An Intra-Cavity Laser Photo-Acoustic Instrument for Measurement of Atmospheric Absorption

In this proposal, we outline a plan to develop novel ultra-sensitive photo-acoustic instrumentation for the measurement of absorption coefficients of aerosol-laden air samples. Its operation is based on piezo-electric amplification of weak photo-acoustic signals. The photo-acoustic assembly in the proposed approach is located inside a laser resonator, allowing an absorption sensitivity of less then 10-9 cm-1 with a very compact, rugged, and fast throughput instrument. An important aspect of the proposed device is that the photo-acoustic assembly can be made virtually insensitive to both coherent and incoherent background acoustic noise, such as induced by mechanical vibrations from a moving or vibrating platform. This attribute makes the proposed device ideal for use in fielded applications. In this proposal, we outline the operation principles of the proposed system and the anticipated performance envelope. For Phase I, we propose to (1) develop a breadboard system, in order to demonstrate the enhanced sensitivity of the proposed approach; (2) determine potential cross-sensitivity to variable environmental parameters; (3) analyze critical performance and design parameters; and (4) develop a Phase II/III strategy, including a conceptual prototype design.