Diamond-based photonics

Definition

Diamond-based photonics refers to the use of diamonds to generate, control and use light. Diamond consists almost entirely of carbon arranged in a unique three-dimensional crystal structure. Besides their hardness, diamonds are characterised by exceptional optical properties. They are translucent across wide wavelength ranges and have extremely high thermal conductivity. Defects in diamonds’ crystalline structure are also exploited for technical purposes. What are known as “nitrogen vacancy centres”, or “NV centres” for short, are particularly relevant for photonics. They occur when a nitrogen atom is incorporated into the lattice instead of a carbon atom, while the neighbouring carbon atom is absent, creating a vacancy. NV centres emit light, are sensitive to magnetic fields and exhibit interesting quantum mechanical properties that persist even at room temperature. 

Both natural and synthetic diamonds are used in diamond-based photonics. Synthetic diamonds are more commonly used due to their controllable properties and the fact that they can be produced in large quantities.  

Current applications and opportunities

Traditional diamond applications include tools such as cutters and drills that play roles in precision machining optical components and manufacturing optical fibres. Diamond is used in photonic systems such as high-power lasers, optical amplifiers and spectroscopes. All these devices generate a great deal of heat during operation, which diamond dissipates efficiently due to its high thermal conductivity. 

New applications are emerging in quantum sensing technology. Diamonds with NV centres can detect individual molecules and atoms in their environment, hence their use as sensors. They enable high-resolution analysis and manipulation of materials, leading to industrial deployment for surface characterisation, geophysical magnetic field measurements and medical magnetic resonance imaging of organs. 

Diamond-based photonics offers tremendous opportunities for science, industry and society. The technology is still in its infancy, enabling new research discoveries that could lead to industrially relevant patents. This field of research is attractive to academically and technically skilled professionals, drawing companies and capital all the while promoting the establishment of new businesses.  

From an economic standpoint, diamond-based photonics offers Switzerland opportunities in interesting niche areas requiring specialised infrastructure such as clean rooms and highly qualified personnel. Knowledge transfer from universities to industry is a challenge domestically, which is why pilot plants such as those at the Swiss Federal Institute of Metrology (Metas) and the Swiss Centre for Electronics and Microtechnology (CSEM) play important roles in sharing and using available knowledge. For society, diamond-based photonics offers advantages not only in mobility navigation and medical diagnostics, but also in secure data transmission in the quantum computing age. 

Challenges

Diamond-based photonics faces several technical challenges. A key aspect is scaling diamonds for mass production of large substrates. While the technology for scaling up production certainly exists, advances in materials research are needed to reduce prices for industrially manufactured diamonds. Control of NV centres also remains underdeveloped. 

Another important question remains: How and in which applications is it worthwhile to use NV sensors, which are currently (still) expensive? Such applications must be identified and developed in a targeted manner through collaboration between science and industry. 

Unlike most fields of research, quantum technologies remain the subject of specific discussions between Switzerland and the EU, which could soon be resolved in Switzerland’s favour. The situation is exacerbated by a slump in funding from the Swiss National Science Foundation (SNSF) and very low acceptance rates for quantum projects at Innosuisse. Additionally, there is often a long time between customers placing orders and paying for expensive equipment – something that is particularly problematic for small Swiss manufacturing companies. Export credit guarantees from banks would be vital. 

Focus on industry

The advantage of diamond-based photonics is currently limited to industrial applications that rely on diamond’s superior properties and benefit from its high light quality and wavelength range. This leads to improved optical device performance and enables energy savings. Furthermore, the diamonds’ outstanding properties enable the development of highly sensitive sensors for monitoring the likes of material quality and environmental conditions. Diamond-based devices can usually be easily integrated into existing optical systems. 

Developing diamond-based photonics technologies requires highly qualified professionals with expertise in precision mechanics, materials science, computer science, engineering, physics and precision manufacturing. Working in interdisciplinary teams is crucial, as are analytical and problem-solving skills. When it comes to applying the technology, engineers are needed for the sensors’ integration in systems, while experienced technicians are required for maintenance and operation. 

ETH Zurich and EPFL offer degree programmes in photonics and quantum engineering that are designed to meet the demand for highly qualified developers. Similar degree programmes are also being developed at universities of applied sciences such as FHNW, Lucerne University of Applied Sciences and Arts and ZHAW. The goal should be to train qualified users. However, graduate numbers are currently insufficient to meet growing demand. 

International perspective

Switzerland’s position in diamond-based photonics development depends on the application. Compared to other countries, Switzerland is strong in niche applications such as sensor technology. However, it risks falling behind in larger and more complex areas like quantum computer development. Although Switzerland is a leader in fundamental research, it is not home to any industrial players. 

Commercialisation is proving more difficult than in leading countries like the USA, as Switzerland has less government funding and there risk appetite among investors is lower. This presents challenges, as many of the technologies described involve high costs and substantial risks.  

Future applications

Three application clusters are emerging:  

1) The application of diamond to printed circuit boards enables the use of light as a signal and transmission medium for chips (see PICs).  

2) NV centres in diamonds can be used as qubits for quantum sensing or communication. Lasers excite these centres, resulting in quantum mechanical phenomena such as spin entanglement that can be used for the above-mentioned areas. NV centres will also play a role in secure information transmission. The quantum internet is still a hypothetical network based on quantum communication that can exchange information securely across large distances using quantum technology. Even though such a network is still far off in the distant future, this application is more probable than the use of NV centres for quantum computers.  

3) Diamond structuring is also likely to become increasingly important in the future. So diamonds with specific optical properties can be designed for high-power lasers. Thanks to the possibility of structuring diamonds, the authenticity of synthetic jewellery diamonds could also be guaranteed. 

Diamond-based photonics has the potential to revolutionise the fields of sensor technology and quantum communication. Diamond’s unique properties, such as its high light transmission and thermal conductivity, could enable groundbreaking innovations in material analysis and secure data transmission. Switzerland has a high level of research expertise and well-trained specialists, giving it a competitive edge in niche applications. However, the high level of financing required and the associated risk for investors present challenges.