1 × 2 optical switch devices based on semiconductor-to-metallic phase transition characteristics of VO₂smart coatings

Abstract

We have successfully fabricated two types of 1 × 2 optical switch devices, namely, all-optical switch (VO2/quartz) and electro-optical switch (VO2/TiO2/ITO/glass) based on the semiconductor-to-metallic phase transition characteristic of vanadium dioxide (VO2) smart coatings. The VO2 active layer, the TiO2 buffer layer and the ITO transparent conductive electrode used in these devices were achieved by reactive pulsed laser deposition. The optical switching of the fabricated devices was investigated at λ = 1.55 µm. The semiconductor (on) to metallic (off) phase transition was controlled by photo-excitation of VO2 in the case of the all-optical switch and by an external electric field applied between the ITO and the VO2 layer in the case of the electro-optical switch. The extinction ratio (on/off) is found to be much higher for the all-optical switch than for the electro-optical switch. For the all-optical switch, extinction ratios of about 22 and 12 dB are obtained in the transmission and reflection modes, respectively. In the case of the electro-optical switch, the extinction ratio is about 12 dB in the transmission mode and 5 dB in the reflection mode. Finally, to explain our optical switching results, we propose a simple model based on the energy band diagram of VO2 in which the charge density increases under an external excitation (either photo-excitation or an electrical field), and then induces the semiconductor-to-metallic phase transition in the VO2 active layer.

Ultrafast insulator-metal phase transition in VO2studied by multiterahertz spectroscopy

“…A large transient pump-induced increase of the conductivity in the THz frequency range was recently reported by several groups. [29][30][31] Therefore, VO 2 has attracted considerable attention due to potential applications such as ultrafast control of light in VO 2 -based photonic crystals, 32 optical switches, [33][34][35] and optical storage devices. 36 Efficient harvesting of this large technological potential demands a thorough understanding of the microscopic physical processes.…”

Optical properties for the Mott transition in VO2

“…2 Owing to its outstanding characteristic, VO 2 has been intensely investigated to be applying for electronic or optical devices. [3][4][5] For describing the MIT in VO 2 , two major mechanisms have been argued: the electronphonon mechanism (the Peierls mechanism 6,7 ) and the electron correlation mechanism (the Mott mechanism 8,9 ). There is much experimental evidence of a strong electronic correlation in VO 2 .…”

Electrically tunable sign of capacitance in planar W-doped vanadium dioxide micro-switches

“…The details of deposition conditions and the switching characteristics of these layers were reported in previous publications [6,7]. Standard photolithography followed by plasma etching was used to pattern the layers into planar micro-switches (100 µm wide by 1000 µm long).…”