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All‐optical neural networks have advantages in higher throughput, higher speed as well as lower energy consumption compared to electrical neural networks. Optical neural networks have already shown great potential in various applications; however, the operation speed of the network is limited by the 2D detector as most optical neural networks rely on space to space projection. Here, a space to time projection approach to build diffractive deep neural network (D2NN) is proposed, which can project spatial intensity distribution into time‐domain intensity variation, thus bypassing the detection speed limit of 2D imaging device. Based on this scheme, high‐speed all‐optical logic gates are theoretically analyzed and experimentally realized. In this case, the network's operation speed is only limited by the photodetector (PD), which can reach GHz levels. Moreover, the method will show great advantage when it comes to wavelengths where 2D detectors are not achievable easily such as infrared, terahertz or microwaves. [ABSTRACT FROM AUTHOR]

Structured illumination has been employed in fluorescence microscopy to extend its lateral resolution. It has been demonstrated that a factor of 2 improvement can be achieved. In this paper, we introduce a novel optical arrangement that can further improve the resolution. It makes use of a fine grating held in close proximity to the sample. The fringe pattern thus projected onto the sample contains grating vectors substantially higher than those that are possible with the conventional structured illumination setup. We will present experimental results to demonstrate the principle of the technique, and will show that, theoretically, it can achieve an imaging NA approaching 4. [c] 2010 Optical Society of America OCIS codes: 180.2520, 050.6624, 110.4850, 350.5730.

The use of aplanatic solid immersion lenses (ASILs) made of high refractive index optical materials provides a route to wide-field high-resolution optical microscopy. We analyze the aberrations that need to be circumvented for wide-field, high-resolution imaging by hybrid optical simulations based on both ray and wave optics. The conclusions on the relationships among ASIL size, fluorescence imaging spectral width, and field of view not only guide us to design the microscopic system demonstrated in this article, but also clearly demonstrate the general design considerations necessary when applying an ASIL in fluorescence microscopy. Based on the simulation results, we develop wide-field high-resolution solid immersion fluorescence (SIF) microscopy employing an ASIL with an effective numerical aperture (NA) of 1.85. We demonstrate wide-field, high-resolution imaging of synthetic and biological samples with our SIF system. In the presence of a gap between the ASIL and the sample, we experimentally demonstrate that the effective NA of the SIF system is determined by the refractive index of the gap medium in addition to that of the ASIL material; thus, in general, degrading the resolution. Future developments of the SIF system to suit routine use and make it achieve still higher resolution by combining SIF and other microscopic techniques are proposed. OCIS codes: 110.0180, 180.2520, 170.2520, 350.5730, 110.0110, 100.2960.

Atomic layers of group‐VI 2D transition metal dichalcogenides (TMDCs) with substantial materials system and unique physicochemical properties have exhibited excellent performances in electronics and optoelectronics. However, photodetectors based on TMDCs suffer from poor sensitivity and optical absorption due to the weak phonon conversion efficiency and optical absorption due to their atomically thin feature. Here, taking advantages of miniaturization and integrability, all‐dielectric TiO2 metalenses are designed based on the Fresnel diffraction effect and integrated with molybdenum ditelluride (MoTe2) photodetectors. Owing to the enhancement of photon utilization efficiency, the corresponding integrated devices exhibit a high responsivity of 135.0 A W–1, an excellent external quantum efficiency of 202.0%, and a specific detectivity of ≈4.05 × 1012 Jones. These results indicate that the optoelectrical properties of 2D materials can be significantly optimized by integration with metalens and will accelerate the evolution of metalens in 2D optoelectronics fields. [ABSTRACT FROM AUTHOR]

We describe a numerical vector diffraction model based on Mie theory that describes the imaging of spherical particles by bright-field, confocal, and interferometric microscopes. The model correctly scales the amplitude-scattered field relative to the incident field so that the forward-scattered and incident light can be interfered to correctly model imaging with copolarization transmission microscopes for the first time to our knowledge. The model is used to demonstrate that amplitude and phase imaging with an interferometric microscope allows subwavelength particle sizing. Furthermore, we show that the phase channel allows much smaller particles to be sized than amplitude-only measurements. The model is validated by experimental measurements. OCIS codes: 180.1790, 180.3170, 120.5050, 290.5820, 290.5850.

2D materials and their van der Waals heterostructures are of great fundamental interest and have potential applications in emerging electronics devices. However, atomically thin photodetector applications have suffered from performance limitations because of low optical absorption. Here, a near‐infrared photodetector based on methylammonium lead halide perovskite quantum dots (MQDs), combined with Ta2NiSe5 van der Waals heterostructures, is fabricated to take advantage of their energy band alignment. An ultrasensitive photoresponse with a detectivity of 6.0 × 1012 Jones for 800 nm illumination is demonstrated. Furthermore, the field‐effect mobility and responsivity are enhanced by factors of 2 and 7.4, respectively, by interfacing Ta2NiSe5 and the MQDs. These results indicate that the optoelectrical properties of 2D ternary Ta2NiSe5 can be significantly optimized via hybridization with MQDs and can accelerate the evolution of MQD‐van der Waals heterostructure‐based devices. [ABSTRACT FROM AUTHOR]

A new scanning common-path interferometric profiler capable of absolute-phase measurement is described. The key element is a computer-generated hologram, which acts as the beam-splitting element. Unlike most absolute phase systems, it can be made entirely common path with respect to piston microphonics and is thus exceptionally stable. In addition to operating in scanning mode, the optical configuration permits simultaneous operation as a single-shot phase measuring interferometer and is thus capable of simultaneous form and texture measurements. The operation and stability of the scanning profiler are demonstrated experimentally.

The imaging resolution in turbid media is severely degraded by light scattering. Resolution can be improved if the unscattered or weakly scattered light is extracted. Here the state of polarization of the emerging light is used to discriminate photon path length, with the more weakly scattered photons maintaining their original polarization state. It is experimentally demonstrated that over a wide range of scatterer concentrations there exist three distinct imaging regimes. It is also shown that within the intermediate regime one of two distinct imaging techniques is appropriate, depending on the particle size. Key words: Polarization, imaging, scattering.

We describe a scanning optical interferometer that can simultaneously perform ellipsometry measurements and thus provides a true surface profile. This is accomplished by projecting the back focal plane of the objective lens onto a CCD array. The measured phase differences between the p- and s-polarization components are converted, by using a specially developed algorithm, to optical phase changes caused by material variations. The compensation process is then applied to extract the true profile of the object surface. Experimental results obtained with the system are shown. Key words: Scanning optical profilometry, ellipsometry, material-related phase shift, interferometry.

The construction and results obtained with a scanning heterodyne differential microscope capable of simultaneously imaging in differential phase and differential intensity modes are described. Interfering the two signal beams with a common reference beam (indirect interference) permits an optimum differential phase and intensity performance to be obtained simultaneously. The considerations that ensure satisfactory performance are discussed. Results that demonstrate the ability to alter electronically the imaging mode and the optical transfer function within each imaging mode are presented. This permits the system performance to be matched to the requirements of each sample. Key words: Differential phase, differential intensity, confocal microscopy, heterodyne interferometer.

We describe results obtained when a modified differential interferometer is used in a new imaging modality that we call extended-focus phase imaging. This modality is the phase analog of extended-focus imaging used in the confocal microscope. Our technique is applied to the measurement of the differential phase response of minute topographical variations on tilted samples. Results are presented that demonstrate the ability of the technique to produce high lateral resolution phase scans on samples with long-range warp and tilt over a range much greater than the depth of field of the objective lens, thus effectively allowing the depth of field of the phase microscope to be increased indefinitely.

A phase-sensitive scanning optical microscope is described that can measure surface height changes down to 0.1 nm. This is achieved by using two heterodyne Michelson interferometers in parallel. One interferometer probes the sample with a tightly focused beam, and the second has a collimated beam that illuminates a large area of the surface, providing a large area on sample reference. This is facilitated by using a specially constructed objective lens that permits the relative areas illuminated by the two probe beams to be varied both arbitrarily and independently, thus ensuring an accurate absolute phase measurement. We subtracted the phase outputs from each interferometer to provide the sample phase information, canceling the phase noise resulting from microphonics in the process. Results from a prototype version of the microscope are presented that demonstrate the advantages of the system over existing techniques.