Abstract: An imaging substrate is provided to facilitate wide field photothermal infrared spectroscopic imaging of samples disposed thereon. The substrate includes at least two reflective layers and at least one spacer layer disposed therebetween which, together, form an optical cavity. The spacer layer(s) exhibit expansion and/or refractive index change as a function of heating by incident infrared illumination. Such localized heating results in a localized change in the effective reflectivity of the substrate by locally tuning/detuning the optical cavity. Thus, the pattern of effective reflectivity of the substrate can be made to correspond to the pattern of infrared absorptivity of a sample mounted on the substrate by illuminating the sample and the substrate with infrared illumination.

Abstract: The disclosure is directed to a method and apparatus for correcting responsivity variation in photothermal imaging. The method includes sending, during a first time period, light-driving signal to a light source so that the light source is configured to output a series of light pulses onto a sample, wherein the sample is under photothermal-induced expansion according to the series of light pulses. The method includes obtaining, during the first time period, first deflection signal from a cantilever. The method includes sending, during a second time period, actuator-driving signal to an electromechanical actuator so that the electromechanical actuator is configured to move according to the actuator-driving signal, wherein the electromechanical actuator is coupled with the sample. The method includes obtaining, during the second time period, second deflection signal from the cantilever and obtaining a photothermal image of the sample based on the first deflection signal and the second deflection signal.

Abstract: The disclosure is directed to a method and apparatus for correcting responsivity variation in photothermal imaging. The method includes sending, during a first time period, light-driving signal to a light source so that the light source is configured to output a series of light pulses onto a sample, wherein the sample is under photothermal-induced expansion according to the series of light pulses. The method includes obtaining, during the first time period, first deflection signal from a cantilever. The method includes sending, during a second time period, actuator-driving signal to an electromechanical actuator so that the electromechanical actuator is configured to move according to the actuator-driving signal, wherein the electromechanical actuator is coupled with the sample. The method includes obtaining, during the second time period, second deflection signal from the cantilever and obtaining a photothermal image of the sample based on the first deflection signal and the second deflection signal.