Transient temperature response of near field scanning optical microscope probes under pulsed illumination

Abstract

Time resolved thermoreflectance imaging with a nanosecond laser is applied to study the transient thermal response of near field scanning optical microscope (NSOM) probes driven by either microsecond (μs) or nanosecond (ns) laser pulses. It is found that when the laser energies are the same, μs and ns laser pulses show similar trend of close to adiabatic heating during the laser pulse and close to conductive cooling after the laser pulse. The peak temperature is almost linear with respect to input laser energy for the energy selected. The peak temperature of the NSOM probe is increased when the aperture size of the probe is smaller and when the incident laser wavelength is shorter. However, compared with μs laser pulses, small physical damages appear around the NSOM aperture, which gradually decreases the optical-thermal energy conversion efficiency in the NSOM probe when ns laser pulses are applied.