Two omega method for active thermocouple microscopy.

We present a contribution to a new mode of scanning thermal microscopy (SThM) based on the use of thermoelectric junction operating in ac active mode. This is the first alternative to 3omega operating mode of a resistive SThM probe for measuring thermophysical parameters of materials at micro- and nanoscale. Whereas a current at omega frequency generates by Joule effect a 2omega thermal oscillation along the wires, the junction thermoelectric voltage can be measured by means of a differential bridge scheme associated to a lock-in amplifier.

Feedback-induced voltage change of a Vertical-Cavity Surface-Emitting Laser as an active detection system for miniature optical scanning probe microscopes.

We propose a novel detection technique for scanning probe microscopy based on the measuring of the feedback-induced voltage change of 780-nm VCSEL operating at constant current in far-field regime when we modulate mechanically the length of a coupled-cavity generating the feedback conditions. The voltage change of the VCSEL is produced by light back reflected from the sample to the laser cavity. Two-dimensional image probing is successfully demonstrated with high temporal resolution, offering a viable solution for miniature parallel scanning probe optical microscopes, such as confocal microscope, where the use of a photodetector is avoided.