Research

12 pages, 9005 KiB

Open AccessArticle

Effects of Electrolyte on Laser-Induced Periodic Surface Structures with Picosecond Laser Pulses

by Shuhei Kodama and Wataru Natsu

Nanomaterials 2021, 11(2), 327; https://doi.org/10.3390/nano11020327 - 27 Jan 2021

Cited by 3 | Viewed by 2468

Short-pulsed laser-induced periodic surface structures (SPLIPSSs) have the possibility to control tribology, wettability and biocompatibility. Nevertheless, the optimal structure depends on each functionality, which has not been clarified. The hybrid process with a short-pulsed laser and electrochemical machining (SPLECM) is, then, proposed to [...] Read more.

Short-pulsed laser-induced periodic surface structures (SPLIPSSs) have the possibility to control tribology, wettability and biocompatibility. Nevertheless, the optimal structure depends on each functionality, which has not been clarified. The hybrid process with a short-pulsed laser and electrochemical machining (SPLECM) is, then, proposed to fabricate micro/nano hybrid structures and to modify the surface composition for providing high functionalities with material surfaces. Electrochemical machining is a well-established micro-elution and deposition method with noncontact between a workpiece and a tool. In this study, the effects of electrolytes on SPLIPSSs were investigated experimentally by the picosecond laser irradiation on 304 stainless steel substrates in various electrolytes. The geometry of SPLIPSSs depended on the types and the concentration of electrolytes. In the case of copper nitrate solution and copper sulfate solution, LIPSSs and spheroidization of copper were obtained. This study demonstrated the possibility of SPLECM to fabricate micro/nano structures and to control surface composition. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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17 pages, 3262 KiB

Open AccessArticle

Color Centers Enabled by Direct Femto-Second Laser Writing in Wide Bandgap Semiconductors

by Stefania Castelletto, Jovan Maksimovic, Tomas Katkus, Takeshi Ohshima, Brett C. Johnson and Saulius Juodkazis

Nanomaterials 2021, 11(1), 72; https://doi.org/10.3390/nano11010072 - 31 Dec 2020

Cited by 30 | Viewed by 5449

Abstract

Color centers in silicon carbide are relevant for applications in quantum technologies as they can produce single photon sources or can be used as spin qubits and in quantum sensing applications. Here, we have applied femtosecond laser writing in silicon carbide and gallium [...] Read more.

Color centers in silicon carbide are relevant for applications in quantum technologies as they can produce single photon sources or can be used as spin qubits and in quantum sensing applications. Here, we have applied femtosecond laser writing in silicon carbide and gallium nitride to generate vacancy-related color centers, giving rise to photoluminescence from the visible to the infrared. Using a 515 nm wavelength 230 fs pulsed laser, we produce large arrays of silicon vacancy defects in silicon carbide with a high localization within the confocal diffraction limit of 500 nm and with minimal material damage. The number of color centers formed exhibited power-law scaling with the laser fabrication energy indicating that the color centers are created by photoinduced ionization. This work highlights the simplicity and flexibility of laser fabrication of color center arrays in relevant materials for quantum applications. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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15 pages, 2918 KiB

Open AccessArticle

Multiscale Hierarchical Micro/Nanostructures Created by Femtosecond Laser Ablation in Liquids for Polarization-Dependent Broadband Antireflection

by Dongshi Zhang, Bikas Ranjan, Takuo Tanaka and Koji Sugioka

Nanomaterials 2020, 10(8), 1573; https://doi.org/10.3390/nano10081573 - 11 Aug 2020

Cited by 19 | Viewed by 2996

Abstract

In this work, we present the possibility of producing multiscale hierarchical micro/nanostructures by the femtosecond laser ablation of transition metals (i.e., Ta and W) in water and investigate their polarization-dependent reflectance. The hierarchical micro/nanostructures are composed of microscale-grooved, mountain-like and pit-rich structures decorated [...] Read more.

In this work, we present the possibility of producing multiscale hierarchical micro/nanostructures by the femtosecond laser ablation of transition metals (i.e., Ta and W) in water and investigate their polarization-dependent reflectance. The hierarchical micro/nanostructures are composed of microscale-grooved, mountain-like and pit-rich structures decorated with hybrid laser-induced periodic surface structures (LIPSSs). The hybrid LIPSSs consist of low/high and ultrahigh spatial frequency LIPSSs (LSFLs/HSFLs and UHSFLs). LSFLs/HSFLs of 400–600 nm in a period are typically oriented perpendicular to the direction of the laser polarization, while UHSFLs (widths: 10–20 nm and periods: 30–50 nm) are oriented perpendicular to the curvatures of LSFLs/HSFLs. On the microstructures with height gradients, the orientations of LSFLs/HSFLs are misaligned by 18°. On the ablated W metasurface, two kinds of UHSFLs are observed. UHSFLs become parallel nanowires in the deep troughs of LSFLs/HSFLs but result in being very chaotic in shallow LSFLs, turning into polygonal nanonetworks. In contrast, chaotic USFLs are not found on the ablated Ta metasurfaces. With the help of Fourier transform infrared spectroscopy, it is found that microgrooves show an obvious polarization-dependent reflectance at wavelengths of 15 and 17.5 μm associated with the direction of the groove, and the integration of microstructures with LSFs/HSFLs/UHSFLs is thus beneficial for enhancing the light absorbance and light trapping in the near-to-mid-infrared (NIR-MIR) range. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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12 pages, 2035 KiB

Open AccessArticle

Ablation in Externally Applied Electric and Magnetic Fields

by Jovan Maksimovic, Soon-Hock Ng, Tomas Katkus, Nguyen Hoai An Le, James W.M. Chon, Bruce C.C. Cowie, Tao Yang, Yves Bellouard and Saulius Juodkazis

Nanomaterials 2020, 10(2), 182; https://doi.org/10.3390/nano10020182 - 21 Jan 2020

Cited by 9 | Viewed by 3427

Abstract

To harness light-matter interactions at the nano-/micro-scale, better tools for control must be developed. Here, it is shown that by applying an external electric and/or magnetic field, ablation of Si and glass under ultra-short (sub-1 ps) laser pulse irradiation can be controlled via [...] Read more.

To harness light-matter interactions at the nano-/micro-scale, better tools for control must be developed. Here, it is shown that by applying an external electric and/or magnetic field, ablation of Si and glass under ultra-short (sub-1 ps) laser pulse irradiation can be controlled via the Lorentz force

F = e E + e [v \times B]

, where

v

is velocity of charge e,

E

is the applied electrical bias and

B

is the magnetic flux density. The external electric E-field was applied during laser ablation using suspended micro-electrodes above a glass substrate with an air gap for the incident laser beam. The counter-facing Al-electrodes on Si surface were used to study debris formation patterns on Si. Debris was deposited preferentially towards the negative electrode in the case of glass and Si ablation. Also, an external magnetic field was applied during laser ablation of Si in different geometries and is shown to affect ripple formation. Chemical analysis of ablated areas with and without a magnetic field showed strong chemical differences, revealed by synchrotron near-edge X-ray absorption fine structure (NEXAFS) measurements. Harnessing the vectorial nature of the Lorentz force widens application potential of surface modifications and debris formation in external E-/B-fields, with potential applications in mass and charge spectroscopes. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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14 pages, 11088 KiB

Open AccessArticle

Ultrasensitive SERS-Based Plasmonic Sensor with Analyte Enrichment System Produced by Direct Laser Writing

by Georgii Pavliuk, Dmitrii Pavlov, Eugeny Mitsai, Oleg Vitrik, Aleksandr Mironenko, Alexander Zakharenko, Sergei A. Kulinich, Saulius Juodkazis, Svetlana Bratskaya, Alexey Zhizhchenko and Aleksandr Kuchmizhak

Nanomaterials 2020, 10(1), 49; https://doi.org/10.3390/nano10010049 - 24 Dec 2019

Cited by 41 | Viewed by 4457

Abstract

We report an easy-to-implement device for surface-enhanced Raman scattering (SERS)-based detection of various analytes dissolved in water droplets at trace concentrations. The device combines an analyte-enrichment system and SERS-active sensor site, both produced via inexpensive and high-performance direct femtosecond (fs)-laser printing. Fabricated on [...] Read more.

We report an easy-to-implement device for surface-enhanced Raman scattering (SERS)-based detection of various analytes dissolved in water droplets at trace concentrations. The device combines an analyte-enrichment system and SERS-active sensor site, both produced via inexpensive and high-performance direct femtosecond (fs)-laser printing. Fabricated on a surface of water-repellent polytetrafluoroethylene substrate as an arrangement of micropillars, the analyte-enrichment system supports evaporating water droplet in the Cassie–Baxter superhydrophobic state, thus ensuring delivery of the dissolved analyte molecules towards the hydrophilic SERS-active site. The efficient pre-concentration of the analyte onto the sensor site based on densely arranged spiky plasmonic nanotextures results in its subsequent label-free identification by means of SERS spectroscopy. Using the proposed device, we demonstrate reliable SERS-based fingerprinting of various analytes, including common organic dyes and medical drugs at ppb concentrations. The proposed device is believed to find applications in various areas, including label-free environmental monitoring, medical diagnostics, and forensics. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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11 pages, 5621 KiB

Open AccessArticle

External Field-Controlled Ablation: Magnetic Field

by Jovan Maksimovic, Soon Hock Ng, Tomas Katkus, Bruce C. C. Cowie and Saulius Juodkazis

Nanomaterials 2019, 9(12), 1662; https://doi.org/10.3390/nano9121662 - 22 Nov 2019

Cited by 15 | Viewed by 3774

Abstract

The femtosecond laser ablation of silicon amidst an externally applied magnetic field in different orientations was investigated with respect to the scanning direction and polarisation of the laser beam, by observation of ablation patterns and debris displacement in a range of fluences, magnetic [...] Read more.

The femtosecond laser ablation of silicon amidst an externally applied magnetic field in different orientations was investigated with respect to the scanning direction and polarisation of the laser beam, by observation of ablation patterns and debris displacement in a range of fluences, magnetic fields strengths, and geometries. Ultra-short

\sim 230

fs laser pulses of 1030 nm wavelengths were utilised in the single and multi-pulse irradiation modes. Ablation with an externally applied magnetic B-field

B_{e x t} \approx 0.15

T was shown to strongly affect debris formation and deposition. The mechanism of surface plasmon polariton (SPP) wave can explain the ablated periodic patterns observed with alignment along the magnetic field lines. The application potential of external field controlled ablation is discussed. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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Graphical abstract

9 pages, 5397 KiB

Open AccessArticle

Laser-Inscribed Stress-Induced Birefringence of Sapphire

by Hua Fan, Meguya Ryu, Reo Honda, Junko Morikawa, Zhen-Ze Li, Lei Wang, Jovan Maksimovic, Saulius Juodkazis, Qi-Dai Chen and Hong-Bo Sun

Nanomaterials 2019, 9(10), 1414; https://doi.org/10.3390/nano9101414 - 03 Oct 2019

Cited by 14 | Viewed by 4052

Abstract

Birefringence of

3 \times 10^{- 3}

is demonstrated inside cross-sectional regions of 100

μ

m, inscribed by axially stretched Bessel-beam-like fs-laser pulses along the c-axis inside sapphire. A high birefringence and retardance of

λ / 4

at mid-visible spectral range (green) can [...] Read more.

Birefringence of

3 \times 10^{- 3}

is demonstrated inside cross-sectional regions of 100

μ

m, inscribed by axially stretched Bessel-beam-like fs-laser pulses along the c-axis inside sapphire. A high birefringence and retardance of

λ / 4

at mid-visible spectral range (green) can be achieved using stretched beams with axial extension of 30–40

μ

m. Chosen conditions of laser-writing ensure that there are no formations of self-organized nano-gratings. This method can be adopted for creation of polarization optical elements and fabrication of spatially varying birefringent patterns for optical vortex generation. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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10 pages, 4490 KiB

Open AccessArticle

Multi-Purpose Nanovoid Array Plasmonic Sensor Produced by Direct Laser Patterning

by Dmitrii V. Pavlov, Alexey Yu. Zhizhchenko, Mitsuhiro Honda, Masahito Yamanaka, Oleg B. Vitrik, Sergei A. Kulinich, Saulius Juodkazis, Sergey I. Kudryashov and Aleksandr A. Kuchmizhak

Nanomaterials 2019, 9(10), 1348; https://doi.org/10.3390/nano9101348 - 20 Sep 2019

Cited by 17 | Viewed by 3045

Abstract

We demonstrate a multi-purpose plasmonic sensor based on a nanovoid array fabricated via inexpensive and highly-reproducible direct femtosecond laser patterning of thin glass-supported Au films. The proposed nanovoid array exhibits near-IR surface plasmon (SP) resonances, which can be excited under normal incidence and [...] Read more.

We demonstrate a multi-purpose plasmonic sensor based on a nanovoid array fabricated via inexpensive and highly-reproducible direct femtosecond laser patterning of thin glass-supported Au films. The proposed nanovoid array exhibits near-IR surface plasmon (SP) resonances, which can be excited under normal incidence and optimised for specific applications by tailoring the array periodicity, as well as the nanovoid geometric shape. The fabricated SP sensor offers competitive sensitivity of ≈ 1600 nm/RIU at a figure of merit of 12 in bulk refractive index tests, as well as allows for identification of gases and ultra-thin analyte layers, making the sensor particularly useful for common bioassay experiments. Moreover, isolated nanovoids support strong electromagnetic field enhancement at lattice SP resonance wavelength, allowing for label-free molecular identification via surface-enhanced vibration spectroscopy. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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7 pages, 1940 KiB

Open AccessArticle

Fabrication of Crystalline Microresonators of High Quality Factors with a Controllable Wedge Angle on Lithium Niobate on Insulator

by Jianhao Zhang, Zhiwei Fang, Jintian Lin, Junxia Zhou, Min Wang, Rongbo Wu, Renhong Gao and Ya Cheng

Nanomaterials 2019, 9(9), 1218; https://doi.org/10.3390/nano9091218 - 29 Aug 2019

Cited by 56 | Viewed by 4454

Abstract

We report the fabrication of crystalline microresonators of high quality (Q) factors with a controllable wedge angle on lithium niobate on insulator (LNOI). Our technique relies on a femtosecond laser assisted chemo-mechanical polish, which allows us to achieve ultrahigh surface smoothness as critically [...] Read more.

We report the fabrication of crystalline microresonators of high quality (Q) factors with a controllable wedge angle on lithium niobate on insulator (LNOI). Our technique relies on a femtosecond laser assisted chemo-mechanical polish, which allows us to achieve ultrahigh surface smoothness as critically demanded by high Q microresonator applications. We show that by refining the polish parameters, Q factors as high as 4.7 × 10⁷ can be obtained and the wedge angle of the LNOI can be continuously tuned from 9° to 51°. Full article

(This article belongs to the Special Issue Laser Printing of Nanophotonic Structures)

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