We present an active physical implementation of the recently introduced plasmon injection loss compensation scheme for Pendry's non-ideal negative index flat lens in the presence of realistic material losses and signal-dependent noise. In this active implementation, we propose to use a physically convolved external auxiliary source for signal amplification and suppression of the noise in the imaging system. In comparison with the previous passive implementations of the plasmon injection scheme for sub-diffraction limited imaging, where an inverse filter post-processing is used, the active implementation proposed here allows for deeper subwavelength imaging far beyond the passive post-processing scheme by extending the loss compensation to even higher spatial frequencies.Although this form of passive inverse filter provides compensation for absorption losses, it is also prone to noise amplification [56]. This is illustrated in figure 1 which shows an object with three Gaussian features separated by λ o /4, where λ o is the free space wavelength. Noise is prominent in the Fourier spectra beyond ky ko = 2.5 as seen in figure 2. However, the compensated image is still reasonably well resolved. Consider now the object shown in figure 3, which has four Gaussians separated by λ o /4. The Fourier spectra of the raw image, shown in figure 4, demonstrates how the feature at

Recently a coherent optical process called plasmon-injection (Π) scheme, which employs an auxiliary source, has been introduced as a new technique to compensate losses in metamaterials. Here, a physical implementation of the Π scheme is proposed for enhanced superlens imaging in the presence of absorption losses and noise. The auxiliary source is constructed by a high-intensity illumination (above 1  mW/μm) of the superlens integrated with a near-field spatial filter. The integrated system enables reconstruction of an object previously unresolvable with the superlens alone. This work elevates the viability of the Π scheme as a strong candidate for loss compensation in near-field imaging systems without requiring nonlinear effects or gain media.

Near-field optics and superlenses for imaging beyond Abbe's diffraction limit are reviewed. A comprehensive and contemporary background is given on scanning near-field microscopy and superlensing. Attention is brought to recent research leveraging scanning near-field optical microscopy with superlenses for new nano-imaging capabilities. Future research directions are explored for realizing the goal of low-cost and high-performance sub-diffraction-limited imaging systems. © 2016 Author(s)

In this paper, the optical properties and imaging performance of a non-ideal Pendry's negative index flat lens with a practical value for loss are studied. Analytical calculations of the optical properties of the lens are performed, and those results are used to further study the lens and corresponding imaging system numerically. An inverse filter emulating the plasmon injection scheme for loss compensation in negative index metamaterials is applied to the results from the imaging system, resulting in a perfect reconstruction of a previously unresolved image that demonstrates sub-diffraction-limited resolution.

We present how to physically realize the auxiliary source described in the recently introduced active plasmon injection loss compensation scheme for enhanced near-field superlensing. Particularly, we show that the characteristics of the auxiliary source described in the active plasmon injection scheme including tunable narrow-band and selective amplification via convolution can be realized by using a hyperbolic metamaterial functioning as a near-field spatial filter. Besides loss compensation, the proposed near-field spatial filter can be useful for real-time high resolution edge detection.