Microspectroscopy Using a Solid Immersion Lens

2001 ◽  
Vol 7 (S2) ◽  
pp. 148-149
Author(s):  
C.D. Poweleit ◽  
J Menéndez
Keyword(s):  
Spatial Resolution ◽  
Focal Plane ◽  
Numerical Aperture ◽  
Normal Incidence ◽  
Spot Size ◽  
Index Of Refraction ◽  
Objective Lens ◽  
Improvement Factor ◽  
Oil Immersion ◽  
Long Time

Oil immersion lenses have been used in optical microscopy for a long time. The light’s wavelength is decreased by the oil’s index of refraction n and this reduces the minimum spot size. Additionally, the oil medium allows a larger collection angle, thereby increasing the numerical aperture. The SIL is based on the same principle, but offers more flexibility because the higher index material is solid. in particular, SILs can be deployed in cryogenic environments. Using a hemispherical glass the spatial resolution is improved by a factor n with respect to the resolution obtained with the microscope’s objective lens alone. The improvement factor is equal to n2 for truncated spheres.As shown in Fig. 1, the hemisphere SIL is in contact with the sample and does not affect the position of the focal plane. The focused rays from the objective strike the lens at normal incidence, so that no refraction takes place.

scholarly journals High-efficiency, large-area lattice light-sheet generation by dielectric metasurfaces

Nanophotonics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 4043-4051
Author(s):  
Fenghua Shi ◽  
Jing Wen ◽  
Dangyuan Lei
Keyword(s):  
Spatial Resolution ◽  
Temporal Resolution ◽  
High Efficiency ◽  
Numerical Aperture ◽  
Light Sheet ◽  
Field Of View ◽  
Objective Lens ◽  
High Temporal Resolution ◽  
Light Sheet Microscopy ◽  
Illumination Efficiency

AbstractLattice light-sheet microscopy (LLSM) was developed for long-term live-cell imaging with ultra-fine three-dimensional (3D) spatial resolution, high temporal resolution, and low photo-toxicity by illuminating the sample with a thin lattice-like light-sheet. Currently available schemes for generating thin lattice light-sheets often require complex optical designs. Meanwhile, limited by the bulky objective lens and optical components, the light throughput of existing LLSM systems is rather low. To circumvent the above problems, we utilize a dielectric metasurface of a single footprint to replace the conventional illumination modules used in the conventional LLSM and generate a lattice light-sheet with a ~3-fold broader illumination area and a significantly leveraged illumination efficiency, which consequently leads to a larger field of view with a higher temporal resolution at no extra cost of the spatial resolution. We demonstrate that the metasurface can manipulate spatial frequencies of an input laser beam in orthogonal directions independently to break the trade-off between the field of view and illumination efficiency of the lattice light-sheet. Compared to the conventional LLSM, our metasurface module serving as an ultra-compact illumination component for LLSM at an ease will potentially enable a finer spatial resolution with a larger numerical-aperture detection objective lens.

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.

On resolving fine periodic microstructures in the optical microscope

1989 ◽  
Vol 47 ◽  
pp. 364-365
Author(s):  
W.S. Putnam ◽  
C. Viney
Keyword(s):  
Liquid Crystalline ◽  
Numerical Aperture ◽  
Polarized Light ◽  
Normal Incidence ◽  
Optical Microscope ◽  
Angle Of Incidence ◽  
Resolution Limit ◽  
Crystalline Materials ◽  
Periodic Microstructures ◽  
Liquid Crystalline Materials

Many sheared liquid crystalline materials (fibers, films and moldings) exhibit a fine banded microstructure when observed in the polarized light microscope. In some cases, for example Kevlar® fiber, the periodicity is close to the resolution limit of even the highest numerical aperture objectives. The periodic microstructure reflects a non-uniform alignment of the constituent molecules, and consequently is an indication that the mechanical properties will be less than optimal. Thus it is necessary to obtain quality micrographs for characterization, which in turn requires that fine detail should contribute significantly to image formation.It is textbook knowledge that the resolution achievable with a given microscope objective (numerical aperture NA) and a given wavelength of light (λ) increases as the angle of incidence of light at the specimen surface is increased. Stated in terms of the Abbe resolution criterion, resolution improves from λ/NA to λ/2NA with increasing departure from normal incidence.

scholarly journals In-Line Analysis of Diffusion Processes in Micro Channels by Long Distance Raman Photometric Measurement Technology—A Proof of Concept Study

Micromachines ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 116
Author(s):  
Julian Deuerling ◽  
Shaun Keck ◽  
Inasya Moelyadi ◽  
Jens-Uwe Repke ◽  
Matthias Rädle
Keyword(s):  
Numerical Aperture ◽  
Spot Size ◽  
Measuring System ◽  
Optical Systems ◽  
Measurement Technology ◽  
Long Distance ◽  
Measuring Point ◽  
Acetone Concentration ◽  
Micro Channels ◽  
Set Up

This work presents a novel method for the non-invasive, in-line monitoring of mixing processes in microchannels using the Raman photometric technique. The measuring set-up distinguishes itself from other works in this field by utilizing recent state-of-the-art customized photon multiplier (CPM) detectors, bypassing the use of a spectrometer. This addresses the limiting factor of integration times by achieving measuring rates of 10 ms. The method was validated using the ternary system of toluene–water–acetone. The optical measuring system consists of two functional units: the coaxial Raman probe optimized for excitation at a laser wavelength of 532 nm and the photometric detector centered around the CPMs. The spot size of the focused laser is a defining factor of the spatial resolution of the set-up. The depth of focus is measured at approx. 85 µm with a spot size of approx. 45 µm, while still maintaining a relatively high numerical aperture of 0.42, the latter of which is also critical for coaxial detection of inelastically scattered photons. The working distance in this set-up is 20 mm. The microchannel is a T-junction mixer with a square cross section of 500 by 500 µm, a hydraulic diameter of 500 µm and 70 mm channel length. The extraction of acetone from toluene into water is tracked at an initial concentration of 25% as a function of flow rate and accordingly residence time. The investigated flow rates ranged from 0.1 mL/min to 0.006 mL/min. The residence times from the T-junction to the measuring point varies from 1.5 to 25 s. At 0.006 mL/min a constant acetone concentration of approx. 12.6% was measured, indicating that the mixing process reached the equilibrium of the system at approx. 12.5%. For prototype benchmarking, comparative measurements were carried out with a commercially available Raman spectrometer (RXN1, Kaiser Optical Systems, Ann Arbor, MI, USA). Count rates of the spectrophotometer surpassed those of the spectrometer by at least one order of magnitude at identical target concentrations and optical power output. The experimental data demonstrate the suitability and potential of the new measuring system to detect locally and time-resolved concentration profiles in moving fluids while avoiding external influence.

scholarly journals Focal Surface Detection of High Numerical Aperture Objective Lens Based on Differential Astigmatic Method

2021 ◽  
Vol 13 (4) ◽  
pp. 1-8
Author(s):  
Jia-Lin Du ◽  
Wei Yan ◽  
Li-Wei Liu ◽  
Fan-Xing Li ◽  
Fu-Ping Peng ◽  
...  
Keyword(s):  
Numerical Aperture ◽  
Objective Lens ◽  
High Numerical Aperture ◽  
Surface Detection ◽  
Focal Surface

Expansion of a Focused Laser Beam in the Turbulent Atmosphere

1971 ◽  
Vol 49 (10) ◽  
pp. 1233-1248 ◽  
Author(s):  
A. D. Varvatsis ◽  
M. I. Sancer
Keyword(s):  
Laser Beam ◽  
Free Space ◽  
Turbulent Atmosphere ◽  
Focal Plane ◽  
Spot Size ◽  
Small Aperture ◽  
Forward Scatter ◽  
Green’S Theorem ◽  
Focused Beams ◽  
Weakly Dependent

This work examines the expansion of a focused laser beam in the turbulent atmosphere. The formulation is based on Green's theorem and the valid assumption that the turbulent atmosphere is a forward-scatter medium for wavelengths of interest (0.6 μ < λ < 11 μ). The main results are: (1) the spot size at the free-space focal plane in the presence of turbulence is independent of the aperture radius, and is only weakly dependent on the wavelength, (2) the focal plane can be significantly shifted for small aperture radii, short wavelengths, and long free-space focal lengths, (3) the effect of the atmosphere is pronounced only close to the free-space focus and very far away, and (4) the turbulent atmosphere has a stronger effect on weakly focused beams rather than strongly focused beams, except very close to the free-space focus, where the effect is more pronounced for strongly focused beams.

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