Blog articles on topics in photonics, particularly laser technology and application. http://www.rp-photonics.com/spotlight.html en-us RP Photonics Consulting GmbH, 2008 Fri, 15 Aug 2008 17:22:46 +0100 http://www.rp-photonics.com/spotlight_2008_08_15.html A print version of the Encyclopedia of Laser Physics and Technology will appear soon. It can already be ordered. Fri, 15 Aug 2008 17:22:00 +0100 http://www.rp-photonics.com/spotlight_2008_08_15.html http://www.rp-photonics.com/spotlight_2008_07_26.html It may be surprising that the linewidth of an optical beat signal can be exactly zero, even if the two optical frequencies both have phase noise, which is not even perfectly correlated. Sat, 26 Jul 2008 18:21:00 +0100 http://www.rp-photonics.com/spotlight_2008_07_26.html http://www.rp-photonics.com/spotlight_2008_07_13.html We are often told a very simplified and actually distorted history of the Michelson-Morley experiment and the following development of science. The article tries to correct such views and puts Einstein's accomplishment in a different perspective. Sun, 13 Jul 2008 11:58:00 +0100 http://www.rp-photonics.com/spotlight_2008_07_13.html http://www.rp-photonics.com/spotlight_2008_07_02.html A curious phenomenon is that a SESAM for passive mode locking of a solid-state laser sometimes lives longer when being operated with a more tightly focused resonator mode. The article explains this on the basis of Q-switching instabilities, which are then more firmly suppressed. Wed, 2 Jul 2008 18:04:00 +0100 http://www.rp-photonics.com/spotlight_2008_07_02.html http://www.rp-photonics.com/spotlight_2008_06_20.html Various kinds of all-in-one ultrafast laser systems have been proposed which could be simpler than a traditional system consisting of a mode-locked laser and a regenerative amplifier. It seems though, that this approach has no real chance to lead to cheaper systems with comparable performance. The article gives some reasons for that opinion. Fri, 20 Jun 2008 16:20:00 +0100 http://www.rp-photonics.com/spotlight_2008_06_20.html http://www.rp-photonics.com/spotlight_2008_06_13.html It is sometimes claimed that the transform limit for pulses is strongly related to Heisenberg's uncertainty limit. The article shows that this is nonsense; there is nothing more than a vague similarity. One should not confuse physics (statements on nature) with mathematics. Fri, 13 Jun 2008 21:08:00 +0100 http://www.rp-photonics.com/spotlight_2008_06_13.html http://www.rp-photonics.com/spotlight_2008_06_06.html Fiber laser products often strictly do not contain a fiber laser, but rather a master oscillator fiber amplifier. This may or may not be relevant for the customer. The high sensitivity of such devices to optical feedback can be a problem of which many people are no aware. Fri, 6 Jun 2008 14:36:00 +0100 http://www.rp-photonics.com/spotlight_2008_06_06.html http://www.rp-photonics.com/spotlight_2008_05_25.html It is interesting to consider the contributions of Albert Einstein to the laser. It turns out that these contributions are in a sense similar to those to the atomic bomb: basic physical principles were revealed, while a lot of work remained to be done to get the thing going. Sun, 25 May 2008 19:05:00 +0100 http://www.rp-photonics.com/spotlight_2008_05_25.html http://www.rp-photonics.com/spotlight_2008_05_13.html Experience shows that self-starting of passively mode-locked lasers is more easily achieved for those lasers with short resonators. The article explains why. Tue, 13 May 2008 12:15:00 +0100 http://www.rp-photonics.com/spotlight_2008_05_13.html http://www.rp-photonics.com/spotlight_2008_05_05.html A frequently encountered question concerns the length of a photon. The article shows that this is not a sensible question, because there is no comprehensive model of a photon to which this question could be applied. Mon, 5 May 2008 14:55:00 +0100 http://www.rp-photonics.com/spotlight_2008_05_05.html http://www.rp-photonics.com/spotlight_2008_04_28.html The term 'polarization' is often used in photonics. It can have totally different meanings. Mon, 28 Apr 2008 15:37:00 +0100 http://www.rp-photonics.com/spotlight_2008_04_28.html http://www.rp-photonics.com/spotlight_2008_04_22.html 'Coherence' is a term about which there is significant confusion in the literature. The article gives some examples and encourages a more precise use. Tue, 22 Apr 2008 11:51:00 +0100 http://www.rp-photonics.com/spotlight_2008_04_22.html http://www.rp-photonics.com/spotlight_2008_04_15.html The term 'modes' belongs to the most often abused terms in photonics. The article discusses some examples and shows that the problem is not just sloppy wording, but the risk of losing the essential meaning. Tue, 15 Apr 2008 18:02:00 +0100 http://www.rp-photonics.com/spotlight_2008_04_15.html http://www.rp-photonics.com/spotlight_2008_04_02.html At a first glance, it seems that the balance between dispersive and nonlinear effects in a soliton pulse cannot be maintained e.g. when the fiber dispersion is reduced to one half the original value. A closer inspection shows that this is not the case. Wed, 2 Apr 2008 17:31:00 +0100 http://www.rp-photonics.com/spotlight_2008_04_02.html http://www.rp-photonics.com/spotlight_2008_03_26.html It is often experienced that those mode-locked lasers generating shorter pulses also offer lower average powers and pulse energies. The article explains some common reasons for that correlation. Wed, 26 Mar 2008 18:18:00 +0100 http://www.rp-photonics.com/spotlight_2008_03_26.html http://www.rp-photonics.com/spotlight_2008_03_17.html This article shows that the development of ultrafast fiber lasers is not just applying known features of mode locking to fiber lasers instead of bulk lasers, but rather involves novel aspects, mainly due to the involved nonlinearities and dispersion. This has important consequences, particularly concerning the technical limitations and the complications of the development process, which requires more physics expertise and is likely to take more time. Mon, 17 Mar 2008 15:49:00 +0100 http://www.rp-photonics.com/spotlight_2008_03_17.html http://www.rp-photonics.com/spotlight_2008_03_10.html It is discussed while most nonlinear processes require phase matching to be efficient, while others don't need that. The reason is not that these processes would be phase-insensitive. Instead, phase matching is automatically established in certain situations. Mon, 10 Mar 2008 16:16:00 +0100 http://www.rp-photonics.com/spotlight_2008_03_10.html http://www.rp-photonics.com/spotlight_2008_03_04.html The article emphasizes that there are different meanings of beam quality, which are not all expressed with an M2 factor. Some beams may cause trouble in applications, even though their M2 value is low. Tue, 4 Mar 2008 19:05:00 +0100 http://www.rp-photonics.com/spotlight_2008_03_04.html http://www.rp-photonics.com/spotlight_2008_02_22.html The article discusses the maximum optical power which can be launched from an incandescent bulb into a single-mode fiber. Fri, 22 Feb 2008 19:02:00 +0100 http://www.rp-photonics.com/spotlight_2008_02_22.html http://www.rp-photonics.com/spotlight_2008_02_14.html Laser development projects can easily fail, in the end requiring far more time and resources than originally anticipated. The reason is usually a non-systematic approach. The article gives a fictional example for a failed process, and suggests a better approach. Thu, 14 Feb 2008 19:16:00 +0100 http://www.rp-photonics.com/spotlight_2008_02_14.html