Transmission-type Resonator Research Articles

Giant enhancement of positive and negative Goos-Hänchen shifts in two-dimensional grating waveguide structures supporting Fano resonances

We propose a two-dimensional grating waveguide structure based on guided-mode resonance (GMR) to greatly enhance the Goos-Hänchen (GH) shift due to the asymmetric Fano peak. In addition, the enhancement of the GH shift is located at the peak of the reflectivity, which enables a more accessible measurement compared to the conventional GH shift enhancement based on Brewster angle or transmission-type resonance. In particular, such structure supports four channels for the GH shift enhancements, with a maximum value of 4.8×104λ0 for the positive one and -6000 λ0 for the negative one. Our results benefit the potential applications for optical sensors, optical filters, optical absorbers and surface plasmon resonators, etc.

Large parametric amplification in kinetic inductance dominant resonators based on 3 nm-thick epitaxial superconductors

Ultra-thin superconducting aluminum films of 3-nm grown on sapphire by molecule-beam epitaxy show excellent superconductivity and large kinetic inductance. This results in a record high Kerr non-linearity of 33 kHz and 3.62 MHz per photon in notch-type and transmission-type resonators, respectively. 4-wave mixing leverages this non-linearity to achieve 12 dB parametric amplification in transmission type resonator, making the ultra-thin film ideal for photon detection and amplification applications.

Enhancing Goos-Hänchen shift based on magnetic dipole quasi-bound states in the continuum in all-dielectric metasurfaces.

Metasurface-mediated bound states in the continuum (BIC) provides a versatile platform for light manipulation at the subwavelength dimension with diverging radiative quality factor and extreme optical localization. In this work, we theoretically propose the magnetic dipole quasi-BIC resonance in asymmetric silicon nanobar metasurfaces to realize giant Goos-Hänchen (GH) shift enhancement by more than three orders of wavelength. In sharp contrast to GH shift based on the Brewster dip or transmission-type resonance, the maximum GH shift here is located at the reflection peak with unity reflectance, which can be conveniently detected in the experiment. By adjusting the asymmetric parameter of metasurfaces, the Q-factor and GH shift can be modulated accordingly. More interestingly, it is found that GH shift exhibits an inverse quadratic dependence on the asymmetric parameter. Furthermore, we theoretically design an ultrasensitive environmental refractive index sensor based on the quasi-BIC enhanced GH shift, with a maximum sensitivity of 1.5×107 μm/RIU. Our work not only reveals the essential role of BIC in engineering the basic optical phenomena but also suggests the way for pushing the performance limits of optical communication devices, information storage, wavelength division de/multiplexers, and ultrasensitive sensors.

Dual quasibound states in the continuum in compound grating waveguide structures for large positive and negative Goos-Hänchen shifts with perfect reflection

Based on the selective excitations of the forward and backward propagating resonant guided modes, we achieve $dual$ bound states in the continuum ($dual$ BICs) in a compound grating waveguide structure composed of a four-part periodic grating layer and a waveguide layer. Assisted by the quasi-BIC corresponding to forward propagating resonant guided mode (quasi-BIC 1) and the one corresponding to backward propagating resonant guided mode (quasi-BIC 2), large $positive$ and $negative$ GH shifts can be simultaneously realized. Also, in contrast to the GH shift enhanced by conventional transmission-type resonance, large positive and negative GH shifts assisted by dual quasi-BICs possess 100% reflectance, which can be more easily detected and utilized. Our work provides a route to design GH-shift-based high-performance sensors, wavelength division (de)multiplexers and light storage devices.

Load Characteristics of Series- and Parallel-Coupled Accelerating Structures

The load characteristics of series- and parallel-coupled standing-waves accelerating structures are presented. The structure with the series coupling consists of a set of accelerating cavities and coupling resonators, sequentially excited by each other. The structure with the parallel coupling contains the accelerating resonators, excited in parallel by a common high-Q transmission-type resonator. The relations are obtained to determine the operating modes of the structures and the efficiency value in the regime of critical coupling. The characteristic features and differences of the dependence of input coupling coefficient on current loads in structures of various types have been revealed.

Microstrip resonator using sputtered Y1Ba2Cu3O7- delta film on (100) MgO

The design, development and measurement of an X-band microstrip resonator fabricated using a sputtered Y1Ba2Cu3O7- delta thin film are presented. The films were grown in situ at 700 degrees C in a hollow cylindrical magnetron sputtering system. The resonator is a capacitive-gap coupled two-port transmission-type resonator in a microstrip configuration. The measurements were carried out in the temperature range 30 K to 300 K using a closed cycle He cryocooler. The resonator patterns on the sputtered Y1Ba2Cu3O7- delta film were generated using conventional photolithography and wet-etch process. Microwave surface resistance values obtained for the above resonator are compared with those of conventional gold resonators.

Precise determination of natural resonant frequency of fixed-tuned transmission-type resonator

Precise determination of natural resonant frequency of fixed-tuned transmission-type resonator