Our paper 'Tunable beam steering enabled by graphene metamaterials' (B. Orazbayev, M. Beruete, and I. Khromova) climbing up the list of Top Downloads in Optics Express.
Our paper 'Tunable beam steering enabled by graphene metamaterials' (B. Orazbayev, M. Beruete, and I. Khromova) in the list of Top Downloads in Optics Express.
We demonstrate tunable mid-infrared (MIR) beam steering devices based on multilayer graphene-dielectric metamaterials. The effective refractive index of such metamaterials can be manipulated by changing the chemical potential of each graphene layer. This can arbitrarily tailor the spatial distribution of the phase of the transmitted beam, providing mechanisms for active beam steering. Three different beam steerer (BS) designs are discussed: a graded-index (GRIN) graphene-based metamaterial block, an array of metallic waveguides filled with graphene-dielectric metamaterial and an array of planar waveguides created in a graphene-dielectric metamaterial block with a specific spatial profile of graphene sheets doping. The performances of the BSs are numerically analyzed, showing the tunability of the proposed designs for a wide range of output angles (up to approximately 70°). The proposed graphene-based tunable beam steering can be used in tunable transmitter/receiver modules for infrared imaging and sensing.
B. Orazbayev, M. Beruete, and I. Khromova Optics Express, Vol. 24, Issue 8, pp. 8848-8861 (2016) doi: 10.1364/OE.24.008848
Dipolar resonances in conductive carbon micro-fibers probed by near-field terahertz spectroscopy
I. Khromova, M. Navarro-Navarro-Cía, I. Brener, J.L. Reno, A. Ponomarev, O. Mitrofanov,
Applied Physics Letters, 107, 021102 (2015)
We observe dipole resonances in thin conductive carbon micro-fibers by detecting an enhancedelectric field in the near-field of a single fiber at terahertz (THz) frequencies. Time-domain analysis of the electric field shows that each fiber sustains resonant current oscillations at the frequency defined by the fiber's length. Strong dependence of the observed resonance frequency and degree of field enhancement on the fibers' conductive properties enable direct non-contact probing of the THz conductivity in single carbon micro-fibers. We find the conductivity of the fibers to be within the range of 1–5×10^4 S/m. This approach is suitable for experimental characterization of individual doped semiconductor resonators for THz metamaterials and devices.
Ultrasensitive terahertz/infrared waveguide modulators based on multilayer graphene metamaterial
Irina Khromova, Andrei Andryieuski and Andrei Lavrinenko
Laser & Photonics Reviews, Volume 8, Issue 6, pages 916–923, November 2014
This paper studies and classifies the electromagnetic regimes of multilayer graphene-dielectric artificial metamaterials in the terahertz/infrared range. The employment of such composites for waveguide-integrated modulators is analysed and three examples of novel tunable devices are presented. The first one is a modulator with excellent ON-state transmission and very high modulation depth: >38 dB at 70 meV graphene's electrochemical potential (Fermi energy) change. The second one is a modulator with extreme sensitivity towards graphene's Fermi energy - a minute 1 meV variation of the latter leads to >13.2 dB modulation depth. The third one is a tunable waveguide-based passband filter. The narrow-band cut-off conditions around the ON-state allow the latter to shift its central frequency by 1.25% per every meV graphene's Fermi energy change.
Dr. Irina Khromova