Manipulation of the refractive index has been of growing interest lately. We consider parameters and possibilities of enhancing the absolute-value limit of the linear index in coherent atomic systems. Starting with a review of how two-level transitions - without and with added coherence effects - do not realistically allow for a significantly enhanced index at fixed atomic density, we discuss a possible way around this using wave mixing. This confirms that the only parameters, besides the medium optical depth/density, that can effectively change the value of the attainable index are the frequencies of the involved transitions.
Refractive index enhancement is crucial in the field of lithography, imaging, optical communications, solar devices and many more. We present a review of advancements in the process of designing high refractive index metamaterials, starting from quantum coupling and photonic bandgap materials to metamaterials utilizing deep subwavelength coupling to achieve ever-high values of refractive index. A crisp and critical impression of each scheme are presented. The understanding of evolution of material design from intrinsic electronic states manipulation to meta-atoms design is not only fascinating…
Atomically thin transition metal dichalcogenides (TMDCs) present a promising platform for numerous photonic applications due to excitonic spectral features, possibility to tune their constants by external gating, doping, or light, and mechanical stability. Utilization of such materials for sensing or optical modulation purposes would require a clever optical design, as by itself the 2D materials can offer only a small optical phase delay - consequence of the atomic thickness. To address this issue, we combine films of 2D semiconductors which exhibit excitonic lines with the Fabry-Perot resonat…
All known optical materials have an index of refraction of order unity. Despite the tremendous implications that an ultrahigh index could have for optical technologies, little research has been done on why the refractive index of materials is universally small, and whether this observation is fundamental. Here, we investigate the index of an ordered arrangement of atoms, as a function of atomic density. At dilute densities, this problem falls into the realm of quantum optics, where atoms do not interact with one another except via the scattering of light. On the other hand, when the lattice co…
Designing integrated photonics, especially to leverage Kerr-nonlinear optics, requires accurate and precise knowledge of refractive index across the visible to infrared spectral ranges. Tantala (Ta_2O_5) is an emerging material platform for integrated photonics and nanophotonics that offers broadband ultralow loss, moderately high nonlinearity, and advantages for scalable and heterogeneous integration. We present refractive-index measurements on a thin film of tantala, and we explore the efficacy of this data for group-velocity dispersion (GVD) engineering with waveguide and ring-resonator dev…
Hot atomic vapors are widely used in non-linear and quantum optics due to their large Kerr non-linearity. While the linear refractive index and the transmission are precisely measured and well modeled theoretically, similar characterization remains partial for the $χ^{(3)}$ non-linear part of the susceptibility. In this work, we present a set of tools to measure and estimate numerically the non-linear index of hot atomic vapors both in the steady state and during the transient response of the medium. We apply these techniques for the characterization of a hot vapor of rubidium and we evidence …
The characterisation of the physical properties of nanoparticles in their native environment plays a central role in a wide range of fields, from nanoparticle-enhanced drug delivery to environmental nanopollution assessment. Standard optical approaches require long trajectories of nanoparticles dispersed in a medium with known viscosity to characterise their diffusion constant and, thus, their size. However, often only short trajectories are available, while the medium viscosity is unknown, e.g., in most biomedical applications. In this work, we demonstrate a label-free method to quantify size…
Metalenses, which exhibit superior light-modulating performance with sub-micrometer-scale thicknesses, are suitable alternatives to conventional bulky refractive lenses. However, fabrication limitations, such as a high cost, low throughput, and small patterning area, hinder their mass production. Here, we demonstrate the mass production of low-cost, high-throughput, and large-aperture visible metalenses using an argon fluoride immersion scanner and wafer-scale nanoimprint lithography. Once a 12-inch master stamp is imprinted, hundreds of centimeter-scale metalenses can be fabricated. To enhanc…
Optical vector network analysis of ultra-narrow transitions in $^{166}$Er$^{3+}$:$^7$LiYF$_4$
我们提出了光学矢量网络分析（OVNA）的同位素纯化$^{166}$ Er $^{3+}$：$^7$ LiYF $_4$晶体。OVNA方法是基于调制光边带的产生和检测，通过使用射频矢量网络分析仪。该技术广泛用于微波光子学领域，用于表征光学器件（如滤波器和高Q谐振器）的光学响应。然而，密集的固态原子系综诱导一个光学边带上的大的相移，这导致在测量的传输响应上的额外功能的外观。我们提出了一个简单的理论模型，它准确地描述了所观察到的光谱，并有助于重建的固态原子系综的吸收分布，以及相应的变化，在附近的原子共振的折射率。
