InFocus series - Spectroscopic microscopes

Broadband frequency-domain thermoreflectance microscope


The thermal properties of the thin films and nanostructures can be measured. Heterodyne detection enables a high modulation frequency of up to 200 MHz, making it possible to observe the size effects of the thermal conductivity and the mean free path (MFP) spectrum.



  • Thermal properties of thin films and minute objects on the order of submicron to several microns can be measured.

    The thermal properties of thin films with sizes on the order of submicrons to several microns can be measured.

  • Heterodyne detection allows for heating frequencies up to 200 MHz, which is difficult with a conventional TDTR and FDTR.

    Heterodyne detection allows heating frequencies of up to 200 MHz, which is difficult with conventional TDTR and FDTR.

  • High resolution Raman spectroscopy is available as an option, which evaluates the crystallinity  and stress in a sample.

    High-resolution Raman spectroscopy can be used as an option to evaluate the crystallinity and stress of a sample.

  • Overview
  • Specifications
  • Papers


InFocus BB-FDTR is a frequency-domain thermoreflectance microscope that exploits the phenomenon where the reflectance of light on the surface of a sample changes with respect to the temperature (i.e., thermoreflectance) to measure the thermal properties of thin films and nanostructures and observe their distribution. The pump CW laser periodically heats the sample surface at a high frequency of up to 200 MHz, and the phase delay of the temperature response is detected using the probe CW laser to measure the thermal properties of the sample.

Similar to the time-domain thermoreflectance (TDTR) method, InFocus BB-FDTR can analyze not only bulk materials but also thin films and nanostructures with sizes on the order of submicrons to several microns. By selecting the measurement conditions, various thermal properties, ​​such as the cross-plane thermal conductivity Kz, in-plane thermal conductivity Kr, interface thermal conductance G, and heat capacity C, can be evaluated. In contrast to the TDTR method, an expensive pulsed laser and cumbersome mechanical moving stage are not necessary.

(Click "Introduction to broadband frequency-domain thermoreflectance (BB-FDTR)" for further information on BB-FDTR.)

In addition, high-resolution Raman spectroscopy can be used as an option. Raman spectroscopy facilitates multifaceted material analysis with a single device by providing additional information such as the sample crystallinity and residual stress.

Evaluation of phonon MFP spectrum

The most significant feature of the InFocus BB-FDTR is heterodyne detection, which realizes broadband periodic heating at a modulation frequency of up to 200 MHz. Changing the modulation frequency of the pump beam changes the thermal penetration depth dp from the sample surface (a). When dp is as long as the MFP of phonons, a quasi-ballistic heat transport effect appears, and the cumulative thermal conductivity kaccum for phonons with an MFP shorter than dp is selectively measured (b).

frequency modulation and MFP spectrum

By utilizing this characteristic, we can deepen our understanding of quasi-ballistic heat transport in nanodevice engineering and thermoelectric conversion materials.

Intuitive control of laser spots using laser beam scanning technology

Using a laser scanning optical system, which is the specialized capability of ScienceEdge, the positions of the pump and probe beams can be instantly changed by simply clicking anywhere on the software’s microscope image. The incident light on the sample surface is kept vertical; thus, spot-shape distortion will not be a cause for concern.

Laser beam scanning

Lineup and specifications


  • Broadband frequency-domain thermoreflectance microscope (InFocus BB-FDTR)
  • Frequency-domain thermoreflectance microscope (InFocus FDTR)


Model InFocus BB-FDTR / InFocus FDTR
Pump laser 488 nm
Spot size: < 1 - 5 μm (Variable)
Probe laser 532 nm
Spot size: < 1 μm
Transducer Au
Frequency modulation range 200 kHz to 200 MHz (InFocus BB-FDTR)
200 kHz to 10 MHz (InFocus FDTR)
Others Mapping function
Anisotropic analysis (Option))
High resolution Raman spectroscopy (Option)

*Product specifications are subject to change without notice. Please be aware of this in advance and check the details each time.
*The product appearance shown is a concept model that may differ from the actual product appearance.


Jun Hirotani, Taisuke Ota
“Measurement Error Reduction in Frequency-Domain Thermoreflectance Techniques”
The 69th JSAP spring meeting 2022, 22p-P03-23 (2022) (Japanese only)