Metals are invisible to IR cameras
Gold bond pads, aluminum contacts, and copper heatsink surfaces have near-zero emissivity. IR imaging produces noise, not temperature data, on any metal surface.
SILICON PHOTONICS & OPTOELECTRONICS
See inside photonic devices IR can't reach.
Metal contacts have near-zero emissivity. Photonic waveguides are too small for IR. Pulsed lasers blind conventional imagers. Thermoreflectance imaging solves all three.
Key measurement specifications
435 nm
Spatial resolution at 50x NUV, 365 nm
500 ps
Time resolution with upgrade option
<1 mK
Thermal sensitivity with lock-in averaging
30%
Thermal resistance reduction polySi vs. SiO₂ passivation
WHY THERMOREFLECTANCE
IR imaging fails where photonics engineers need it most.
Three fundamental physics problems make conventional IR cameras unreliable for photonic device characterization. Thermoreflectance imaging solves each one.
Spatial resolution is too coarse
LWIR cameras resolve ~30 µm per pixel. Silicon photonic waveguides are 7–10 µm wide. A localized hot spot at the waveguide input is physically invisible to IR at any magnification.
Laser emission overwhelms the detector
GaAs lasers at 808 nm and InP lasers at 1310/1550 nm: the device's own optical output floods any co-located imager. A filter and gated illumination scheme are required to separate the thermal signal from the laser output.
Limitation — conventional IR
Where IR thermal imaging falls short in photonics
- Underestimates peak temperature by more than 30% due to poor spatial resolution
- Cannot measure metal contacts, bond pads, or heatsink surfaces
- Time resolution of 33–116 ms cannot capture microsecond transient response.
- Laser output contaminates the IR signal; requires device to be off for stable measurement
Advantage — thermoreflectance
What Microsanj thermoreflectance delivers
- Sub-micron spatial resolution resolves 7.4 µm waveguide hot spots directly
- Dual-mode TR + IR in a single system: use each where it fits.
- Time resolution down to 50 ns standard, 500 ps with upgrade for full transient capture
- Wavelength-selectable LED illumination filters independently of laser output wavelength
SUPPORTED DEVICES
From flip-chip lasers to silicon photonics platforms
Characterization results across every major photonic device class, all using Microsanj thermoreflectance systems.
InP Flip-Chip Laser
III-V Laser Diode
Transient thermal response at 100x magnification, resolving two distinct material regions (InP substrate vs. InP-modified material) under a 250 mA pulse. Time range 1 µs to 100 µs captured in a single acquisition.
GaAs High-Power Laser
High-Power Laser Bar
Surface temperatures of the GaAs laser facet and the CuW heatsink are measured simultaneously. Requires a filter to block the 808 nm laser output during TR imaging. Both topside and front-facet imaging configurations supported.
Ge/Si Waveguide Photodiode
Silicon Photonics — Detector
3D heat distribution mapped along a 250 µm waveguide with a 7.4 µm channel width. Peak surface temperature exceeds 200°C at the waveguide input. Results validated quantitatively against a COMSOL finite-element simulation.
Ge/Si UTC Photodetector
High-Power Photodetector
Thermal impedance measured at 520 K/W, 1.7× lower than a comparable InP/InGaAs device using thermoreflectance to verify the COMSOL simulations; substrate-induced heating distinguished from junction heating.
InGaAs/InP MUTC Photodiode
High-Linearity Photodetector
Surface temperature mapped on 34 µm and 40 µm diameter mesa devices under varying heat generation levels. Thermal runaway onset was identified and compared against an ANSYS simulation for packaging design optimization.
Optoelectronic Packaging
Die Attach — Package Thermal
Passivation layer comparison for semiconductor laser bars mounted on silicon substrates: poly-silicon reduces thermal resistance by ~30% vs. silicon dioxide. Solder voids and thermal islands in the copper heatsink were identified non-invasively.
MEASUREMENT + SIMULATION
Validate your thermal models before they cost you
Analytical and finite-element thermal models for photonic devices make assumptions about heat source distribution, thermal conductivity, and boundary conditions that are difficult to verify from first principles alone.
Thermoreflectance imaging provides a direct, spatially resolved surface temperature measurement to validate or refine COMSOL, ANSYS, and Beamprop models before a design is committed to fabrication.
- Ge/Si waveguide photodiode: TR measurement and COMSOL surface temperature agree quantitatively within the margin of error.
- Ge/Si UTC detector: COMSOL thermal impedance simulation verified by TR at 40 mW dissipated power
- Absorption coefficient refined: TR data indicated α closer to 4,570 cm⁻¹ than the assumed 4,000 cm⁻¹ for tensile-strained Ge
- Heat generation in waveguide depletion region shown to follow absorption profile, a direct measurement, not an assumption
SYSTEM SPECIFICATIONS
Built for photonics — configured for your device
The SanjSCOPE™ EZ-THERM and NT220 series support every photonic characterization scenario, with software-selectable wavelengths and interchangeable objectives.
Spatial resolution (TR)
435 nm @ 50x NUV, 365 nm illum.
Illumination wavelengths (VIS)
365, 405, 455, 470, 530, 625, 780 nm
Time resolution (NT220)
50 ns standard / 500 ps upgrade
Illumination wavelengths (NIR)
940, 1030, 1064, 1120, 1210, 1370 nm
Time resolution (EZ-THERM)
5 µs or 50 µs
Imaging modes
TR (VIS/NIR) + IR dual mode
Thermal sensitivity (IR, lock-in)
<10 mK (NETD, 5 min avg)
Temperature calibration
Thermocouple, embedded sensor, TC-100 stage
Thermal sensitivity (TR, lock-in)
<1 mK (lock-in averaging)
Sensor pixels (CMOS VIS)
2048 × 2048 (EZTR-VIS4)
Ready to characterize your photonic device?
Our applications team has hands-on experience with laser, photodetector, and silicon photonics characterization. Tell us your device and measurement goals.
