Modulation and Control Technology for Generating Movable Super-Diffraction Optical Needle by Oblique Incidence

The movable super-diffraction optical needle (MSON) is a tightly focused beam like a “needle”, which can realize vector scanning on the focusing plane. Not only does it have a long focal depth, but its resolution also exceeds the diffraction limit. The modulation and control technology required for generating MSON by oblique incidence is explored in this manuscript for the purpose of processing high-aspect-ratio, sub-wavelength structures. As the optical needle generated by traditional methods is static and sensitive to variation of the angle information of the incident beam, here we introduce a confocal scanning system by using a two-dimensional galvanometer system, a scan lens, and a tube lens to control the oblique incidence angle. The effects of the oblique incidence angle on the resolution, depth of focus, uniformity, and side lobes of the MSON were analyzed. Further, the voltage-controlled liquid crystal located between the scan lens and the 2D galvanometer system can be used to compensate for the additional phase difference caused by oblique incidence. The aspect ratio is defined as the ratio of depth of focus to resolution. By modulating and controlling the light field, the MSON with high aspect ratio (7.36), sub-diffractive beam size (0.42λ), and long depth of focus (3.09λ) has been obtained with homogeneous intensity, and suppressed side lobes. High speed, high axial positioning tolerance, and high-resolution laser processing can also be achieved, which removes the restrictions presented by traditional laser processing technology, for which high resolution and long depth of focus cannot be achieved simultaneously.

Download Full-text

High-resolution particle separation by inertial focusing in high aspect ratio curved microfluidics

Scientific Reports ◽

10.1038/s41598-021-93177-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Javier Cruz ◽

Klas Hjort

Keyword(s):

High Resolution ◽

Aspect Ratio ◽

High Aspect Ratio ◽

Biological Fluids ◽

Essential Feature ◽

Particle Separation ◽

Size Difference ◽

Inertial Focusing ◽

Complex Samples ◽

Wide Range

AbstractThe ability to focus, separate and concentrate specific targets in a fluid is essential for the analysis of complex samples such as biological fluids, where a myriad of different particles may be present. Inertial focusing is a very promising technology for such tasks, and specially a recently presented variant, inertial focusing in High Aspect Ratio Curved systems (HARC systems), where the systems are easily engineered and focus the targets together in a stable position over a wide range of particle sizes and flow rates. However, although convenient for laser interrogation and concentration, by focusing all particles together, HARC systems lose an essential feature of inertial focusing: the possibility of particle separation by size. Within this work, we report that HARC systems not only do have the capacity to separate particles but can do so with extremely high resolution, which we demonstrate for particles with a size difference down to 80 nm. In addition to the concept for particle separation, a model considering the main flow, the secondary flow and a simplified expression for the lift force in HARC microchannels was developed and proven accurate for the prediction of the performance of the systems. The concept was also demonstrated experimentally with three different sub-micron particles (0.79, 0.92 and 1.0 µm in diameter) in silicon-glass microchannels, where the resolution in the separation could be modulated by the radius of the channel. With the capacity to focus sub-micron particles and to separate them with high resolution, we believe that inertial focusing in HARC systems is a technology with the potential to facilitate the analysis of complex fluid samples containing bioparticles like bacteria, viruses or eukaryotic organelles.

Download Full-text

Analysis and characterization of high-resolution and high-aspect-ratio imaging fiber bundles

Applied Optics ◽

10.1364/ao.54.009422 ◽

2015 ◽

Vol 54 (32) ◽

pp. 9422 ◽

Cited By ~ 4

Author(s):

Nojan Motamedi ◽

Salman Karbasi ◽

Joseph E. Ford ◽

Vitaliy Lomakin

Keyword(s):

High Resolution ◽

Aspect Ratio ◽

High Aspect Ratio ◽

Fiber Bundles ◽

Ratio Imaging

Download Full-text

The Use of Metallographic and SEM Analysis for Characterization of Sidewall Surfaces in MEMS Devices with DRIE Processing

International Symposium on Microelectronics ◽

10.4071/isom-2010-wp5-paper3 ◽

2010 ◽

Vol 2010 (1) ◽

pp. 000703-000706

Author(s):

Colin Stevens ◽

Robert Dean ◽

Samuel Lawrence ◽

Lee Levine

Keyword(s):

Aspect Ratio ◽

High Aspect Ratio ◽

Measurement Techniques ◽

Sem Analysis ◽

Defect Structures ◽

Mems Devices ◽

Depth Of Focus ◽

Surface Conditions ◽

Side Walls

The Bosch Deep Reactive Ion Etch Process is commonly used for the manufacture of MEMS and MOEMS devices that require deep high aspect ratio trenches. In many cases fully released, high aspect ratio features can be generated in one pass. However the process must be understood to avoid generating some of the defect structures that are characteristic of the process. Defects such as scalloping, silicon grass, and undercutting at the interface of a nonconductive layer can be controlled by process parameters and optimization. Measurement and characterization of the defective structures is a key element of controlling them. The use of SEM measurement techniques for characterizing the small features associated with scalloping and silicon grass is essential. No other technique is capable of providing the large depth of focus required to visualize these features. The use of metallographic techniques furthers understanding of the surface conditions on the side walls of these deep trenches.

Download Full-text