The article highlights a breakthrough in integrated photonics: a compact, monolithic multi-plane light conversion device fabricated directly inside fused silica glass using femtosecond laser writing. Developed at Tampere University under the guidance of Oussama Korichi, this MPLC device stacks multiple birefringent, polarization-controlling planes inside a single glass chip.
This setup enables sophisticated light transformations with impressively high efficiency. The work pushes forward the idea of truly compact, alignment-free photonic components for communications, quantum tech, sensing, and imaging.
Below, let’s dig into how this device works, what it can do, and why it could matter for future photonic systems.
What is the MPLC device and how it works
At its core, the MPLC is a monolithic, volumetric device built directly in fused silica. The glass chip packs between 10 and 30 modulation planes into a compact volume—roughly 0.7 mm × 0.7 mm × 10 mm.
This dense design means you get a lot of optical control in a single chunk of glass. Each plane is patterned with anywhere from 200×200 up to 500×500 pixels, with pixel sizes ranging from 2 to 8 μm, all created using femtosecond laser writing.
The patterned planes use Type II laser-induced nanogratings to create controlled birefringence. Each layer acts as a spatially varying half-waveplate, giving vectorial control over light’s amplitude and polarization.
As light travels through the stack, it picks up a sequence of polarization and phase changes in a tightly integrated way. You don’t need bulky external optics anymore.
This architecture is compact and scalable. The monolithic, multilayer design offers a robust platform for beam manipulation, and you sidestep the realignment headaches that come with traditional multi-element optics.
Key design aspects
The device’s performance depends on precise control of nanoscale birefringence and careful layering. Up to 30 planes can fit inside, each engineered to play its part in the overall transformation.
The planar geometry—about 0.7 mm square in cross-section, 10 mm long—gives a substantial optical path in a tiny footprint. It’s a versatile platform for complex mode and polarization processing, all in a compact form.
- Planar density: 10–30 modulation planes within a millimeter-scale thickness
- Pixel resolution: 200×200 to 500×500 per plane
- Feature size: 2–8 μm per pixel
- Birefringence mechanism: Type II laser-induced nanogratings
Performance and efficiency
Measured transmission efficiencies are strong: about 89% per modulation plane at 808 nm and 94% per plane at 1550 nm. That’s a big step up from earlier laser-written geometric-phase elements, and it cuts down cumulative loss as you stack more planes.
In practice, this means higher throughput for complex, multilayer light transformations. It also fits better with long-distance telecom channels.
Capabilities and demonstrations
The MPLC design opens up a bunch of optical operations, including beam-splitting, mode conversion, and polarization control. One cool demonstration: the device can manipulate topological light structures like optical Skyrmions, which are catching interest for data storage and advanced imaging.
There are two standout demonstrations. A 15-mode spatial mode sorter shows the device can separate multiple spatial modes in a compact element. Meanwhile, a 12-mode combined polarization and spatial mode sorter handles both polarization and spatial information at once—so you can pack multiple data streams into a single photonic channel.
Since the device is monolithic and volumetric, it dodges the footprint and alignment headaches of conventional optics. The team sees particular promise for telecom applications at 1550 nm, where they demonstrated a miniaturized multiplexer, and also for quantum information, sensing, and advanced imaging.
Fabrication parameters and future work
Key fabrication parameters—pulse duration, pulse energy, and scanning speed—control the formation of the nanoscale grating structures and the resulting birefringence. Fine-tuning these is crucial for reliable, reproducible optical retardance across all planes.
Fabrication parameters
Researchers plan to expand wavelength-dependent characterization, check long-term stability, and scale up the laser-writing process for more planes. They’re aiming to integrate multiple MPLC devices into complex photonic circuits, paving the way for fully integrated, multiport photonic chips that combine mode sorting, polarization control, and on-chip signal routing in a single, robust element.
Future directions
As this technology matures, scalability and integration will probably lead the way. The idea of merging high-efficiency, monolithic MPLCs with other on-chip components could change everything.
That could mean compact, high-capacity networks for both classical and quantum information. If that happens, we might need to rethink how we design and use next-generation photonic systems.
Here is the source article for this story: Glass Components Now Manipulate Multiple Light Structures Simultaneously