A CO trace gas detection system based on continuous wave DFB-QCL

•A low cost board-level laser controller which can provide the functions of wavelength tuning and modulation was developed.•A low cost board-level analog orthogonal lock-in amplifier which can extract second harmonic wavelength modulation spectroscopy was developed.•The low cost CW DFB-QCL based CO detection system has a great improvement in detectivity and precision compared with our previous work.