dataset for <Laser frequency locking and intensity normalization in wavelength modulation spectroscopy for sensitive gas sensing>

The center spacing between two second harmonic peaks demodulated from the rising and falling edges of a scanning triangular wave (for wavelength scan), is employed as frequency locking reference. Amplitude of the directly acquired sine signal (for wavelength modulation) in the interval apart from absorption feature is employed as intensity normalization reference.

A 50 ppm CH4:N2 sample sealed in a multi-pass cell at 1 atm was employed as the target analyte for demonstration. The frequency locking significantly improves measurement accuracy, and the introduced intensity normalization method realized a ~3 times SNR improvement as compared to the commonly used 1f normalization method under frequency locking conditions.