Thermally driven optical switching in Bi nanostructures

Abstract

Thermally induced transmission and reflectivity changes are investigated in thin films formed by Bi nanostructures embedded in amorphous Al2O3. The Bi nanostructures are formed by coalesced nanoparticles forming a quasi-network close to the percolation threshold. Upon heating above the Bi melting temperature (>574 K), the transmission of the film increases abruptly, up to 18% in respect to the initial value, which is related to Bi melting. Upon cooling, the high transmission state remains up to temperatures as low as 436 K, thus evidencing a wide melting–solidification hysteresis cycle. The existence of transient morphological changes within the embedded nanostructure related to the contraction of Bi upon melting seems to have a significant contribution to the large transmission contrast between the molten and solid states of the Bi nanostructures. This large contrast together with the large width of the cycle makes this nanostructured film promising for a thermally driven optical switch.

Multifunctional Bismuth‐Doped Nanoporous Silica Glass: From Blue‐Green, Orange, Red, and White Light Sources to Ultra‐Broadband Infrared Amplifiers

“…Bismuth is a semimetal, and its relatively low melting point (574 K) makes it attractive for thermally induced phase transformations. [35] This characteristic has important applications for thermal-optical switching, [36] light-induced reflectivity tuning, [37] and enhancement of second-harmonic generation. [38] However, despite its attractive properties, its performance is still limited due to the scarcity of hosts with high thermal resistance.…”

Potential of bismuth nanoparticles embedded in a glass matrix for spectral-selective thermo-optical devices

“…Such active behaviour cannot be achieved using Ag or Au, thus requiring the development of nanostructures based on some of the so-called "alternative plasmonic materials." 7,8 Among the long list of such materials, poor metals such as Ga, 9,10 Sn, 11 or Bi 12 have the capability of displaying plasmonic or plasmonic-like effects in the near ultraviolet-to-near infrared range and show a relatively low melting point. Nanostructures made of such poor metals are thus interesting building blocks for spectralselective thermo-optical devices based on the optical contrast between their solid and liquid phases.…”

“…[13][14][15][16][17][18][19][20] The physical properties of Bi nanostructures embedded in such robust matrices have been characterized upon heating-cooling cycles using different techniques including Raman, X-ray, and optical transmission. 12,[21][22][23][24] The embedded nanostructures always show a higher melting temperature compared to the solidification one; therefore, giving rise to characteristic hysteresis loops of the measured physical property as a function of the temperature that have been explained by superheating and supercooling phenomena (see Refs. 22 and 23 and references therein).…”

Vanadium–Al2O3 nanostructured thin films prepared by pulsed laser deposition: Optical switching

“…This can explain why in the case of V_250 a transition temperature that is observed is compatible with the formation of V 2 Finally it is interesting to note that Fig. 3 shows that the changes in transmission associated with the phase transition for the film V_500 take place over a temperature range of more than 80 K, and for the V_250 film it occurs over a range of 130 K. These very broad transition ranges have been found and discussed for VO 2 nanoparticles undergoing solid-state phase transitions [13], as well as in other nanoparticle systems undergoing phase transition such as melting-solidification [14]. The broadening is due to a broad size distribution of the nanoparticles, as not all of them undergo the transformation at the same temperature.…”