“There is currently a lot of unrest in the cooling market”

The higher the performance and precision requirements and the smaller the available installation space, the more important thermal management becomes in photonic systems. Cooling is a science in itself that must meet a complex set of challenges. As well as cooling performance, the focus is on reliable, low-maintenance operation, energy efficiency, environmentally friendly coolants and vibration and noise prevention. In the interview, Jan Meise, CEO of AMS Technologies AG from Martinsried near Munich, Germany, and the company’s expert for thermal management, Dr. Konrad Laufs, talk about technological approaches for efficient cooling, customer-specific requirements and important markets for cooling technology.

Mr. Meise, would you like to give us a short description of your company?

Jan Meise: We are a medium-sized company with almost 100 employees, which was established in 1982 by US-born Eric Protiva as an electronics distributor. Back then, the mainstays were power electronics, thermal management and photonics. We often supported development projects from our European customers by assembling customized photonic systems, using components from international manufacturers. We have been increasingly developing and manufacturing in-house since 2010. Our focus is on customer-specific photonic systems and solutions for thermal management. We manufacture the latter in Poland and the lasers in the UK. Our head office and development department are located in Martinsried near Munich. We see ourselves as a provider that also offers customer-specific solutions with real added value in niche markets and also supports their integration. With this approach, we recently turned over more than EUR 30 million.

Dr. Laufs, what are the different approaches for cooling photonic systems?

© Messe München

Dr. Konrad Laufs: For systems with low cooling requirements, thermoelectric coolers based on Peltier elements are used in most cases. They convert electrical power directly into a directed heat flow and have the advantage that there is no liquid and no moving parts. However, their coefficient of performance is limited. But their cooling performance is adequate for miniaturized systems and many laser applications in biophotonics and medicine. In industrial laser material processing, the cooling requirements are much higher and, in many cases, are in excess of 20 kilowatts (kW). Only liquid coolers are capable of this. We operate more in the middle range, where system efficiency is often lacking. Even if lasers have only a few watts of power, they are sometimes cooled with powers in the kW range. In some cases, we see setups where the liquid cooler is located in the adjacent room and connected to the laser via meter-long water hoses. Our requirement is different: we integrate the liquid coolers in close proximity to the laser diode and minimize heat loss by continuously adjusting the compressor’s cooling capacity to match the laser’s power loss. Particularly in the mid-range segment, customers can leverage a lot of efficiency potential with customized thermal management systems.

How are cooling requirements changing in photonics?

Laufs: All three segments are experiencing change, which is causing a lot of unrest. On the one hand, there is an issue with replacing the existing refrigerant. While the problem with refrigerators was resolved easily by using simple hydrocarbon compounds, the situation in photonics is more complicated. The latest systems use water as a refrigerant. For this to work, it has to be fed into a vacuum and be compressed in a turbo compressor. The systems are complex and, to date, are available only in the high-performance area. There is also unrest with regard to Peltier elements. Because of the raw material availability, they are produced mainly in Russia. As a result of the war and the sanctions that have been imposed, the supply chains have been interrupted. We are now establishing new contact to providers in the U.S.A. and Ukraine. But the situation is still tense. This is another reason why ideas are needed to provide low to medium cooling capacities efficiently. The key is miniaturization. Recently, we developed a solution using the refrigerant isobutane for a mobile cosmetic laser, in which we used miniaturized compressors, evaporators and condensers. In general, the focuses are on adapting the systems as much as possible to suit the actual cooling requirements of the lasers, reducing installation space and preventing noise and vibration.

To what extent can you work with off-the-shelf solutions?

Meise: In photonics, cooling requirements are usually very specific and the solutions have to be tailored to different requirements in every project. However, so that we can still offer our products at a reasonable price, we rely on modularization. Our modular system is growing steadily, which enables us to respond quickly to customers’ requests and implement projects within months rather than years. To expand our modular system, we collaborate with major compressor manufacturers in the household appliance market. Admittedly, their products are not perfectly suitable for cooling lasers because refrigerators are designed for lower temperatures than the 20 degrees Celsius that is optimal for laser systems. Nevertheless, the collaboration bears fruit. For instance, with one manufacturer we are currently developing a very efficient, compact compressor with inverter for readjustment which is specifically designed for the higher evaporation temperatures in photonics. We also offer our customers a test kit with an IoT (Internet of Things) interface with which they can carry out preliminary work in-house for an optimum system design. Via the interface, we are able to view process data and, based on this, provide support in designing the system. With networked solutions such as this we can also re-program the coolers to optimize their efficiency along the operating profiles. This allows system optimization to be brought forward to the proof-of-concept phase, which considerably reduces the overall development time.

You spoke of the need for new ideas beyond thermoelectrics to cool miniaturized photonic systems efficiently. Are there approaches for this?

Dr. Laufs: Yes. With direct evaporation in which micro-cooling plates are used as evaporators, we can completely eliminate the water circuit. That saves space because none of the circuit components are required. And it minimizes maintenance as there is no need to replenish the water or prevent corrosion and leaks. The evaporator plate is attached directly to the laser diode and dissipates its heat by direct evaporation of the refrigerant. Unfortunately, this approach is not suitable for all laser systems. On the one hand, the line lengths are not arbitrarily scalable; in other words, if there are several meters between the diode and the laser head, direct evaporation is not an option. And, on the other hand, with a system such as this, you have to know the precise load profiles to be able to re-adjust accordingly. But the technology is ready for the market: we are using direct evaporation successfully in the medical area.

What disciplines, competences and infrastructure do you use to design cooling solutions for specific customers?

Meise: The key to designing the system is design competence. Probably about 80 percent of all quality problems can be attributed to bad system design. This is why our process chain begins with a clean CAD design and CFD simulations. In the second step, we procure suitable components from our suppliers before our refrigerant engineers begin the proof-of-concept phase and test the system thoroughly—including in our climatic chamber. We have very well-equipped laboratories to test and validate prototypes. The entire process takes place in the cloud so that the teams are always at the same stage of development. We have been pushing ahead with digitization at full speed since 2015 and have moved our business completely to the cloud. That improved and considerably accelerated our communication and collaboration processes. We reach the proof-of-concept phase sooner, detect errors and areas where optimization is required earlier and can focus on the fine tuning in the subsequent development stages. In this agile approach, we involve our customers early in the iteration loops, which, on balance, helps us get better results faster

To what extent do climate and environmental targets influence your research and development?

Dr. Laufs: Naturally, the refrigerant issue I spoke of has a major influence. The industry must replace the climate-damaging tetrafluoroethane (R134a) with “green” refrigerants—and it is far from clear which solutions will prevail. On the other hand, it seems that energy consumption does not play a role when it comes to thermal management. It is not uncommon to see simultaneous cooling and electrical heating in the same system to maintain a constant temperature. Only recently has the photonics industry started to pay more attention to the energy efficiency of its processes and leverage savings potentials with controlled systems.

As a provider of an enabling technology, you have deep insights into the photonics market. Are there any particularly dynamic market segments and exciting target markets for your cooling solutions?

Meise: We are experiencing particular dynamism in LiDAR applications for vehicles. A lot of venture capital has flowed into this market over the last few years. We have picked up on this trend and made narrowband lasers developed here useful for a niche application: LiDAR measurements in wind potential analyses. This is often how we go about it. If innovations don’t make the leap into the mass market, then thanks to our market insights we often find niche applications in which they offer added value. I also see photonic integrated circuits (PICs) as a dynamic area of innovation. However, from a thermal management aspect there is not much of a market opening up here. A Peltier element is well able to dissipate its low waste heat. But integrated photonics is spreading from data centers and telecommunications applications to other market segments, such as biophotonics and medical. We are keeping a close eye on developments, just as we are on the advent of quantum technologies, which are receiving huge sums of funding cash worldwide. There are a lot of lasers in use in this area, which often require a lot of cooling. This is why this is an interesting market. In June, from our LASER booth we will certainly take a detour to the World of QUANTUM. However, the life sciences will remain the core market for our thermal management solutions. This is where we generate a large part of our revenue and help the manufacturers integrate specific cooling solutions into their increasingly miniaturized systems. With our expertise and high implementation speed, we can make inroads in this exciting and very demanding market.