Photothermal optical modulation of ultra-compact hybrid Si-VO_2 ring resonators

Ryckman, Judson D.; Diez-Blanco, V.; Nag, Joyeeta; Marvel, Robert E.; Choi, B.K.; Haglund, Richard F.; Weiss, Sharon M.

doi:10.1364/oe.20.013215

Cited by 92 publications

(62 citation statements)

References 34 publications

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“…8 The integration of VO 2 on silicon waveguides has been intensively studied for applications in optical switches that are compatible with current silicon photonics, because this is expected to have advantages over conventional silicon-based optical switches in terms of device size. [9][10][11][12] To develop high-performance switches, VO 2 films that display large changes in their refractive index across the MIT have to be fabricated directly on silicon waveguides. However, VO 2 films on silicon are generally polycrystalline due to mismatches in structural properties; consequently, they have lower crystallinities than do epitaxial films or the bulk material, giving rise to deteriorations in their optical properties.…”

Section: Introductionmentioning

confidence: 99%

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Shibuya

Sawa

2015

AIP Advances

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We systematically examined the effects of the substrate temperature (TS) and the oxygen pressure (PO2) on the structural and optical properties polycrystalline V O2 films grown directly on Si(100) substrates by pulsed-laser deposition. A rutile-type V O2 phase was formed at a TS ≥ 450 °C at PO2 values ranging from 5 to 20 mTorr, whereas other structures of vanadium oxides were stabilized at lower temperatures or higher oxygen pressures. The surface roughness of the V O2 films significantly increased at growth temperatures of 550 °C or more due to agglomeration of V O2 on the surface of the silicon substrate. An apparent change in the refractive index across the metal–insulator transition (MIT) temperature was observed in V O2 films grown at a TS of 450 °C or more. The difference in the refractive index at a wavelength of 1550 nm above and below the MIT temperature was influenced by both the TS and PO2, and was maximal for a V O2 film grown at 450 °C under 20 mTorr. Based on the results, we derived the PO2 versus 1/TS phase diagram for the films of vanadium oxides, which will provide a guide to optimizing the conditions for growth of V O2 films on silicon platforms.

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Section: Introductionmentioning

confidence: 99%

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Shibuya

Sawa

2015

AIP Advances

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“…The decreased modal index leads to a blueshift of the resonant wavelength of the ring, as demonstrated in previous all optical measurements. [18,19] Figures 3a and 3c indeed show blueshifted resonances when VO 2 switches from the monoclinic to rutile state. A larger blueshift is observed with the larger VO 2 patch and we believe the entire VO 2 patch is being switched in both cases, as discussed in the next paragraph.…”

Section: Analysis and Discussionmentioning

confidence: 81%

Hybrid silicon-vanadium dioxide electro-optic modulators

et al. 2016

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Small-footprint, low-power devices that can modulate optical signals at THz speeds would transform next-generation onchip photonics. We describe a hybrid silicon-vanadium dioxide (Si-VO 2 ) electro-optic ring resonator modulator as a candidate platform for achieving this performance benchmark. Vanadium dioxide (VO 2 ) is a strongly correlated material exhibiting a semiconductor-to-metal transition (SMT) accompanied by large changes in electrical and optical properties. While VO 2 can be switched optically on a sub-picosecond time scale, the ultimate electrical switching speed remains to be determined. In a 5 µm radius Si-VO 2 ring resonator, we achieve 1.5 dB modulation in response to a 10 ns square voltage pulse of 2.5 V. In the steady state regime, we report a modulation depth of 10 dB. The larger modulation depth at longer timescales is attributed to a Joule heating contribution. Experimental results, corroborated by FDTD simulations, reveal the relationship between the portion of a VO 2 patch undergoing the SMT and the resulting effects on the Si-VO 2 device performance. This work indicates that with further reduction of VO 2 patch sizes and increase in resonator Q factor, there is promise for the Si-VO 2 ring resonator electro-optic modulator as a competitive option for on-chip photonics technology.

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“…Figures 1(c) and (d) show the voltage across the wire as the applied current was gradually increased. In both wires, the voltage initially increased between points (1)- (2) with the current. After point (2), VO 2 underwent a phase transition causing a reduction in resistivity and a voltage drop.…”

Section: Device Geometry and Fabricationmentioning

confidence: 99%

“…Not only does the electrical conductivity of the material change by several orders of magnitude across the phase transition, the real and imaginary parts of the refractive index also change by O(1) in the telecom wavelength bands [1] . VO 2 has recently been utilized on plasmonic and silicon devices to achieve compact (< 5 m long) and low power optical switches with large extinction ratios > 10 dB [1,2]. A drawback is that the device operation used the thermo-optic switching of VO 2 , which had switching times in the range of tens of microseconds.…”

Section: Introductionmentioning

confidence: 99%

Current-Controlled Optical Modulation in Thin VO2 Wires

et al. 2014

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We measured the current-voltage and infrared optical transmission characteristics of thin film VO 2 wires over the metal-insulator phase transition. The phase transition had electrical or thermal characteristics depending on the wire geometry and applied current.OCIS codes: (160.4760) Optical properties, (160.2100) Electro-optic materials, (160.3130) Integrated optics materials IntroductionThe dimensions of state-of-art optoelectronic devices are often limited to tens of microns, mainly due to the weak changes in the real or imaginary parts of the refractive index in conventional optical materials, such as silicon, germanium, lithium niobate, and compound semiconductors, with applied electrical signals. The large dimensions of these devices increase the real estate requirement and energy consumption of optoelectronic devices. For the ultimate miniaturization of optoelectronic devices, highly tunable materials should be considered.The phase transition material, vanadium dioxide, VO 2 , has attracted significant interest in the field of micro-and nano-photonics in recent years. VO 2 can reversibly change between a metallic and insulator phase when it is heated beyond the transition temperature, T > 67 0 C, but the phase transition can also be induced electronically, optically, and mechanically. Not only does the electrical conductivity of the material change by several orders of magnitude across the phase transition, the real and imaginary parts of the refractive index also change by O(1) in the telecom wavelength bands [1] . VO 2 has recently been utilized on plasmonic and silicon devices to achieve compact (< 5 m long) and low power optical switches with large extinction ratios > 10 dB [1,2]. A drawback is that the device operation used the thermo-optic switching of VO 2 , which had switching times in the range of tens of microseconds.To improve upon the performance, phase transition of VO 2 needs to be better understood. In this work, we report the first directly imaged electrically-induced optical modulation of thin VO 2 wires at the infrared wavelengths near 1550 nm. We find that the geometry of the wire significantly affects the phase transition. Under some conditions, we can observe a two-step phase transition in VO 2 , which we can separately attribute to thermally and electronically induced effects. This result opens the path toward high-speed VO 2 optoelectronic devices that suppress the thermally-induced transition.

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Photothermal optical modulation of ultra-compact hybrid Si-VO_2 ring resonators

Cited by 92 publications

References 34 publications

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Optimization of conditions for growth of vanadium dioxide thin films on silicon by pulsed-laser deposition

Hybrid silicon-vanadium dioxide electro-optic modulators

Current-Controlled Optical Modulation in Thin VO2 Wires

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