Quantum Light Enables Self-Illuminating Optical Biosensors

In the healthcare world, biosensors are gaining significant traction as a diagnostic tool. These electrical devices measure biological or chemical signals and convert them into electrical signals. 

They are utilized in everything from disease monitoring and drug discovery to non-invasive detection of microorganisms that cause diseases and markers that signal viruses in bodily fluids like sweat, saliva, urine, and blood.

Biosensors are also finding applications in food inspection and safety, agriculture, environmental studies, biotechnology, and medical utilities. Driven by all this demand, the global biosensor market is already targeting tens of billions annually.

A typical biosensor consists of a few main components:

• Bio receptor
• Transducer
• Analyte
• Display

Here, the analyte is a substance of interest that’s being identified and measured. For instance, in a biosensor that’s designed to detect glucose, glucose is an analyte.

A bioreceptor is a biological component, such as DNA, cells, enzymes, or antibodies, that recognises the analyte. The process of signal generation occurs in the form of heat, light, or a change upon the interaction of the bioreceptor with the analyte, and is called bio-recognition.

The transducer converts the bio-recognition event into a measurable optical or electrical signal. Display is simply a user interpretation system that generates data in graphic, numeric, or any other form that’s understandable by the user. 

Now, there are about four types of biosensors based on their transduction method, viz., electrochemical, thermal, piezoelectric, magnetic, and optical biosensors. Each of these types uses a different mechanism to convert a biological interaction into a measurable signal.

When it comes to optical biosensors, specifically, they are known for their added benefit in sensing applications due to their extreme sensitivity, selectivity, and rapid measurements. They also provide real-time detection of biological and chemical substances in a specific and cost-effective manner. 

The way optical biosensors work is by converting light signals into electrical signals with activity based on the optical field’s interaction with a bioreceptor or bio-recognition element.

These biosensors are classified as “label-free,” where signals are produced directly upon the interaction of the analyte material with the transducer, and “label-based,” where signals generated are amplified by luminescent, fluorescent, or colorimetric methods. 

While offering distinct advantages in comparison to traditional analytical techniques, optical biosensors require external light sources, which restricts their deployment to laboratory settings and prevents their usage in healthcare and environmental monitoring settings.

To overcome challenges in its widespread real-life applications, researchers in the Bionanophotonic Systems Laboratory in EPFL’s School of Engineering have utilized quantum physics to detect the presence of biomolecules without needing an external light source.

Pushing the Boundaries of Optical Biosensing

To detect biological analytes, optical biosensors utilize light waves. While using nanophotonic structures that ‘squeeze’ light at the surface of a tiny chip to focus the light waves down to the nanometer level can improve their performance significantly, as we noted above, this needs external light sources, which involves bulky equipment, as such preventing its usage for rapid diagnostics and in point-of-care settings.

So, to eliminate the need for an external light source in a light-based biosensor, the researchers turned to quantum physics. 

They have introduced a plasmonic sensor with an embedded source of light, provided by quantum tunnel junctions. 

Plasmonic metal nanostructures have actually been actively investigated for optical sensors due to their unique abilities to support strong optical field enhancement as well as deep-subwavelength light confinement through localized surface plasmon resonances and propagating surface plasmon polaritons (SPPs).

LSPR is the collective oscillating motion of conduction electrons near the surface of nanostructured noble metals when illuminated by light. This leads to the creation of a localized electromagnetic field with distinct optical properties.

SPPs, meanwhile, are electromagnetic surface waves that arise when excited surface plasmons couple with photons and travel along the interface between a metal and a dielectric material. 

It is on the basis of these that biosensing devices have been surpassing the detection performance of conventional optical sensors, facilitating their widespread use and commercialization. 

In fact, Surface Plasmon Resonance (SPR) biosensors based on flat metal films have become one of the standard label-free techniques to real-time monitor biomolecular interactions.

Nanoplasmonic biosensors, which are the combination of nanomaterials, LSPR or SPR, and optical biosensors, meanwhile allow a reduction in the required sample volumes, enabling the observation of real-time single-cell secretion. 

Advances in the field are now looking into quantum plasmonic sensing systems that can discover novel opportunities for improved device performance that go down to the level of single-molecule detection. But despite all the progress made in the nanophotonics field, there is still a need for an external light source to excite SPPs.

Combined with bulky equipment like prisms or gratings, which limits the usability of plasmonic sensors. To advance its usage in biochemical research and medical diagnostics, we need miniaturized and integrated devices.

Leveraging Inelastic Electron Tunneling for On-Chip Light Generation

Published in Nature Photonics¹ in collaboration with researchers at ETH Zurich, ICFO, and Yonsei University, EPFL engineers have showcased an on-chip label-free optical biosensor that is self-illuminating and leverages quantum tunnelling, a phenomenon in which a particle passes through a potential energy barrier that it classically cannot cross.

By harnessing the inelastic electron tunneling, the researchers have created a device that only needs a steady flow of electrons in the form of applied electrical voltage to both illuminate and identify molecules. 

“If you think of an electron as a wave, rather than a particle, that wave has a certain low probability of ‘tunneling’ to the other side of an extremely thin insulating barrier while emitting a photon of light. What we have done is create a nanostructure that both forms part of this insulating barrier and increases the probability that light emission will take place.”

– Researcher Mikhail Masharin

For their device design, the engineers have used a multilayer film where the insulator is between two metals. 

Here, gold (Au) nanowires are placed on top of a thin aluminum layer, which is the tunneling barrier, separating them from an aluminum (Al) film at the bottom. 

The top surface uses a plasmonic metasurface that serves dual purposes, which forms the core of the innovation. The nanostructure’s gold layer serves as an electric contact for the tunnel junction as well as an optical interface to facilitate the coupling of inelastic quantum electron tunneling, accompanied by light emission, to free-space radiation.

What this means is that the metasurface shows special properties that create the conditions for quantum tunneling and control the resulting light emission. 

The control is enabled by the arrangement of the metasurface, which is in a mesh of gold nanowires. These act as ‘nanoantennas’ to concentrate the light at the nanometer volumes needed for the efficient detection of biomolecules.

The arrangement impacts the internal quantum efficiency of the tunneling process by enhancing the radiative component of the electromagnetic density of optical states, in turn improving radiative quantum efficiency and, as a result, enhancing the detected signal. 

In simpler terms, their nanostructure basically creates the right conditions for an electron to pass through it and cross a barrier of aluminum oxide to come to the ultrathin layer of gold (Au). In this process, some of the electron’s energy is transferred to the collective excitation (aka plasmon), which then emits a photon. 

In order to produce an efficient and spatially uniform LIET (light emission from inelastic electron tunneling), the researcher used a flexible metasurface design that was optimized for biosensing. The first author, Jihye Lee, who is a former Bionanophotonic Systems Lab researcher and is currently an engineer at Samsung Electronics:

“Inelastic electron tunneling is a very low-probability process, but if you have a low-probability process occurring uniformly over a very large area, you can still collect enough photons. This is where we have focused our optimization, and it turns out to be a very promising new strategy for biosensing.” 

The device design makes sure that the spectrum and intensity of the light change when it comes in contact with biomolecules, providing a powerful technique for label-free, real-time detection.

Quantum Biosensors: Compact, Scalable, and Real-Time

With the innovative, compact device, the researchers have significantly advanced the capabilities of sensors currently available on the market.

As Hatice Altug, head of Bionanophotonic Systems Laboratory, stated:

“Tests showed that our self-illuminating biosensor can detect amino acids and polymers at picogram concentrations – that’s one-trillionth of a gram – rivaling the most advanced sensors available today.”

Another important point here is the use of quantum mechanics to achieve the breakthrough, which essentially takes it further into the practical realm.

Much has been explored about quantum mechanics, a fundamental theory of physics that deals with the properties and behavior of particles at the atomic and subatomic levels, which was first introduced about a century ago.

During this time, quantum mechanics has helped advance industries by underpinning numerous modern technologies, including semiconductors for electronics, lasers, and magnetic resonance imaging (MRI). It is also paving the way for future innovations, such as quantum computing and advanced cybersecurity. 

According to Julian Kelly, director of hardware at Google Quantum AI, we may be about “five years out from a real breakout, kind of practical application that you can only solve on a quantum computer.”

Quantum computers, according to him, “can access the way the universe works at the most fundamental level.”

Nvidia (NVDA -0.5%) CEO Jensen Huang is of a similar view. He believes quantum computing has the potential to “deliver extraordinary impact,” but added that “the technology is insanely complicated.”

Amidst this, EPFL engineers have embedded quantum light sources directly into chip-scale devices, revolutionizing biosensing technology that can be used for industrial monitoring, including water testing, air quality control, and food safety. Their breakthrough can also unlock new devices in quantum detection and smart sensors.

LIET sensor architecture here actually offers a smaller device footprint, due to plasmonic antennas acting as both a light source and as a sensing element, compared with designs that integrate plasmonic structures on top of photodetectors or LEDs

The researchers tested their device with biomolecules and nanometre-thick polymers and found that both the emitted light’s intensity and the spectral profile are modulated by the local refractive index changes produced by the analyte’s presence. This means LIET devices can be used as compact and sensitive on-chip optical biosensors for point-of-care applications.

The sensing device, as per the study, has sufficient emitted power to operate with the most common light detectors. The quantum platform is scalable and compatible with sensor manufacturing methods, making it feasible for widespread production and distribution.

“Our work delivers a fully integrated sensor that combines light generation and detection on a single chip. With potential applications ranging from point-of-care diagnostics to detecting environmental contaminants, this technology represents a new frontier in high-performance sensing systems,” said Bionanophotonic Systems Lab researcher Ivan Sinev.

With less than a square millimeter of active area needed for sensing, the design can certainly open up exciting prospects to realize a practical electro-optical biosensor and new applications. 

Also, it can potentially lead to new handheld devices in contrast to current table-top setups, that fit perfectly into settings like doctor’s offices, nursing homes, and remote clinics, where bulky lab equipment is simply impractical. 

Its label-free nature and real-time monitoring capability further make the quantum biosensor perfect for tracking biomarkers in diseases such as infections, cancer, and metabolic disorders.

Beyond all this, the platform can help provide fundamental scientific insights that can help advance other fields, including nano-optics, materials science, and quantum computing.

Click here to learn about the current state of quantum computing.

Top Quantum Biosensor Investment Opportunities

Now, time to take a deep dive into investment options, both established and emerging, in the field of quantum-driven biosensing.

Established Players & Platforms

When it comes to analytical instruments and diagnostics, Agilent Technologies (A -1.21%) is among the notable names that can potentially integrate the new tech into their product lines.

The company stands out for its specialization in diagnostics, life sciences, and applied markets. It offers software and laboratory automation solutions as well as reagents, instruments, and consumables. In addition to active pharmaceutical ingredients for oligo-based therapeutics, it also offers instruments and software to identify, quantify, and analyze the biological properties of substances.

Earlier this year, Agilent collaborated with ABB Robotics to deliver automated laboratory solutions, making processes such as research and quality control faster and more efficient.

With a market capitalization of $33.45 billion, Agilent shares are currently trading at $117.76, down 12.16% year-to-date (YTD), but not far from their 2021 peak of around $180. It has an EPS (TTM) of $ 4.06 and a P/E (TTM) of 28.98, with a 0.84% dividend yield also available. 

Financially, the company recently reported its Q2 2025 results, which showed a growth of 6% in revenue at $1.67 billion while GAAP net income was $215 million and earnings per share (EPS) were $0.75.

In the world of photonics/optics, meanwhile, AMS (AMS-Osram) is the one that may benefit from nanoscale light-emitting components.

The Austria-based AMS designs and produces integrated analog microchips and offers its services in the areas of sensors, sensor interfaces, power management, and mobile entertainment in the communications, medical technology, and automotive markets.

At the Sensors Converge 2025 last month, AMS featured its latest multi-zone, direct Time-of-Flight sensor that provides over 20 times the number of pixels as previous ones, even at low power, in a compact all-in-one module.

The billion-dollar market cap company, which offers a full-service foundry specializing in sensor technologies, has an EPS (TTM) of -1.51 and a P/E (TTM) of -6.82.

For Q1 2025, it recorded revenue of EUR 820 million while reporting improved profitability and a free cash flow outlook above EUR 100 million for FY25. At the time, it also revealed plans to sell a portion of its business to generate over half a billion dollars in capital to reduce the company’s debt.

Quantum & Nanotech Specialists

If we look in the quantum realm, Applied Materials (AMAT -0.35%) is known for providing deposition and nanofabrication tools, making systems like theirs essential to scaling the production of biosensors. 

The materials engineering solution company operates through three segments: Semiconductor Systems; which manufactures a range of primarily 300 mm equipment used to fabricate semiconductor chips or ICs, Display; comprising primarily of products for manufacturing LCDs, OLEDs, and other technologies for smartphones, tablets, PCs, televisions, monitors, and laptops, and Applied Global Services (AGS); which manufactures 200mm and provides spares and automation software to the fabrication plant.

When it comes to the market performance of the $146 billion market cap company, its shares as of writing are trading at $182.10, up 11.8% YTD. Its EPS (TTM) is 8.21, and the P/E (TTM) is 22.20. The dividend yield that shareholders can earn is above 1%. 

As for financials, the company reported a GAAP gross margin of 49.1% for Q2 2025 and a non-GAAP gross margin of 49.2%. Meanwhile, record GAAP EPS came in at $2.63, and non-GAAP EPS was $2.39. Cash from operations generated during this period was $1.57 billion while Applied Materials distributed $2 billion to shareholders, including $1.67 bln in share repurchases and $325 mln in dividends.

Its CEO, Gary Dickerson, attributed high-performance, energy-efficient AI computing as the dominant driver of innovation.

Early-Stage & Spin-Outs

In early-stage ventures, the likes of Lux Capital are known for investing in emerging technologies, including material science, biochemistry, electronics, aerospace, and infrastructure. The venture capital (VC) firm has also been helping academics advance technological discovery with plans to invest at least $100 million to support promising research in sectors like biotech and AI.

Breakthrough Energy Ventures (BEV) is another one that might target similar quantum-nanotech platform companies.

Founded by Bill Gates, BEV is made up of twenty investors from all over the world. The fund has invested in everything from smart sensors, storage solutions, and biotech to AI and sustainability. It has also committed to investing over a billion dollars in new technologies through the Breakthrough Energy Coalition (BEC).

In the future, it is also possible that we may see startups spun out from EPFL, ETH, or ICFO with a focus on quantum tech and become commercial players. This isn’t anything new, though. Over the years, many university spin-offs have emerged to transform technological inventions that were developed from the research they carried out at their universities.

For instance, Akamai, Boston Dynamics, OKCupid, Cambridge Mobile Telematics, iRobot, RSA Security, Nimble VR, Meraki, and many more have all spun off from the Massachusetts Institute of Technology (MIT).

Even EPFL has seen many spinouts such as Bionomous, Dronistics, Hydromea, MindMaze, Sensars, SenseFly, Kandou, Nexthink, and more spanning across various sectors.

ETH Zurich has seen spin-off companies in areas like AI, machine learning, biotechnology, pharmaceuticals, and robotics, while at least ten firms have spun off from ICFO, including LuxQuanta, which uses quantum technologies to provide data security.

Conclusion

Optical biosensors are important in the fields of precise medical diagnostics, personalized medicine, and environmental monitoring. By bringing us a self-illuminating plasmonic biosensor, the latest innovation presents a shift that combines quantum tunneling with photonics into a self-contained chip. 

This not only challenges conventional sensor design but also stands out as a practical implementation of quantum mechanics, going beyond experimentation to scalable technologies with the potential to gain widespread adoption.

By embedding quantum light sources directly into chip-scale devices, the researchers have created a new frontier in biosensing technology, promising versatility, compactness, and unprecedented sensitivity across sectors.

Click here for a list of top quantum computing companies.

Studies Referenced:

1. Lee, J.; Wu, Y.; Sinev, I.; et al. Plasmonic Biosensor Enabled by Resonant Quantum Tunnelling. Nat. Photon. 2025. https://doi.org/10.1038/s41566-025-01708-y