Photothermal Interferometric (PTI) – Based Particle Absorption Monitor
Poster PDF
Authors
Timothy B Onasch — Aerodyne Research, Inc.
J. Barry McManus — Aerodyne Research, Inc.
Andrew Freedman — Aerodyne Research, Inc.
Category
Absorbing aerosol
Description
We present results from a project to develop a Photothermal Interferometric (PTI) – based particle absorption monitor. In this technique, an excitation laser heats the absorbing particle, causing a small temperature jump and therefore a small change in the index of refraction which is detected by an interferometer. A major advantage of this technique compared to photoacoustic monitors is that the modulation frequency of the excitation laser is arbitrary and allows the user to demodulate the signal at frequencies where there is minimal ambient noise. In this Phase I project, we employed a commercially available fiber-based Michelson interferometer that operated at 1.5 microns. Noise levels as low as 10 Mm-1 in a 10 second sampling period were reached. We intend to proceed by building a modified Jamin interferometer which should allow us to reach noise levels at least an order of magnitude lower than observed with the commercial interferometer.
