Case Study CS-LDTC16 Rev. A

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Figure 5. Performance of CO-LITES sensor based on optimized MPC and QTF3. a) 2f signal of the CO-LITES sensor with

different CO concentrations. b) The linear relationship between 2f signal amplitude and CH

4 concentration. c) Allan variance

analysis for CO-LITES sensor. d) Continuous noise detection in the sensor and corresponding normal distribution.1

By achieving ppq-level sensitivity, researchers designed a

CO-LITES sensor that could revolutionize CO detection and

measuring applications in urban environmental monitoring,

semiconductor manufacturing, interplanetary exploration,

and human health assessment.

WAVELENGTH'S ROLE

In the CO-LITES gas sensing system, achieving ultra-high

sensitivity in the ppq level for CO detection relies heavily

on laser wavelength and output stability. Since the system

detects CO absorption at a narrow spectra line, any drift or

instability in wavelength could directly affect signal accuracy

and detection limits.

Researchers used the QCL1500 LAB quantum cascade

laser driver for its high precision control at low noise

levels. With the ability to maintain a narrow linewidth, the

QCL1500 LAB provided consistent laser current to the QCL

for maximum signal-to-noise ratio while minimizing jitter and

current inconsistencies.

Alongside the current control, the laser temperature also

required precise regulation as small temperature changes

can shift the laser's center wavelength. With the TC10 LAB

temperature controller, researchers could maintain the laser

temperature at 35ºC with stability as low as 0.0009ºC. This

ensured that the current modulation from the driver, not

thermal drift, changed the laser wavelength.

The QCL1500 LAB and TC10 LAB enabled consistent and

repeatable scans, maintaining constant current and stable

temperature to the QCL for ultra-sensitive CO detection

using the LITES design. These benchtop instruments with

intuitive touchscreens provided the high-performance

needed for this novel gas sensing system to achieve ppq

gas detection.