Tuning Efficiency of Distributed Feedback Laser Diode for Wavelength Modulation Spectroscopy

A new defined parameter, tuning efficiency (TE), is proposed to evaluate the tuning performance of distributed feedback laser diode (DFB-LD). The TE is defined as the ratio of output wavelength response to power response of DFB-LDs when working in a current driving mode. Simulations and experiments are performed to study its influence on harmonic signal, signal-to-noise ratio (SNR), and residual amplitude modulation (RAM) effect in wavelength modulation spectroscopy (WMS). It is the first time to be found that the parameter TE would change as driving frequency of DFB-LD getting changed; in addition, different DFB-LDs result in changes in TE. A WMS-based water vapor sensing system is constructed to discuss the TE's influence on gas detection applications, and the experimental results show highly consistent with the simulations. In conclusion, the TE is a robust parameter guiding us to choose favorable DFB-LDs for gas sensing applications.