CRDS Modules – Ultra-Sensitive Gas Detection for Environmental and Industrial Applications

Technical Specifications

Our crds gas modules are engineered to meet the stringent requirements of industrial automation, environmental monitoring, and semiconductor fabrication.

The Physics Behind Cavity Ring-Down Spectroscopy

To truly understand the value of ultra-sensitive gas detection, one must look at the underlying physics. In standard direct-absorption spectroscopy, a laser beam passes through a gas sample once, and the drop in light intensity is measured. At parts-per-billion (ppb) levels, this intensity drop is so microscopic that it is often lost in background electronic noise. This is where high-quality crds gas modules change the rules of physics.

Inside the module, a laser pulse is injected into a highly reflective optical cavity (typically consisting of mirrors with >99.99% reflectivity). The light pulse bounces back and forth thousands of times, creating an optical path length of several kilometers within a space of just a few centimeters. Each time the light reflects, a tiny fraction escapes and is captured by a highly sensitive photodetector. When the laser is abruptly turned off, the light intensity inside the cavity decays exponentially. This decay time is known as the "ring-down time."

The genius of this technique is that the ring-down time is strictly dependent on the absorption of the gas sample, and completely independent of the initial laser intensity. If a specific target gas is present, it absorbs the light, causing the ring-down time to decrease faster. By precisely measuring this time difference, Sartec's crds gas modules calculate gas concentrations down to ppt levels, providing absolute measurement stability for your analytical instruments.

Frequently Asked Questions