Interferometry Lasers

Lasers and Interferometry

RPMC has many years of experience supplying application specific lasers. We provide a wide selection of interferometry lasers. Whether it’s one of our single-mode HeNe lasers, with an excellent TEM00 beam, high stability, and long service life, one of our single-frequency, CW DPSS lasers, with high spectral stability and pointing stability, or one of our other options such as laser diodes, laser diode modules, or ultra compact DPSS modules, we should have the right laser to match your requirements. If you do not see the exact configuration you are looking for, please contact us! We are able to provide customizable options on most of our standard products, and can usually provide a fully customized solution to fit your exact needs!

Interferometry Applications: Distance/Surface Measurement, Gravitational Waves, and More

Interferometry refers to a wide range of techniques that rely on the superimposition of two coherent light paths, most often split from a single source, to form an interference pattern. This interference arises from path differences between the two beams, one reference light path, and one incident sample light path, resulting in measurable changes to the fringe pattern. This measurement technique can be used for a wide variety of different applications – from simple distance or surface measurements to structure and stress to the measurement of gravitational waves. A typical experimental setup is, in theory, quite simple. A highly stable, coherent laser is split in two, to create separate and identical beams. One is a reference arm with a fixed path, while the other forms the moving sample incident beam. Initially, the two beams are in phase, having been split from the same coherent source. If the two path lengths are the same, they will still be in phase when they reach the detector. However, slight deviations in the path of the sample beam will change its phase relative to the reference beam and so will produce associated deviations in the interference pattern. It is these deviations in the interference pattern that are the measurable output.

Critical Laser Source Requirements Common to Interferometry Applications

• Spectral Stability – Firstly, the source requires high spectral stability to ensure that pattern changes are caused by the sample, rather than laser effects. Longer coherence lengths, and therefore narrower linewidths, will partly determine the resolution of the measurement, along with consideration of the wavelength used
• Pointing Stability – High beam pointing stability ensures a consistent measurement on the selected sample position, whereas high beam quality reduces the possible complexities in analyzing the measurement result
• Power Level – Finally it is important to consider the available power level in comparison to the sample size, as higher power enables the imaging of larger areas

Why is Polarization Switching Unsuitable for Interferometry?

A common problem for HeNe laser customers is the issue of polarization switching, which is the sudden change of the polarization of different modes, especially in shorter tubes, which can be particularly detrimental when operating frequency stabilized HeNe laser tubes. This phenomenon is sometimes referred to as ‘mode hopping.’ However, this is not accurate. While somewhat similar to polarization switching, mode hopping involves (mostly in single-frequency lasers) the laser’s operation on a single resonator mode, which suddenly switches to another mode, causing the optical power to switch over to this new mode. Polarization switching shares this feature of erratic output power. However, with this phenomenon, the output power fluctuations are due to the swapping of the two perpendicularly polarized modes’ polarization states rather than the swapping from one particular mode to another.

Read the full article here.

Stable, Narrow Linewidth, CW DPSS Lasers for Precision Interferometry

Interferometry is one of the most widely used precision measurement techniques known to humankind. The precision provided by interferometers has enabled countless scientific discoveries and breakthroughs. These discoveries range from the Michelson and Morley Experiment in 1887, which led to the discovery that electromagnetic waves could propagate through the vacuum of space without needing an “aether” to detecting gravitational waves in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO). In addition to these groundbreaking discoveries, interferometry is also used daily for applications including infrared spectroscopy, telecommunications, and metrology. It would be impossible to review all aspects of interferometry, so we will instead focus on an application of importance to laser engineers: the testing of surface flatness of optical elements with a technique called Fizeau Interferometry. This blog will briefly introduce the fundamental physical principles of interference. Then we will get into the specifics of the Fizeau Interferometer, explaining why this interferometer is uniquely suited for measuring the surface flatness of optical elements, and how high-quality DPSS lasers greatly benefit this application.

Read the full article here.

How Can We Help?

With many years experience providing single-mode, single-frequency (narrow linewidth), stable, and long coherence length interferometry lasers to researchers, engineers, and other R&D and laboratory professionals, we have the experience to ensure you get the right product for the application. Working with RPMC ensures you are getting trusted advice from our knowledgeable and technical staff on a wide range of laser products.  RPMC and our manufacturers are willing and able to provide custom solutions for your unique application.

If you have any questions, or if you would like some assistance please Contact Us here. Furthermore, you can email us at info@rpmclasers.com to talk to a knowledgeable Product Manager.

Alternatively, use the filters on this page to assist in narrowing down the selection of interferometry lasers for sale. Finally, head to our Knowledge Center with our Lasers 101 page and Blogs, Whitepapers, and FAQ pages for further, in-depth reading.

Finally, check out our In Stock Lasers page: This page contains all the laser products that we keep on-hand and ready to ship!