Mid-infrared photothermal heterodyne imaging (MIR-PHI) techniques described herein overcome the diffraction limit of traditional MIR imaging and uses visible photodiodes as detectors. MIR-PHI experiments are shown that achieve high sensitivity, sub-diffraction limit spatial resolution, and high acquisition speed. Sensitive, affordable, and widely applicable, photothermal imaging techniques described herein can serve as a useful imaging tool for biological systems and other submicron-scale applications.

Systems and methods for sensing vibrational absorption induced photothermal effect via a visible light source. A Mid-infrared photothermal probe (MI-PTP, or MIP) approach achieves 10 mM detection sensitivity and sub-micron lateral spatial resolution. Such performance exceeds the diffraction limit of infrared microscopy and allows label-free three-dimensional chemical imaging of live cells and organisms. Distributions of endogenous lipid and exogenous drug inside single cells can be visualized. MIP imaging technology may enable applications from monitoring metabolic activities to high-resolution mapping of drug molecules in living systems, which are beyond the reach of current infrared microscopy.

A method using a laser to propagate a laser beam through an optically-transparent medium, wherein the laser has a power level beyond a critical value P.sub.cr, and wherein the laser beam interacts with the optically transparent medium to generate a laser-induced plasma filament (LIPF); and adjusting the power level to qualitatively detect chemical components within the optically-transparent medium.

Mid-infrared photothermal heterodyne imaging (MIR-PHI) techniques described herein overcome the diffraction limit of traditional MIR imaging and uses visible photodiodes as detectors. MIR-PHI experiments are shown that achieve high sensitivity, sub-diffraction limit spatial resolution, and high acquisition speed. Sensitive, affordable, and widely applicable, photothermal imaging techniques described herein can serve as a useful imaging tool for biological systems and other submicron-scale applications.

A method using a laser to propagate a laser beam through an optically-transparent medium, wherein the laser has a power level beyond a critical value P.sub.cr, and wherein the laser beam interacts with the optically transparent medium to generate a laser-induced plasma filament (LIPF); and adjusting the power level to qualitatively detect chemical components within the optically-transparent medium.

Mid-infrared photothermal heterodyne imaging (MIR-PHI) techniques described herein overcome the diffraction limit of traditional MIR imaging and uses visible photodiodes as detectors. MIR-PHI experiments are shown that achieve high sensitivity, sub-diffraction limit spatial resolution, and high acquisition speed. Sensitive, affordable, and widely applicable, photothermal imaging techniques described herein can serve as a useful imaging tool for biological systems and other submicron-scale applications.

The present invention provides a system and method for spectroscopic imaging. In one embodiment, a system includes: a sample stage for holding a sample to be analyzed; a first light source for generating a pulse of infrared light; a second light source for generating a probing beam of infrared light; an optical system to direct the pulses of infrared light and the probing beam of infrared light at the sample, such that a temperature change is induced in an area of the sample. The duration of the pulse of infrared light is shorter than or equal to a cooling time constant of resolution scale inclusions within the sample such that the temperature change is independent of inclusion size. Light detectors are configured to detect light from the sample and digitization electronics convert data from the light detectors into signal data indicative of a chemical composition of the sample.