Energy-redistribution signatures in transmission microscopy of Rayleigh and Mie particles

Comment on "Optimal detection angle in sub-diffraction resolution photothermal microscopy: application for high sensitivity imaging of biological tissues"

A recent publication [Opt. Express, 22(16), 18833-18842 (2014)] discusses the optimal detection aperture in photothermal single particle microscopy. This new theory is in contradiction with rigorous ab-initio electrodynamic calculations. Nonetheless, the experimentally verified conclusion that a maximum signal occurs at a finite numerical detection aperture remains valid and is in accord with existing models.

Sensitivity enhancement of photothermal microscopy with radially segmented balanced detection

A novel detection method is proposed for highly sensitive photothermal microscopic imaging. This method is based on the characteristics of an angular-dependent photothermal signal; it improves signal intensity by up to two times and rejects the intensity noise of the probe beam. The subdiffraction resolution photothermal imaging of mouse skin melanoma is demonstrated using a laser diode-based photothermal microscopy system to evaluate this method. We confirm that the signal intensity is enhanced 1.7 times compared with the conventional detection method. Moreover, the intensity noise of the laser diode used for the probe beam is effectively reduced by approximately 31 dB, even for a sample with non-uniformity of the refractive index and stationary absorption. This method is implemented by means of a commonly used balanced detector and is thus potentially useful for high-speed imaging.

Thermal diffusivity measured using a single plasmonic nanoparticle

Photothermal single particle microscopy is used to measure thermal diffusivities in solid and liquids.