We demonstrate single-mode laser emission in single nanowires. By folding a 200 nm diameter CdSe nanowire to form loop mirrors, single-mode laser emission around 738 nm wavelength is obtained with line width of 0.12 nm and low threshold. The mode selection is realized by the vernier effect of coupled cavities in the folded nanowire. In addition, the loop structure makes it possible to tune the nanowire cavity, opening an opportunity to realize a tunable single-mode nanowire laser.

Several existing strategies for estimating the axial intensity derivative in the transport-of-intensity equation (TIE) from multiple intensity measurements have been unified by the Savitzky-Golay differentiation filter--an equivalent convolution solution for differentiation estimation by least-squares polynomial fitting. The different viewpoint from the digital filter in signal processing not only provides great insight into the behaviors, the shortcomings, and the performance of these existing intensity derivative estimation algorithms, but more important, it also suggests a new way of improving solution strategies by extending the applications of Savitzky-Golay differentiation filter in TIE. Two novel methods for phase retrieval based on TIE are presented--the first by introducing adaptive-degree strategy in spatial domain and the second by selecting optimal spatial frequencies in Fourier domain. Numerical simulations and experiments verify that the second method outperforms the existing methods significantly, showing reliable retrieved phase with both overall contrast and fine phase variations well preserved.

In digital holographic microscopy, if an optical setup is well aligned, the phase curvature introduced by the microscope objective (MO) together with the illuminating wave to the object wave is a spherical phase curvature. It can be physically compensated by introducing the same spherical phase curvature in the reference beam. Digital holographic microscopy setups based on the Michelson interferometric configuration with MO and an adjustable lens are presented, which can well perform the quasi-physical phase compensation during the hologram recording. In the reflection mode, the adjustable lens serves as both the condensing lens and the compensation lens. When the spatial frequency spectra of the hologram become a point spectrum, one can see that the phase curvature introduced by imaging is quasi-physically compensated. A simple plane numerical reference wavefront used for the reconstruction can give the correct quantitative phase map of the test object. A theoretical analysis and experimental demonstration are given. The simplicity of the presented setup makes it easy to align it well at lower cost.

In this review we will focus on recent progress in the field of two-dimensional (2D) and three-dimensional (3D) display technologies. We present the current display materials and their applications, including organic light-emitting diodes (OLEDs), flexible OLEDs quantum dot light emitting diodes (QLEDs), active-matrix organic light emitting diodes (AMOLEDs), electronic paper (E-paper), curved displays, stereoscopic 3D displays, volumetric 3D displays, light field 3D displays, and holographic 3D displays. Conventional 2D display devices, such as liquid crystal devices (LCDs) often result in ambiguity in high-dimensional data images because of lacking true depth information. This review thus provides a detailed description of 3D display technologies.

We propose a technique in which intensity images are reconstructed from a digital hologram to provide inputs for the transport-of-intensity equation for unwrapped phase recovery. By doing this, we avoid shifting of the sample or the camera in the experiment, a method commonly employed while using the method of transport-of-intensity equation for phase retrieval. Computer simulations as well as experimental results have been demonstrated to verify the effectiveness of the proposed idea. The underlying numerical technique can also be viewed as an alternative to existing phase-unwrapping algorithms.