Overcoming losses in superlenses with synthetic waves of complex frequency

Superlenses made of plasmonic materials and metamaterials have been exploited to image features of sub-diffractional scale. However, their intrinsic losses impose a serious restriction on the imaging resolution, which is a long-standing problem that has hindered wide-spread applications of superlenses. Optical waves of complex frequency exhibiting a temporally attenuating behavior have been proposed to offset the intrinsic losses in superlenses via virtual gain, but the experimental realization has been missing due to the challenge involved in preparing the illumination with temporal decay. Here, by employing multi-frequency measurement, we successfully implement a synthetic optical wave of complex frequency to experimentally observe deep-subwavelength superimaging patterns enabled by the virtual gain. Our work represents a practical approach to overcoming the intrinsic losses of plasmonic systems for imaging and sensing applications.Comment: 17 pages, 3 figure

Synthesized complex-frequency excitation for ultrasensitive molecular sensing

Detecting trace molecules remains a significant challenge. Surface-enhanced infrared absorption (SEIRA) based on plasmonic nanostructures, particularly graphene, has emerged as a promising approach to enhance sensing sensitivity. While graphene-based SEIRA offers advantages such as ultrahigh sensitivity and active tunability, intrinsic molecular damping weakens the interaction between vibrational modes and plasmons. Here, we demonstrate ultrahigh-sensitive molecular sensing based on synthesized complex-frequency waves (CFW). Our experiment shows that CFW can amplify the molecular signals (~1.2-nm-thick silk protein layer) detected by graphene-based sensor by at least an order of magnitude and can be universally applied to molecular sensing in different phases. Our approach is highly scalable and can facilitate the investigation of light-matter interactions, enabling diverse potential applications in fields such as optical spectroscopy, metasurfaces, optoelectronics, biomedicine and pharmaceutics.Comment: 21 pages, 4 figure

Recovering lossless propagation of polaritons with synthesized complex frequency excitation

Surface plasmon polaritons and phonon polaritons offer a means of surpassing the diffraction limit of conventional optics and facilitate efficient energy storage, local field enhancement, high sensitivities, benefitting from their subwavelength confinement of light. Unfortunately, losses severely limit the propagation decay length, thus restricting the practical use of polaritons. While optimizing the fabrication technique can help circumvent the scattering loss of imperfect structures, the intrinsic absorption channel leading to heat production cannot be eliminated. Here, we utilize synthetic optical excitation of complex frequency with virtual gain, synthesized by combining the measurements taken at multiple real frequencies, to restore the lossless propagations of phonon polaritons with significantly reduced intrinsic losses. The concept of synthetic complex frequency excitation represents a viable solution to compensate for loss and would benefit applications including photonic circuits, waveguiding and plasmonic/phononic structured illumination microscopy.Comment: 20 pages, 4 figure

Synthesized complex-frequency excitation for ultrasensitive molecular sensing

Detecting trace molecules remains a significant challenge. Surface-enhanced infrared absorption (SEIRA) based on plasmonic nanostructures, particularly graphene, has emerged as a promising approach to enhance sensing sensitivity. While graphene-based SEIRA offers advantages such as ultrahigh sensitivity and active tunability, intrinsic molecular damping weakens the interaction between vibrational modes and plasmons. Here, we demonstrate ultrahigh-sensitive molecular sensing based on synthesized complex-frequency waves (CFW). Our experiment shows that CFW can amplify the molecular signals (~1.2-nm-thick silk protein layer) detected by graphene-based sensor by at least an order of magnitude and can be universally applied to molecular sensing in different phases. Our approach is highly scalable and can facilitate the investigation of light-matter interactions, enabling diverse potential applications in fields such as optical spectroscopy, metasurfaces, optoelectronics, biomedicine and pharmaceutics