What are PCSELs?

PCSELs are a unique type of semiconductor laser. To understand them, it’s useful to compare them to two other types of semiconductor laser:

• Edge Emitting semiconductor Lasers (EELs) bounce light back and forth in a horizontal channel and emit light from the side of the chip, similarly to gas or solid-state lasers.  While powerful, the resulting beam is often “astigmatic” or oval-shaped, requiring bulky lenses to correct it.
• VSCELs Emit light from the top surface. Light is bounced between two horizontal mirrors, with a hole in the center of the top mirror. They emit a focused beam but struggle with high power levels.

PCSELs are conceptually similar to VSCELs, but use a photonic crystal lattice instead of mirrors. While a mirror is only able to reflect the light, the crystal lattice is able to manipulate the light’s direction, shape and phase via Bragg diffraction. This allows for both light to be reflected at a specific angle regardless of its origin (or static steering), and for dynamic electronic steering using heat or electrical current.

Advances in lithography methods, such as Nanoimprint Lithography (NIL) have made PCSELs more feasible at scale. In addition to FSO, automotive LiDAR and biomedical imaging are drivers of demand.

Advantages

Because the light emitted from a PCSEL is inherently focused, optical correction and the associated weight and cost are not required. VCSELs are also more stable across different temperatures, which helps maintain stability of connection and specific wavelengths.

Usage

In April 2026, Vector Photonics announced it had demonstrated the use of PCSELs for FSO communication in a real world environment, across the River Clyde in Glasgow over a distance of 500m. The communication system was built by Fraunhofer Centre for Applied Photonics (CAP), part of Fraunhofer UK, and achieved data rates of 50 Mb/s.

References

https://www.optica-opn.org/home/industry/2026/april/vector_photonics_achieves_free_space_communications_with_pcsels/

https://www.photonics.com/Articles/PCSELs-May-Redefine-Diode-Lasers-in-Industry-and/a70867

armysbir.army.mil/topics/pcsel-for-advanced-laser-systems/

ieephotonics.org/announcements/ieee-researchers-provide-mathematical-solutions-to-study-2d-light-interaction-in-photonic-crystal-lasers/

https://www.sciencedirect.com/science/article/abs/pii/S0030401825011277

https://www.rp-photonics.com/photonic_crystal_surface_emitting_lasers.html

https://datahorizzonresearch.com/photonic-crystal-surface-emitting-laser-diode-market-20673