Thermal Lens Microscope

Abstract

We developed a novel laser microscope based on the thermal lens effect induced by a coaxial beam comprised of excitation and probe beams. The signal generation mechanism was confirmed to be an authentic thermal lens effect from the measurement of signal and phase dependences on optical configurations between the sample and the probe beam focus, and therefore, the thermal lens effect theory could be applied. Two-point spatial resolution was determined by the spot size of the excitation beam, not by the thermal diffusion length. Sensitivity was quite high, and the detection ability, evaluated using a submicron microparticle containing dye molecules, was 0.8 zmol/µm 2 , hence a distribution image of trace chemical species could be obtained quantitatively. In addition, analytes are not restricted to fluorescent species, therefore, the thermal lens microscope is a promising analytical microscope. A two-dimensional image of a histamine molecule distribution, which was produced in mast cells at the femtomole level in a human nasal mucous polyp, was obtained.

Comparison of Performance Parameters of Photothermal Procedures in Homogeneous and Heterogeneous Systems

“…3 The locality and high spatial resolution of TLS have led to wide-scale applications of thermal-lens microscopy (TLM) as a state-of-the-art method. [4][5][6][7] TLM perfectly fits micro-totalanalytical systems (μTAS) (reactions and separations occurring at high rates in nanoscale volumes). 4,[8][9][10] To exploit the full potential of TLM-μTAS, tuning the reaction conditions of integrated chemistry on the microscale is even more crucial.…”

Photothermal Microscopy for High Sensitivity and High Resolution Absorption Contrast Imaging of Biological Tissues

“…In previous reports, a low-NA condenser or an iris diaphragm placed after the condenser was used to pass only a part of the probe beam at a small angle for maximization of SNR [13,20,21]. However, as the probe beam at a large angle is modulated out of phase with respect to that at a small angle, signal intensity improves by up to two times if the inner portion and outer portion of transmitted probe beam is separated into two and then detected by a balanced (differential) detector [22].…”

Fast Screening Techniques for Neurotoxigenic Substances and Other Toxicants and Pollutants Based on Thermal Lensing and Microfluidic Chips

“…In addition, microfluidic chips can serve as a platform for the mixing of analytes and reagents, liquid or solid-phase extraction, phase separation, the concentration of gaseous analytes, the growing of cell cultures, as well as sample heating, which can be performed online during the course of chemical analysis. 9 Since its introduction, 79 TLM underwent significant development and transformations to become a user-friendly analytical system. Focal-point controlled units for both the excitation and probe lasers have been introduced to allow for the optimization of instruments with state-of-the-art achromatic objective lenses.…”