ABSTRACT
Light beams bearing orbital angular momentum (OAM) are used in various scientific and engineering applications, such as microscopy, laser material processing, and optical tweezers. Precise topological charge control is crucial for efficiently using vortex beams in different fields, such as information encoding in optical communications and sensor systems. This work presents a novel method for optimizing an emitting micro-ring resonator (MRR) for emitting vortex beams with variable orders of OAM. The MRR consists of a ring waveguide with periodic structures side-coupled to a bus waveguide. The resonator is tunable due to the phase change material Sb2Se3 deposited on the ring. This material can change from amorphous to crystalline while changing its refractive index. In the amorphous phase, it is 3.285 + 0i, while in the transition to the crystalline phase, it reaches 4.050 + 0i at emission wavelength 1550 nm. We used this property to control the vortex beam topological charge. In our study, we optimized the distance between the bus waveguide and the ring waveguide, the bending angle, and the width of the bus waveguide. The optimality criterion was chosen to maximize the flux density of the radiated energy emitted by the resonator. The numerical simulation results proved our method. The proposed approach can be used to optimize optical beam emitters carrying OAM for various applications.
ABSTRACT
The design of a refractometric sensing system for liquids analysis with a sensor and the scheme for its intensity interrogation combined on a single photonic integrated circuit (PIC) is proposed. A racetrack microring resonator with a channel for the analyzed liquid formed on the top is used as a sensor, and another microring resonator with a lower Q-factor is utilized to detect the change in the resonant wavelength of the sensor. As a measurement result, the optical power at its drop port is detected in comparison with the sum of the powers at the through and drop ports. Simulations showed the possibility of registering a change in the analyte refractive index with a sensitivity of 110 nm per refractive index unit. The proposed scheme was analyzed with a broadband source, as well as a source based on an optoelectronic oscillator using an optical phase modulator. The second case showed the fundamental possibility of implementing an intensity interrogator on a PIC using an external typical single-mode laser as a source. Meanwhile, additional simulations demonstrated an increased system sensitivity compared to the conventional interrogation scheme with a broadband or tunable light source. The proposed approach provides the opportunity to increase the integration level of a sensing device, significantly reducing its cost, power consumption, and dimensions.
Subject(s)
Optics and Photonics , Refractometry , Equipment Design , Photons , LightABSTRACT
Herein we propose a design of a wavelength-tunable integrated vortex beam emitter based on the silicon-on-insulator platform. The emitter is implemented using a PN-depletion diode inside a microring resonator with the emitting hole grating that was used to produce a vortex beam. The resonance wavelengths can be shifted due to the refractive index change associated with the free plasma dispersion effect. Obtained numerical modeling results confirm the efficiency of the proposed approach, providing a resonance wavelength shift while maintaining the required topological charge of the emitted vortex beam. It is known that optical vortices got a lot of attention due to extensive telecommunication and biochemical applications, but also, they have revealed some beneficial use cases in sensors. Flexibility in spectral tuning demonstrated by the proposed device can significantly improve the accuracy of sensors based on fiber Bragg gratings. Moreover, we demonstrate that the proposed device can provide a displacement of the resonance by the value of the free spectral range of the ring resonator, which means the possibility to implement an ultra-fast orbital angular momentum (de)multiplexing or modulation.
ABSTRACT
Herein, we have discussed three major methods which have been generally employed for the generation of optical beams with orbital angular momentum (OAM). These methods include the practice of diffractive optics elements (DOEs), metasurfaces (MSs), and photonic integrated circuits (PICs) for the production of in-plane and out-of-plane OAM. This topic has been significantly evolved as a result; these three methods have been further implemented efficiently by different novel approaches which are discussed as well. Furthermore, development in the OAM detection techniques has also been presented. We have tried our best to bring novel and up-to-date information to the readers on this interesting and widely investigated topic.
ABSTRACT
An all-optical computer has remained an elusive concept. To construct a practical computing primitive equivalent to an electronic Boolean logic, one should utilize nonlinearity that overcomes weaknesses that plague many optical processing schemes. An advantageous nonlinearity provides a complete set of logic operations and allows cascaded operations without changes in wavelength or in signal encoding format. Here we demonstrate an all-optical majority gate based on a vertical-cavity surface-emitting laser (VCSEL). Using emulated signal coupling, the arrangement provides Bit Error Ratio (BER) of 10-6 at the rate of 1 GHz without changes in the wavelength or in the signal encoding format. Cascaded operation of the injection-locked laser majority gate is simulated on a full adder and a 3-bit ripple-carry adder circuits. Finally, utilizing the spin-flip model semiconductor laser rate equations, we prove that injection-locked lasers may perform normalization operations in the steady-state with an arbitrary linear state of polarization.
ABSTRACT
In this paper, we experimentally demonstrate simultaneous wavelength and orbital angular momentum (OAM) multiplexing/demultiplexing of 10 Gbit/s data streams using a new on-chip micro-component-tunable MEMS-based Fabry-Perot filter integrated with a spiral phase plate. In the experiment, two wavelengths, each of them carrying two channels with zero and nonzero OAMs, form four independent information channels. In case of spacing between wavelength channels of 0.8 nm and intensity modulation, power penalties relative to the transmission of one channel do not exceed 1.45, 0.79 and 0.46 dB at the hard-decision forward-error correction (HD-FEC) bit-error-rate (BER) limit 3.8 × 10-3 when multiplexing a Gaussian beam and OAM beams of azimuthal orders 1, 2 and 3 respectively. In case of phase modulation, power penalties do not exceed 1.77, 0.54 and 0.79 dB respectively. At the 0.4 nm wavelength grid, maximum power penalties at the HD-FEC BER threshold relative to the 0.8 nm wavelength spacing read 0.83, 0.84 and 1.15 dB when multiplexing a Gaussian beam and OAM beams of 1st, 2nd and 3rd orders respectively. The novelty and impact of the proposed filter design is in providing practical, integrable, cheap, and reliable transformation of OAM states simultaneously with the selection of a particular wavelength in wavelength division multiplexing (WDM). The proposed on-chip device can be useful in future high-capacity optical communications with spatial- and wavelength-division multiplexing, especially for short-range communication links and optical interconnects.
ABSTRACT
We demonstrate an on-chip device capable of wavelength-selective generation of vortex beams, which is realized by a spiral phase plate integrated onto a microelectromechanical system (MEMS) tunable filter. This vortex MEMS filter, being capable of functioning simultaneously in both wavelength and orbital-angular-momentum (OAM) domains at the 1550 nm wavelength regime, is considered as a compact, robust, and cost-effective solution for simultaneous OAM- and wavelength-division multiplexed optical communications. The experimental OAM spectra for azimuthal orders 1, 2, and 3 show an OAM state purity >92% across a wavelength range of more than 30 nm.
