Optical transceivers that function under a high-speed rate condition are demanded to have more optical power ability to overcome the power losses which is a cause of the need of using a larger RF line connected to the Mach-Zehnder modulator for fulfilling the high-speed condition. The classic solution to this problem is to use a better power laser with a high level of 120 milliwatts. However, this solution can be complicated for a photonic chip circuit due to the high cost and nonlinear effects, which can increase the system noise. Therefore, we propose a better solution to increase the power level using a 4x1 power combiner which is based on multimode interference using a silicon nitride slot waveguide structure. Results show that the combiner can function well over the O-band spectrum with high combiner efficiency of at least 98.1% and after a short light coupling propagation of 28.8 μm. This new study shows how it is possible to obtain a transverse electric mode solution for four Gaussian coherent sources using Si3N4 slot waveguides technology. This new technology can be utilized for combining multiple coherent sources that work with a photonic chip at the O-band range.
One of the common methods to increase data bitrate using visible light communication (VLC) fibers system is to use wavelength division multiplexing (WDM). However, the implementation of WDM requires additional components and more energy consumption which can limit the system performances. To overcome these issues, we propose a new method for designing an RGB multiplexer based on multicore polymer optical fiber (MC-POF). The new design is based on replacing seven air-holes areas with polycarbonate (PC) layers along the fiber length. The PC layer length sizes are suitable to the light coupling of the operating wavelengths which allows us to control the light switching between closer PC layers and to obtain an RGB multiplexer device without adding more devices. Results show that after a 20 mm light propagation the PC MC-POF RGB multiplexer can be obtained with a low power loss of 0.6 to 1.02 dB, large bandwidth of 7.3 to 28.4 nm and good isolation between the transmission of the input RGB channels.
In this work, we demonstrate for the first time to our knowledge, a green light wavelength demultiplexer device, based on multi Slot waveguide (SW) structures. Gallium Nitride (GaN) surrounding Silica (SiO2) were chosen for confining the light inside the SW region and found to be suitable for operation within the visible light spectrum. The proposed device as well as his geometry, aims and optimized to demultiplex wavelength in the green light range with wavelengths of 500, 510, 520 and 530 nm. The device is composed of six SW units and six S-bands (SB). A full vectorial beam propagation method (FV-BPM) and coupling mode theory used to study and analyze the demultiplexer device. The proposed device obtains losses better than 0.1275 dB, crosstalk as well as –21.135 dB and full width at half maximum (FWHM) smaller than 9.5 nm, in an overall compact size of only 104 μm. The proposed device has the ability to increase the data bit rate in visible light communication (VLC) system that works with wavelength division multiplexing (WDM) technology.
One of the main obstacles that limited the performances in visible light networking system is the ability to transmit high data communication rate. Wavelength division multiplexing (WDM) is a good solution for increasing data bitrate communication of photonic crystal fiber (PCF) and multicore polymer optical fiber (MC-POF) based visible light communication (VLC) system. In order to overcome this obstacle, we propose two new designs for an RGB demultiplexer, one is based on silicon-nitride (Si3N4) multicore PCF structure and the second is based on polycarbonate (PC) MC-POF structure. The new design is based on replacing several air-holes areas with Si3N4 rods in PCF and PC rods in POF over the fiber length which enables controlling the light propagation direction between the core layers. The locations of the Si3N4 / PC rods and the key geometrical parameters of the device were optimized and analyzed utilizing the beam propagation method (BPM) combined with Matlab codes. Results show that RGB operated wavelengths can be demultiplexed after light propagation of 5.5 mm for PCF and 20 mm for POF with an excellent crosstalk of -19.436 to - 26.474 dB and a large bandwidth of 5.6 to 16.3 nm.
The advance progress of the visible light networking systems requires powerful and new devices that enable high data rate light transmission with low losses. Therefore, we introduce a new design for a 1×8 green light intensity splitter based on the multimode interference coupler (MMI) in a gallium-nitride (GaN) - silicon-oxide (SiO2) slot waveguide structure. Simulation results show that after a propagation length of 16.55μm the power of the green light signal (536 nm) is split into eight output beams with equal power and low transmission losses of 0.11dB. In addition, the splitter operates in the visible light spectrum from 460-670nm. Therefore, this device can increase performance in network communication systems that work in the visible light range.
Optical filters are required to have narrow band-pass filtering in the spectral C-band for applications such as signal tracking, sub-band filtering or noise suppression. These requirements lead to a variety of filters such as Mach-Zehnder interferometer inter-leaver in silica, which offer thermo-optic effect for optical switching, however, without proper thermal and optical efficiency. In this paper we propose tunable thermo-optic filtering device based on coated silicon slab resonator with increased Q-factor for the C-band optical switching. The device can be designed either for long range wavelength tuning of for short range with increased wavelength resolution. Theoretical examination of the thermal parameters affecting the filtering process is shown together with experimental results. Proper channel isolation with an extinction ratio of 20dBs is achieved with spectral bandpass width of 0.07nm.
Over the last few years, there is a growing interest in photoacoustic imaging using nanoparticles techniques due to the improved penetration depth and resolution. Working with such nanoparticles usually requires pulsed laser illumination to generate an acoustic signal in the right frequencies. However, these pulsed lasers are considered expensive and complicated with respect to continuous-wave (CW) illumination. We design and simulate a special nanostructure with overall dimensions of 190×50× (26–34) nm, which blinks with fast temporal periodicity of 20 to 40 ns, under CW illumination and can be used for the generation of acoustic signals. This blinking is done using the enhanced optical absorption of metallic nanoparticles due to localized surface plasmon resonance (SPR) and the thermal expansion to generate heating–cooling cycles of the nanostructure. The CW laser wavelength is adapted to the localized SPR of the metallic nanostructure at the NIR region, which provides maximum penetration depth of light into biological tissues.
We propose a novel 8-channel wavelength multimode interference (MMI) demultiplexer in slot waveguide structures that operated at 1530 nm, 1535 nm, 1540 nm, 1545 nm, 1550 nm, 1555 nm, 1560 nm and 1565 nm wavelengths. Gallium nitride (GaN) surrounded by silicon (Si) was founded as suitable materials for the slot-waveguide structures. The proposed device was designed by seven 1x2 MMI couplers, fourteen S-band and one input taper. Numerical investigations were carried out on the geometrical parameters by using a full vectorial-beam propagation method (FVBPM). Simulation results show that the proposed device can transmit 8-channel that works in the whole C-band (1530- 1565 nm) with low crosstalk ((-19.97)-(-13.77) dB) and bandwidth (1.8-3.6 nm). Thus, the device can be very useful in optical networking systems that work on dense wavelength division multiplexing (DWDM) technology.
We propose a novel 8-channel wavelength demultiplexer based on photonic crystal fiber (PCF) structures that operate at 1530nm, 1535nm, 1540nm, 1545nm, 1550nm, 1555nm, 1560nm and 1565nm wavelengths. The new design is based on replacing some air-holes zones with silicon nitride and lithium niobate materials along the PCF axis with optimization of the PCF size. The reason of using these materials is because that each wavelength has a different value of coupling length. Numerical investigations were carried out on the geometrical parameters by using a beam propagation method (BPM). Simulation results show that the proposed device can transmit 8-channel that works in the whole C-band (1530- 1565nm) with low crosstalk ((-16.88)-(-15.93) dB) and bandwidth (4.02-4.69nm). Thus, the device can be very useful in optical networking systems that work on dense wavelength division multiplexing (DWDM) technology.
Hardware implementation of artificial neural networks facilitates real-time parallel processing of massive data sets. Optical neural networks offer low-volume 3D connectivity together with large bandwidth and minimal heat production in contrast to electronic implementation. Here, we present a DMD based approaches to realize energetically efficient light coupling into a multi-core fiber realizing a unique design for in-fiber optical neural networks. Neurons and synapses are realized as individual cores in a multi-core fiber. Optical signals are transferred transversely between cores by means of optical coupling. Pump driven amplification in Erbium-doped cores mimics synaptic interactions. In order to dynamically and efficiently couple light into the multi-core fiber a DMD based micro mirror device is used to perform proper beam shaping operation. The beam shaping reshapes the light into a large set of points in space matching the positions of the required cores in the entrance plane to the multi-core fiber.
This paper presents a method for modifying the point spread function (PSF) into a doughnut-like shape, through the utilization of the plasma dispersion effect (PDE) of silicon-coated gold nanoparticles. This modified PSF has spatial components smaller than the diffraction limit, and by scanning the sample with it, super-resolution can be achieved. The sample is illuminated using two laser beams. The first is the pump, with a wavelength in the visible region that creates a change in the refractive index of the silicon coating due to the PDE. This creates a change in the localized surface plasmon resonance wavelength. Since the pump beam has a Gaussian profile, the high intensity areas of the beam experience the highest refractive index change. When the second beam (i.e., the probe) illuminates the sample with a near-infrared wavelength, this change in the refractive index is transformed into a change in the PSF profile. The ordinary Gaussian shape is transformed into a doughnut shape, with higher spatial frequencies, which enables one to achieve super-resolution by scanning the specimen using this PSF. This is a step toward the creation of a nonfluorescent nanoscope.
A monolithic coherent combiner scheme for combining multiple fiber lasers based on a photonic crystal fiber is described. Beam propagation method (BPM) simulations show that the beam combiner efficiency can reach 96% for a 4×1 combiner, 94% for an 8×1 combiner, and 91% for a 16×1 combiner, provided the fiber lasers are phase matched. In addition, a 2×1 intensity polarization combiner is proposed and simulated through full vectorial BPM, yielding a combining efficiency of 95%. This concept can lead to a rugged and efficient combiner for multiple fiber lasers.
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