scholarly journals Terahertz Nano-Imaging with s-SNOM

2021 ◽  
Author(s):  
Matthias M. Wiecha ◽  
Amin Soltani ◽  
Hartmut G. Roskos
Keyword(s):  
Spatial Resolution ◽  
Terahertz Radiation ◽  
Near Field ◽  
Diffraction Limit ◽  
Length Scale ◽  
Field Techniques ◽  
The Poor ◽  
Imaging And Spectroscopy ◽  
Nano Imaging ◽  
Large Wavelength

Spectroscopy and imaging with terahertz radiation propagating in free space suffer from the poor spatial resolution which is a consequence of the comparatively large wavelength of the radiation (300 μm at 1 THz in vacuum) in combination with the Abbe diffraction limit of focusing. A way to overcome this limitation is the application of near-field techniques. In this chapter, we focus on one of them, scattering-type Scanning Near-field Optical Microscopy (s-SNOM) which − due to its versatility − has come to prominence in recent years. This technique enables a spatial resolution on the sub-100-nm length scale independent of the wavelength. We provide an overview of the state-of-the-art of this imaging and spectroscopy modality, and describe a few selected application examples in more detail.

Nanoscale Optical Microscopy and Spectroscopy Using Near-Field Probes

2018 ◽  
Vol 9 (1) ◽  
pp. 365-387 ◽  
Author(s):  
Richard J. Hermann ◽  
Michael J. Gordon
Keyword(s):  
Optical Microscopy ◽  
Spatial Resolution ◽  
Near Field ◽  
Chemical Properties ◽  
Diffraction Limit ◽  
Optical Signals ◽  
The Past ◽  
Properties Of Materials ◽  
Imaging And Spectroscopy ◽  
And Chemical Properties

Light-matter interactions can provide a wealth of detailed information about the structural, electronic, optical, and chemical properties of materials through various excitation and scattering processes that occur over different length, energy, and timescales. Unfortunately, the wavelike nature of light limits the achievable spatial resolution for interrogation and imaging of materials to roughly λ/2 because of diffraction. Scanning near-field optical microscopy (SNOM) breaks this diffraction limit by coupling light to nanostructures that are specifically designed to manipulate, enhance, and/or extract optical signals from very small regions of space. Progress in the SNOM field over the past 30 years has led to the development of many methods to optically characterize materials at lateral spatial resolutions well below 100 nm. We review these exciting developments and demonstrate how SNOM is truly extending optical imaging and spectroscopy to the nanoscale.

Intensity of Diffraction of Laser Irradiating a Microparticle in Nanostructure Processing

2009 ◽  
Vol 83-86 ◽  
pp. 1282-1287
Author(s):  
Ching Yen Ho ◽  
Mao Yu Wen ◽  
C. Ma
Keyword(s):  
Electromagnetic Wave ◽  
Near Field ◽  
Wave Theory ◽  
Spot Size ◽  
Diffraction Limit ◽  
Materials Processing ◽  
Small Aperture ◽  
Laser Technology ◽  
Field Techniques ◽  
20 Nm

Traditional materials processing in the nanometer range using laser technology is very difficult with conventional optics due to the diffraction limit of the beam wavelength, a near-field technology has been developed to circumvent the diffraction limit, permitting the spot size to be reduced down to 20 nm. In most near-field techniques, this technology is achieved by placing a small aperture or microparticle between the sample and the light source. Therefore this paper will analytically investigate the profile of the intensity for diffraction of laser irradiating an aperture or microparticle in nanostructure processing. Classical electromagnetic wave theory is employed to calculate the intensity for diffraction of laser irradiating a microparticle or aperture. The results will reveal the differences between an aperture and micoparticle for diffraction of laser. The effect of laser parameters on the intensity and distribution of diffraction will be also discussed.

Fabrication of High-Index Refractive Microlenses for Near-Field Optics

1999 ◽  
Author(s):  
D. A. Fletcher ◽  
K. B. Crozier ◽  
G. S. Kino ◽  
C. F. Quate ◽  
K. E. Goodson
Keyword(s):  
Spatial Resolution ◽  
Near Infrared ◽  
Focal Point ◽  
Near Field ◽  
Numerical Aperture ◽  
Diffraction Limit ◽  
Index Of Refraction ◽  
Optical Systems ◽  
Optical Efficiency ◽  
Lens Formation

Abstract The minimum spatial resolution of optical systems in the diffraction limit is approximately the free space wavelength divided by twice the numerical aperture (NA) of the system. NA is defined as the product of the index of refraction at the focal point and the sine of the maximum convergence angle of the light. Resolution below the diffraction limit in air can be achieved with a solid immersion lens (SIL) by scanning a sample within the near field of a spot formed in a high refractive-index lens material in the manner of Mansfield and Kino (1990). This paper presents a technique for microfabricating high-NA SILs in silicon with diameters on the order of 10 μm. Silicon has a higher index than previously demonstrated SILs, and it transmits well in the mid-infrared and near-infrared wavelength ranges, making it an ideal choice for high-resolution thermometry and spectroscopy. However, traditional methods for manufacturing SILs are time consuming, labor intensive, and expensive and cannot typically be used to make lenses smaller than 1 mm in diameter. We review current microlens fabrication techniques and describe the fabrication process developed for this work. We include a method for lens formation using acetone vapor to reflow photoresist pillars that can be used to make aspherical as well as spherical lenses. Microlenses etched in single-crystal silicon with diameters on the order of 10 μm and NAs as high as 3.0 are shown. Wafer-scale fabrication offers the opportunity to integrate microlenses onto MEMs structures such as scanning probes for optical imaging, lithography, spectroscopy, and thermometry with high optical efficiency and spatial resolution.

Laser Nano-Machining Using Near-Field Optics

2004 ◽  
Author(s):  
Haseung Chung ◽  
Katsuo Kurabayashi ◽  
Suman Das
Keyword(s):  
Refractive Index ◽  
Spatial Resolution ◽  
Near Field ◽  
Numerical Aperture ◽  
Diffraction Limit ◽  
High Density ◽  
Index Of Refraction ◽  
Optical Technique ◽  
Near Field Optics ◽  
Maximum Angle

A near-field optical technique, using a new type of solid immersion lens (SIL), has been developed and applied to various areas, for example, high-density optical storage, near-field-scanning-optical-microscope probes, photolithography. Solid immersion microscopy offers a method for achieving resolution below the diffraction limit in air with significantly higher optical throughput by focusing light through a high refractive-index SIL held close to a sample [1]. The minimum resolution of a focusing system is inversely proportional to numerical aperture (NA), where NA = n sinθ, θ is the maximum angle of incidence, and n is the index of refraction at the focal point. Light with vacuum wavelength λ can be focused by an aberration-free lens to a spot whose full width at half maximum (FWHM) is λ/(2 NA) in the scalar diffraction limit, equivalent to Sparrow’s criterion for spatial resolution. In a medium of refractive index n, the effective wavelength is λeff = λ/n and corresponding effective numerical aperture is NAeff = n2sinθ. When a SIL is used, improvements in NAeff and spatial resolution are proportional to the refractive index of the SIL material. Fletcher et al. demonstrated imaging in the infrared with a microfabricated SIL [1, 2]. Baba et al. analyzed the aberrations and allowances for an aspheric error, a thickness error, and an air gap when using a hemispherical SIL for photoluminescence microscopy with submicron resolution beyond the diffraction limit [3]. Terris et al. developed and applied a SIL-based near-field optical technique for the writing and reading domains in a magneto-optic material [4]. Song et al. proposed the new concept of a SIL for high density optical recording using the near-field recording technology [5]. In this paper, we propose a sub-micron scale laser processing technique with spatial resolution beyond the diffraction limit in air using near-field optics. Our goal is to eventually develop a massively parallel nano-optical direct-write nano-manufacturing technique.

Plasmonic near-field nano-imaging and spectroscopy

2004 ◽  
Author(s):  
Satoshi Kawata ◽  
Hiroyuki Watanabe ◽  
Yasushi Inouye
Keyword(s):  
Near Field ◽  
Imaging And Spectroscopy ◽  
Nano Imaging

High-resolution Raman imaging by optically tweezing a dielectric microsphere

2007 ◽  
Vol 1025 ◽  
Author(s):  
Johnson Kasim ◽  
T. Yu ◽  
Y. M. You ◽  
J. P. Liu ◽  
A. K. H. See ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
High Resolution ◽  
Optical Tweezers ◽  
Spatial Resolution ◽  
Near Field ◽  
Diffraction Limit ◽  
Raman Imaging ◽  
Polystyrene Microsphere

AbstractWe show a different method in doing near-field Raman imaging with sub-diffraction limit spatial resolution. A dielectric microsphere (for example polystyrene microsphere) is trapped by optical tweezers. The microsphere is used to focus the laser to the sample, and also to collect the scattered Raman signals. We show the capability of this method in imaging various types of samples, such as SiGe/Si structures, gold nanopattern and carbon nanotubes. This method is comparatively easier to perform, better repeatability, and stronger signal than the normal near-field Raman techniques.

Electromagnetic Simulation Optimizes Design of a Sub-20 nm Resolution Optical Microscope

2006 ◽  
Vol 14 (5) ◽  
pp. 28-31
Author(s):  
Erik J. Sanchez
Keyword(s):  
Light Microscopy ◽  
Spatial Resolution ◽  
Near Field ◽  
Optical Microscope ◽  
Diffraction Limit ◽  
Electromagnetic Simulation ◽  
Fundamental Limit ◽  
Scanning Optical Microscopy ◽  
20 Nm ◽  
Near Field Scanning

Recent advances in nanotechnology and nanoscience are highly dependent on our newly acquired ability to measure and manipulate individual structures on the nanoscale. A drawback of light microscopy is the fundamental limit of the attainable spatial resolution dictated by the laws of diffraction at about 250 nanometers. This diffraction limit arises from the fact that it is impossible to focus light to a spot smaller than half its wavelength. The challenge of breaking this limit has led to the development of near-field scanning optical microscopy (NSOM).

A review of optical near-fields in particle/tip-assisted laser nanofabrication

2009 ◽  
Vol 224 (5) ◽  
pp. 1113-1127 ◽  
Author(s):  
Z B Wang ◽  
N Joseph ◽  
L Li ◽  
B S Luk'yanchuk
Keyword(s):  
Numerical Methods ◽  
Near Field ◽  
Diffraction Limit ◽  
Evanescent Waves ◽  
Optical Diffraction ◽  
Theoretical Modelling ◽  
Theoretical Methods ◽  
Field Techniques ◽  
Field Distributions ◽  
Sample System

Nanofabrication by using lasers with a spatial resolution beyond the optical diffraction limit is a challenging task. One of the solutions is to use near-field techniques, in which evanescent waves dominate over free waves in the vicinity of scattering objects and sub-diffraction-limited focus (as small as ∼10 nm) can be achieved. Theoretical modelling of near-field phenomena is extremely important for the understanding of these near-field techniques, especially for some cases where it is not possible to directly measure the near-fields. In this article, a brief review of the existing near-field laser nanofabrication techniques is given. Different theoretical methods for the computation of optical near-fields, including both analytical and numerical methods, are then presented. The optical near-field distributions of different micro/nano-systems (isolated particles, aggregated particles, particles on the substrate, particles in liquid, and the tip-sample system) are then reviewed in detail within the framework of laser nanofabrication.

scholarly journals Tip-enhanced photoluminescence nano-spectroscopy and nano-imaging

Nanophotonics ◽  
2020 ◽  
Vol 9 (10) ◽  
pp. 3089-3110 ◽  
Author(s):  
Hyeongwoo Lee ◽  
Dong Yun Lee ◽  
Min Gu Kang ◽  
Yeonjeong Koo ◽  
Taehyun Kim ◽  
...  
Keyword(s):  
Spatial Resolution ◽  
Near Field ◽  
High Sensitivity ◽  
Nano Scale ◽  
Biomedical Sensing ◽  
Enhanced Photoluminescence ◽  
Device Applications ◽  
Quantum Materials ◽  
Nano Imaging ◽  
Low Dimensional

AbstractPhotoluminescence (PL), a photo-excited spontaneous emission process, provides a wealth of optical and electronic properties of materials, which enable microscopic and spectroscopic imaging, biomedical sensing and diagnosis, and a range of photonic device applications. However, conventional far-field PL measurements have limitations in sensitivity and spatial resolution, especially to investigate single nano-materials or nano-scale dimension of them. In contrast, tip-enhanced photoluminescence (TEPL) nano-spectroscopy provides an extremely high sensitivity with <10 nm spatial resolution, which allows the desired nano-scale characterizations. With outstanding and unique optical properties, low-dimensional quantum materials have recently attracted much attention, and TEPL characterizations, i. e., probing and imaging, and even control at the nano-scale, have been extensively studied. In this review, we discuss the fundamental working mechanism of PL enhancement by plasmonic tip, and then highlight recent advances in TEPL studies for low-dimensional quantum materials. Finally, we discuss several remaining challenges of TEPL nano-spectroscopy and nano-imaging, such as implementation in non-ambient media and in situ environments, limitations in sample structure, and control of near-field polarization, with perspectives of the approach and its applications.

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