Nonlinear co-generation of graphene plasmons for optoelectronic logic gates

Surface plasmons in graphene provide a compelling strategy for advanced photonic technologies thanks to their tight confinement, fast response and tunability. Recent advances in the field of all-optical generation of graphene’s plasmons in planar waveguides offer a promising method for high-speed signal processing in nanoscale integrated optoelectronic devices. Here, we use two counter propagating frequency combs with temporally synchronized pulses to demonstrate deterministic all-optical generation and electrical control of multiple plasmon polaritons, excited via difference frequency generation (DFG). Electrical tuning of a hybrid graphene-fiber device offers a precise control over the DFG phase-matching, leading to tunable responses of the graphene’s plasmons at different frequencies and provides a powerful tool for high-speed logic operations. Our results offer new insights for plasmonics on hybrid photonic devices based on layered materials and pave the way to high-speed integrated optoelectronic computing circuits.

Analysis of highly efficient DFG in an electro-optic material exhibiting polarization rotation using TIR-based ORQPM technique

This paper is a numeric-analytical work for highly efficient difference-frequency generation (DFG) by the integrated effect of total-internal-reflection-based optical rotation quasi-phase-matching (ORQPM) and nonresonant quasi-phase-matching techniques in a thin yttrium oxide-coated rectangular slab of magnesium oxide-doped lithium niobate crystal. The conversion efficiency of 37.2% has been obtained by ray-optics analysis, corresponding to an idler wavelength of 1570[Formula: see text]nm. Moreover, the guided-wave approach has also been analyzed for more accurate and realistic outcomes, yielding a peak conversion efficiency of 1.64%. The impact of the influencing factors like surface roughness, absorption, and nonlinear law of reflection has also been incorporated in the computer-aided simulation for providing a pragmatic understanding of the whole study.

Mid-Infrared Frequency Generation via Intermodal Difference Frequency Generation in AlGaAs-On-Insulator Waveguides

We investigate theoretically mid-infrared (MIR) generation via difference frequency generation in multimode AlGaAs-on insulator (AlGaAs-OI) waveguides. The large refractive index difference between the AlGaAs core and the silica cladding shrinks the modes size down to the sub-μm2 scale, and, together with AlGaAs strong second-order nonlinear polarization, empowers strong nonlinear effects. As a result, efficient MIR generation is obtained in few-cm long waveguides with sub-μm2 transverse section, where higher order modes are exploited to achieve the phase-matching condition. These observations suggest that multimode AlGaAs-OI waveguides could represent a novel promising platform for on-chip, compact MIR sources.

THz-Photonics Transceivers By All-Dielectric Phonon-Polariton Nonlinear Nanoantennas

The THz spectrum (spanning from 0.3 THz to 30 THz) offers the potential of a plethora of applications, ranging from the imaging through non transparent media to wireless-over-fiber communications and THz-photonics. The latter framework would greatly benefit from the development of optical-to-THz wavelength converters. Exploiting Difference Frequency Generation in a nonlinear all dielectric nanoantenna, we propose a compact solution to this problem. By means of a near-Infrared pump beam (at ω1), the information signal in the optical domain (at ω2) is converted to the THz band (at ω3 = ω2 − ω1). The approach is completely transparent with respect to the modulation format, and can be easily integrated in a metasurface platform for simultaneous frequency and spatial moulding of THz beams.

NIR-to-NIR Imaging: Extended Excitation Up to 2.2 μm Using Harmonic Nanoparticles with a Tunable hIGh EneRgy (TIGER) Widefield Microscope

Near-infrared (NIR) marker-based imaging is of growing importance for deep tissue imaging and is based on a considerable reduction of optical losses at large wavelengths. We aim to extend the range of NIR excitation wavelengths particularly to values beyond 1.6 μm in order to profit from the low loss biological windows NIR-III and NIR-IV. We address this task by studying NIR-excitation to NIR-emission conversion and imaging in the range of 1200 up to 2400 nm at the example of harmonic Mg-doped lithium niobate nanoparticles (i) using a nonlinear diffuse femtosecond-pulse reflectometer and (ii) a Tunable hIGh EneRgy (TIGER) widefield microscope. We successfully demonstrate the existence of appropriate excitation/emission configurations in this spectral region taking harmonic generation into account. Moreover, NIR-imaging using the most striking configurations NIR-III to NIR-I, based on second harmonic generation (SHG), and NIR-IV to NIR-I, based on third harmonic generation (THG), is demonstrated with excitation wavelengths from 1.6–1.8 μm and from 2.1–2.2 μm, respectively. The advantages of the approach and the potential to additionally extend the emission range up to 2400 nm, making use of sum frequency generation (SFG) and difference frequency generation (DFG), are discussed.

Architecture for microcomb-based GHz-mid-infrared dual-comb spectroscopy

Dual-comb spectroscopy (DCS) offers high sensitivity and wide spectral coverage without the need for bulky spectrometers or mechanical moving parts. And DCS in the mid-infrared (mid-IR) is of keen interest because of inherently strong molecular spectroscopic signatures in these bands. We report GHz-resolution mid-IR DCS of methane and ethane that is derived from counter-propagating (CP) soliton microcombs in combination with interleaved difference frequency generation. Because all four combs required to generate the two mid-IR combs rely upon stability derived from a single high-Q microcavity, the system architecture is both simplified and does not require external frequency locking. Methane and ethane spectra are measured over intervals as short as 0.5 ms, a time scale that can be further reduced using a different CP soliton arrangement. Also, tuning of spectral resolution on demand is demonstrated. Although at an early phase of development, the results are a step towards mid-IR gas sensors with chip-based architectures for chemical threat detection, breath analysis, combustion studies, and outdoor observation of trace gases.

Polarization Imaging of Liquid Crystal Polymer Using Terahertz Difference-Frequency Generation Source

We performed the polarization imaging of a liquid crystal polymer with a terahertz difference-frequency generation (THz DFG) source. The DFG source is an easy-to-operate and practical THz source. Liquid crystal polymers (LCPs) are suitable for applications such as fuel cell components, aircraft parts, and next-generation wireless communication materials. Accordingly, the demand for evaluating the orientation of liquid crystals, which affects the properties of the polymers, is set to increase. Since LCPs exhibit birefringence in the THz range due to the orientation of the liquid crystal molecules, we can determine the alignment of the molecules from the direction of the optical axis.