Beam Splitter Research Articles

Triangular cross-section beam splitters in silicon carbide for quantum information processing

AbstractTriangular cross-section color center photonics in silicon carbide is a leading candidate for scalable implementation of quantum hardware. Within this geometry, we model low-loss beam splitters for applications in key quantum optical operations such as entanglement and single-photon interferometry. We consider triangular cross-section single-mode waveguides for the design of a directional coupler. We optimize parameters for a 50:50 beam splitter. Finally, we test the experimental feasibility of the designs by fabricating triangular waveguides in an ion beam etching process and identify suitable designs for short-term implementation.

All-optical polarization scrambler based on polarization beam splitting with an amplified fiber ring

Optical-fiber-based polarization scramblers can reduce the impact of polarization sensitive performance of various optical fiber systems. Here, we propose a simple and efficient polarization scrambler based on an all-optical Mach-Zehnder structure by combining a polarization beam splitter and an amplified fiber ring. To totally decoherence one polarization split beam, a fiber ring together with an amplifier is incorporated. The ratio of two orthogonal beams can be controlled by varying the amplification factor, and we observe different evolution trajectories of the output state of polarizations on the Poincaré sphere. When the amplification factor exceeds a certain threshold, the scrambler system exhibits nearly ideal polarization scrambling behavior. A commercial single wavelength laser with a linewidth of 3 MHz is utilized to characterize the scrambling performance. We found that when the sampling rate is 1.6 MSa/s, a scrambling speed up to 2000krad/s can be obtained for the average degree of polarization being less than 0.1. We also exploit these random polarization fluctuations to generate random binary numbers, indicating that the proposed technique is a good candidate for a random bit generator.

Ultra-sensitive measurement of small optical rotation angles using quantum entanglement based on a quasi-Wollaston prism beam splitter

The measurement of optical rotation is fundamental to optical atomic magnetometry. Ultra-high sensitivity has been achieved by employing a quasi-Wollaston prism as the beam splitter within a quantum entanglement state, complemented by synchronous detection. Initially, we designed a quasi-Wollaston prism and intentionally rotated the crystal axis of the exit prism element by a specific bias angle. A linearly polarized light beam, incident upon this prism, is divided into three beams, with the intensity of each beam correlated through quantum entanglement. Subsequently, we formulated the equations for optical rotation angles by synchronously detecting the intensities of these beams, distinguishing between differential and reference signals. Theoretical analysis indicates that the measurement uncertainty for optical rotation angles, when using quantum entanglement, exceeds the conventional photon shot noise limit. Moreover, we have experimentally validated the effectiveness of our method. In DC mode, the experimental results reveal that the measurement uncertainty for optical rotation angles is 4.7 × 10−9 rad, implying a sensitivity of 4.7 × 10−10 rad/Hz1/2 for each 0.01 s measurement duration. In light intensity modulation mode, the uncertainty is 48.9 × 10−9 rad, indicating a sensitivity of 4.89 × 10−9 rad/Hz1/2 per 0.01 s measurement duration. This study presents a novel approach for measuring small optical rotation angles with unprecedentedly low uncertainty and high sensitivity, potentially playing a pivotal role in advancing all-optical atomic magnetometers and magneto-optical effect research.

3DOF displacement sensor based on the self-imaging effect of optical micro-gratings

In recent years, there has been an increasing demand for a multiple degrees of freedom (DOF) measurement system with high performance and high integration. Here, we report a 3DOF displacement sensor based on the self-imaging effect of optical micro-gratings. The optical field distribution behind a micro-grating with a period of 3 µm is analyzed theoretically. The transmission properties of a double-grating structure are investigated in theory. In the experiment, 3DOF displacement measurement within a range of 1 mm is demonstrated. Using an interpolation circuit with a subdividing factor of 1000, displacement measurement with a theoretical resolution of 3 nm is realized. The experimental resolution is ∼8nm. An error within 2 µm is obtained experimentally within a range of 1 mm for 3DOF measurement. With a few optical components such as a beam splitter prism and beam expanders, the sensor shows potential in developing ultra-compact multi-DOF displacement measuring systems. Together with a nanometric resolution, the 3DOF displacement sensor has shown great potential in applications such as high-precision mechanical engineering and semiconductor processing.

Research on reconfigurable waveguide devices based on liquid crystal on silicon

AbstractDue to the limitation of materials, PIC cannot achieve large magnitude phase modulation in a small size, and lacks the reconfigurable ability. Because of its birefringence characteristic, liquid crystal can be used in the liquid crystal on silicon (LCoS) device to achieve a large amount of phase modulation in a small size and has the capacity of reconstruction. Based on the experimental results of LCoS devices and basic liquid crystal waveguide devices, the liquid crystal waveguide device is prepared. While retaining the LCoS spatial optical phase modulation capability, the liquid crystal waveguide and phase modulation capability are realized. The beam splitter, optical switch, and Mach–Zehnder interferometer structure are constructed, which verifies the feasibility of the liquid crystal waveguide phase modulator.

Accuracy of linear transformations performed on a nonideal Mach–Zehnder interferometer

We consider a mathematical model of a planar Mach–Zehnder interferometer with nonideal beam splitters. For this model, we obtain two fidelity estimates of the matrix–vector multiplication in the form of dependences of the multiplication error on the beam splitting error in directional couplers. The first estimate is obtained as a measure of the difference between the transfer matrices implemented by interferometers and is presented in the form of the norm of the difference between two unitary matrices corresponding to ideal and non-ideal interferometers. The second estimate is obtained as a measure of the difference in output intensities. It is shown that in the latter case the fidelity depends both on the beam splitter error and on the parameters of the input signals. We verified the second estimate using computer simulations of MZI in COMSOL Multiphysics.

Analysis of Optical Power Splitter with Resonator Structure Constructed by Two-Dimensional MDM Plasmonic Waveguide

Analysis of Optical Power Splitter with Resonator Structure Constructed by Two-Dimensional MDM Plasmonic Waveguide

A versatile Raman setup with time-gating and fast wide-field imaging capabilities

Raman spectroscopy is a well-established method for chemical identification, with a wide variety of applications. The two major limitations are that fluorescence can hamper detection, and that Raman imaging is slow; it typically takes multiple hours to measure even a small surface area. We have developed a multimodal setup that mitigates these limitations. The setup has a point-scanning mode that allows for time-gated as well as continuous Raman spectroscopy, and both modes use an 80 MHz, 532 nm excitation laser with up to 20 W of power. The fluorescence suppression capabilities of the setup were demonstrated by comparing time-gated to continuous detection of a Dracaena leaf. Raman bands showed a 4-8 times improvement in signal-to-background ratio, and one band that was invisible in the continuous measurement, became visible in the time-gated measurement.The setup also has a 4-band simultaneously detected wide-field mode. Using a set of beam splitters, the Raman signal from the sample is split. This signal is imaged onto four separate cameras, each with a specific band-pass filter. The wide-field data were processed using principal component analysis with k-means clustering. To illustrate the wide-field capabilities of the setup, a 1mm2 sample containing aspirin, caffeine and paracetamol was measured using 10 W excitation power. A 10-second measurement enabled identification of the compounds, and a 1-second measurement showed promising results. This brings the setup close to real-time imaging, showing great potential for applications in quality control or for measuring samples that change over time.

Continuously wavelength‐tuneable general transmittance function in first‐order fibre multiwavelength filter based on composite combination of wave retarders

AbstractThe wavelength tunability of a general transmittance function (GTF) is investigated in a first‐order fibre multiwavelength filter based on a polarisation‐diversified fibre loop, which utilised a composite combination of wave retarders. The filter consists of a polarisation beam splitter, two equal‐length high birefringence fibre (HBF) segments, and two different sets of wave retarders with each set positioned before each HBF segment. Specifically, a combination of a set of dual quarter‐wave retarders (QWRs) and another set of a QWR and a half‐wave retarder is focused upon. By considering the effect of the four wave retarders and two HBF segments on the output polarisation state (OPS) of each element in the filter, the four wave retarder angles (WRAs) are identified that caused all polarisation states on the OPS trace of the second HBF move in the direction of wavelength decrease, resulting in a redshift of the GTF. 360 WRA sets are derived that enabled tuning the GTF by one free spectral range SR. For eight sets chosen from the WRA sets, inducing a wavelength shift of SR/8 for each set order, wavelength‐shifted spectra are calculated. Finally, this theoretical prediction is experimentally verified, confirming the wavelength tunability of the GTF of the filter.

A Semianalytically Synthesized Ultrathin Photolithographic Metagrating for Sub-THz Beam Splitting

Compact and efficient devices for radiation beam manipulation are in increasing demand by terahertz technologies. Herein, we introduce an ultrathin metal-polymer photolithographic metagrating operating as a transmissive beam splitter with a wide refraction angle of 58∘ at sub-THz frequencies. Harnessing this recently proposed complex media platform, composed of sparse periodic arrays of meta-atoms, constraints of conventional metasurfaces with densely packed unit cells can be alleviated. The devised splitter, synthesized semianalytically and demonstrated experimentally, features deeply subwavelength thickness due to the unique manufacturing process employed, serving as a promising alternative to thick waveguide-based metagratings previously reported for this frequency range.

Quantum beam splitter based on free charged particles

Quantum beam splitter based on free charged particles

Performance analysis of a novel solar Linear Fresnel concentrator system based on spectral beam splitting

Photothermal and photovoltaic are the most common and commercialized ways of utilizing solar energy. However, they cannot use solar energy efficiently. SBS (spectral beam splitting) technology is an efficient solar energy utilization technology that can realize the full spectrum utilization of solar energy. The current work involved: (1) Proposing a SBS-LFCs (linear Fresnel concentrator system) based on spectral beam splitting. In this system, the SBS photovoltaic panel replaces the conventional linear Fresnel concentrator lens, which can realize photovoltaic and photothermal utilization at the same time; (2) Developing a spectral splitting thin films configuration using the Needle method whose transmittance is higher than 90% against 380 nm-1100 nm band range; (3) Designing the SBS photovoltaic panel structure. The cover glass surface is covered with a SBS thin film. The SBS photovoltaic panel replaces the concentrator lens of LFCs; (4) Taking four typical days as examples, the annual power generation of a SBS linear Fresnel focusing system was predicted. The outcome indicates that the total conversion efficiency of solar thermal power in the system is 23.8%, 23.5%, 23.5%, and 23.6% on the spring equinox, summer solstice, autumn equinox, and winter solstice, respectively. Compared to conventional monocrystalline silicon cells, the photoelectric conversion efficiency has been improved by 14.6%, 12.8%, 12.5%, and 14.1%, respectively.

Environmental and economic impacts of photovoltaic integration in concentrated solar power plants

This study conducted an environmental and economic assessment of an innovative hybrid energy generation system, a CSP+ plant, which integrates photovoltaic (PV) panels in a concentrated solar power (CSP) setup. The CSP+ concept uses a beam splitter that transmits part of the incident solar spectrum towards the PV cells for electricity generation and reflects ultraviolet and infrared light to the receiver tube for heating. This system allows more efficient use of solar radiation in a compact system with optimal efficiency.The environmental impacts were assessed using the life cycle assessment (LCA) methodology, focusing on the climate change impact category. The economic impacts were calculated using the levelized cost of electricity (LCOE) and the levelized cost of heat (LCOH). Both assessments considered a cradle-to-grave perspective in three scenarios (SC). SCI considered only electricity generation, while SCII involved the combined production of electricity and heat. These scenarios were compared to conventional CSP and PV technologies (SCIII) and benchmark values from the literature.The LCA results showed SCII was the most preferable: the impacts on climate change were reduced by up to 83% for electricity production and up to 97% for heat production compared to benchmark values. In SCII, the LCOE and the LCOH in the CSP+ plant were lower than the average benchmark values, with reductions of up to 70% for electricity and 40% for heat. The sensitivity analysis showed that the environmental performance was strongly influenced by the operating lifetime. For economic performance, the weighted cost of capital was the most influential factor.

A new teaching-learning sequence to promote secondary school students’ learning of quantum physics using Dirac notation

This paper describes the design of a new teaching-learning sequence on quantum physics aimed at upper secondary school students. In this teaching-learning sequence, GeoGebra simulations and interactive screen experiments are used to investigate the behaviour of a single photon at beam splitter and single photon interference in a Michelson interferometer. We propose a minimal formalism using Dirac notation, which avoids complex numbers and elaborate vector calculus, to make a quantitative description of the quantum optics experiments accessible to secondary school students. With this new educational pathway, we take into account findings from physics education research, which suggest that the introduction of a mathematical formalism tailored to students’ abilities might help them to overcome naive-realist views of quanta or space-time descriptions of quantum phenomena, while at the same time facilitating a transition to a functional understanding of quantum models.

Dielectric topological metasurfaces based in-plane control of light propagation by using valley degrees of freedom

Metasurface has garnered widespread attention due to its remarkable ability of precise light manipulation. The emergence of topological photonics has brought novel topological phenomena and holds the promise of introducing new optical functionalities to the metasurfaces. In this paper, by introducing valley degrees of freedom into metasurfaces, we design and numerically simulate topological-nanostructure-enabled on-chip chiral light propagation and multistage beam splitting, as well as holographic display by integrating a beam-splitting metasurface with valley photonic crystals (VPCs). Importantly, the proposed on-chip topological optical devices exhibit broadband response covering 1480–1660 nm and low transmission losses with the maximum efficiency reaching 82 %. Our work is expected to bring new optical functionalities to the metasurface based devices and can be widely applied in fields of optical fiber communications, on-chip optical transportation and smart wearable devices, which require high-efficiency, broadband and highly-integrated optoelectronic elements and devices.

Open dynamics of entanglement in mesoscopic bosonic systems

Abstract A key issue in Quantum Information is finding an adequate description of mesoscopic systems that is simpler than full quantum formalism yet retains crucial information about non-classical phenomena like entanglement. In particular, the study of fully bosonic systems undergoing open evolution is of great importance for the advancement of photonic quantum computing and communication. In this paper, we propose a mesoscopic description of such systems based on boson number correlations. This description allows for tracking Markovian open evolution of entanglement of both non-Gaussian and Gaussian states and their sub-Poissonian statistics. It can be viewed as a generalization of the reduced state of the field formalism [Entropy 2019, 21(7), 705], which by itself does not contain information about entanglement. As our approach adopts the structure of the description of two particles in terms of first quantization, it allows for broad intuitive usage of known tools. Using the proposed formalism, we show the robustness of entanglement against low-temperature damping for four-mode bright squeezed vacuum state and beam-splitted single photon. We also present a generalization of the Mandel Q parameter. Building upon this, we show that the entanglement of the state obtained by beam splitting of a single occupied mode is inherited from sub-Poissonian statistics of the input state.

Splitting of Optical Spatial Modes via Stern‐Gerlach Effect

AbstractStern‐Gerlach (SG) effect, initially found for unveiling the existence of quantized electron spins, is now a general concept describing a state‐dependent separation. It is widely explored in optics to achieve a function of optical splitting, but the current schemes always require a polarization‐ or wavelength‐dependent process, thus showing limitations for broader applications. Here, spatial modes of an optical field are employed as another degree of freedom to demonstrate an SG effect. Two modes of a pair of coupled waveguides are found to be in analog to the electron spins. They are able to undergo a splitting upon a spatially‐dependent waveguide coupling, which plays the role of a non‐uniform magnetic field. In an experiment, such a splitting is realized in two coupled non‐parallel slab waveguides, and its strength is adjusted at ease by varying the parameters of this proposed structure. This SG‐related optical splitting may find applications in the field of optical sensing and signal processing.

Polarization‐directed nanophotonic routers based on two‐dimensional inorganic molecular crystals

AbstractPhotonic and plasmonic hybrid nanostructures are the key solution for integrated nanophotonic circuits with ultracompact size but relative low loss. However, the poor tunability and modulability of conventional waveguides makes them cumbersome for optical multiplexing. Here we make use of two‐dimensional molecular crystal, α‐Sb2O3 as a dielectric waveguide via total internal reflection, which shows polarization‐sensitive modulation of the propagating beams due to its large polarization mode dispersion. Both experiments and simulations are performed to verify such concept. These Sb2O3 nanoflakes can be coupled with plasmonic nanowires to form nanophotonic beam splitters and routers which can be easily modulated by changing the polarization of the incidence. It thus provides a robust, exploitable and tunable platform for on‐chip nanophotonics.image

Single-shot characterization of special multi-soliton and noise-like pulse emissions in a mode-locked fiber laser

Single-shot characterization of three categories of multi-pulse emissions in a passively mode-locked fiber laser based on nonlinear polarization rotation is experimentally reported. The mechanism to control the intracavity polarization state relies on a polarizer beam splitter cube together with a half-wave and a quarter-wave retarders. With a precise adjustment of the retarders, the fiber laser can reach different mode locking regimes involving noise-like pulses (NLP) and solitons. These regimes include (i) NLP emission exhibiting broad-bandwidth supercontinuum spectrum, (ii) multiple soliton emission in the form of soliton bunches with rectangular-shaped envelope, and (iii) NLP emission with complex pulse patterns, such as the one obtained from the breakup of a rectangular NLP, or the harmonic mode locking regime exhibiting multiple, uniformly spaced NLP wave packets. The experimental results presented in this work provide useful information for a better understanding of different types of multi-pulse emission from the same fiber laser system, complementing the studies focused on the nature and physical mechanisms underlying NLP emission.

Tunable multifunctional terahertz metasurface based on an indium antimonide medium

Active adjustable terahertz multifunctional devices are crucial for the application of terahertz technology. In this paper, we propose a composite metasurface structure based on an indium antimonide metal octagonal pattern, which achieves different functional switching by controlling the phase state of indium antimonide material under different ambient temperatures. When indium antimonide exhibits in the dielectric state, by stacking and encoding the unit cell, the designed metasurface has the functions of two-beam splitting beam superposition, vortex beam and quarter beam superposition, and dual vortex beam superposition for circularly polarized and linearly polarized wave incidence. When indium antimonide appears in the metallic state, the encoding metasurface alters the modulation function of incident circularly polarized and linearly polarized terahertz waves. This terahertz metasurface provides a new approach for the design of multifunctional devices that can flexibly regulate terahertz wave metasurfaces.