Quantum communication has long promised unbreakable encryption, but the hardware has struggled to escape the lab. A new generation of laser-written glass chips is changing that equation, carving three-dimensional light circuits directly into transparent blocks that can survive real-world conditions. The result is a platform that can generate, route and detect single photons with a robustness that silicon photonics has struggled to match, putting quantum key distribution and other secure protocols within reach of telecom operators, hospitals and power grid operators.
Instead of relying on cleanroom lithography, researchers are using ultrafast pulses to “draw” waveguides inside glass, much like a 3D printer for light. That shift is not just a manufacturing curiosity. It opens a path to compact, integrated quantum photonic systems that can plug into existing fiber networks, operate at room temperature and scale in ways that bulky table-top experiments never could.
From lab curiosity to glass-etched circuitry
The core idea behind these devices is deceptively simple: use a tightly focused femtosecond laser to locally change the refractive index of glass, then stitch those modified regions into waveguides that steer individual photons. Work highlighted by Jul shows how researchers can generate single photons and guide them through intricate glass circuits, turning a once-fragile optical bench into a solid-state platform that fits in the palm of a hand, while teams at the University of Jena and the University of Twente refine how such circuits handle single photon generation and routing in practice. That shift from mirrors and bulk crystals to monolithic glass is as profound for quantum optics as the move from vacuum tubes to silicon was for classical electronics.
In parallel, theorists and experimentalists have been building a broader toolkit for integrated quantum photonics. An Abstract on femtosecond laser direct writing describes how an Integrated photonic quantum chip can implement quantum computation, quantum simulation and Bell state generation using carefully designed waveguide networks validated through simulation. Instead of treating glass as a passive medium, these designs treat it as an active substrate where quantum interference, entanglement and measurement all unfold within a few cubic centimeters, a precondition for any realistic quantum communication node.
QLASS and the race for practical quantum networks
If laser-written glass is the medium, QLASS is the industrial-scale experiment in turning it into infrastructure. The Project known as QLASS brings together experts from top research groups, emerging SMEs and established industry players to build Quantum Glass-based Photonic Integrated Circuits that can host single-photon sources, interferometers and detectors on the same chip. The aim is not a one-off demonstrator but a set of design rules and fabrication strategies to enhance QPIC performance in ways that telecom operators and satellite providers can actually deploy.
Reporting from QBN describes how QLASS is explicitly targeting the limitations of current QPIC technology by using femtosecond laser writing to fabricate 3D waveguides with complex geometries that go far beyond planar platforms. That three-dimensionality is not a gimmick, it is a way to route many channels of quantum information in parallel without the crosstalk and bending losses that plague flat chips, a prerequisite for any metropolitan-scale quantum key distribution network.
Why glass, and not just better silicon?
Silicon photonics has a decade-long head start, so it is fair to ask why researchers are so excited about glass. One answer is flexibility. Work on Photonic circuits written by femtosecond laser in glass shows that passive and active optical components can be integrated on a single chip with three-dimensional routing, something that is far harder to achieve with standard CMOS processes. Another is environmental robustness, since glass waveguides can be engineered to match the properties of standard telecom fibers, reducing coupling losses and making it easier to drop quantum hardware into existing ducts under city streets.
Durability is also improving. A recent arXiv report on Laser written waveguides to the sample edge notes that such structures in glass represent an area of intense research and have progressed significantly since early demonstrations, including better control of propagation losses and mode profiles. A follow up version of the same work on Laser written waveguides emphasizes that guiding light cleanly to the chip edge is crucial for packaging and long-term stability, which directly affects how these devices will behave in telecom racks or satellite payloads that see temperature swings and mechanical stress.
Single photons, quantum chips and secure keys
At the heart of quantum communication is the ability to create and manipulate single photons on demand. Jul reports that Their goal is to generate single photons and guide them through glass circuits, a capability that underpins quantum key distribution and entanglement-based networking. In parallel, Now a team at the Fraunhofer Institute for Applied Optics and Precision Engineering IOF in Jena, Germany has developed a compact photon source that can be coupled to an optical ground station, as described in a report on Fraunhofer IOF. That kind of source, when integrated into glass waveguides, could form the backbone of satellite-to-ground quantum links that feed secure keys into terrestrial networks.
On the processing side, Dec guidance from the Technical University of Denmark frames the quantum chip as the platform that enables us to utilise quantum mechanics for calculations, information processing, encryption and quantum sensing, among other things, a definition captured in a Dec explainer. When that chip is made of glass and written by a femtosecond laser, it can host both the photon source and the logic that encodes keys or entangled states, reducing losses and error rates that plague fiber-coupled discrete components.
Economic realism and the silicon benchmark
For all the excitement, glass-based quantum chips will be judged against the brutal economics of silicon. Engineers working on quantum dot lasers have already shown how III-V materials can be integrated on silicon to create efficient on-chip light sources, as detailed in a report on Laser integrated on silicon. That work sets a high bar for cost, yield and integration with existing CMOS fabs, and it is reasonable to assume that telecom operators will prefer solutions that can ride on the same supply chains that produce 5G baseband chips and data center switches.
Yet glass has a counterintuitive economic advantage: it can be processed with relatively simple laser systems outside of ultra-clean semiconductor fabs. European researchers highlighted in a feature on Scientists Are Building a Quantum Computer With Chips Made out of Glass argue that this could lower the barrier to entry for specialized quantum hardware, especially for regional foundries that cannot justify a full CMOS line. If that vision holds, we may see a split market where silicon handles dense classical processing and glass-based QPICs provide secure links and specialized quantum functions.
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*This article was researched with the help of AI, with human editors creating the final content.
