Doing Things Properly: It's the Economy, Stupid!

Posted on 2009-06-29. Permanent link: http://www.rp-photonics.com/spotlight_2009_06_29.html

Well, I know that the phrase “It's the Economy, Stupid!” has been used in a different context (in Bill Clinton's campaign for presidency) and with a different meaning, but anyway it applies very nicely to issues which I encounter again and again in my job. The phrase is often exactly the right answer to the question: Why should we do certain things properly? Of course, explicitly asking that question would often be the first step toward a reasonable solution.

Example Case: a Fiber Manufacturer

Let's look at an example. A company is selling rare-earth-doped fibers for fiber lasers and amplifiers. They produce these fibers themselves, and are obviously experts in the fabrication. They believe, however, that they do not need to know much about how the fibers are used in amplifiers. For example, a customer may ask how long a certain fiber should be for some amplifier, and what gain would be achievable with a certain pump power. One may argue that it is the customer's job to find out such things. But obviously that attitude (don't care what the fibers can do, only want to sell them) will not help to expand business. Of course, it would cost some time and money to get some powerful software for simulating the performance of fibers in amplifiers and lasers. However, it is a tiny fraction of what it costs to set up the fiber fabrication, and may often be the key for transforming fabrication capabilities into sales. Clearly, it is a matter of economy and not a luxury to

Another Example: Resonator Design with Trial & Error

Another common case is related to resonator design for solid-state lasers. Quite a number of laser manufacturers appear to believe that you can get away without developing resonator designs based on a decent understanding of the underlying physics. They may have some basic ABCD matrix software, sufficient for calculating most of the basic properties of a given design, but not for taking into account issues like alignment sensitivity and particularly not for finding optimized designs. Still more importantly, they don't have anybody with sufficient expertise, so they don't even know what could be done. The likely results are that a lot of undirected trial & error experiments are done and non-optimum designs go into production. A proper laser development process could be much more efficient.

Admittedly, there is no easy way of acquiring not only the required software, but also the corresponding technical expertise. Particularly smaller companies may not be able to afford integrating into their team a technical guru, who's expertise couldn't be utilized all the time. However, why not get designs made by an external resonator design expert? Why not spend a fraction of the turn-over generated with a single laser system in order to get the design for many lasers right? It should be a no-brainer to realize that saving a little money there is stupid in economic terms, and not just unsatisfactory for a perfectionist.

Doing Things Properly – But How Properly?

Perfection is not always what one should aim for. Economically, it is entirely right not to drive everything to perfection. However, there are key issues where doing too little will either become too expensive (e.g. by wasting resources) or, what is often even more important, cripple the potential for generating income. There is often a long chain of achievements required for getting from a first idea to the generation of turnover: you must properly analyze the idea in technical terms, analyze its market potential, get the capital and the right people, have good designs worked out, set up the production and service infrastructure, and reach potential customers in effective ways. The worst one can do is often to create (or not fix) a bottleneck in that chain:

• Invest into a nice looking new technology, but don't do a proper feasibility study and comparative assessment, and thus overlook some nasty problems.
• Set up a nice production facility, but use non-optimized product designs.
• Have a lot of marketing activities, but fail to prove competence when people start asking questions or look at the product documentation.
• Hire a technical team but fail to keep them up to date and inspired by not providing continuing education, e.g. in the form of staff training courses.

Underinvestment at one single location may cripple the success of the whole project or company. It is thus essential to locate and fix such bottlenecks in order to unleash the business potential which would otherwise remain blocked.

I probably don't need to say much against the argument “… but the economic downturn forces us to minimize cost!” Well, if you are struggling against imminent shutdown and can no longer think about long-term efficiency, that may be right. But if you have a business with a potential for success, then the essential point will be to release any breaks.

See also the earlier article on time to market.

Coherence – a Black-or-White Issue?

Posted on 2009-06-23. Permanent link: http://www.rp-photonics.com/spotlight_2009_06_23.html

Ref.: encyclopedia article on coherence; Spotlight article of 2006-09-22

Lasers are often said to be special light sources because they emit coherent light, whereas other light sources are incoherent. However, is this really a “black and white” issue?

Beginning with spatial coherence, there can really be gradual differences. Many lasers exhibit nearly the highest possible degree of spatial coherence, which would imply perfectly well-defined wavefronts of the output. Others exhibit a substantially reduced degree of spatial coherence, which is associated with a reduced beam quality. Compared with some really “incoherent” light source such as an incandescent lamp, the spatial coherence is still very high – sufficient to form a well directed laser beam, even if its focusability is not as high as for some other laser beams. That big difference in the degree of coherence between even poor lasers and other light sources justifies the practice of calling lasers coherent light sources, in contrast to incoherent sources like bulbs.

Concerning temporal coherence, the situation is somewhat more complicated. Some very carefully stabilized single-frequency lasers, used as optical frequency standards in frequency metrology, exhibit an extremely high temporal coherence, associated with a linewidth below 1 Hz (to be compared with the mean frequency of hundreds of terahertz). Most other lasers have a temporal coherence which is lower by many orders of magnitude. The largest optical bandwidth is reached by some few-cycle mode-locked titanium-sapphire lasers (see also: ultrafast lasers), emitting octave-spanning spectra. Looking at this huge bandwidth, one might believe that such lasers have an extremely low level of temporal coherence – comparable with that of a light bulb. This, however, is not true; the issue has been discussed in an earlier Spotlight article. Essentially, one has to consider that the spectrum (viewed with sufficiently high spectral resolution) forms a frequency comb, consisting of very narrow equidistant lines. So we see not only that lasers exhibit very different levels of temporal coherence, but also that one misses essential aspects when trying to quantify the temporal coherence with a single number such as a coherence length or optical bandwidth.

As a final remark, optical processes and certain techniques are called coherent or incoherent, depending on whether they are sensitive to (relative) optical phases. This is really a black-and-white issue. For example, coherent beam combining works only with interferometric stability of mutual phase relations, whereas spectral beam combining is not sensitive to such phases, as it exploits differences in optical frequency.

Prizes of the European Physical Society

Posted on 2009-06-08. Permanent link: http://www.rp-photonics.com/spotlight_2009_06_08.html

Ref.: announcement of the EPS

The European Physical Society has announced the following research prizes:

• Tobias Kippenberg has received the Fresnel Prize (fundamental) for his pioneering work on ultra-high-Q microresonators for optical frequency comb generation and on optomechanical phenomena.
• Romain Quidant has received the Fresnel Prize (applied) for his work on engineering plasmon properties of metallic nanostructures, extending optical concepts and photonic functionalities down to the nanometer scale.
• Fernando G. S. L. Brandao and Alexei Ourjoumtsev obtained the Ph. D. Thesis Prizes (fundamental) for work in quantum optics (quantum information theory, novel quantum states).
• John C. Travers and Deran Maas obtained the Ph. D. Thesis Prizes (applied) for work on supercontinuum generation (Travers) and novel pulsed semiconductor lasers (Maas).

Besides these junior awards, there have been the following senior researcher prizes:

• Alain Aspect received the Senior Prize for Fundamental Aspects of Quantum Electronics and Optics for his numerous contributions to the fields of quantum and atom optics. He is famous e.g. for his 1982 experiment on quantum entanglement.
• Thomas Ebbesen received the Senior Prize for Applied Aspects of Quantum Electronics and Optics for work on novel optical properties of nanostructured metals and in particular for his discovery of how light can be efficiently transmitted through subwavelength holes.

I had the great honor of serving as the chair of the Junior Awards Committee, taking care of the Fresnel Prizes and the Ph. D. Thesis Prizes. I am glad that a very smooth and clean selection process was possible in collaboration with the other committee members (J. Dudley, F. Wagner, R. De La Rue, D. Meschede, K. Moelmer, and V. Zadkov). At this point I would like to remark that Deran Maas, with whom I once interacted at ETH Zürich, won his prize without a score from my side. I am fully convinced that he deserves the prize, but any potential conflict of interest must be properly handled.

Protecting Ethical Standards

It is unfortunately not always easy to avoid that improper behavior of some colleagues influences the decisions for such prizes. Personally, I have witnessed situations where some person was nominated for a prize not because of his achievements, but simply because he was considered an ally who was supposed to act in the favor of the nominator at later occasions. There are even persons who do not hesitate to put some pressure on colleagues to nominate them, or to suggest shady deals. Some seem not even to realize that this is definitely an improper behavior, undermining the whole sense which such prizes can make: giving recognition to those who deserve it for their scientific contributions or for their service to the community. In the interest of the whole scientific community, we should do our best to discourage such behavior and enforce ethical standards. I would have been prepared to raise my voice in the prize committees where I participated, but gladly have not encountered improper conduct at these occasions.

5 Years of RP Photonics Consulting

Posted on 2009-06-02. Permanent link: http://www.rp-photonics.com/spotlight_2009_06_02.html

In these days, RP Photonics Consulting GmbH celebrates the 5^th anniversary of its start. The company was founded in late May 2004. Since that time, the visibility and turnover exhibited steady and strong growth, and RP Photonics has become a well established enterprise. Its standing is unusually strong for a small and relatively young company.

One of the most important factors behind that success is the unusual marketing concept, which is based not on regularly firing the usual advertising fireworks (such as bombarding all exhibitors of some trade show with unwanted e-mails, telephone calls and faxes), but rather on providing substantial and long-lasting benefits to many. This applies not only to some group of customers, but to the worldwide community of photonics research and development. The key element is the Encyclopedia of Laser Physics and Technology, which has grown to a huge open-access resource of high-quality information on laser technology and other subjects of photonics. This helped to convince many that there is not only a huge technical and scientific know-how available, but also the ability to communicate clearly and to focus on vital issues rather than getting lost in esoteric fringe issues. Also, it demonstrates the orientation toward long-term benefits for everybody and thus the sincerity of the general approach.

Marketing is not everything, though. RP Photonics does not only steadily attract more customers, but also maintains its reputation with a consistent practice of reliability, quality, efficiency and customer orientation. Customers are extremely pleased, for example, to obtain competent and very helpful advice quickly and without doing any painfully complicated paperwork beforehand.

Main Activities

The main activities of RP Photonics have not changed much since the beginning:

• Optimization of various kinds of laser sources, preferably starting in the early stages with feasibility studies and technology reviews, most often with design work and also with problem solving for already existing hardware.
• Advice for laser applications, for example concerning the best suited laser type (e.g. bulk laser or fiber laser?).
• Simulation software, particularly for Q-switched lasers and fiber lasers and amplifiers, used both in industry and scientific research.
• Continuing education in the form of specialized training courses, both in the form of publicly announced courses (normally associated with major scientific and technical conferences) and with tailored courses on a customer's premises.

The technical areas, customer groups and customer locations are similarly diverse. Customers are companies of all sizes (more frequently medium and small companies), in a few cases research institutes, mostly spread over whole Europe and the U.S. The activities are also spread over many areas and industrial sectors. Obviously, this high level of diversity is particularly helpful in an economic crisis as we experience it in these days. RP Photonics is not dependent on any particular industrial sector or even a particular company.

The Future: Sustainable Development

For the following years, no substantial changes are to be expected. As its main priority, RP Photonics will work hard to preserve its excellent reputation and the unusually high level of customer satisfaction. No short-term incentive could be strong enough to sacrifice even a tiny bit of this value. Sustainability is the key for long-term survival, not a luxury item for good times and certainly not just a currently popular buzzword.

Interference Effects with Imbalanced Intensity Levels

Posted on 2009-05-22. Permanent link: http://www.rp-photonics.com/spotlight_2009_05_22.html

Ref.: encyclopedia article on interference

It is well known that interference of optical beams (e.g. laser beams) can lead to fancy interference patterns. What often surprises people, however, is that interference fringes can be rather pronounced even in situations whether the intensities of the two interfering beams are very different.

As an example, would you expect a strong interference effect when one beam has a 100 times smaller intensity than the other one? The calculation is actually simple. The amplitude of the stronger beam is only 10 times higher, as the intensity is proportional to the square of the amplitude. In the extreme cases of destructive and constructive interference, the total amplitude is 90% and 110%, respectively, compared with that of the stronger beam alone. From that we see that the total intensity varies between 81% and 121% of that of the stronger beam alone. And that effect may already be clearly visible!

As another example, consider the optical intensity inside and outside a dielectric mirror structure for a monochromatic incident beam, as shown in the graph above. The counterpropagating beams form a standing-wave pattern. The initially surprising finding is that we appear to get completely destructive interference, even though the mirror reflectivity at the relevant wavelength is only 83.6%. Despite that imbalance of intensities, interference can get the resulting intensity down to below 1% of the incident intensity, and in the graph this can hardly be distinguished from zero.

Take these effects are a warning: interference effects are in many situations stronger than one would expect without having in mind that interference means adding amplitudes, not intensities.