Blog articles on topics in photonics, particularly laser technology and application. http://www.rp-photonics.com/spotlight.html en-us RP Photonics Consulting GmbH, 2010 Mon, 15 Mar 2010 10:17:18 +0100 http://www.rp-photonics.com/spotlight_2010_03_15.html It is well known that the phenomenon of spatial walk-off can degrade the beam quality in nonlinear conversion processes. The article shows, however, that this is not necessarily the case, even in cases with strong walk-off. Mon, 15 Mar 2010 10:17:00 +0100 http://www.rp-photonics.com/spotlight_2010_03_15.html http://www.rp-photonics.com/spotlight_2010_03_09.html It is discussed why in the context of modeling of fiber amplifiers and lasers it is normally reasonable to treat nonlinear effects only to a limited extent. Tue, 9 Mar 2010 08:50:00 +0100 http://www.rp-photonics.com/spotlight_2010_03_09.html http://www.rp-photonics.com/spotlight_2010_03_03.html The article explains why 'threshold' values are often given for the onset of nonlinear effects, how Raman and Brillouin scattering lead to nonlinear power losses, and how nonlinear effects can be reduced in fiber amplifiers. Wed, 3 Mar 2010 12:33:00 +0100 http://www.rp-photonics.com/spotlight_2010_03_03.html http://www.rp-photonics.com/spotlight_2010_02_26.html A new paper of Dr. Paschotta appeared in Optics Express. It presents news results on the timing jitter and phase noise of mode-locked fiber lasers. Fri, 26 Feb 2010 09:39:00 +0100 http://www.rp-photonics.com/spotlight_2010_02_26.html http://www.rp-photonics.com/spotlight_2010_02_06.html It is pointed out that the selection process for papers at scientific conferences and journals often favors papers reporting advances in performance, while not rating highly papers which primarily advance our understanding and give new perspectives. In an attempt to improve this, we should think carefully about the right criteria for scoring and accepting papers. Sat, 6 Feb 2010 11:32:00 +0100 http://www.rp-photonics.com/spotlight_2010_02_06.html http://www.rp-photonics.com/spotlight_2010_01_29.html This opinion piece discusses the thesis that the photonics and laser industry is not mature in many places, and what could be done to make life easier. Fri, 29 Jan 2010 18:20:00 +0100 http://www.rp-photonics.com/spotlight_2010_01_29.html http://www.rp-photonics.com/spotlight_2010_01_22.html A record-high power level for a fiber laser has recently been achieved by IPG with an indirect pump scheme. The article explains the reasoning behind this. Fri, 22 Jan 2010 16:43:00 +0100 http://www.rp-photonics.com/spotlight_2010_01_22.html http://www.rp-photonics.com/spotlight_2010_01_11.html It is explained why the beam from a green laser pointer is much better visible in air than for a red laser, even though the difference in output power is not that large. The main reason turns out to be the wavelength-dependent sensitivity of the human eye. Mon, 11 Jan 2010 17:19:00 +0100 http://www.rp-photonics.com/spotlight_2010_01_11.html http://www.rp-photonics.com/spotlight_2009_12_31.html Etalons are often used as spectral filters and are tuned by tilting. The article discusses how tilting affects the transmission wavelengths and the transmission loss via a reduction in beam overlap. Thu, 31 Dec 2009 19:14:00 +0100 http://www.rp-photonics.com/spotlight_2009_12_31.html http://www.rp-photonics.com/spotlight_2009_12_13.html The article explains how to use the Nyquist equations for calculating thermal noise (Johnson noise) in a resistor, particularly in the context of a photodiode circuit. Sun, 13 Dec 2009 11:22:00 +0100 http://www.rp-photonics.com/spotlight_2009_12_13.html http://www.rp-photonics.com/spotlight_2009_12_08.html One would normally expect that forcing a laser to operate on a wavelength deviating from that of the free-running laser will reduce the output power. The article describes various situations, however, where forced tuning even increases the output power. Tue, 8 Dec 2009 20:17:00 +0100 http://www.rp-photonics.com/spotlight_2009_12_08.html http://www.rp-photonics.com/spotlight_2009_11_22.html The article shows that focusing a laser beam does not mean creating a demagnified image of the original beam profile. This has implications in the context of beam quality and beam shaping. Sun, 22 Nov 2009 10:57:00 +0100 http://www.rp-photonics.com/spotlight_2009_11_22.html http://www.rp-photonics.com/spotlight_2009_11_18.html The readers are reminded of additional photonics resources on the RP Photonics website. Wed, 18 Nov 2009 21:01:00 +0100 http://www.rp-photonics.com/spotlight_2009_11_18.html http://www.rp-photonics.com/spotlight_2009_11_13.html Photodetection involves both optical and electrical powers, which can lead to some confusion. The article explains that difference and discusses some important issues, partly related to the square-law dependence of the electrical signal power on the optical input power. Fri, 13 Nov 2009 16:26:00 +0100 http://www.rp-photonics.com/spotlight_2009_11_13.html http://www.rp-photonics.com/spotlight_2009_11_03.html The article discusses the coherence properties of light from incandescent lamps (light bulbs). It shows that it is important to distinguish between spatial and temporal coherence, and that both aspects of coherence are not totally excluded for bulbs. Tue, 3 Nov 2009 10:51:00 +0100 http://www.rp-photonics.com/spotlight_2009_11_03.html http://www.rp-photonics.com/spotlight_2009_10_19.html A case of scientific fraud has been reported at ETH Zurich. It is necessary to foster a serious discussion on scientific integrity, risk factors for science fraud, the responsibility of scientists and group leaders in particular, and on ways to overcome certain corrupt practices (concerning authorships, for example). Mon, 19 Oct 2009 19:25:00 +0100 http://www.rp-photonics.com/spotlight_2009_10_19.html http://www.rp-photonics.com/spotlight_2009_10_12.html It is curious that extremely hot bodies, such as some stars, emit what is called cold light. That term actually has two different meanings. Another interesting point is that many people always prefer warm light, although in offices they would do better with cold light. Mon, 12 Oct 2009 17:00:00 +0100 http://www.rp-photonics.com/spotlight_2009_10_12.html http://www.rp-photonics.com/spotlight_2009_10_08.html The 2009 Nobel Prize in Physics has been awarded to Charles K. Kao, Willard S. Boyle and George E. Smith. The articles focuses on the pioneering work of Charles K. Kao on optical fibers. Thu, 8 Oct 2009 15:15:00 +0100 http://www.rp-photonics.com/spotlight_2009_10_08.html http://www.rp-photonics.com/spotlight_2009_10_03.html Although it seems trivial to calculate the intensity of a laser beam, there is considerable confusion in the literature. A common mistake leads to results which are 2 times too low. Sat, 3 Oct 2009 14:34:00 +0100 http://www.rp-photonics.com/spotlight_2009_10_03.html http://www.rp-photonics.com/spotlight_2009_09_27.html It is explained why lasers can have a low pump threshold power even if the gain medium has a very short upper-state lifetime. Sun, 27 Sep 2009 10:40:00 +0100 http://www.rp-photonics.com/spotlight_2009_09_27.html