All-Optical Hybrid VO$_{2}$/Si Waveguide Absorption Switch at Telecommunication Wavelengths

Abstract

Vanadium dioxide (VO2) is one of the most promising materials for developing hybrid photonic integrated circuits (PICs). At telecommunication wavelengths, VO2 exhibits a large change on the refractive index (∆n ∼ 1 and ∆κ ∼ 2.5) between its insulating and metallic state. Such insulating-to-metal transition (IMT) can be triggered by light, which could enable alloptical hybrid VO2-waveguide devices. Here, we experimentally demonstrate an all-optical absorption switch using a hybrid VO2/Si waveguide fully compatible with the silicon photonics platform. All-optical characterization was carried out for TE polarization and at telecommunication wavelengths using an in-plane approach. The temporal dynamics were retrieved by using pump-probe measurements. Our results show an extinction ratio of 0.7 dB/µm with a maximum switchable length of 15 µm, a switching speed as low as 318 ns and an energy per switch of 15.8 nJ. The inherit large optical bandwith of a nonresonant waveguide poses this device as a promising candidate for developing all-optical and broadband silicon PICs.

Toward Nonvolatile Switching in Silicon Photonic Devices

“…Reproduced with permission. [ 93 ] Copyright 2021, IEEE.…”

“…However, until now, switching times from several seconds to hundreds of picoseconds have been achieved for hybrid photonic waveguide devices driven by optical pumping. [93,[101][102][103][104] Only very recently, sub-ps switching times with switching energies between 6 and 360 nJ have been reported for a hybrid VO 2 /Si photonic waveguide with out-of-plane optical pumping. [105] Therefore, a photothermal mechanism is still mostly dominant, and the difference in the timescales may be explained by the different characteristics of the control light source and the size of the VO 2 patch.…”

“…c) Hysteretic variation of the imaginary part of the refractive index as a function of temperature at a wavelength of 1550 nm. Reproduced with permission [93]. Copyright 2021, IEEE.…”

The mechanism of semiconductor to metal transition in the hydrogenation of VO2: a density functional theory study

“…6–8 Moreover, this phase transition is accompanied by changes of some special properties, such as optical behavior, 9–11 electrical conductivity, 12,13 etc. These fascinating characteristics originate from the interplay between the lattice and orbital degrees of freedom, which make VO 2 a promising material for application in thermodynamic window coatings, 14,15 smart optoelectronic switches, 10,12,16 memory materials, 17,18 actuators, 19–22 photonics technologies, 23–27 diffractive elements, 28–30 etc.…”

Ultra-Compact Efficient Thermally Actuated Mach-Zehnder Modulator Based on VO2

“…Also, it exhibits a substantial variation of the refractive index during a phase transition phenomenon that drastically changes both the real and imaginary parts of the refractive index of VO2 [10,11]. This phase transition can be induced, either thermally [3,12,13], electrically [14,15], or optically [16,17]. As a result, a range of optical devices based on VO2 including switches [18,14], metasurfaces [19,20], polarizers [21], absorption modulators [22,23], modulators based on resonating structures including micro ring resonator (MRRs) [24] and Bragg gratings [10], and devices for the realization of advanced modulation schemes such as four-level pulse amplitude modulation (PAM4) [25] have been introduced recently.…”