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Photothermal technology:
commom-path (single beam) interferometry
- ultimate sensitivity
- Gouy phase shift + Rayleigh range = PCI technology
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About Stanford Photo-Thermal Solutions

Stanford Photo-Thermal Solutions (SPTS) was founded in November 2002 to build a business in the field of optical equipment R&D, manufacturing of novel optical systems and consulting in various issues associated with optical materials. Photo-thermal Common-path Interferometer (PCI) technology is in the focus of our current activity. The technology was developed in 1997-2000 at the Ginzton Lab at Stanford University.

Our first apparatus was designed in the 1997-98 timeframe. It belongs to a class of pump/probe thermal lens instruments which are used to detect the very weak phase distortions of a probe beam which are introduced in a material under test by the absorption of a pump laser. The original motivation for the instrument was to study induced absorption effects and optical damage in nonlinear optical crystals. The use of two lasers, one laser to introduce the absorption, and the second laser to monitor this absorption is the key element of our original design. SPTS offers custom-made instruments of this type PCI-02.

The detailed theory of PCI was developed at Stanford University. It was shown that an improved thermal lens configuration could be implemented as a common-path interferometer. Here, a single probe beam is used to create an interferometric pattern. The concept has been successfully used for evaluation of various optical effects:
Model 02 with two pump ports.
  • Low absorption in the bulk optical materials for high power applications such as sapphire, YAG, fused silica, LiNbO3, KTP, TeO2, etc.;
  • Green light-induced IR absorption in lithium niobate/tantalate family of crystals including periodically-poled crystals;
  • Gray track kinetics and gray track shape in KTP family of crystals;
  • Absorption losses in multilayered HR dielectric mirrors and AR coatings deposited onto fused silica, TeO2 and sapphire substrates;
  • Surface defects and surface contamination of substrates: fused silica, sapphire, LiNbO3, KTP and TeO2.

PPSLT tested at 532 nm
through the edge.

Coating tested at 532 nm.
First custom-built PCI instrument was shipped by the end of the year 2003. During the next year our model PCI-02 and a more compact version configured with an input port for one pump, our model PCI-03 were shipped to major laser companies in the USA, as well as to Israel, China and France.
Model 03 with one pump port.
Stanford Photo-Thermal Solutions

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