Robust COTS objective for diffraction-limited, high-NA, long front working distance imaging

A spherical aberration-free microscopy system for live brain imaging

Design of a catadioptric mid-wave infrared telecentric microscope with high numerical aperture and long working distance

We have developed a novel transmissive nematic liquid crystal device which is capable of compensating spherical wavefront aberration that occurs during the operation of optical pickup systems. In order to increase the storage capacity, next generation optical data storage systems beyond CD and DVD will use according to the Blu-Ray specification (BD) blue laser light and an objective lens with high numerical aperture (N.A.) of 0.85. However, such high N.A. systems have an inherent higher sensitivity on aberrations. For example spherical aberration is inversely proportional to the wavelength and grows with the fourth power of N.A. of the objective lens. In an optical pickup system there are two sources for spherical aberration: The first one is the variation of the substrate thickness due to manufacturing tolerances under mass production conditions. The second one concerns disks with multiple data-layers, which cause spherical aberration when layers are switched, as the objective lens can only be optimized for a single layer thickness. We report a method for effective compensation of spherical aberration by utilizing a novel liquid crystal device, which generates a parabolic wavefront profile. This particular shape makes the device highly tolerant against lateral movement. A sophisticated electrode design allows us to reduce the number of driving electrodes down to two by using the method of conductive ladder mashing. Further evaluation in a blue-DVD test drive has been carried out with good results. By placing the device into an optical pick-up we were able to readout a dual-layer ROM disk with a total capacity of 50 gigabytes (GB). A data-to-clock jitter of 6.9% for the 80 μm and of 8.0% for the 100 μm cover layer could be realized.

Scanning technology is widely used in current lithography. During scanning, any point on the wafer scanning through the field of view (FOV) is successively affected by varying levels of polarization aberrations (PAs) that depend on the position within the FOV. However, current computational lithography studies for extreme ultraviolet lithography (EUVL) neglect this effect of the "dynamic PA" caused by scanning. Consequently, the optimization results cannot meet the actual imaging requirements, leading to a decline in image quality for the lithographic projection objective, particularly in high numerical aperture (NA) EUVL systems. This paper establishes a dynamic PA model for NA0.55 EUVL and proposes a source optimization method employing this model to increase image quality. The model samples the FOV points in the scanning direction at equal intervals based on the characteristics of the EUVL pulsed lasers. Then, it calculated the images at different sampling points and the iterative exposure of the resist, considering the impact of PA from each sampling point. The optimization strategy of source parameters based on this model is realized. Experimental results demonstrate that this SO method effectively reduces pattern errors by 15.5%-28.2%, and the process window is expanded by 15.0%-22.2%.

Self-organization of nano-void array for photonic crystal device

The paper is devoted to characterization of topography of micro optical elements with very high numerical aperture using digital holographic microscope. For very high numerical aperture we mean the one larger than numerical aperture of optical system conjugating the object plane with the detector plane. In this case the optical system is not capable of capturing any information about micro element areas with high numerical aperture (high shape gradients). In the paper we are presenting method that can be used for recovering high numerical aperture shape from few measurements with digital holographic microscope working in transmission and reflective configuration. We are focusing on metrology of microlenses of high numerical aperture. Within the presented method measurement of tilted object is necessary. When the element is tilted then some of optical field is coming from "new high gradient element area", when the element is tangential the area of high gradient is producing field with numerical aperture larger that numerical aperture of the measurement optical system. In our paper we therefore use data captured for tilted sample in order to reconstruct micro element topography within a region of high numerical aperture. Such data are then defocused to tilted plane and only then can be used for topography reconstruction.

Fabrication of microneedles using two photon-polymerization with low numerical aperture

As minimum feature size shrinks to a metal pitch of 21 nm, the current extreme ultra violet (EUV) lithographic tool with a numeric aperture (NA) of 0.33 will face resolution limit for some critical layers. High NA (0.55) EUV with anamorphic optics or EUV double patterning (DP) at 0.33 NA are being considered for the next generation of lithographic technology. Both the high NA EUV system and EUV DP will enhance resolution relative to current EUV single patterning (SP). Nevertheless, in order to be able to compare EUV DP and High NA EUV processes, important lithographic factors including image contrast, mask three dimension (M3D) effects, process variation band, stochastic effects and local critical dimension uniformity need to be investigated to understand their contributions to process variations. This study was carried out using rigorous lithographic model simulations in Sentaurus Lithography, where strong M3D effects in EUVL are computed physically. We have simulated patterns with both isomorphic and anamorphic optical proximity corrections (OPC) using the rigorous model. The study focuses on 3nm node Via layer designs. These vias need to connect to metal features which have pitches of 21 nm. Simulation results using 0.33 NA SP, 0.33 NA DP, and 0.55 NA anamorphic SP are presented. The benefit of using an alternative mask absorber and a thinner resist as well as the impact of stochastic effects have also been explored. Although a 0.55 NA EUV is expected to produce a superior image to 0.33 NA EUV and to have less impact from overlay errors and stochastic effects, an analysis of process margins of 0.33 NA EUV SD and DP versus 0.55 NA anamorphic systems helps to better understand the benefits, challenges and optimal insertion point for introducing High-NA EUV.

Hybrid-type 3-axis actuator for active tilt compensation in optical pickup

We present experimental demonstration of tilt-mirror assisted transmission structured illumination microscopy (tSIM) that offers a large field of view super resolution imaging. An assembly of custom-designed tilt-mirrors are employed as the illumination module where the sample is excited with the interference of two beams reflected from the opposite pair of mirror facets. Tunable frequency structured patterns are generated by changing the mirror-tilt angle and the hexagonal-symmetric arrangement is considered for the isotropic resolution in three orientations. Utilizing high numerical aperture (NA) objective in standard SIM provides super-resolution compromising with the field-of-view (FOV). Employing low NA (20X/0.4) objective lens detection, we experimentally demonstrate sim (0.56 mmtimes0.35 mm) size single FOV image with sim1.7- and sim2.4-fold resolution improvement (exploiting various illumination by tuning tilt-mirrors) over the diffraction limit. The results are verified both for the fluorescent beads as well as biological samples. The tSIM geometry decouples the illumination and the collection light paths consequently enabling free change of the imaging objective lens without influencing the spatial frequency of the illumination pattern that are defined by the tilt-mirrors. The large and scalable FOV supported by tSIM will find usage for applications where scanning large areas are necessary as in pathology and applications where images must be correlated both in space and time.

Laparoscope is the essential tool for minimally invasive surgery (MIS) within the abdominal cavity. However, the focal length of a conventional laparoscope is fixed. Therefore, it suffers from the tradeoff between field of view (FOV) and spatial resolution. In order to obtain large optical magnification to see more details, a conventional laparoscope is usually designed with a small working distance, typically less than 50mm. Such a small working distance limits the field of coverage, which causes the situational awareness challenge during the laparoscopic surgery. We developed a multi-resolution foveated laparoscope (MRFL) aiming to address this limitation. The MRFL was designed to support a large working distance range from 80mm to 180mm. It is able to simultaneously provide both wide-angle overview and high-resolution image of the surgical field in real time within a fully integrated system. The high-resolution imaging probe can automatically scan and engage to any subfield of the wide-angle view. During the surgery, MRFL does not need to move; therefore it can reduce the instruments conflicts. The FOV of the wide-angle imaging probe is 80° and that of the high-resolution imaging probe is 26.6°. The maximum resolution is about 45um in the object space at an 80mm working distance, which is about 5 times as good as a conventional laparoscope at a 50mm working distance. The prototype can realize an equivalent 10 million-pixel resolution by using only two HD cameras because of its foveation capability. It saves the bandwidth and improves the frame rate compared to the use of a super resolution camera. It has great potential to aid safety and accuracy of the laparoscopic surgery.

We describe a method of optical refocusing for high numerical aperture (NA) systems that is particularly relevant for confocal and multiphoton microscopy. This method avoids the spherical aberration that is common to other optical refocusing systems. We show that aberration-free images can be obtained over an axial scan range of 70 mum for a 1.4 NA objective lens. As refocusing is implemented remotely from the specimen, this method will enable high axial scan speeds without mechanical interference between the objective lens and the specimen.

Single‐nanoparticle and single‐molecule fluorescence detection delivers unparalleled capabilities for quantifying concentrations, hydrodynamic sizes, and molecular dynamics for biosensing assays or environmental monitoring. Metalenses offer a promising route to miniaturizing high‐NA objective lenses, but their use in fiber‐integrated probes for quantitative single‐particle analysis remains largely unexplored. In this work, we introduce an achromatic metalens integrated with a solid‐core optical fiber (AMOF) as a compact sensing head that enables remote epi‐fluorescence correlation spectroscopy (FCS) in aqueous solutions. We achieve remote epi‐fluorescence monitoring of polystyrene nanoparticles of sizes from 110 nm to 4 µm and streptavidin biomolecules in the far‐red spectral range within a defined focal volume. By systematically varying the optical fiber core diameters, we reveal and quantify a design trade‐off between single‐nanoparticle sensitivity and detection volume, enabling accurate determination of particle concentration and size down to low picomolar‐femtomolar regimes through remote FCS. The robust operation of the AMOF head over meter‐scale fiber lengths without complicated alignment demonstrates that high numerical aperture (NA) achromatic metalenses can be effectively combined with optical fibers for remote single‐particle fluorescence analysis. This approach opens promising opportunities for in situ diagnostics, environmental nanoparticle monitoring, and remote emitter characterization.

We demonstrate an all-optical strategy for realizing spherical three-dimensional (3D) super-resolution (∼λ3/22) spot arrays of pure longitudinal magnetization by exploiting a 4π optical microscopic setup with two high numerical aperture (NA) objective lenses, which focus and interfere two modulated vectorial beams. Multiple phase filters (MPFs) are designed via an analytical approach derived from the vectorial Debye diffraction theory to modulate the two circularly polarized beams. The system is tailored to constructively interfere the longitudinal magnetization components, while simultaneously destructively interfering the azimuthal ones. As a result, the magnetization field is not only purely longitudinal but also super-resolved in all three dimensions. Furthermore, the MPFs can be designed analytically to control the number and locations of the super-resolved magnetization spots to produce both uniform and nonuniform arrays in a 3D volume. Thus, an all-optical control of all the properties of light-induced magnetization spot arrays has been demonstrated for the first time. These results open up broad applications in magnetic-optical devices such as confocal and multifocal magnetic resonance microscopy, 3D ultrahigh-density magneto-optic memory, and light-induced magneto-lithography.

We discuss the statistical properties of speckle of the logarithmically transformed signal in optical coherence tomography (OCT) both theoretically and experimentally. OCT signals of Intralipid solution with different volume particle concentrations ρ (correspondingly, scattering coefficient μ(s) ranges from 1.25 to 25.11 mm(-1)) were measured and analyzed under two different focusing conditions [numerical apertures (NAs) of the objective lens of 0.13 and 0.25]. We found that the effect of the speckle noise can be suppressed by displaying OCT images in the logarithmic scale and by using the objective lens with a higher NA. We also found that the speckle properties are correlated with the scattering properties of the sample, which may be used to characterize the scattering properties of biological tissue. The simulated OCT image and the in vitro OCT image of a rat liver are used as examples to demonstrate the feasibility of the method.