اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدOn the fundamental limitations of imaging with evanescent waves
103
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
There has been significant interest in imaging and focusing schemes that use evanescent waves to beat the diffraction limit, such as those employing negative refractive index materials or hyperbolic metamaterials. The fundamental issue with all such schemes is that the evanescent waves quickly decay between the imaging system and sample, leading to extremely weak field strengths. Using an entropic definition of spot size which remains well defined for arbitrary beam profiles, we derive rigorous bounds on this evanescent decay. In particular, we show that the decay length is only $w / pi e approx 0.12 w$, where $w$ is the spot width in the focal plane, or $sqrt{A} / 2 e sqrt{pi} approx 0.10 sqrt{A}$, where $A$ is the spot area. Practical evanescent imaging schemes will thus most likely be limited to focal distances less than or equal to the spot width.
قيم البحث
اقرأ أيضاً
Abbes resolution limit, one of the best-known physical limitations, poses a great challenge for any wave systems in imaging, wave transport, and dynamics. Originally formulated in linear optics, this Abbes limit can be broken using nonlinear optical
interactions. Here we extend the Abbe theory into a nonlinear regime and experimentally demonstrate a far-field, label-free, and scan-free super-resolution imaging technique based on nonlinear four-wave mixing to retrieve near-field scattered evanescent waves, achieving sub-wavelength resolution of $lambda/15.6$. This method paves the way for application in biomedical imaging, semiconductor metrology, and photolithography.
Significant enhancement of evanescent spatial harmonics inside the slabs of media with extreme optical anisotropy is revealed. This phenomenon results from the pumping of standing waves and has the feature of being weakly sensitive to the material lo
sses. Such characteristics may enable subwavelength imaging at considerable distances away from the objects.
Breaking the diffraction limit is always an appealing topic due to the urge for a better imaging resolution in almost all areas. As an effective solution, the superlens based on the plasmonic effect can resonantly amplify evanescent waves, and achiev
e subwavelength resolution. However, the natural plasmonic materials, within their limited choices, usually have inherit high losses and are only available from the infrared to visible wavelengths. In this work, we have theoretically and experimentally demonstrated that the arbitrary materials, even air, can be used to enhance evanescent waves and build low loss superlens with at the desired frequency. The operating mechanisms reside in the dispersion-induced effective plasmons in a bounded waveguide structure. Based on this, we constructed the hyperbolic metamaterials and experimentally verified its validity in the microwave range by the directional propagation and imaging with a resolution of 0.087 wavelength. We have also demonstrated that the imaging potential can be extended to terahertz and infrared bands. The proposed method can break the conventional barriers of plasmon-based lenses and bring new possibilities to the field of superresolution imaging from microwave to infrared wavelengths.
Quantum channels underlie the dynamics of quantum systems, but in many practical settings it is the channels themselves that require processing. We establish universal limitations on the processing of both quantum states and channels, expressed in th
e form of no-go theorems and quantitative bounds for the manipulation of general quantum channel resources under the most general transformation protocols. Focusing on the class of distillation tasks -- which can be understood either as the purification of noisy channels into unitary ones, or the extraction of state-based resources from channels -- we develop fundamental restrictions on the error incurred in such transformations and comprehensive lower bounds for the overhead of any distillation protocol. In the asymptotic setting, our results yield broadly applicable bounds for rates of distillation. We demonstrate our results through applications to fault-tolerant quantum computation, where we obtain state-of-the-art lower bounds for the overhead cost of magic state distillation, as well as to quantum communication, where we recover a number of strong converse bounds for quantum channel capacity.
Insulating antiferromagnets are efficient and robust conductors of spin current. To realise the full potential of these materials within spintronics, the outstanding challenges are to demonstrate scalability down to nanometric lengthscales and the tr
ansmission of coherent spin currents. Here, we report the coherent transfer of spin angular momentum by excitation of evanescent spin waves of GHz frequency within antiferromagnetic NiO at room temperature. Using element-specific and phase-resolved x-ray ferromagnetic resonance, we probe the injection and transmission of ac spin current, and demonstrate that insertion of a few nanometre thick epitaxial NiO(001) layer between a ferromagnet and non-magnet can even enhance the flow of spin current. Our results pave the way towards coherent control of the phase and amplitude of spin currents at the nanoscale, and enable the realization of spin-logic devices and spin current amplifiers that operate at GHz and THz frequencies.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
