Nonlinear laser wave mixing in a common graphite furnace atomizer is presented as a zeptomole-level, sub-Doppler, high-resolution atomic absorption spectrophotometric method. A nonplanar three-dimensional wave-mixing optical setup is used to generate the signal beam in its own space. Signal collection is efficient and convenient using a template-based optical alignment. The graphite furnace atomizer offers advantages including fast and convenient introduction of solid, liquid, or gas analytes, clean atomization environment, and minimum background noise. Taking advantage of the unique features of the wave-mixing optical method and those of the graphite furnace atomizer, one can obtain both excellent spectral resolution and detection sensitivity. A preliminary concentration detection limit of 0.07 parts-per-quadrillion and a preliminary mass detection limit of 0.7 ag or 8 zmol are determined for rubidium using a compact laser diode as the excitation source.

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A fiber-based wave-mixing probe is presented as a simple spectroscopic measurement tool with minimum optical alignment requirements for trace-concentration analytes. For a multi-photon nonlinear laser-induced grating method to become widely accessible, the optical setup must be compact, easy to align and portable. We demonstrate a significant improvement in the forward-scattering (self-diffraction) wave-mixing optical setup using optical fibers for both laser input and signal output interfaces. There is considerable flexibility inherent in the design, since the wavemixing probe can be used in multiple configurations. Wave-mixing spectroscopy is presented as an effective and sensitive analytical method for trace analysis, offering advantages such as detection in very small sample volumes, remote and in-situ analyses, and convenient and efficient alignment enhancements obtained by the use ofoptical fibers.

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