Holographic microrefractometer

Hagay Shpaisman, Bhaskar Jyoti Krishnatreya, David G. Grier

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


In-line holographic microscopy of micrometer-scale colloidal spheres yields heterodyne scattering patterns that may be interpreted with Lorenz-Mie theory to obtain precise time-resolved information on the refractive index of the suspending medium. We demonstrate this approach to spatially resolved refractometry with measurements on calibrated refractive index standards and use it to monitor chemical concentration in a microfluidic channel. Using commercially available colloidal spheres as probe particles and a standard video camera for detection yields values for the fluid's refractive index at the position of each probe particle in each holographic snapshot with a demonstrated resolution of 2 × 10 -3 refractive index units (RIU) and a potential resolution surpassing 10 -4 RIU. The combination of spatial resolution, temporal resolution, multi-point in situ access, and technical simplicity recommends this technique for cost-effective lab-on-a-chip applications.

Original languageEnglish
Article number091102
JournalApplied Physics Letters
Issue number9
StatePublished - 27 Aug 2012
Externally publishedYes

Bibliographical note

Funding Information:
We acknowledge valuable conversations with Fook Chiong Cheong. This work was supported in part by the National Science Foundation through Award Number DMR-0922680 and also by a grant from Procter and Gamble.


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