We present a differential laser absorption spectroscopy(DLAS)system operating at 1550 nm for rapid and sensitive gas concentration measurements.A dual-wavelength toggling mechanism is presented,which significantly red...We present a differential laser absorption spectroscopy(DLAS)system operating at 1550 nm for rapid and sensitive gas concentration measurements.A dual-wavelength toggling mechanism is presented,which significantly reduces data processing,hence supporting a high update rate and data robustness against fast-changing environmental conditions.We showcase the ability to toggle between two wavelengths separated by 90 pm in 14μs and with minimal chirp(~1 pm),facilitating sensitive DLAS measurements at 8 kHz update rate.This performance is achieved by driving a 1550 nm diode laser with a modified square-wave current pulse,overcoming the thermal time constant limited wavelength-modulation response of the diode laser.A sensitive feedback mechanism ensures excellent long-term wavelength stability better than 1.4 pm peak-to-peak at 8 kHz toggling over 20 h,As a performance test,we measured the volumetric ratio(VMR)of hydrogen cyanide(HCN)gas in a fiber-coupled gas cell with lessthan 0.2%peak-to-peak variation over 20 h at 40 Hz.A best sensitivity in VMR of 8×10^(-6) was achieved at 25 ms integration time.The simplicity and high update rate of our system make it well-suited for gas monitoring in dynamic atmospheric and industrial environments.Further,it offers potential utility in applications requiring precise wavelength control,such as injection seeding of pulsed lasers.A simple analytical model is derived,which,in detail,supports the experimental results,hence offering a tool for future design optimization.展开更多
文摘We present a differential laser absorption spectroscopy(DLAS)system operating at 1550 nm for rapid and sensitive gas concentration measurements.A dual-wavelength toggling mechanism is presented,which significantly reduces data processing,hence supporting a high update rate and data robustness against fast-changing environmental conditions.We showcase the ability to toggle between two wavelengths separated by 90 pm in 14μs and with minimal chirp(~1 pm),facilitating sensitive DLAS measurements at 8 kHz update rate.This performance is achieved by driving a 1550 nm diode laser with a modified square-wave current pulse,overcoming the thermal time constant limited wavelength-modulation response of the diode laser.A sensitive feedback mechanism ensures excellent long-term wavelength stability better than 1.4 pm peak-to-peak at 8 kHz toggling over 20 h,As a performance test,we measured the volumetric ratio(VMR)of hydrogen cyanide(HCN)gas in a fiber-coupled gas cell with lessthan 0.2%peak-to-peak variation over 20 h at 40 Hz.A best sensitivity in VMR of 8×10^(-6) was achieved at 25 ms integration time.The simplicity and high update rate of our system make it well-suited for gas monitoring in dynamic atmospheric and industrial environments.Further,it offers potential utility in applications requiring precise wavelength control,such as injection seeding of pulsed lasers.A simple analytical model is derived,which,in detail,supports the experimental results,hence offering a tool for future design optimization.
