Chip-scale atomic birefringent diffractive-optical-elements

The principle of Fourier transform spectrometer is based on the relationship of Fourier-Transform between interferogram and spectrum. The spectral information of Fourier transform imaging spectrometer (FTIS) reconstructed from raw interferogram by data processing. So there are two kinds of signal-to-noise ratio (SNR) to evaluate instrument performance, one regarding interferogram and the other regarding reconstructed spectrum. Because the raw interferogram is intuitive, the interferogram SNR is studied usually. On the contrary, the spectrum SNR is studied less because of the complexity of the data processing from interferogram to spectrum. The research about the effect of the interference fringe visibility on the spectrum SNR is especially few. This paper present a research work on the relations between the interference fringe visibility and the spectrum SNR. Firstly, the reduction of fringe visibility caused by imaging lens defocus was analyzed. Secondly, the changes of the average spectrum signal and noise caused by the reduction of fringe visibility were calculated. For average spectrum signal, the math deductions are done base on Fourier transform theory. The average noise with different input signal optic-electrons number are simulated. the results show that the average spectrum signal is directly proportional to the fringe visibility, and the effect of fringe visibility on the noise related to signal can be ignorable. Finally, In order to demonstrate above results, the imaging experiment was done with white-light source, using LASIS (Large aperture static imaging spectrometer) based on Sagnac Interferometer. The average spectrum SNRs under different fringe visibility are calculated and analyzed. The experimental results show that: the average spectrum SNRs increase from 42.7 to 62.4.along with the fringe visibility increasing from 0.5051 to 0.687. the reconstructed spectrum SNR is directly proportional to the fringe visibility. As a result, the interferogram fringe visibility can be used to estimate the reconstructed spectrum SNR, and evaluate the performance of FTIS before data processing.

Quantum photonic devices are candidates for realizing practical quantum computers and networks. The development of integrated quantum photonic devices can greatly benefit from the ability to incorporate different types of materials with complementary, superior optical or electrical properties on a single chip. Semiconductor quantum dots (QDs) serve as a core element in the emerging modern photonic quantum technologies by allowing on-demand generation of single-photons and entangled photon pairs. During each excitation cycle, there is one and only one emitted photon or photon pair. QD photonic devices are on the verge of unfolding for advanced quantum technology applications. In this review, we focus on the latest significant progress of QD photonic devices. We first discuss advanced technologies in QD growth, with special attention to droplet epitaxy and site-controlled QDs. Then we overview the wavelength engineering of QDs via strain tuning and quantum frequency conversion techniques. We extend our discussion to advanced optical excitation techniques recently developed for achieving the desired emission properties of QDs. Finally, the advances in heterogeneous integration of active quantum light-emitting devices and passive integrated photonic circuits are reviewed, in the context of realizing scalable quantum information processing chips.

In telecommunications technology, transmitting and receiving signals is not possible without an integrated antenna. Recently, novel approaches of transmitting and receiving signals using advancement in quantum technology as “information coherent transfer” have been emphasized which overcomes the limitations of superconducting qubits. In the present investigation, a compact-sized circular-ring antenna was designed for a 12 GHz centre frequency. The antenna was topped with Gd(x)-doped YIG (x = 0.0, 0.1, 0.2, 0.3) thin disks to investigate its tunable operation over the tri-band (C to Ku) frequencies due to the photon–magnon coupling, which enables coherent qubit information transmission from an electromagnetic (EM) carrier to the magnons. The proposed prototype of the antenna is validated using HFSS simulation. To characterize the frequency tunability of the designed antenna, we measured the return loss (S11) via a vector network analyzer as a function of dc magnetic field. Different concentrations of Gd-doped YIG ferrites (Gdx-YIG) have been loaded on ring antennas to observe strong anti-crossing phenomena with the application of an external magnetic field. The designed antenna has a tunability of around 300% for a small applied magnetic field up to 3.7 kOe. The maximum gain of dual resonance antenna is 1.4 for higher magnetic field of 3.7 kOe. The highest efficiency and lowest bandwidth of 30% and 14% respectively, for Gd0.1-YIG disk are observed. The measured normal mode splitting spectrum as a function of bias magnetic field that gives the maximum coupling strength is 153 MHz for a Gd concentration of 0.1. For practical applications, such antennas are suitable for use in tunable tri-band or multi-band applications (C to Ku).

Unidirectional solidification of Pb-33 at%Bi and Sn-1.0 at%Cd alloys was performed under magnetic fields up to 8 MA/m (10 T). The rejection of the lighter Bi at the solidifying front strongly initiates the convection in the Pb-Bi alloy, while the rejection of the heavier Cd stabilizes the diffusion layer in the Sn-Cd alloy. For the Pb-33 at%Bi alloy, a periodic structure was observed at growth rates of 0.42 and 0.56μm/s under any magnetic fields up to 8 MA/m. The imposition of the magnetic field clearly increased length of the periodic structure formation. On the other hand, no significant effect of the magnetic fields on the banded structure was observed for the Sn-1.0 at% Cd alloy. The experimental results were consistently explained by the proposed model that considered instability of the side-by-side growth. The periodic structure originated in the peritectic systems itself and the unsteady flow in melt may act as a trigger. The periodic structure observed in peritectic systems can he generalized as the dissipative structure.

Permanent magnet structures are described in which the longitudinally oriented flux supply magnets of a conventional periodic structure are clad with radially oriented toroidal magnets shaped to confine the flux to the working space of the stack bore. Such cladding increases the useful magnetic field in the working space and eliminates potentially deleterious stray fields outside of the structure. Alternatively, cladding can be used to reduce the mass and bulk of the magnet stack without a reduction in field strength. Similar cladding techniques can be used for constant field sources, as well as for other periodic structures such as wigglers. These are compared with their conventional counterparts with regard to field-produced per unit structural mass.

Femtosecond-laser micromachining is an enabling technology that allows maskless realization of fully integrated photonic, microfluidic and micromechanical devices. Indeed, direct femtosecond laser writing can be used in transparent materials both for the fabrication of high-quality waveguides, and, possibly combined with chemical etching, for the realization of microfluidic channels. Moreover it can be used for surface structuring and functionalization, for the realization of high aspect-ratio microholes and microchannels by direct surface ablation, and for the fabrication of 3D micro/nanostructures by means of two-photon-polymerization. In this presentation, the basics of femtosecond laser writing will be summarized, and the main aspects influencing induced material modifications will be discussed. The main focus will be on femtosecond laser micromachining in transparent materials (typically glasses and crystals) where nonlinear absorption of light results in strongly localized permanent modifications of the material itself. At lower laser fluence "gentle" modifications can be induced, allowing direct writing of high quality optical waveguides. Waveguides characteristics can be optimized to make them suitable for the realization of integrated quantum circuits. At higher laser fluence nanogratings can be formed inside the material that allow selective chemical etching of microchannels. By combining waveguides and microchannels fully-integrated micro-optofluidic devices for sensing can be realized. Some typical applications will be presented, with particular focus on quantum technologies, to better illustrate the versatility and peculiarities of the technique. The results obtained show the strong potential of this microfabrication technology, paving the way to increasingly compact and multifunctional integrated quantum photonic and microfluidic devices.

An optical bistable device can be useful not only for optical memory but also for optical sensing by using its binary signal process characteristics. In this case, if a nonlinear Faraday medium is used in the optical bistable device, some interesting features can be obtained as already shown by the present author. Those unique characteristics are that, by controlling the polarization direction by an external magnetic field, a multiple interference can also be controlled not only by the phase associated with an optical path variation but also the polarization direction.This paper describes a theoretical analysis of the fluctuation of transmission and reflection as a function of an absorption in a medium besides the incident intensity reduction and discusses the bistability characteristics and the threshold values against the parameters. It is shown that the control of the bistable function, the realization of a low threshold value, and the increase of a discontinuous power variation ratio (= optical intensity ratio between on and off in the binary signal process) at the threshold value are accomplished as the result of the introduction of the external magnetic field control method. Therefore, it can be concluded that a Faraday medium is very useful for an optical bistable device.

Single-photonemitters (SPEs) are crucial in quantumcommunicationand information processing. In 2D transition metal dichalcogenides(TMDs), SPEs are realized through inhomogeneous strain, while in combinationwith 2D magnets, a high spontaneous out-of-plane magnetization canbe induced due to proximity effects. Here, an alternative is proposedthat consists of suspending a TMD monolayer (WSe2) on afew-layer antiferromagnet (CrSBr) with in-plane magnetic ordering.The resulting heterostructure exhibits localization centers at lowerenergies than expected. Among them, a bright SPE with a high degreeof polarization selection is identified. This suffers a clear energyshift driven by an in-plane magnetic field, and interestingly, thisshift is correlated with the metamagnetic transition of CrSBr, suggestinga new kind of proximity-type effect. Unlike regular SPEs in WSe2 (sensitive to out-of-plane magnetic fields), our SPE demonstratessensitivity to both in-plane and out-of-plane magnetic fields. Theadded tunability at significantly lower fields offers a promisingdirection for developing magnetically responsive quantum emitters,paving the way for more practical applications in quantum technologies.

An external DC magnetic field may change the dispersion diagram of periodic structures, so that tunable reciprocal and non-reciprocal plamonic components may be constructed. In this study, the effect of an external DC magnetic field on the dispersion diagram of plasmonic periodic structures will be investigated by the effective refractive index method. Investigations are focused on the Voigt and Faraday configurations, although it can be extended to other configurations. In this regard, the wave equation for both structures is solved, eigenpropagation constants and eigenpolarisation are derived. Then, the effective propagation constant and finally, the dispersion diagram for the Voigt and Faraday structures will be derived. The effect of the bias field is investigated on the aforementioned structures. It is seen that tunable periodic structures can be achieved by the magnetoplasmonic configurations. Different dispersion diagrams can be obtained for different modal waves. For both structures, there is a transmission band for frequencies below the plasma frequency, especially for extremely low frequencies, where in the absence of a magnetic field, wave transmission is impossible. There is no limit on the period of structure, the period of structure in the simulation varies from zero to 1.6λp.

Photon loss is destructive to the performance of quantum photonic devices and therefore suppressing the effects of photon loss is paramount to photonic quantum technologies. We present two schemes to mitigate the effects of photon loss for a Gaussian Boson Sampling device, in particular, to improve the estimation of the sampling probabilities. Instead of using error correction codes which are expensive in terms of their hardware resource overhead, our schemes require only a small amount of hardware modifications or even no modification. Our loss-suppression techniques rely either on collecting additional measurement data or on classical post-processing once the measurement data is obtained. We show that with a moderate cost of classical post processing, the effects of photon loss can be significantly suppressed for a certain amount of loss. The proposed schemes are thus a key enabler for applications of near-term photonic quantum devices.

Gaussian Boson Samplers are photonic quantum devices with the potential to perform intractable tasks for classical systems. As with other near-term quantum technologies, an outstanding challenge is to identify specific problems of practical interest where these devices can prove useful. Here, we show that Gaussian Boson Samplers can be used to predict molecular docking configurations, a central problem for pharmaceutical drug design. We develop an approach where the problem is reduced to finding the maximum weighted clique in a graph, and show that Gaussian Boson Samplers can be programmed to sample large-weight cliques, i.e., stable docking configurations, with high probability, even with photon losses. We also describe how outputs from the device can be used to enhance the performance of classical algorithms. To benchmark our approach, we predict the binding mode of a ligand to the tumor necrosis factor-α converting enzyme, a target linked to immune system diseases and cancer.

Semiconductor quantum dots (QDs) are high-quality nanocrystals that provide three-dimensional carrier confinement on the scale of the de Broglie wavelength. This makes them ideal candidates as light emitters, especially in the emerging field of photonic quantum technologies, where they can act as quantum light sources. However, their self-assembled epitaxial growth leads to randomness in position and emission wavelength, which hinders their scalable integration into photonic quantum devices. This review summarizes and highlights advances in the site-controlled growth of high-quality epitaxial QDs, with a particular focus on the buried stressor concept. Compared to other QD positioning techniques based for instance on nanohole arrays, nanowire arrays, and arrays of inverted pyramids as dot nucleation centers, the buried stressor growth method is distinguished by its ability to achieve not only spatial accuracy and precision, but also control of the local QD density in combination in an industry-compatible process flow. Therefore, the buried stressor growth technique is highly suitable for the development of both QD-based quantum light sources and microlasers. The buried stressor site-controlled QD growth technique involves the sub-surface embedding of a nano-engineered stressor material, which generates localized strain fields at the growth surface that control the nucleation of QDs. We provide an in-depth review of the underlying mechanisms and technological implementations, and discuss the differences and comparative advantages of the buried stressor method over other techniques for site-controlled growth of QDs. We also address persistent challenges, such as scalability and integration with existing semiconductor technologies, and outline potential future research directions.

Quantum computing introduces a revolutionary approach to solving problems that are computationally beyond the reach of classical systems. Among its most promising applications is the simulation of many-body systems, where strong particle interactions lead to complex quantum behaviors. Traditional computational techniques often fail due to exponential resource requirements, but quantum simulators can efficiently model these interactions through entanglement and superposition. Recent advances in superconducting qubits, trapped ions, and photonic quantum devices have enabled small- scale experimental demonstrations of spin models, Hubbard systems, and correlated electron dynamics. These developments offer new insights into condensed matter physics and quantum phase transitions. As quantum technologies continue to evolve, they hold the potential to transform the study of materials, superconductivity, and other many-body phenomena with remarkable precision and scalability.

Magnetoplasma waves and inhomogeneous (complex) waves in an infinite semiconductor superlattice in a magnetic field are studied, and dispersion curves are obtained. It is shown analytically and numerically that, in periodic structures, among inhomogeneous waves, there are many complex waves for which the imaginary part of the wave vector is greater than the real part. The effect of dissipation in a medium on the dispersion curves of magnetoplasma waves is examined. The dependence of the minimum phase velocity on the collision frequency and the magnetic field strength is studied.

The characteristics of two-dimensional periodical structures in a magnetized plasma are studied using kinetic simulations. Ridges (i.e. spikes in electron and ion density) are formed and became more pronounced with an increase of magnetic field incidence angle in the plasma volume in the cylindrical chamber. These ridges are shifted relative to each other, which results in the formation of a two-dimensional double-layer structure. Depending on Larmor radius and Debye length up to 19 potential steps appear across the oblique magnetic field. The electrical current gathered into the channels is associated with the electron and ion density ridges.