The new RP Photonics Buyer's Guide

Posted on 2012-08-06 as a part of the Photonics Spotlight.

Permanent link: http://www.rp-photonics.com/spotlight_2012_08_06.html

Author: Dr. Rüdiger Paschotta, RP Photonics Consulting GmbH

The RP Photonics website has been substantially expanded by the introduction of the new RP Photonics Buyer's Guide. This is a large database of suppliers for photonics products. Hundreds of suppliers are listed already (by name and by products), and more will follow.

Some may ask whether we need another buyer's guide, as there are several already. The answer is yes, as the RP Photonics Buyer's Guide has several unique features, providing a high value:

• It is intimately connected with the Encyclopedia of Laser Physics and Technology, which has become extremely popular. This gives the users immediate access to supplementary high-quality scientific and technical information. Readers of encyclopedia articles can move to the buyer's guide with a single click.
• The page layout is simple and clear, not excessively covered with advertising, so that the user experience will make it attractive to use this resource.
• Both for users and suppliers, it is easy to use.

For these reasons, we expect the RP Photonics Buyer's Guide to become another very popular service of RP Photonics for the worldwide photonics community.

Any so far missing suppliers are welcome to register, using a simple registration form.

The advertising opportunities have also been greatly expanded:

• Suppliers can have enhanced entries for better visibility of their companies and products.
• The banners in the right column of all encyclopedia pages are now also displayed in the buyer's guide and thus obtain a further increased value.
• Banners and company profiles can also host videos.

New Raman Lasers

Posted on 2012-03-12 as a part of the Photonics Spotlight.

Permanent link: http://www.rp-photonics.com/spotlight_2012_03_12.html

Author: Dr. Rüdiger Paschotta, RP Photonics Consulting GmbH

Ref.: J. Shi et al., “Highly efficient Raman distributed feedback fibre lasers”, Opt. Express 20 (5), 5082 (2012); encyclopedia article on Raman lasers; J. Lin et al., “Continuous-wave VECSEL Raman laser with tunable lime-yellow-orange output”, Opt. Express 20 (5), 5219 (2012)

Two interesting papers on Raman lasers appeared in a recent issue of Optics Express:

Raman DFB Fiber Laser

VECSEL with Intracavity Raman Conversion

Conflicting Definitions of s and p Polarization

Posted on 2012-03-03 as a part of the Photonics Spotlight.

Permanent link: http://www.rp-photonics.com/spotlight_2012_03_03.html

Author: Dr. Rüdiger Paschotta, RP Photonics Consulting GmbH

It is quite common to talk about s-polarized and p-polarized laser beams, incident on optical surfaces or diffraction gratings. Therefore, it is quite disturbing that there are conflicting definitions in the scientific literature:

• Usually, p-polarized light is understood to have an electric field direction parallel to the plane of incidence on a device, and s-polarized light has the electric field oriented perpendicular to that plane. (Actually, the letters have a German origin: s = senkrecht = perpendicular, p = parallel.) According to that definition, we can obtain vanishing reflectivity of a surface at Brewster's angle for p polarization. That's easy to remember: “p” is closer to “B” (like “Brewster”), so Brewster's trick works with p polarization.
• In the context of diffraction gratings, the opposite definition can be found. Here, “s” still means perpendicular, but in that case perpendicular not to the plane of incidence, but to the lines of the grating. So for s polarization, the electric field vector is perpendicular to the lines, i.e., it lies in the plane of incidence.

So there is another trap to fall into! When reading some paper, we have to find out which definition has been used.

By the way, some people call a laser beam s-polarized, when its polarization is vertical, i.e., perpendicular to the lab's floor. It is better, though, to restrict the terms s polarization and p polarization to cases where the polarization direction with respect to a plane of incidence is relevant. For example, if you have a Brewster-angled prism in the common orientation where the reflected beam stays horizontal in direction, s polarization according to the first definition above is vertical. However, if you turn the prism such that the reflected beam goes upwards, that will change, of course.