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Refractive index as the new monitoring standard


Optiqua's patented optical chip is based on an integrated version of the Mach-Zehnder Interferometer (MZI). This is a highly sensitive sensor for Refractive Index ("RI") changes. Refractive index is a useful generic indicator of water quality as any substance, when dissolved in water, will change the refractive index of the water matrix in proportion to its own RI as well as its concentration. The generic Optiqua sensor chip operates at a sensitivity level equivalent to parts per million (ppm) levels for any chemical contaminant.

The relationship between the refractive index and the concentration of a contaminant is linear. The Optiqua sensor accurately measures changes in refractive index in the order of magnitude of 10-7 RI, which corresponds to low ppm level concentrations for most chemicals. This makes it an extremely useful parameter for detection and monitoring purpose. In combination with assays, as used in the MiniLab, analyte detection of specific substances down to the low ppb levels is possible.



Optiqua Cleanroom



Patented Innovations


Optiqua's patented optical sensor technology is based on an integrated version of Mach-Zehnder Interferometer (MZI). The basic layout of the MZI consists of an input channel wave-guide (#1 in figure below) that splits into two identical branches (#3), a sensing branch exposed to the water sample (#4) and a reference branch, and are then combined again to form the output wave-guide. The MZI works as an optical scale, measuring minute differences in refractive index as seen by the sensing branch versus the reference branch.



MZI Chip


Patented light path architecture:
  • Netherlands, Patent number NL 1006323 C2
  • Europe, Patent number EP 0990184 B1
  • USA, Patent number US 6618536 B1
  • Japan, Patent number JP 3562651 B2
  • Other patents pending