This thesis provides a simulated model for 1f-normalized 2f + 3f signals to increase SNR in wavelength
modulation spectroscopy (WMS) applications. 1f-normalized signals inWMS are commonly
used to eliminate measurement dependence on the optical-electrical gain and average laser intensity.
Typically, even harmonics are chosen because their peaks are centered at the nominal wavenumber
of the absorption feature, and the second harmonic (2f) of the WMS signal is most commonly
selected because of its relatively high signal power. This work demonstrates the increase in SNR
that is achieved by summing the second and third harmonics (2f + 3f) by providing a simulated
model of the first, second, and third harmonics of the WMS signal. The simulation accounts for
real tunable laser diode characteristics to account for signal asymmetry and nonlinear intensity
modulations. Experimental data will be collected to compare SNR between 1f-normalized 2f and
1f-normalized 2f + 3f signals.