Crystalline Supermirrors: from concept to reality

Here I provide a brief overview of how two scientists from the University of Vienna stumbled upon an enabling technology, born from “blue sky” research in the burgeoning field of quantum optomechanics, and made a successful transition from academia to industry. The fruit of this endeavor is “Crystalline Mirror Solutions,” or CMS, a high-tech start-up commercializing high-performance optics for laser-based precision measurement and manufacturing systems. Although it was not apparent at the outset, there were ultimately two key elements that led to the success of this endeavor: The first was of course the conception of the basic technology itself, while the second relied on effective “local” infrastructure and funding organizations to ultimately bring this idea out of the laboratory and to the commercial market.

Artist's rendition of an optical cavity employing crystalline supermirrors. Credit: Brad Baxley,

Artist’s rendition of an optical cavity employing crystalline
supermirrors. Credit: Brad Baxley,

In the first instance, a novel idea was generated from the fusion of two seemingly disparate fields, namely expertise in fundamental quantum optics, as contributed by Professor Markus Aspelmeyer, and expertise in Materials Science and semiconductor microfabrication brought by myself, Dr. Garrett Cole. This unique example of technical cross-fertilization was facilitated by a Marie Curie International Incoming Fellowship (IIF) which brought me to Austria from California in the fall of 2008. The aim of this grant was to apply my engineering background to ongoing cavity optomechanics experiments in Vienna in order to develop quantum-enabled devices. The combination of these divergent disciplines, specifically that of basic research, aiming to push the limits of scientific knowledge, with the more practical engineering side, exploiting advanced microfabrication techniques to turn these basic concepts into reality, helped to sow the initial seeds for success. Realizing a technical breakthrough is one thing, but executing on it is admittedly the more difficult aspect, and this is where the second key element comes in to play. Fortunately, Markus and I were able to draw from the fertile grounds of Europe’s quantum optics hub in Vienna for both Austrian and EU funding in order to transform our idea from an initial concept into physical reality in the form of engineering prototypes. As detailed in this write-up, working with these agencies, we received additional assistance in setting up the legal and financial framework of our company, as well as in securing protection for the intellectual property produced along the way.

In order to provide the requisite technical background for our innovation, we have to go back a few years, actually more than one hundred… Linear optical cavities, most notably the namesake interferometer demonstrated by Charles Fabry and Alfred Perot, have been key optical elements for both applied and fundamental scientific applications since their initial demonstration in 1897. The design of such a system is deceptively simple: light is passed through a pair of parallel high-reflectivity mirrors and interference between the multitude of reflections between the mirrors generates well-defined fringes or optical resonances emerging from the device, from which spectral properties of light can be deduced and accurate measurement of space—and in combination with other elements, time—can be realized.

Building upon more than a century of progress, state-of-the-art Fabry-Perot cavities have reached a point where their ultimate performance is limited by fundamental thermo-mechanical fluctuations, or Brownian motion, of the components of the cavities themselves. Recently, these unavoidable fluctuations have materialized as a barrier to ever more precise measurements of time and space, such as those obtained using advanced optical atomic clocks and interferometric gravitational wave detectors. As a consequence of this limitation, researchers in the optical precision measurement community have been searching for more than a decade now for a means to minimize the adverse affects of this so-called “thermal noise.” A breakthrough in this area requires the development of mirrors, or, more specifically, mirror materials, that also exhibit high mechanical quality. The latter point may not be obvious at first glance, but based on statistical mechanics, most notably the fluctuation dissipation theorem, one finds that enhanced stability, realized through a reduction in the Brownian noise, is obtained by minimizing the intrinsic mechanical damping of the mirrors. Working in the field of cavity optomechanics at the Vienna Center for Quantum Science and Technology, we happened upon such a solution.

In this case Markus and I were investigating the potential for observing macroscopic quantum phenomena in high-performance microfabricated resonators. By a fortuitous coincidence, our optomechanical systems had similar technical requirements as that of ultra-stable optical cavities, namely the simultaneous need for high optical and mechanical quality factors. Unbeknownst to us (at least initially), in pursuing the development of ever better micro-resonators, we had stumbled upon a mirror technology that promised to solve the long-standing thermal noise issue in Fabry-Perot cavities. Stemming from this finding, initial discussions with researchers from the precision measurement community motivated us to pursue the potential for applying our low-loss mirrors to “macroscopic” (centimeter-scale) systems, rather than the micromechanical devices we were focused on in Vienna.

Ultimately, the proprietary manufacturing process that is now the heart of CMS built upon all of my prior experience, combining aspects of semiconductor mirrors borrowed from surface-emitting lasers, an epitaxial layer transfer technique gleaned from advanced nanofabrication processes, along with my more recent work in Vienna, which had yielded an extensive knowledge of mechanical dissipation processes. After more than two years of development, these areas were combined to create our novel “crystalline coating” technology. Ultimately, this coating process involves separating and then directly bonding (using no adhesives or intermediate films) high-quality single-crystal semiconductor heterostructures onto curved optical substrates. With this process we circumvent two previous impediments to applying high-quality monocrystalline structures in general optics applications, including the difficulty of direct crystal growth on a curved optical surface, and the fact that the typical glass optical substrates, with their amorphous structure, lack the order required for seeded crystal growth. Compared with existing optical coating technology, our crystalline coatings yield an immediate tenfold reduction in mechanical loss, with a further order of magnitude improvement possible at cryogenic temperatures. Thus, coating Brownian noise levels can be reduced by up to a factor of ten with our mirrors, leading to significant performance enhancements in precision optical interferometers requiring the ultimate levels of stability.

With the technical foundation in place, the more difficult aspect was in bringing this unique mirror technology “out of the laboratory and into the light” as we have previously described it. As luck would have it, our external collaborators encouraged us by demanding the product before it even existed. This greatly simplified our decision as to whether or not we should pursue commercialization of this technology, as we already had an immediate customer base knocking on our door. During this transition, the University of Vienna was instrumental in establishing the relevant support contacts outside of our scientific network. After an initial consultation with INiTS (a Viennese business incubator of the Vienna Business Agency, the University of Vienna, and the Vienna University of Technology), Markus and I received financing from both the AWS-operated JITU pre-seed program of the BMWFJ and the newly established Proof of Concept initiative of the European Research Council. One critical aspect at this early stage was the fact that the financial support offered by AWS and the ERC made prototype development possible. These initial prototypes resulted in our first technical demonstrator, entitled, “Tenfold reduction of Brownian noise in high-reflectivity optical coatings,” which was published in the August 2013 issue of Nature Photonics, covering research pursued in collaboration with the University of Vienna and our collaborators from JILA in Boulder, Colorado. Once the technology was proven, we were overwhelmed by the interest in our coatings from the precision measurement community. At this point it was clear that the only way to effectively fulfill the demand was by formally spinning off the technology and forming a start-up company, leading to the founding of CMS GmbH.

CMS is fortunate in that we had an immediate customer base and, coupled with the excellent funding opportunities for high-tech startups in Europe, we could pursue prototype development and even initial sales without the need for outside private investment. The process of growing a company is not without its headaches, there are of course growing pains, dead ends from a business and technical perspective, and there were times (and continue to be instances) where we have to risk our own personal finances, as meager as they may be, to bridge small gaps in funding. One key piece of advice for those considering taking on such a risky endeavor is to build up and rely upon a trusted network of contacts to assist with issues that will inevitably be out of reach to the typical knowledge base of a scientist or engineer. Seeking out expert opinions from friends, family, and colleagues for legal and financial matters, including such heady topics as corporate and patent law, accounting, etc. can be extremely helpful. In this area we have been fortunate to be able to draw from our individual networks and have even brought some friends into the fold, particularly our new CEO, Dr. Christian Pawlu.

Though we seemingly operate in a niche field, improving the sensitivity of optical precision measurement systems has a far reaching impact, from fundamental scientific research efforts to advanced technologies including trace chemical analysis, inertial navigation, and broadband communications. As a newcomer and small player in this arena, CMS has grown to encompass nearly 10 staff members covering two continents (with operations in Vienna, Austria and Santa Barbara, CA) and continues to generate not only significant business interest from both the scientific community and industrial partners, but also high-impact publications and awards for our young enterprise. On the scientific front, CMS has teamed up with partners at the leading national metrology laboratories to build the world’s most stable clocks, as well as to pursue the development of prototype gravitational wave detector optics along with members of the LIGO Scientific Collaboration. If Charles and Alfred were around to witness the technical revolutions stemming from the invention of their elegant interferometer, itself developed in the pursuit of fundamental optical and atomic physics, I think that they would be quite pleased with the progress over the last century.

In conclusion, as has been demonstrated time and time again, under the proper conditions, fundamental research will yield entirely unexpected technological innovations. In that vein, CMS now stands as another example of how the exploration of foundational questions can generate an unexpected high-tech product, standing in stark contrast to the pervasive myth that one can “force” innovation to occur through some form of regimented milestone-driven processes. Ambitious researchers, when given the freedom to operate within their respective areas of expertise and, even more importantly, coupled with a supportive and well-financed spin-off infrastructure, can realize a successful transition to budding entrepreneurs. It has been a very rewarding, yet at times tumultuous, experience, but if given a second chance I would nonetheless pursue it again. The text above provides one admittedly unproven example, and is somewhat biased as it is of course my own personal experience, but I hope that this post inspires others to consider this path. Even more importantly, I hope that this story provides policy makers with some background on the environment necessary to ensure that these ideas are spawned in the first place and, once developed, can ultimately be nurtured and guided towards success.

View More: Cole, Co-Founder of Crystalline Mirror Solutions, obtained his PhD in Materials from UC Santa Barbara in 2005. Since completing his doctorate, he has held positions ranging from the first employee of a high-tech startup, to a postdoctoral position at Lawrence Livermore National Laboratory, a Marie Curie Fellow of the Austrian Academy of Sciences, and most recently an assistant professor of Physics at the University of Vienna. Leveraging his expertise in microfabrication, tunable surface-emitting lasers, and cavity optomechanics, Dr. Cole developed the proprietary substrate-transfer process at the heart of CMS and, along with Markus Aspelmeyer, co-founded the venture in 2012.


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