New diffractive imaging techniques using coherent x-ray beams have made possible nanometer-scale resolution imaging by replacing the optics in a microscope with an iterative phase retrieval algorithm. However, to date very high resolution imaging (< 40nm) was limited to large-scale synchrotron facilities. Here, we present a significant advance in image resolution and capabilities for desktop soft x-ray microscopes that will enable widespread applications in nanoscience and nanotechnology. Using 13nm high harmonic beams, we demonstrate a record 22nm spatial resolution for any tabletop x-ray microscope. Finally, we show that unique information about the sample can be obtained by extracting 3-D information at very high numerical apertures.

Terahertz waves provide a better contrast in imaging soft biomedical tissues than X-rays and unlike X-rays, they cause no ionisation damage, making them a good option for biomedical imaging. Terahertz absorption imaging has conventionally been used for cancer diagnosis. However, the absorption properties of a cancerous sample are influenced by two opposing factors: an increase in absorption due to a higher degree of hydration and a decrease in absorption due to structural changes. It is therefore difficult to diagnose cancer from an absorption image. Phase imaging can thus be critical for diagnostics. We demonstrate imaging of the absorption and phase-shift distributions of 3.2 mm × 2.3 mm × 30-μm-thick human hepatocellular carcinoma tissue by continuous-wave terahertz digital in-line holography. The acquisition time of a few seconds for a single in-line hologram is much shorter than that of other terahertz diagnostic techniques and future detectors will allow acquisition of meaningful holograms without sample dehydration. The resolution of the reconstructions was enhanced by sub-pixel shifting and extrapolation. Another advantage of this technique is its relaxed minimal sample size limitation. The fibrosis indicated in the phase distribution demonstrates the potential of terahertz holographic imaging to obtain a more objective, early diagnosis of cancer.

We report here on terahertz (THz) digital holography on a biological specimen. A continuous-wave (CW) THz in-line holographic setup was built based on a 2.52 THz CO₂ pumped THz laser and a pyroelectric array detector. We introduced novel statistical method of obtaining true intensity values for the pyroelectric array detector’s pixels. Absorption and phase-shifting images of a dragonfly’s hindwing were reconstructed simultaneously from single in-line hologram. Furthermore, we applied phase retrieval routines to eliminate twin image and enhanced the resolution of the reconstructions by hologram extrapolation beyond the detector area. The finest observed features are 35 μm width cross veins.

In the past few decades, the applications of terahertz (THz) spectroscopy and imaging technology have seen significant developments in the fields of biology, medical diagnosis, food safety, and nondestructive testing. Label-free diagnosis of malignant tumours has been obtained and also achieved significant development in THz biomedical imaging. This review mainly presents the research status and prospects of several common continuous-wave (CW) THz medical imaging systems and applications of THz medical imaging in biological tissues. Here, we first introduce the properties of THz waves and how these properties play a role in biomedical imaging. Then, we analyse both the advantages and disadvantages of the CW THz imaging methods and the progress of these methods in THz biomedical imaging in recent ten years. Finally, we summarise the obstacles in the way of the application of THz bio-imaging application technology in clinical detection, which need to be investigated and overcome in the future.

A novel speckle reduction technique for digital holography is proposed. Multiple off-axis holograms are recorded using a circularly polarized illumination beam and a rotating linearly polarized reference beam. The speckle noise in the reconstructed images is suppressed by averaging these fields. We demonstrate the effectiveness of this technique experimentally and conduct additional statistical evaluation.

A speckle noise suppression method in digital holography is proposed by the angular diversity with a phase-only spatial light modulator (SLM). The minimal angular difference of illumination beams is quantitatively analyzed to ensure the noncorrelation of any two speckle patterns, and then the phase-only SLM is employed to generate a series of tilted illumination beams. Comparing with the typical methods, the tilted illumination beams are controlled dynamically and accurately, which makes it possible to record a large number of holograms. Finally, using an image-plane digital holographic system, 117 holograms are recorded respectively, and the synthesized reconstructed images are obtained with the greatly suppressed speckle noise which is in good agreement with the theoretical results. The experimental results demonstrate the effectiveness, repeatability, and practicability of the proposed approach.