You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Simultaneous two and three photon resonant enhancement of third-order NLO susceptibility in an azo-dye functionalized polymer film. We report the observation of simultaneous two and three photon resonances, enhancing the third-order NLO susceptibility in a thin film of an azo-dye polymer. The possibility of 2-3 orders of magnitude increase in χ((3)) susceptibility is sustained by quantum mechanical calculations. This improves the applications of azo-polymers in all optical signal processing as well as in nonlinear optical imaging.
{"Chemical": ["azo"]}