Aluminum Nanoparticles as Fiducials for Nanoscale Temperature Measurements
In plasmon energy expansion thermometry (PEET), electron energy-loss spectroscopy (EELS) is used to determine the plasmon energy in a suitable thermometric material [1]. Since the plasmon energy scales with the material’s density, temperature changes can be determined using knowledge of the material’s thermal expansion coefficient. Many in situ transmission electron microscopy experiments could benefit from having thermometric fiducials, i.e. localized thermometers within the field of view. Nanoparticles of aluminum, with their narrow bulk plasmon resonance and large thermal expansion coefficient [2, 3], are particularly well suited to act as such fiducial thermometers.
Nanoscale temperature measurement during temperature controlled in situ TEM using Al plasmon nanothermometry.
Over recent years, the advent of microelectromechanical system (MEMS)-type microheaters has pushed the limits of temperature controlled in situ transmission electron microscopy (TEM). In particular, by enabling the observation of the structure of materials in their application environments, temperature controlled TEM provides unprecedented insights into the link between the properties of materials and their structure in real-world problems, a clear knowledge of which is necessary for rational development of functional materials with new or improved properties. While temperature is the key parameter in such experiments, accessing the precise temperature of the sample at the nanoscale during observations still remains challenging. In the present work, we have applied aluminium plasmon nanothermometry technique that monitors the temperature dependence of the volume plasmon of Al nanospheres using electron energy loss spectroscopy for in situ local temperature determination over MEMS-type microheaters. With access to local temperatures between room temperature to 550 ∘C, we have assessed the spatial and temporal stabilities of these microheaters when they operate at different setpoint temperatures both under vacuum and in the presence of a static H2 gas environment. Temperature comparisons performed under the two environments show discrepancies between local and setpoint temperatures.
Coherent pulsed injection seeding of two gain-switched semiconductor lasers
High-power, narrow-spectrum, short pulses at a wavelength near 830 nm are needed for optical logic applications. The authors report the generation of two coherent trains of pulses by pulsed injection seeding of two gain-switched semiconductor lasers with one mode-locked master oscillator. The available power was doubled and both lasers emit in nearly identical spectral lines. Short pulses (30-50 ps) are generated at a repetition rate of 1.9 GHz. The spectrum is reduced to a single mode cluster and shows a 1.7 AA wide chirp suitable for pulse compression. The peak power is 0.1 W for each pulse train. The capability of this technique for coherent power combining is demonstrated.<<ETX>>