a novel low - power and compact laser spectroscopic sensor is described herein . embodiments of the disclosed sensor utilize state - of - the - art microprocessors and digital processing techniques to reduce power consumption and integrate functions into a small device . in particular , novel software methods are disclosed which allow the use of low - power microprocessors which draw no more than about 0 . 02 w of power . such low - power enables long battery life and allows embodiments of the sensor to be used in portable applications . in addition , the system architecture and methods described in this disclosure allow a single integrated embedded processor to control all the subsystems necessary for a laser spectroscopic sensor further reducing sensor size and power consumption . in addition , a power efficient method of calibrating a photoacoustic laser spectroscopic sensor is disclosed .