Characterization of focusing grating couplers for telecom wavelengths in the first and second diffraction order

In this work we studied how focusing grating couplers, developed for telecommunication C-band wavelength range, can be applied in the near infrared range. In the paper we presented prospects of usage of both first and second diffraction maxima of theoretically computed diffraction grating couplers for photonic aims. The dependence of the central wavelength of the grating on the etching depth of the photonic layer, on the period and filling factor of the grating was studied. We have compared our experimental results with numerical study, performed using finite elements method of solving differential equations. The work is important for different photonic applications and introduces new prospects in application of the already fabricated devices, developed for telecommunication wavelengths.

Black phosphorus phase retarder based on anisotropic refractive index dispersion

Black phosphorus (BP) has gained wide interest as a promising layered material for its unique physical properties. In particular, the anisotropic optical property of BP can act as a retarder or a polarizer in nano-optoelectronic devices, for which quantitative qualification of the phase retardation and the anisotropic refractive index dispersion are essential. Here, we report the anisotropic refractive index and extinction coefficient dispersions of BP in the visible and near infrared range of 540–1500 nm, and then characterize optical phase retardation in a BP flake. Cauchy absorbent equations are provided for the refractive index dispersions along both armchair and zigzag directions, which well reproduce the experimentally measured reflectance and transmittance contrast spectra of BP flakes. Furthermore, we demonstrate that a linear polarized light through BP becomes elliptical, a finding that agrees well with simulation results using the obtained anisotropic refractive index dispersions. The two-dimensional phase retarder in this work is expected to find various applications in novel polarization-sensitive nano-optoelectronic devices.

Tuning of Graphene-Based Optical Devices Operating in the Near-Infrared

Graphene is a material with exceptional optical, electrical and physicochemical properties that can be combined with dielectric waveguides. To date, several optical devices based on graphene have been modeled and fabricated operating in the near-infrared range and showing excellent performance and broad application prospects. This paper covers the main aspects of the optical behaviour of graphene and its exploitation as electrodes in several device configurations. The work compares the reported optical devices focusing on the wavelength tuning, showing how it can vary from a few hundred up to a few thousand picometers in the wavelength range of interest. This work could help and lead the design of tunable optical devices with integrated graphene layers that operate in the NIR.

Investigation of the Possibility to Use Ge p-i-n Photodiodes in Infrared SPR Sensors

Considered in this work are the possibility and advantages of applying a Ge photodiode to measure the surface plasmon resonance (SPR) in the near infrared range (IR). The investigations were performed using the prototype of IR SPR refractometer that operates with two fixed wavelengths (1310 and 1552 nm) for excitation of surface plasmons in a thin gold film in the Kretschmann optical scheme. The obtained results of experiments enabled us to draw the conclusion that application of the Ge photodiode in the SPR sensor at the wavelength 1.5 µm allows increasing the sensitivity and response magnitude as well as widening the dynamic range of this sensor device.