Prism Coupler

Sairon Prism Coupler (SPA-4000)

Sairon Prism Coupler has been supplied mainly with leading companies, research institutes, and universities in Asia including Korea, Japan, China, Taiwan, Singapore, Malaysia, etc. Now we have partnered with JY TECH in South Korea, which is the manufacturer of Sairon Prism Coupler. This excellent technology is available to all our EU customers.


What is Prism Coupler?

Prism Coupler is a measurement system to examine thin film properties such as refractive index, thickness or even loss. It utilize the prism coupling method.In the prism coupling method, unlike ellipsometry, reflection from the backside of substrate is less likely influence a measurement result. This means that special attention is not needed to measure a layer of film even on the transparent substrate.Also, the prism coupling method is less influenced by surface or boundary conditions as it utilizes propagating waves inside the thin film.Prism Coupler can measure the dependence of refractive index on wavelength by changing a incident laser beam. In order for prism coupler to obtain refractive index and thickness of the film at the same time, it needs to find at least two modes. To do so, sample thickness generally has to be as long as laser wavelength, or more.

Introduction Video

Key features

  • Loss measurement of high quality film with low propagation waveguide loss (~0.05dB/cm)
  • High resolution measurement for both refractive index and thickness of thin film
  • High accuracy measurement of bulk or substrate materials
  • Dn/dT measurement
  • VAMFO Measurement for thick film
  • Dual layer film measurement
  • Index profile for the film with graded index
  • No information requirement of lower layer for dual layer film
  • Unrelated film / Substrate combinations


Basic configuration

  • 632.8 nm He-Ne Laser
  • GGG(n=1.965) prism & Holder (index :<1.8)
  • One controller and PC interface(RS-232)  
  • Si-photodiode Detector
  • TE measurement
  • Analysis software (O/S : MS Windows)  


  • TM Mode option for each wavelength
  • Ge-Detector for Infrared Laser
  • Rutile (n=2.865) prism for high index refraction (index:1.8~2.45)
  • Solid state Laser ,Laser Diode Module(405~1550 nm);user choice
  • Sample Rotation system (-90 ~ +90 degree)
  • Thermo optic coefficient measurement system (dn/dT)
  • Liquid measurement system
  • Propagation LOSS measurement system


Measurements Specifications
Refractive Index  
Index measuring range (GGG prism) 1.0 to 1.8
Index measuring range (Rutile prism) 1.8 to 2.45
Index accuracy ±0.001
Index resolution ±0.0005
Thickness measuring range 0.4 to 20 um
Thickness accuracy ± 0.5%
Thickness resolution ±0.01 um
(index only)
 Index accuracy ± 0.001
Index resolution ± 0.0001
(index only)
 Index measuring range 1.0 to 2.4
Index accuracy ± 0.0005
Temperature measuring range Room Temp to 150 ℃
Loss Measurement  
Measuring limitation below 0.05 dB/cm


English   ●French

German            ●Russian

System comparison

In this document, you can compare Prism Coupler with other common systems for refractive index measurement.

English   ●French

German            ●Russian

Contact us

For further inquiry, information, sample test, please feel free to contact us.