Increasing the resolution of the reconstructed image in terahertz pulse time-domain holography

Nikolay S Balbekin,Nikolay V Petrov,Andrey V Belashov,Andrei Gorodetsky,Maksim S Kulya

doi:10.1038/s41598-018-36642-3

Abstract

In this paper, we present a novel numerical approach for increasing the resolution of retrieved images of objects after their diffraction patterns are recorded via terahertz pulse time-domain holography (THz PTDH). THz PTDH allows for spectrally resolved imaging with high spatial resolution and does not require the fine alignment of complex optics in the THz path. The proposed data post-processing method opens up the possibility to reconstruct holograms recorded with spatially restricted THz detectors, and overcome the diffraction limit even for the lower-frequency spectral components. The method involves an iterative procedure of backward-forward wavefront propagation to simulate the field distribution beyond the initially recorded hologram area. We show significant improvement in both the object reconstruction and contrast across the whole spectrum, with qualitative resolution enhancement at lower frequency spectral components.

Highlights

Since its first demonstration back in 1980s1, terahertz (THz) radiation has found numerous spectroscopic and imaging applications[2]
The PTDH resolution enhancement approach we offer can be applied to any coherent wavefront THz detector, and, as there are currently no array photoconductive antennas (PCAs) detectors, we propose the following layouts for full wavefront electro-optical sampling (EOS) using either a synchronous, or asynchronous approach (Fig. 1)
We proposed the solution for resolution and field of view enhancement in THz pulse time domain holography (THz PTDH)

Summary

Introduction

Since its first demonstration back in 1980s1, terahertz (THz) radiation has found numerous spectroscopic and imaging applications[2]. For visible range holography, Latyshevskaia et al proposed a self-extrapolation technique[49] which allows for overcoming the Abbe criterion and resulting resolution enhancement of the reconstructed objects by padding the hologram and iteratively filling the padded area with the numerically propagated wavefront. To record THz pulse time domain hologram one must first record the amplitude and phase of a collimated wavefront at the detection plane, place the object of interest to record the diffraction pattern with the same detector.

Results

Conclusion