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Understanding ultrafast

APE is celebrating 20 years of ultrafast laser diagnostics and OPOs, as Warren Clark discovers

Although more than 20 years has passed since the fall of the Berlin Wall, few appreciate the implications on the scientific community that the collapse of communism had on those east of the Iron Curtain. The restructuring of state-funded science in the months that followed meant that institutions, such as the renowned Academy of Sciences, were being shut down.

It meant that in a very short space of time, hundreds of scientists found themselves out of work – and many of them in East Berlin. Among them were Jan Popien, Edlef Büttner and Thomas Lindemann, who decided to use the knowledge they had gained during their time at the Academy of Sciences to start up their own photonics-based venture. While the initial attempt didn’t work out for them personally, their second has lasted more than 20 years.

APE (Angewandte Physik and Elektronik – or Applied Physics and Electronics) was formed in 1992, with the first product being an autocorrelator for scientific applications, where it would be used to measure the pulse of ultrafast lasers (a field in its infancy back then). With a main application of ultrafast lasers being time-resolved spectroscopy, it is vital to know the length of the excitation pulse.

‘We had all been involved in developing optical instrumentation for spectroscopy at the Academy of Sciences,’ says Büttner. ‘So it was obvious for us to use that expertise in developing our first products.’

‘We had a look at the market, and discovered that the existing products available were rather limited,’ says Popien. ‘We saw an opportunity within diagnostics for ultrafast lasers, as a lot of equipment is needed to run a laser.’

APE’s early customers were largely drawn from the research community, who were using lasers in fields such as material diagnostics, semiconductors and chemistry. Further diagnostic products were developed to serve this market, including wave meters and laser spectrum analysers.

However, the real growth of the company began in 1995 with the introduction of APE’s first optical parametric oscillator (OPO), a product used to expand the accessible wavelength range of the laser via a non-linear conversion technique.

‘At the time, the functionality of Ti:Sapphire ultrafast lasers was limited to the 1µm wavelength,’ says Büttner. ‘There was a lot of interest in using them above this range – and eventually below it – so our OPO was developed to meet this demand.’

The initial product expanded the range up to 1.3µm, but further development increased this up to the telecom range (1.5µm), and down to the visible range (500-700nm) via the development of new crystals to improve handling and tuning.

(L-R) APE founders Thomas Lindemann, Jan Popien and Edlef Büttner

The introduction of the OPO also brought about another major development in the growth of APE – a collaboration with Coherent, which began with the OEM production of a wave meter, but really expanded with the OPO products. ‘The basis of the cooperation was that we, as APE, were able to produce and sell these OPOs in Europe, with Coherent taking on everywhere else,’ says Popien. ‘We agreed that any products were badged as both Coherent and APE.’

‘It was a win-win situation for both of us,’ adds Büttner, ‘as the OPO add-on extended the range and capacity of Coherent’s Ti: Sapphire laser, and in return for us, going with a major laser manufacturer helped us sell many more OPOs than we would otherwise have been able to sell. It also enabled us to concentrate on our main business of developing and manufacturing the products. We were not a distribution company, nor did we have a large sales team.’

The collaboration with Coherent continues to this day, and the intervening years have seen the development of several new OPO products, including an automated hands-free system, which sits well with Coherent’s own automated Ti:Sapphire laser, aimed specifically at biologists.

‘Now, of course, we are a combination of an OEM producer and niche manufacturer of specialist products,’ says Popien. ‘We have continued to develop the diagnostics side of the business alongside OPOs. We now have a very large portfolio of instruments – larger than many companies of a similar size.’

‘When it comes to the European market at least – APE is considered a synonym for laser diagnostics. Many customers refer to their autocorrelator as their “APE”, for example,’ says Büttner.

Over the past decade, APE has continued to expand the number of instruments within its overall product range, but they all fall into three major categories: laser diagnostics, OPOs, and ultrafast laser accessories. ‘We have broadened our product range as the ultrafast laser market itself has broadened,’ says Popien.

Indeed, one market that has developed significantly in recent years has been the biology and life sciences sector. ‘This is a stable and large market,’ says Büttner. ‘But it has presented us with a different customer. We are no longer dealing with physicists, but biologists, and they don’t necessarily know anything about lasers. This is why we’ve developed products that are largely automated and hands-free, enabling us to bring lasers to markets that previously had not been able to deal with their complexity.’

Simplicity of operation has been at the heart of every product that APE has developed, going right back to its first autocorrelator. ‘Even that product featured factory calibration,’ says Popien, ‘which is something that was not available from our competitors. We’re always looking to make products as simple as possible, in terms of operation.’

All three founders of APE are still involved in the company, which has grown to 55 employees and is based in Berlin. Thomas Lindemann is technical director, Jan Popien is head of R&D (technical design), and Edlef Büttner is head of R&D (physics). There is also an associated company in the USA, APE Inc, based in Fremont, California, where the three founders sit on the board of directors.

A recently-developed line of OPOs has been produced solely under the APE brand (as opposed to being supplied via Coherent as an OEM), which has necessitated an expansion of the direct sales team. Its laser diagnostics products are sold directly in Central Europe, and via distribution worldwide.

Popien highlights the strengths of APE: ‘We have been in business for more than 20 years. There are not many companies in photonics that have that kind of track record. We have year-on-year growth and have integrated ourselves with the market – and allied ourselves one of the industry’s major laser manufacturers. We also have in-house manufacturing offering high-quality production for low and medium volume numbers. And of course, we have excellent personnel across all aspects of instrument design and production, including electronics, software and so on.’

Recent fluctuations in the economy have not affected APE as much as others because its market has remained stable, but also because their presence worldwide smooths out local instabilities. Looking forward, Popien and Büttner are confident that 2012 will bring increased sales volumes.