Photothermal Imaging



Thermal imaging using Quadriwave Shearing Interferometry (TIQSI) is a non-invasive thermal microscopy technique developed by Dr. G. Baffou – Institut Fresnel in collaboration with Phasics S.A which enables to characterize the heat generation arising from illuminated nanostructures as the nanoscale level [1].
TIQSI is based on the measurement of the thermal-induced refractive index variation of a known medium via the wavefront measurement which is converted into a temperature variation value.

Thermal imaging using Quadriwave shearing interferometry porvides the 3D temperature map of an area surrounded the sample. (From the courtesy of Guillaume Baffou)
[1] Thermal Imaging of Nanostructures by Quantitative Optical Phase Analysis. Dr G.Baffou Institut Fresnel – ref ACS Nano 6, 3 (2012) 2452 – 2458 – DOI : 10.1021/nn2047586

Main Application

Published work:

  • Physics: Thermophoresis effect analysis
  • Nanofabrication : Characterization of nanoparticles samples
  • Cells biology: Study of cells response to thermal stress
  • Nanochemistry : Hydrothermal chemistry at room pressure

Unpublished and ongoing studies:

  • Synthesis of nanometric structures: measurement of absorption, phase shift, index and dielectric permittivity…
  • Study of interaction between nanoparticles (NP) and cells: cell destruction by NP heating, use of NP as contrast agents. Detection, counting and monitoring of nanoparticles in biological samples
  • Study of the behavior of gold nanoparticles in a biological environment: detection and characterization of isolated nanoparticles
  • Detection and measurement of local heating induced by high-power laser illumination on samples
  • Characterization of samples via the measurement of thermal diffusion properties



The local temperature gradient around a heated sample modifies the refractive index distribution of the surrounding medium. An incoming optical wavefront is thus curved when going through the sample.
By measuring the wavefront deformation thanks to our SID4 camera, it is possible to calculate the corresponding temperature variation δT.


Thermal imaging using Quadriwave shearing interferometry provides the 3D temperature map of an area surrounded the sample ( from the courtesy of Guillaume Baffou)


The variation of the wavefront δW results from the variation of the refractive index δn. By knowing the relation between the refractive index and the temperature, the temperature variation value δT is derived from δW via an inversion problem algorithm :
Variation of the wavefront dw result
Array of illuminated nanoparticles

Quantitative Phase (left) and Temperature (right) images of an array of illumintaed gold nanoparticles – Bar scale = 30µm



  • 1K-Temperature resolution
  • Live temperature imaging for temperature variation up to ∆T = 20K
  • Temperature variation measurement range from ∆T = 0K to more than 200K
  • Diffraction-limited spatial resolution for most of microscope objectives


  • Label-free modality
  • Wide field technology, no scanning required
  • Stable and reliable-over-time measurement
  • Spatially and temporally localized
  • Provides temperature and heat source power density fields
  • Easy to implement on conventional microscopes



Based on the quadriwave lateral shearing interferometry the SID4 wavefront analyzer provides the quantitative phase, or optical path difference (OPD), image from which the temperature map of the heated sample is derived.

Phase temperature signal measurement process
1- MICROSCOPE: The SID4 camera is plugged to conventional optical microscope. A laser source module is added to induce the beam heating proces
2- DETECTION SYSTEM: Four replicas are generated by the diffraction grating and create an interferogram on the sensor. The phase is encoded in the interfernce fringe deformation.
3- PHASE & TEMPERATURE IMAGES: The phase image as well as the temperature and intensity images are computed in real-time and diplsayed on the user’s screen.

Set Up

Thermal imaging Microscope with sample
In this representation, the heating device assembly consists in a nano-structured plate illuminated by a laser light source. The sample sets close by the nano-particles plate gets heated and white-light illumination is used to provide the quantitative phase image and thus the temperature map.

► TIQSI SET UP includes:

    • A conventional white-light microscope
    • A SID4 wavefront analyzer
    • An acquisition and analysis software
    • A heating device assembly


Thermal imaging TISQI set up

Scientific publications

Scientific reports

Microscale Temperature Shaping Using SLM on Gold Nanoparticles

Optical Society of America

Quantitative model of the image of a radiating dipole through a microscope

ACS Nano

Opto-Thermoelectric Manipulation

Small Journal

Photothermal Control of Heat-Shock Protein Expression at the Single Cell Level


Light-Assisted Solvothermal Chemistry Using Plasmonic Nanoparticles


Three-dimensional temperature imaging around a gold microwire

ACS Nano

DOI: 10.1021/nn2047586

Thermal Imaging of Nanostructures by Quantitative Optical Phase Analysis