Reverse photoacoustic standoff spectroscopy

A standoff spectroscopy system comprising:

• a quantum cascade laser light source that emits pulsed light;
• a target that is illuminated by the light source;
• wherein at least some of the pulsed light at the target is scattered;
• and
• a quartz crystal tuning fork distanced from the target, the quartz crystal tuning fork being used as a detector that measures the scattered pulsed light from the target, wherein the scattered pulsed light from the target produces a photoacoustic wave on the surface of the detector creating a mechanical vibration of the detector.

A system for standoff spectroscopy comprising:

• a target;
• a source array comprising a plurality of sources that each emit a pulsed light beam with different pulse frequencies onto the target at a predetermined frequency;
• and
• a detector array located a distance from the target, the detector array comprising a plurality of detectors that each have a predetermined resonant frequency, wherein the resonant frequency for each of the detectors corresponds with the predetermined frequency from one of the sources, further wherein each of the detectors measures, on a surface of that detector, an optical scattering, reflection, or refraction by the target of the pulsed light beam from the corresponding one of the sources.

A system for standoff spectroscopy of a target comprising:

• a quantum cascade laser array that emits pulsed light beams onto the target;
• a collection optic that receives scattered, reflected, and/or refracted light from the pulsed light beams being rejected by the target;
• and
• a quartz crystal tuning fork array that receives the scattered, reflected, and/or refracted light from the collection optic and generates a vibration on each of the quartz crystal tuning forks in the array.