Probing gigahertz coherent acoustic phonons in TiO2 mesoporous thin films

Oliveira, E. R. Cardozo de; Xiang, C.; Esmann, Martin; Abdala, Nicolás López; Fuertes, M. Cecilia; Bruchhausen, A. E.; Pastoriza, H.; Perrin, Bernard; Soler-Illia, Galo J.A.A.; Lanzillotti‐Kimura, N. D.

doi:10.1016/j.pacs.2023.100472

Cited by 10 publications

(12 citation statements)

References 73 publications

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“…We fabricated open-cavity acoustic resonators composed of mesoporous SiO 2 thin films using a sol-gel method in a dip coating approach. 9,13,14 The resonator architecture consisted of an acoustic distributed Bragg reflector (DBR) of 3 periods of dense SiO 2 /TiO 2 multilayers to prevent phonon diffusion towards the substrate, a 30-nmthick nickel acousto-optical transducer for efficient acousto-optical transduction, and the mesoporous SiO 2 thin film serving as the resonant cavity, as shown in Fig. 1(a).…”

Section: Resultsmentioning

confidence: 99%

Mesoporous-based responsive acoustic resonators operating in the GHz range

Cardozo de Oliveira,

Xiang,

Vensaus

et al. 2024

Nanophotonics X

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The manipulation of ultra-high-frequency acoustic phonons in the tens of gigahertz to sub-terahertz range offers a promising avenue for technological advancements. This control can be achieved by means of semiconductor superlattices, such as GaAs/AlAs, which requires costly fabrication processes in order to achieve atomically flat interfaces to avoid phonon scattering and dephasing. In addition, acoustic resonators based on such systems are bound to fixed frequency operations. Mesoporous materials, with pores at the nanoscale, are good candidates to overcome such limitations. It has been shown that multilayered resonators based on mesoporous SiO 2 and TiO 2 support acoustic resonances in the 5-100 GHz range. These materials are susceptible to liquids and vapors infiltration into the pores, causing the modification of the effective optical and elastic parameters. Here we present a design of open-cavity acoustic resonators of SiO 2 mesoporous thin films (MTFs) responsive to the environment. The resonator is composed of an acoustic distributed Bragg reflector, to avoid phonon diffusion towards the substrate, followed by a nickel acousto-optical transducer, and the MTF on top. We characterize the resonator by using coherent phonon generation and detection experiments in a reflectivity pump-probe setup, and compare it with a simplified structure. The experimental results show that the acoustic signals in the open-cavity resonator have improved performance. Our findings unveil a promising platform for nanoacoustic reconfigurable optoacoustic devices based on soft, inexpensive fabrication methods. As a perspective to this work, we aim at studying the dependence of the acoustic resonances on the environment humidity.

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Section: Resultsmentioning

confidence: 99%

Mesoporous-based responsive acoustic resonators operating in the GHz range

Cardozo de Oliveira,

Xiang,

Vensaus

et al. 2024

Nanophotonics X

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“…In the article [14] , mesoporous TiO 2 resonators for coherent acoustic phonons up to 90 GHz with quality factors up to 7 are demonstrated by means of ultrafast transient pump-probe reflectometry and interferometry. The experimental results and theoretical modelling suggest a pathway for engineering more complex structures for nanoacoustic sensing and reconfigurable optoacoustic nanodevices based on cost-effective fabrication methods, such as sol-gel techniques.…”

Section: Regular Articlesmentioning

confidence: 99%

Special issue introduction: Ultrafast photoacoustics

Gusev,

Audoin,

Wright

2024

Photoacoustics

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“…A potential candidate for active tunable acoustic resonator are the mesoporous thin films (MTFs), with pores at the nanoscale. 13,14 Oxide-based MTFs can be conceived with soft fabrication processes based on sol-gel and dip coating approach. 15,16 The high surface-to-volume ratio plays a major role on the chemical functionalization of these materials.…”

Section: Introductionmentioning

confidence: 99%

Design of responsive mesoporous-based open-cavity acoustic resonators operating in the GHz range

Cardozo de Oliveira,

Vensaus,

Soler-Illia

et al. 2024

Metamaterials XIV

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Designing acoustic resonators at ultra-high frequencies is a promising pathway for important technological advancements, including quantum technologies. Resonators operating in the tens-of-gigahertz range are usually based on semiconductor multi-layered distributed Bragg reflectors (DBRs). However, their inherent lack of tuning capability imposes constraints on specific applications, such as sensing. Mesoporous materials, with pores at the nanoscale, could potentially bridge the gap for responsive acoustic resonators. These cost-effective materials support gigahertz acoustic resonances, and their high surface-to-volume ratio allow for engineering resonators with novel functionalities, such as optoacoustic sensors or switches. For instance, the infiltration of liquids and vapors into the pores modifies the material's optical and elastic parameters, leading to direct modification of the acoustic resonances. Here, we theoretically propose open-cavity multi-layered acoustic resonators based on SiO 2 mesoporous materials that are responsive to the environment, e.g., relative humidity changes. The resonators are formed by a DBR of dense SiO 2 /TiO 2 multilayers, followed by a Ni acousto-optical transducer, to both generate and detect acoustic phonons, and finalized by the mesoporous as the last layer, so it has access to the environment. In this design, gigahertz acoustic phonons can be effectively confined at the mesoporous layer. On one hand, the acoustic DBR prevents their leakage toward the substrate, and on the other hand, they cannot propagate through the air, creating an ideal acoustic mirror at the mesoporous-air interface. We present two case studies based on this approach and show, by numerical simulations using transfer matrix method, the responsiveness and tunability of such resonators upon ambient humidity changes. The simulation results also indicate that these devices can be characterized through transient reflectivity experiments. Our study could guide the way for designing effective nanoacoustic sensing and adaptable devices, utilizing cost-effective fabrication techniques.

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Probing gigahertz coherent acoustic phonons in TiO2 mesoporous thin films

Cited by 10 publications

References 73 publications

Mesoporous-based responsive acoustic resonators operating in the GHz range

Mesoporous-based responsive acoustic resonators operating in the GHz range

Special issue introduction: Ultrafast photoacoustics

Design of responsive mesoporous-based open-cavity acoustic resonators operating in the GHz range

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