RoHS-compliant infrared (IR) LEDs and detectors boost performance and ease the manufacture of capnography monitors

  • Hamamatsu Corporation

Today’s medical device OEMs look to improve performance levels and extend operating lifetimes in even smaller form factors. As medical device product lifecycles shrink, the need for innate RoHS compliance at the component level helps speed time to market. Given these challenges, OEMs are turning to safe, high-performance semiconductor technologies to replace traditional lamps for fast, accurate absorption analysis without the need for cooling. Today’s capnography device engineers spec in the latest MIR LED technologies to deliver on promises of high sensitivity for real-time, precise CO2 detection.

Capnography monitor

Optical CO2 measurement is best done in the mid-infrared

Graph of CO2 absorption wavelengths in near-infrared and mid-infrared

Carbon dioxide has absorption bands in the near-IR, but the band near 4.26 µm is orders of magnitude stronger.

What characteristics matter the most when it comes to mid-IR LEDs and detectors?

Sensitivity of infrared LEDs and detectors

Since capnography monitors measure levels of carbon dioxide absorption, the data significantly affects patient treatment and outcomes. It’s critical for the provider to receive accurate, real-time results to properly assess the patient’s condition. Precision, which equates to a lower margin of error, relies on the sensitivity levels of the detector inside the monitor. Maximum precision levels require mid-IR LEDs to deliver 3+ micron light and achieve parts per million sensitivity levels (assuming proper calibration). 

Managing temperature

OEMs turn to today’s mid-IR detectors for sensitivity, but many current detectors implement cooling to mitigate temperature variance factors. Future instruments would benefit from removing cooling systems and integrating detectors that resist temperature variance. InAsSb detectors provide just that. Removing cooling would save on cost, power consumption, and form factor.

Stability + reliability

Traditional lamps are a common source of IR light, but they come with drawbacks. When it comes to gas analysis, lamps are inefficient because they provide wide IR emissions and not just the absorption wavelengths. LEDs can center on the absorption wavelength (in this case 4.26 microns) and therefore provide higher power efficiency. Also, this efficiency drives longer lifetimes, with MIR LEDs standing to last 10k+ hours of operation. Lamps also are not known to modulate quickly and commonly have warm-up times. MIR LEDs respond on the order of microseconds and can provide much higher measurement rates.


The chart below illustrates how Hamamatsu’s line of LEDs performs as a function of input current.


L15895 series

Graph of MIR LEDs’ radiant flux vs. input current

RoHS compliance

While infrared detectors are highly stable and perform as needed, they often contain hazardous substances like lead, cadmium, and mercury. Medical device OEMs must meet stringent compliance with a gamut of regulations, so designing products with RoHS-compliant components like InAsSb helps avoid lengthy permitting processes, ultimately reducing time to market.

Technologies for efficient CO2 absorption measurement

As MIR LEDs become more powerful and efficient sources, an emerging generation of compact MIR detectors offers effective performance. Hamamatsu’s line of mid-IR LEDs features high peak power/output, high reliability, and low power consumption for the most efficient CO2 absorption measurement. Flexible configurations meet your needs as detectors are available as an SMD (surface mount device) or mounted to a PCB board.


If you need help optimizing the performance of your next capnography monitor, turn to Hamamatsu. Compare our specs and talk to our experts today. 

Related topic

Learn more about how our IR detectors and IR light sources are used for gas analysis.

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