Light Splitters Research Articles

Gottesman-Kitaev-Preskill qubit synthesizer for propagating light

Practical quantum computing requires robust encoding of logical qubits in physical systems to protect fragile quantum information. Currently, the lack of scalability limits the logical encoding in most physical systems, and thus the high scalability of propagating light can be a game changer. However, propagating light also has difficulty in logical encoding due to weak nonlinearity. Here, we propose a synthesizer that encodes Gottesman-Kitaev-Preskill (GKP) qubits in propagating light by exploiting the nonlinearity of photon detectors. This synthesizer is based on an approach what we call Gaussian breeding, leading to the following four advantages: (i) systematic and rigorous synthesis of arbitrary GKP qubits, (ii) use of minimal resources, (iii) high fidelity and high success probability, and (iv) robustness against loss. There has been no protocol that incorporates all these advantages, and thus the proposed synthesizer excels in both performance and feasibility. By employing our method, one can generate GKP qubits using a few to several squeezed light sources, beam splitters and photon detectors.

Optics of a multiple color gas puff imaging diagnostic on the HL-2A tokamak

The optics of a new Multiple Color Gas Puff Imaging (MC-GPI) diagnostic on the HL-2A tokamak is presented. MC-GPI utilizes the helium I (He I) line ratio technique to infer plasma density ne and electron temperature Te in edge plasma simultaneously. A compact four-channel beam splitter and dichroic mirrors enable the selection of the intensities of He I lines at specific wavelengths, i.e., λ=587.6 nm, λ=667.8 nm, λ=706.5 nm and λ=728.1 nm. The transmittance of these four specific He I lines after passing through the optical fiber bundle and the beam splitter is 34%, 33%, 33% and 30%, respectively. The temporal resolution of MC-GPI is 100μs and the spatial resolution is 2.5 mm × 2.5 mm. This diagnostic has been experimentally tested on an optical table as well as on a linear plasma device to verify its capability for ne and Te measurements. A newly designed light splitter with double-layer layout is under developing to absorb the stray light, aiming at improve the performance of the diagnostic.

Femtosecond Laser Fabrication of SiC Microlens Arrays as Integrated Light Homogenizer and Splitter

Silicon carbide (SiC) plays a vital role in special optics because of its stable physicochemical and excellent optical properties; however, making the fabrication of SiC considerably more difficult. In this study, femtosecond laser-assisted inductively coupled plasma etching (ICP) technology is proposed to achieve the efficient fabrication of large-area microlens arrays on the surface of silicon carbide. As an illustration, the microlens array was used for high-quality beam homogenization (uniformity is up to 90%) of the transmitted and reflected Gaussian light beams with a wavelength of 532 nm. The beam-splitting ratio can be dynamically adjusted (from 1.2 to 3.2) by controlling the angle of the incident light, indicating that the SiC microlens arrays can act as an integrated optical homogenizer and beam splitter. This method demonstrates the broad application prospects of SiC in miniaturized and integrated special optics and provides new ideas for further applications of SiC in integrated optical systems.

High-sensitivity refractive index sensor based on 3 × 3 microfiber coupler structure

In this study, a 3 × 3 microfiber coupler sensing structure is fabricated by the fusion taper technology, and the mode coupling distribution of its light energy is numerically simulated by the beam propagation method. Results confirmed that the sensing structure produces regular and stable mode coupling within an 11–25 µm effective coupling region. The 3 × 3 microfiber coupler is used as a light splitter. In addition, it can also perform refractive index (RI) sensing. The RI characteristics of the proposed sensor are further verified experimentally. Experimental findings reveal that the RI sensitivity is inversely proportional to the effective coupling region diameter, and the sensitivity is 5223.83 nm/RIU when the effective coupling region diameter is 11 µm.

Effective Detection of the Machinability of Stainless Steel from the Aspect of the Roughness of the Machined Surface

Reliable measurement of surface roughness (Ra) is extremely important for quality control of production processes. The cost of the equipment and the duration of the measurement process are very high. The aim of this work is to develop a device for non-destructive measurement of specific roughness levels on stainless steel using computer vision. The device should be structurally simple, affordable, accurate, and safe for practical use. The purpose of the device is to effectively detect the level of roughness of the treated surface obtained by the water jet cutting process. On the basis of the obtained results, it is possible to adjust the parameters during the cutting process. The principle of operation of the device is based on measuring the intensity of the visible spectrum of the light reflected from the surface of the sample to be measured and correlating these values with the values of the measured roughness. After testing several variants of the device, the so-called vertical measurement variant was developed using the following equipment: violet light LED, optical filter and light splitter, USB 2.0 web camera, Arduino microcontroller, personal computer, and LabView programming interface.

Beaconless angle-of-arrival tracking with improved receiver sensitivity and tracking precision for free-space optical communications

One of the technically challenging issues of free-space optical communication systems is the mitigation of angle-of-arrival (AoA) fluctuations, mainly arising from the vibration of receiving end and atmospheric turbulence. A common approach is to employ an AoA tracking system at the receiver. Beacon-based AoA tracking requires the beacon light, thus the system could be complicated and bulky when implemented. Beaconless AoA tracking could help to minimize the optical components required. This tracking typically requires an optical beam splitter to direct the received optical signal both to the beam position sensor and data photo-detector (PD). However, the presence of beam splitter results in optical power loss and tracking imprecision. In this paper, we propose a design of AoA tracking system based on an integrated beam positioning sensor and data PD to obviate the need for beacon light and beam splitter. We carry out a proof-of-concept experimental demonstration of AoA tracking systems for a 10-Gb/s free-space optical link over 104 m, comparing its performance with that of the conventional system. The demonstration shows a loss reduction of >2.9 dB by using the proposed design. It also shows that the proposed design improves the tolerance to AoA fluctuation by more than a factor of 2 at a target bit-error ratio of 10−3. The tracking time is measured to be 171 ms at an AoA fluctuation of 250 μrad. We show that the loop controller and fast steering mirror bandwidths are the main factors limiting the tracking time.

Refractive index sensing based on multiple Fano resonances in a plasmonic defective ring-cavity system

A type of coupled plasmonic resonant system using a metal–insulator -metal (MIM) waveguide is proposed and investigated for generating multiple Fano resonances in this paper. The multi-mode interference coupled-mode theory (MICMT) is mainly employed to analyze the system theoretically, and these results agree well with the results numerically obtained with the finite-difference time-domain (FDTD) method. In this proposed system, multiple asymmetrical Fano-resonant peaks are achieved in the spectra by employing two waveguides separated by a metallic baffle and coupled with a defective ring cavity at one side of the MIM waveguide. According to standing wave theory, we can easily manipulate these Fano peaks by adjusting the main parameters of the defective ring cavity, such as the radius and the notch range. As a result, the structures with three and nine ultra-sharp Fano resonances are obtained and discussed, and the sensitivities and figures of merit (FOMs) are also represented. Furthermore, the phase shifts and the group delays that are induced by the mode interactions are investigated. The designed structures show great potential for the high integrated optical circuits of chip-scale optical sensors, slow light devices or splitters.

Simultaneous measurement of temperature and strain based on SCF-based MZI cascaded with FBG

A novel seven-core fiber (SCF)-based sensor capable of simultaneous measurement of temperature and strain was proposed and experimentally demonstrated. The sensor consists of a fiber Bragg grating (FBG) and a SCF-based Mach-Zehnder interferometer (MZI). The MZI is formed by splicing a short section of SCF between two single-mode fibers (SMFs), and in the meantime, two fiber tapers that act as light splitter and coupler are formed at both ends of the SCF by the fusion splicing method. In addition, the FBG with a central wavelength of 1547.98 nm is cascaded at the end of one fiber taper, and thus simultaneous measurement of temperature and strain can be realized. The experiment result shows that the SCF-based MZI is only sensitive to temperature and has the higher temperature sensitivity of 93.11 pm/°C, while the FBG is sensitive to temperature and strain with sensitivities of 11.46 pm/°C and 0.627pm/µε, respectively. The corresponding temperature and strain resolutions of the sensor are 0.21°C and 27.95µε, respectively. The proposed sensor has the advantages of simple fabrication and high repeatability and has potential applications in many fields such as engineering machinery and building structure health monitoring.

Development of a multi-color gas puff imaging diagnostic on HL-2A tokamak.

A Multi-Color (MC) gas puff imaging diagnostic has been developed on HL-2A tokamak. This diagnostic can simultaneously measure two-dimensional (2D, radial, and poloidal) electron density and temperature distributions with a good spatial resolution of 2.5 × 2.5 mm2 and a temporal resolution of about 100 µs at best in edge plasmas. The 2D electron density and temperature distributions are inferred from the ratios of intensities of three different neutral helium emission lines; therefore, it is also referred to as helium beam probe or beam emission spectroscopy on thermal helium. A compact light splitter is used to split the inlet visible emission beam into four channels, and the specific neutral helium lines of the wavelengths λ1 = 587.6 nm, λ2 = 667.8 nm, λ3 = 706.5 nm, and λ4 = 728.1 nm are measured, respectively. This MC diagnostic has been experimentally tested and calibrated on a linear magnetic confinement device Peking University Plasma Test device, and the measured 2D electron density and temperature distributions are compared with the Langmuir probe measurements.

In-Fiber Mach-Zehnder Interferometer Exploiting a Micro-Cavity For Strain and Temperature Simultaneous Measurement

An in-fiber Mach-Zehnder interferometer (MZI) with a micro-cavity (MC) exploited for strain and temperature simultaneous measurement. The research is carried out experimentally and simulatively. The MC fabricated by splicing a hollow quartz tube between two single-mode fibers serves as a light splitter for the two arms of MZI beams and a Fabry–Perot interferometer (FPI) component at the same time. Thus both functions of the MZI and FPI were implemented in a single sensor. With aid of the different response of the MZI and FPI to the strain and temperature, this device can achieve a simultaneous measurement and the strain/temperature cross-sensitivity issue has been alleviated. Such a composite interference structure, possess the characteristics of easy making, high performance-price ratio provides a promising approach to implement strain and high-temperature simultaneous measurement.

Results of Vitreous Floaters Treatment Using a Yag-Laser Device with a Coaxial Light Splitter

Purpose: to evaluate the efficiency of vitreous floaters removal using the Nd: YAG-laser DIXION LPULSA SYL-9000 with a coaxial light splitter. Patients and Methods. The study involved 24 patients (24 eyes) with Weiss ring-type floating vitreous opacities. All patients underwent laser vitreolysis on a Nd: YAG-laser DIXION LPULSA SYL-9000 with a coaxial light splitter. Laser procedures were performed at OPTIMED Laser Recovery Center. The age of the patients was from 47 to 81 years (average 58.3 ± 8.9 years). Among the patients 15 (62.5 %) were women and 9 (37.5 %) — men. Before procedure, a complete ophthalmological examination including registration of best corrected visual acuity (BCVA), autorefractometry, pneumotonometry, biomicroscopy, fundus examination, ultrasonic biometry, ultrasound B-scan was performed. Statistical processing was performed using Statistica v.10.0.0 (StatSoft®, Inc.) and Excel (Microsoft Office Professional 2016) software. The patients were observed for three months before the procedure. Follow-up examination was performed one day after the procedure. Results. After laser vitreolysis procedure all patients had a subjective vision quality improvement. In 18 (75 %) patients, floating “flies” completely disappeared. The remaining patients noted the disappearance of a large floating spot. Conclusion. The laser vitreolysis on the Nd: YAG-laser with a coaxial light splitter allows to improve the quality and visual acuity in patients with vitreous floater. The obtained results demonstrated that Nd: YAG-laser DIXION LPULSA SYL-9000 is effective and could be recommended for treatment of symptomatic vitreous floaters.

Modeling a $1 \times 8$ MMI Green Light Power Splitter Based on Gallium-Nitride Slot Waveguide Structure

The advance progress of the visible light communication field requires new and powerful components that enable high speed light transmission with low losses. Therefore, we propose a novel design for a $1\times 8$ green light power splitter based on the multimode interference coupler in a gallium-nitride- silicon-oxide slot waveguide structure. Simulation results show that after a propagation length of $16.55~\mu \text{m}$ the energy of the green light signal (536 nm) is split into eight output beams with equal energy and low transmission losses of 0.11 dB. In addition, the splitter operates in the visible light spectrum from 460 to 670 nm. Therefore, this splitter can increase performance in network communication system that work in the visible light range.

In-plane visible light communication made with InGaN turning mirror

The refractive index contrast between AlGaN and InGaN leads to the formation of an optically-confined InGaN waveguide structure. Therefore, we propose a simple fabrication procedure to achieve on-chip photonic integration including a light source, waveguide, beam splitter, turning mirror and photodiode on an III-nitride-on-silicon platform. By inserting InGaN/GaN multiple-quantum-well active layer inside the InGaN waveguide, the emitted light is confined and coupled to the light waveguide. The in-plane light propagation that is directly observed due to the visible light emission is manipulated by the beam splitter and turning mirror. The waveguide–splitter–mirror-integrated III-nitride photonic circuit experimentally demonstrates an in-plane data transmission at 50 Mbps using visible light, suggesting its great potential for diverse applications in on-chip power monitoring, high-resolution blue printing and in-plane light communication.

Spectral Correction Method of Multi-Channels Near-Infrared Spectrometer and Applications

Near-infrared (NIR) spectrometer based on semiconductor lasers can combine light source and splitter into one, which is an important direction for development of miniature instruments. In order to avoid random interference caused by inconsistency between light sources, the novel evaluation indicators for global stability of multi-channels spectral system were proposed based on the correlation between dynamic deviation spectra of any two channels. The NIR analysis of moisture for corn powder samples based on the partial least squares combined with Savitzky-Golay (SG) smoothing was taken as an example, and a spectral correction method for enhancing prediction performance of multi-channels spectral system was further provided using above evaluation indicators. The experiment results showed that the global stability evaluation indicators significantly increased after SG smoothing correction. Meanwhile, the root-mean-square errors of prediction for corn moisture reduced from 0.373 to 0.283 (%), and the correlation coefficient between predicted and actual values was improved from 0.702 to 0.855. The above results indicated that by improving global stability indicators, the prediction ability of multi-channels spectral system can be improved. The proposed method provided a valuable reference for designing multi-channels diminutive spectrometer with high prediction performance, which had significance for large-scale application of NIR technology.

Optical remote sensor calibration using micro-machined multiplexing optical focal-planes

Traditional calibration approaches for optical remote sensor are based on single-pixel illumination through collimated light using measuring angles. However, the vibration of rotating turntable and accuracy of angle measurement affect the calibration accuracy. In this paper, we propose a new geometrical calibration approach with micromachined multiplexing optical focal plane (MOFP) combined with a collimating device for optical remote sensor. A micromachined procedure is used to manufacture an MOFP using the optimized aperture size. The MOFP, which can produce only one image with multiple diffraction points to calibrate the interior parameters of optical remote senor, is applied as collimated light splitters. Experiments show that this method is sufficient and can be used particularly in ground applications, as well as, in principle, on-orbit calibration.

Light reflector, amplifier, and splitter based on gain-assisted photonic band gaps

We study both the steady and the dynamic optical response of cold atoms trapped in an optical lattice and driven to the three-level $\mathrm{\ensuremath{\Lambda}}$ configuration. These atoms are found to exhibit gain without population inversion when an incoherent pump is applied to activate spontaneously generated coherence. Gain-assisted double photonic band gaps characterized by reflectivities over 100% then grow up near the probe resonance due to the periodic distribution of the atomic density. These band gaps along with the neighboring allowed bands of transmissivities over 100% can be tuned by modulating the control field in amplitude, frequency, and, especially, phase. Consequently it is viable to realize a reflector, an amplifier, or a splitter when a weak incident light pulse is totally reflected in the photonic band gaps, totally transmitted in the allowed bands, or equally reflected and transmitted in the intersecting regions. Our results have potential applications in all-optical networks with respect to fabricating dynamically switchable devices for manipulating photon flows at low-light levels.

Some considerations on the transmissivity of trirefringent metamaterials

Nonlocal effects in metal–dielectric (MD) periodic nanostructures may typically be observed when the plasmonic particles and gaps are on the scale of a few tens of nanometers, enabling under certain conditions (succinctly for epsilon near zero) a collimated beam to split into three refracted signals. We developed a method for precisely evaluating the categorized transmissivity in an air/trirefringent metamaterial interface, which uses a fast one-dimensional Fourier transform and finite element solvers of Maxwell’s equations. In periodic arrays of MD nanofilms, it is proved a tunable transmissivity switch of the multirefracted beams under varying angle of incidence and wavelength, while keeping reduced levels of reflectivity. Low-loss trirefringent nanomaterials may enable the development of ultracompact and tunable light splitters and modulators.

Printable planar lightwave circuits with a high refractive index

We report a novel nanofabrication method to fabricate printable integrated circuits with a high refractive index working in the visible wavelength range. The printable planar ligthwave circuits are directly imprinted by ultra-violet nanoimprinting into functional TiO2-based resist on the top of planar waveguide core films. The printed photonic circuits are composed of several elementary components including ridge waveguides, light splitters and digital planar holograms. Multi-mode ridge waveguides with propagation losses around 40 dB cm−1 at 660 nm wavelength, and, on-chip demultiplexers operated in the visible range with 100 channels and a spectral channel spacing around 0.35 nm are successfully demonstrated.

Performance of genetic algorithms in search for water splitting perovskites

We examine the performance of genetic algorithms (GAs) in uncovering solar water light splitters over a space of almost 19,000 perovskite materials. The entire search space was previously calculated using density functional theory to determine solutions that fulfill constraints on stability, band gap, and band edge position. Here, we test over 2500 unique GA implementations in finding these solutions to determine whether GA can avoid the need for brute force search, and thereby enable larger chemical spaces to be screened within a given computational budget. We find that the best GAs tested offer almost a 6 times efficiency gain over random search, and are comparable to the performance of a search based on informed chemical rules. In addition, the GA is almost 10 times as efficient as random search in finding half the solutions within the search space. By employing chemical rules, the performance of the GA can be further improved to approximately 12–17 better than random search. We discuss the effect of population size, selection function, crossover function, mutation rate, fitness function, and elitism on the final result, finding that selection function and elitism are especially important to GA performance. In addition, we determine that parameters that perform well in finding solar water splitters can also be applied to discovering transparent photocorrosion shields. Our results indicate that coupling GAs to high-throughput density functional calculations presents a promising method to rapidly search large chemical spaces for technological materials.

PRINCIPLES OF GRAVITATIONAL WAVES DETECTION THROUGH ATOM INTERFEROMETRY

The output of a simple Mach-Zehnder atom interferometer (with light field beam splitters) is studied in order to obtain sensitivity curves for GW signals in the paraxial approximation by using the ABCD matrices techniques and first order perturbation theory for mirroratom interaction; order of magnitude of relevant physical parameters for a realistic GW detector through atom interferometry is deduced, both for single- and coupled-interferometers configurations. Finally a synthetic overview of ongoing activities of the Florence-Urbino group in this field is presented.