters for modern photonic systems. For instance, the mushroom and pentagon VCSELs significantly reduced speckle, offering cleaner images compared to conventional designs, making them excellent candidates for display, biomedical imaging, and machine vision systems.
“This is not just an academic exercise. These lasers could power next-gen sensors, communication systems, and computing hardware,” says co-author Dr. Omar Alkhazragi.
By offering a simple, cost-neutral method to tune laser performance, this work lays the foundation for the next generation of multifunctional VCSELs—ones that are tailored not just by material or doping, but by shape.
Journal
Light Science & Applications
Article Title
Shaping the light of VCSELs through cavity geometry design