S425C In Stock

The S425C by ThorLabs is a thermal power sensor head, a versatile and reliable solution for general broadband power measurements of low and medium power light sources. Designed to optimize wavelength ranges from 90 nm to 20 µm and power ranges from 2 mW to 10 W (20 W during intermittent use), the S425C provides 100 µW resolution and a typical response time of 0.6 s.

The S425C is the ideal choice for measuring broadband spectra from amplified spontaneous emission (ASE) sources, light emitting diodes (LEDs), filament lamps, swept-wavelength lasers, and other sources. It offers a significant advantage over photodiode sensors due to its ability to measure pulsed sources with high pulse peak powers or long-duration pulses without saturation. This makes it the preferred choice for applications that cannot tolerate the strong wavelength dependencies and/or saturation thresholds of photodiode sensors.

The S425C’s housing features an SM1 (1.035"-40) internal thread concentric with the input aperture, making it easy to integrate with compatible SM1-threaded accessories, external optics, fiber adapters, light shields, and apertures. The heat sink is also removable, allowing for integration into custom systems or the attachment of a larger heat sink by loosening two M4 screws. Two 8-32 (M4) threaded mounting holes allow for post-mounting of the sensor head. Additionally, the S425C can be mounted on compatible Ø1/2" posts using an 8-32 or M4 tap. The S425C is compatible with a C-Series connector and can be quickly exchanged with other sensors using this connector.

The S425C operates with fast (<0.6 s) natural response times, and its removable heat sink provides a high degree of flexibility to those interested in integrating it into custom setups or replacing the included heat sink with one that is water or fan-cooled. However, it is important to note that the replacement heat sink must provide adequate heat dissipation for the application. To ensure measurement accuracy, it is recommended to allow the sensor head to settle to room temperature before performing a zero adjustment. Additionally, the S425C should be post-mounted instead of handheld to avoid thermal contributions from body heat that could negatively impact measurement accuracy. The active detector area should also be protected from air flow and other thermal disturbances.