We report a novel approach for realizing tunable/reconfigurable terahertz (THz) mesh filters on the basis of micromachined mesa‐array structures. In this approach, different filter patterns are generated virtually using photogenerated free carriers in a semiconducting mesa‐array structure to achieve superior tunability and reconfigurability. Micromachined mesa‐array structures enable the formation of high fidelity, optically generated mesh filter structures for THz frequencies. To evaluate the proposed filter designs, the optically patterned spatial modulation properties of mesa‐array structures were first evaluated. Reconfigurable mesh filter prototypes were then designed and simulated using silicon mesa arrays with 50 × 50 μm2square mesa unit cells. Simulations show that reconfigurable bandpass filters (BPFs) operating in the frequency range of 108–489 GHz with insertion losses of 0.82–1.13 dB can be achieved. By employing smaller unit cells, the frequency tuning range and filtering performance can be further improved. In addition to BPFs, other filter functionalities can also be realized utilizing the proposed approach. The wide tuning range and reconfigurability of the mesh filters demonstrate that the proposed approach is promising for developing tunable/reconfigurable circuits and components for advanced THz sensing, imaging, and communications.
We present a photoinduced reconfigurable metasurface to enable high spatial resolution terahertz (THz) wave modulation. Conventional photoinduced THz wave modulation uses optically induced conductive patterns on a semiconductor substrate to create programmable passive THz devices. The technique, albeit versatile and straightforward, suffers from limited performance resulting from the severe lateral diffusion of the photogenerated carriers that undermines the spatial resolution and conductivity contrast of the photoinduced conductive patterns. The proposed metasurface overcomes the limitation using a metal-jointed silicon mesa array with subwavelength-scaled dimensions on an insulator substrate. The structure physically restrains the lateral diffusion of the photogenerated carriers while ensuring the electrical conductivity between the silicon mesas , which is essential for THz wave modulation. The metasurface creates high-definition photoconductive patterns with dimensions smaller than the diffusion length of photogenerated carriers. The metasurface provides a modulation depth of −20 to −10 dB for the THz waves between 0.2 to 1.2 THz and supports a THz bandpass filter with a tunable central frequency. The new, to the best of our knowledge, design concept will benefit the implementation of reconfigurable THz devices.
more » « less- Award ID(s):
- 1711631
- NSF-PAR ID:
- 10368798
- Publisher / Repository:
- Optical Society of America
- Date Published:
- Journal Name:
- Optics Letters
- Volume:
- 47
- Issue:
- 11
- ISSN:
- 0146-9592; OPLEDP
- Page Range / eLocation ID:
- Article No. 2750
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Substrate-integrated waveguides (SIWs) have recently attracted increasing attention for the development of terahertz (THz) circuits and systems. However, conventional SIWs employ fixed metallic vias to form the waveguide sidewalls, resulting in limited tunability and reconfigurability. In this paper, we report a novel approach for the realization of high-performance tunable and/or reconfigurable THz SIW structures. In this approach, photo-induced free carriers are generated in a high-resistivity silicon pillar-array structure to form well-defined, highly conductive, vertical sidewalls. The wave propagation properties of these optically-defined photo-induced SIWs (PI-SIWs) have been evaluated using full-wave electromagnetic simulations. Higher-functionality THz components, including a single-pole double-throw switch and a phase shifter were also designed and simulated. Based on these example circuits, PI-SIWs using pillar-array structures appear to be attractive candidates for the development of tunable and reconfigurable THz components for THz sensing, imaging, and communication systems.
-
more » « less
Abstract Polaritons enable subwavelength confinement and highly anisotropic flows of light over a wide spectral range, holding the promise for applications in modern nanophotonic and optoelectronic devices. However, to fully realize their practical application potential, facile methods enabling nanoscale active control of polaritons are needed. Here, we introduce a hybrid polaritonic-oxide heterostructure platform consisting of van der Waals crystals, such as hexagonal boron nitride (hBN) or alpha-phase molybdenum trioxide (α-MoO3), transferred on nanoscale oxygen vacancy patterns on the surface of prototypical correlated perovskite oxide, samarium nickel oxide, SmNiO3(SNO). Using a combination of scanning probe microscopy and infrared nanoimaging techniques, we demonstrate nanoscale reconfigurability of complex hyperbolic phonon polaritons patterned at the nanoscale with high resolution. Hydrogenation and temperature modulation allow spatially localized conductivity modulation of SNO nanoscale patterns, enabling robust real-time modulation and nanoscale reconfiguration of hyperbolic polaritons. Our work paves the way towards nanoscale programmable metasurface engineering for reconfigurable nanophotonic applications.
-
The rapid growth of point-of-care tests demands for biomolecule sensors with higher sensitivity and smaller size. We developed an optofluidic metasurface that combined silicon photonics and nanofluidics to achieve a lateral flow-through biosensor to fulfill the needs. The metasurface consists of a 2D array of silicon nanoposts fabricated on a silicon-on-insulator substrate. The device takes advantage of the high-Q resonant modes associated with the optical bound state and the nanofluidic delivery of analyte to overcome the problem of diffusion-limited detection that occurs in almost all conventional biosensors and offer a high refractive index sensitivity. We used rigorous coupled wave analysis and finite element analysis to design and optimize the device. We will present its photonic band diagram to identify the optical bound state and high-Q resonance modes near 1550 nm. The device was fabricated using e-beam lithography followed by a lift-off and reactive ion etching process. Reflectance of the sensor was measured using a tunable laser and a photodetector. The preliminary result shows a refractive index sensitivity of 720 nm/RIU. Furthermore, we implemented the optical metasurface as a lateral flow-through biosensor by covering the nanoposts using a PDMS cover. The nanofluidic channels are formed between the nanoposts for the flow of samples. The lateral flow-through sensor was used to detect the epidermal growth factor receptor (ErbB2), a widely used protein biomarker for breast cancer screening. The results show that the device can quantitatively measure the binding of ErBb2 antibody and ErBb2 by the continuous monitoring of the resonant wavelength shift.more » « less
-
more » « less
During the past decade, metasurfaces have shown great potential to complement standard optics, providing novel pathways to control the phase, amplitude, and polarization of electromagnetic waves utilizing arrays of subwavelength resonators. We present dynamic surface wave (SW) switching at terahertz frequencies utilizing a mechanically reconfigurable metasurface. Our metasurface is based on a microelectromechanical system (MEMS) consisting of an array of micro-cantilever structures, enabling dynamic tuning between a plane wave (PW) and a SW for normal incidence terahertz radiation. This is realized using line-by-line voltage control of the cantilever displacements to achieve full-span (
) phase control. Full-wave electromagnetic simulations and terahertz time-domain spectroscopy agree with coupled mode theory, which was employed to design the metasurface device. A conversion efficiency of nearly 60% has been achieved upon switching between the PW and SW configurations. Moreover, a nearly 100 GHz working bandwidth is demonstrated. The MEMS-based control modality we demonstrate can be used for numerous applications, including but not limited to terahertz multifunctional metasurface devices for spatial light modulation, dynamic beam steering, focusing, and beam combining, which are crucial for future “beyond 5G” communication systems.
