A portable low-power integrated current and temperature laser controller for high-sensitivity gas sensor applications.

Abstract

A low-noise, low power, high modulation-bandwidth design integrated laser current and temperature driver with excellent long-term stability is described. The current driver circuit is based on the Hall-Libbrecht design. A high sensitivity and a stable driver current were obtained using a differential amplifier and an integral amplifier. The set-point voltage for the current driver came from an ultra-compact, ultra-low temperature coefficient voltage reference chip or the digital to analog convertor output of a microcontroller or a modulation signal. An integral temperature chip, referred to as ADN8834, was used to drive the thermoelectric cooler controller of the distributed feedback (DFB) laser. The internal amplifier acquired the feedback current of the temperature sensor. The proportional-integral-derivative parameters such as proportion, integration, and derivative were set by external resistors. The short- and long-term stability and linearity of the developed laser driver were tested using a DFB laser with a central wavelength of 6991 cm-1. The laser driver was validated for high-sensitivity gas sensing of CO2 and C2H2 via a laser absorption spectroscopy experiment. The limits of detection were less than 11.5 ppm and 0.124 ppm for CO2 and C2H2, respectively. Direct absorption measurements and the 1-f and 2-f demodulation signals confirmed the capabilities of the proposed laser driver system in high-sensitivity gas sensing applications. The driver unit can readily be accommodated into many portable laser sensing devices for industrial applications.