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 Thu, 02 Sep 2010 20:42:57 +0100 http://www.rp-photonics.com/spotlight_2010_09_02.html The article first explains a number of technical aspects, all showing that LEDs can be more energy efficient than any other light sources. Nevertheless, it then shows that rebound effects may well turn this into effectively more consumption, rather than less. The reason is basically that people generally use (and waste) more of what is available cheaply. Thu, 2 Sep 2010 20:34:00 +0100 http://www.rp-photonics.com/spotlight_2010_09_02.html http://www.rp-photonics.com/spotlight_2010_07_27.html When mode-locked high-power lasers were developed, a serious concerning was damage to the SESAMs used for mode locking. It turned out, however, that this issue was much smaller than expected, while other problems came up in the area of dispersion compensation. The concept of power scaling shows more clearly why this had to go that way. Tue, 27 Jul 2010 18:20:00 +0100 http://www.rp-photonics.com/spotlight_2010_07_27.html http://www.rp-photonics.com/spotlight_2010_07_12.html It is explained why it is so essential for cost-effective development and production to engage a highly qualified laser expert very early on. Mistakes made in the early stage can be very expensive. Mon, 12 Jul 2010 09:49:00 +0100 http://www.rp-photonics.com/spotlight_2010_07_12.html http://www.rp-photonics.com/spotlight_2010_06_09.html It is explained that a simple combination of a polarizer and a quarter waveplate can sometimes be used instead of a Faraday isolator. However, this approach has its limitations. Wed, 9 Jun 2010 20:54:00 +0100 http://www.rp-photonics.com/spotlight_2010_06_09.html http://www.rp-photonics.com/spotlight_2010_05_14.html The Encyclopedia of Laser Physics and Technology has become the victim of plagiarism, but RP Photonics fights against that - successfully so far. Fri, 14 May 2010 10:47:00 +0100 http://www.rp-photonics.com/spotlight_2010_05_14.html http://www.rp-photonics.com/spotlight_2010_04_26.html The article explains the difference between resolution and accuracy of a measurement, and describes an example case where the accuracy can be much higher than the resolution of a detector chip. Mon, 26 Apr 2010 14:47:00 +0100 http://www.rp-photonics.com/spotlight_2010_04_26.html http://www.rp-photonics.com/spotlight_2010_04_16.html It is discussed why laser diodes, in contrast to active fibers, cannot be made with very small refractive index contrast in order to obtain single-mode guidance in combination with very large mode areas. The key problem arises from the refractive index variations caused by the spatially varying carrier density. Fri, 16 Apr 2010 11:23:00 +0100 http://www.rp-photonics.com/spotlight_2010_04_16.html http://www.rp-photonics.com/spotlight_2010_04_08.html Curious behavior is observed when a nearly rectangular beam shape is generated. This, however, can be well understood considering Fourier optics. Thu, 8 Apr 2010 11:43:00 +0100 http://www.rp-photonics.com/spotlight_2010_04_08.html http://www.rp-photonics.com/spotlight_2010_03_22.html All-in-one concepts, where several functions are integrated into a single component, often look attractive at a first glance. The article shows, however, that moderate advantages often come at a high price. A modular approach is often much more powerful and practical. Mon, 22 Mar 2010 11:22:00 +0100 http://www.rp-photonics.com/spotlight_2010_03_22.html 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