Output Arms Research Articles

A spatial electrostatic beam splitter for polar molecules in weak-field-seeking states

A spatial electrostatic beam splitter composed of six charged poles for polar molecules in weak-field-seeking states is proposed. First, the schematic diagram is given. With the help of finite element software the spatial distribution of the electrical field is calculated. The dynamic process of the loading and splitting polar molecules is simulated using the classical Monte Carlo method. The influences of the longitudinal velocity of the incident molecular beam and the voltages on the loading efficiency are studied. Two output arms of the beam splitter can be cut off at a certain position to adjust the splitting ratio of the molecular beam. Then the influences of the voltages and cutting positions on the splitting ratio are investigated. The results indicate that the splitting ratio can be manipulated conveniently from 0% to 100%.

Electro-mechanical control of an on-chip optical beam splitter containing an embedded quantum emitter.

We demonstrate electro-mechanical control of an on-chip GaAs optical beam splitter containing a quantum dot single-photon source. The beam splitter consists of two nanobeam waveguides, which form a directional coupler (DC). The splitting ratio of the DC is controlled by varying the out-of-plane separation of the two waveguides using electromechanical actuation. We reversibly tune the beam splitter between an initial state, with emission into both output arms, and a final state with photons emitted into a single output arm. The device represents a compact and scalable tuning approach for use in III-V semiconductor integrated quantum optical circuits.

Design data for quick development of folded H plane tee at high average power level

At high average power level, waveguide-based structures are indispensable in microwave systems due to their higher power handling capacity. These structures are often used to perform power division and combination operation. Folded H plane tee is one of the many components that can be used for the power division application. Its advantage is that the output arms and input arms are in a single plane along a single axis, thus taking less space in the overall system. However, their proper thermal management is indispensable for its use, as high surface temperature of the waveguide reduces its power handling capacity at high power level. This paper presents quick, easy design steps and methodology for obtaining the structure of a folded H plane tee at any given frequency of operation. Further, a scheme for the thermal management for high input power level (500 kW continuous wave) is presented. The proposed methodology is tested at various frequencies in COMSOL Multiphysics, CST Microwave Studio and HFSS with excellent results. A prototype structure was fabricated for use at 3.7 GHz, which exhibited good agreement with the simulation results.

Cladding waveguide splitters fabricated by femtosecond laser inscription in Ti:Sapphire crystal

Highly-compact devices capable of beam splitting are intriguing for a broad range of photonic applications. In this work, we report on the fabrication of optical waveguide splitters with rectangular cladding geometry in a Ti:Sapphire crystal by femtosecond laser inscription. Y-splitters are fabricated with 30 μm × 15 μm and 50 μm × 25 μm input ends, corresponding to two 15 μm × 15 μm and 25 μm × 25 μm output ends, respectively. The full branching angle θ between the two output arms are changing from 0.5° to 2°. The performances of the splitters are characterized at 632.8 nm and 1064 nm, showing very good properties including symmetrical output ends, single-mode guidance, equalized splitting ratios, all-angle-polarization light transmission and intact luminescence features in the waveguide cores. The realization of these waveguide splitters with good performances demonstrates the potential of such promising devices in complex monolithic photonic circuits and active optical devices such as miniature tunable lasers.

Decoding of Multilevel Stokes-Vector Modulated Signal by Polarization-Analyzing Circuit on InP

Of-late research on Stokes vector receivers for the short-reach optical communications has gained significant attention due to its capability to decode information in multidimension using cost-effective direct-detection technique. Here, we consider the use of InP for potentially low-cost direct-detection-based Stokes vector (SV) receiver. It consists of a 1 × 4 multimode interference power splitter with different combination of polarization converters on output arms, so that input SV is projected onto distinct vectors on the Stokes space. By using the fabricated device, we experimentally demonstrate decoding of two-level and four-level SV-modulated signals at 3 Gbaud. With the potential of monolithically integrating high-speed InP photodetector array on the same chip, it paves the way to realize compact and low-cost SV receivers for multilevel SV modulation formats in future short-reach optical communication links.

Design of an integrated multi-arm power splitter using photonic crystal waveguide

This paper proposes a novel design of an integrated multi-arm power splitter based on photonic crystal waveguides. A 1×5 power splitter is proposed by introducing line defects to form a one input waveguide arm and five output waveguide arms. The plane wave expansion method (PWE) is used to investigate the dispersion characteristics of the light coupling between the guided modes in the photonic band gap (PBG) from 0.037 ω/2πc to 0.095 ω/2πc frequency range. Using Finite-Difference Time Domain (FDTD) method, we calculated the power splitting across each output arm; 52.2% in arm C, 16.9% in arm D, 14.6% in arm E, 12.1% in arm A and 3.4% in arm B. The total observed transmission efficiency of the splitter is 99.2%. Further, the time response of electric field along the Y direction (Ey) which is perpendicular to the X-Z plane is studied. The output arms C, E, D and B show beam shaped envelope response while the remaining output arm A exhibit negligible variation with time. The compact and low cost proposed design contributes to the state of art progress in the field of photonics integrated circuits (PICs) technology where the power splitter plays a prominent role of splitting optical power between all the optical elements integrated in the chip.

Generation, guiding and splitting of triggered single photons from a resonantly excited quantum dot in a photonic circuit.

We demonstrate resonance fluorescence from single In-GaAs/GaAs quantum dots embedded in a rib waveguide beamsplitter structure operated under pulsed laser excitation. A systematic study on the excitation laser pulse duration depicts that a sufficiently small laser linewidth enables a substantial improved single-photon-to-laser-background ratio inside a waveguide chip. This manifests in the observation of clear Rabi oscillations over two periods of the quantum dot emission as a function of laser excitation power. A photon cross-correlation measurement between the two output arms of an on-chip beamsplitter results in a g(2)(0)=0.18, demonstrating the generation, guiding and splitting of triggered single photons under resonant excitation in an on-chip device. The present results open new perspectives for the implementation of photonic quantum circuits with integrated quantum dots as resonantly-pumped deterministic single-photon sources.

Broad Band Equal-Length And Equal-Width Substrate Integrated Waveguide Four Channel Power Divider

In this letter a novel broad band substrate integrated waveguide (SIW) power divider is proposed. It consist of four output channels made by SIW with equal length and equal width. Design equations and process are given with mathematical analysis. The propagation constant of the output signals have been adjusted by utilize only four via in the middle of the output arms. As a result a novel equal output power divider, is obtained accordingly. The experimental results of a prototype at 10 GHz shows 3.1 GHz bandwidth in both simulation and measurement results. Return loss and transmission coefficients have good agreement with simulation results in considered band.

Compact Size, Equal-Length and Unequal-Width Substrate Integrated Waveguide Four Channel Phase Shifter

Objectives: In the past decade, Substrate Integrated Waveguide (SIW) phase shifters have attracted a lot of attentions, they are key components extensively deployed in phased array antennas, electronic scanning radars and other applications. In this paper a novel SIW four channel phase shifter is proposed. Methodology: It consists of five ports from which four ports act as output channels and the remaining is applied as a feed port. Also this substrate is integrated with a waveguide phase shifter designed to operate at 10 GHz. Phase channels are made by SIW with equal length and unequal width. The width of the phase channels differ from each other and can be controlled. The equations and the process of the whole design are preceeded by mathematical analysis. The propagation constant of the output signals and output phases in output channels have been adjusted by changing only the width of the output arms. Findings: As a result, a novel phase shifter is obtained. The experimental results of the prototype at 10GHz represents 22.5, 45, 67.5 degrees phase difference between one of the outputs in comparison to other outputs respectively. The measured bandwidth is 1.3 GHz bandwidth which has conformity with the simulation results. With the change of the position, the number of added vias and the width of output channels, a different phase shift can be obtained. The measurement of return loss and transmission coefficients are in good agreement with the simulation results in the proposed band. Application/Improvements: Therefore, such a SIW phase shifter is a good candidate for development of a compact size and integrated microwave systems.

Dynamical generation and detection of entanglement in neutral leviton pairs

The entanglement of coherently split electron-hole pairs in an electronic conductor is typically not considered accessible due to particle number conservation and fermionic super-selection rules. We demonstrate here that current cross-correlation measurements at the outputs of an electronic Mach-Zehnder interferometer can nevertheless provide a robust witness of electron-hole entanglement. Specifically, we consider neutral excitations generated by modulating the transmission of an unbiased quantum point contact periodically in time. For an optimized modulation profile, an entangled state with one positively-charged leviton (a hole) and one negatively-charged leviton (an electron) gets delocalized over the two paths of the interferometer and is detected at the output arms. We evaluate the influence of finite electronic temperatures and dephasing corresponding to recent experiments.

On-chip beamsplitter operation on single photons from quasi-resonantly excited quantum dots embedded in GaAs rib waveguides

We present an on-chip beamsplitter operating on a single-photon level by means of a quasi-resonantly driven InGaAs/GaAs quantum dot. The single photons are guided by rib waveguides and split into two arms by an evanescent field coupler. Although the waveguides themselves support the fundamental TE and TM modes, the measured degree of polarization (∼90%) reveals the main excitation and propagation of the TE mode. We observe the preserved single-photon nature of a quasi-resonantly excited quantum dot by performing a cross-correlation measurement on the two output arms of the beamsplitter. Additionally, the same quantum dot is investigated under resonant excitation, where the same splitting ratio is observed. An autocorrelation measurement with an off-chip beamsplitter on a single output arm reveal the single-photon nature after evanescent coupling inside the on-chip splitter. Due to their robustness, adjustable splitting ratio, and their easy implementation, rib waveguide beamsplitters with embedded quantum dots provide a promising step towards fully integrated quantum circuits.

Experimental generation of squeezed cat States with an operation allowing iterative growth.

We present what is, to our knowledge, the first implementation of a "cat breeding" operation, which allows an iterative growth of cat states. We thus report the experimental generation of a squeezed cat state from two single photon Fock states, which can be seen as cat states with zero amplitude. These Fock states are mixed on a symmetrical beam splitter, and the generation is heralded by a homodyne measurement in one of the two output arms. The output state has a fidelity of 61% with an even squeezed cat state of amplitude α=1.63. This hybrid operation opens up new prospects in quantum optics, as the protocol depicted here can be iterated in order to produce new kinds of mesoscopic states.

Simultaneous photoacoustic and optically mediated ultrasound microscopy: an in vivo study.

We propose the use of thermoelastic (TE) excitation of an ultrasonic (US) detector by backscattered laser radiation as a means of upgrading a single-modality photoacoustic (PA) microscope to dual-modality PA/US imaging at minimal cost. The upgraded scanning head of our dual-modality microscope consists of a fiber bundle with 14 output arms and a 32MHz polyvinylidene difluoride (PVDF) detector with a 34 MHz bandwidth (-6 dB level), 12.7 mm focal length, and a 0.25 numerical aperture. A single optical pulse delivered through the fiber bundle to the biotissue being investigated, in combination with a metalized surface on the PVDF detector allows us to obtain both PA and US A-scans. To demonstrate the in vivo capabilities of the proposed method we present the results of bimodal imaging of the brain of a newborn rat, a mouse tail and a mouse tumor.

Development of a position sensor based on a four quadrant structured optic fiber bundle

This article reports on the development of a new kind of 2D displacement sensor based on an optic fiber bundle whose fiber arrangement has been customized to provide an input sensitive surface with four quadrants. The fibers of each quadrant are regrouped to form four output arms. The aim is to reach behavior similar to that of a quad cell photodiode when illuminated by a laser spot. In this paper, we present the motivations for developing such a sensor and its design. Prior to the fabrication of a first prototype, the optic fiber bundle has been modelled and compared to a quad cell photodiode. It has an active surface which is 10 mm in diameter and which comprises 40 000 fibers of 50 µm core diameter. For this experimental test, a specific electronic conditioning circuit has been developed to process the signals. From both modelled and experimental results, fiber optic bundle and quad cell photodiode behavior has proved to be very similar, provided that the number of fibers is sufficient to achieve a statistical effect on the detected displacement, i.e. the laser spot diameter is rightly chosen as a function of the fiber diameter. For the use of the bundle as position sensor, a laser spot size of 5 mm has been fixed to achieve a good compromise between sensitivity and displacement range. With this spot size, sensitivity and displacement range have been experimentally evaluated to 2 mV µm−1 and 3.8 mm respectively with a corresponding displacement resolution of 5 nm in the best case.

Cross Junction Spin Wave Logic Architecture

Backward volume magnetostatic spin wave interference in ferromagnetic cross is explored. Spin waves are excited at the two input arms of the cross, interference signal amplitude, and phase are detected in the other two, output arms of the cross. Spin wave scattering defines the out of phase interference in the output arms of the cross: the constructive (destructive) interference is observed at different input wave phase shifts in different output arms of the cross. Numeric simulations are in a good agreement with experiment. Based on the observed interference, we propose the cross junction spin wave logic device that operates as an OR or NOR logic gates. Spin wave phase represents the logic information. Destructive and constructive interference in the cross center determines the phase of the device output.

Concurrent Dualband Diplexer for Nanoscale Wireless Links

This letter reports the design and full wave analysis of a compact and low-loss filter-based concurrent dualband diplexer for high-density multiband photonic integrated circuits. The proposed diplexer consists of a chamfered T-junction in nanoplasmonic metal-insulator-metal waveguide and two bandpass filters (BPF) inserted in the two output arms. Plasmonic BPF have been designed using stepped width resonator. These filters are concurrently operating at 1427-/1665-nm and 1355-/1595-nm wavelength. The optimized chamfered T-junction has return loss >8 dB, whereas insertion loss of each dualband BPF is <;5 dB.

High Power CW Testing of 3.7-GHz Klystron for SST1 LHCD System

A 3.7-GHz lower hybrid current drive (LHCD) system has been designed and installed for driving noninductive plasma current for steady-state operation of steady-state super-conducting tokamak-1 machine. Currently, its capability has been enhanced up to 2 MW by adding two additional klystrons, each capable of providing 500 kW, continuous wave (CW) power, to LHCD system. After performing factory acceptance test of these klystrons, they are installed and commissioned at site, at rated power, for more than 1000 s, before connecting them to main LHCD system. The auxiliary systems like supporting power supply system (magnet, filament, ion pump, etc.), active heat management system, protection system, transmission line pressurization system, low power RF drive system, and so on are interconnected with klystron system through versa module europa (VME)-based data acquisition and control system for remote CW operation of klystron at rated power. The klystron is protected by fast interlock protection in an event of arc or an electrical parameters excursion beyond a set window. The slow interlock is invoked in case of cooling failures, pressurization of waveguides, and so on. The klystron has two output arms and a recombiner is used to recombine power coming out from both the arms. The output power from the recombiner of the klystron is split into two arms, employing 3-dB power divider. This reduces the high power requirement of water dummy loads (DLs) to 250-kW CW. A directional coupler is included in both the arms for measuring forward and reflected power. The reflected power signal is fed to low power RF drive control, which removes the RF drive once reflected power beyond a threshold power is detected within 5 μs. The forward power signal is used for monitoring RF power being dumped into the water loads. The calorimetric measurements, employing Pt-100 sensors, are also carried out on water dummy loads. Our measurements suggest that the maximum RF power ( ~500-kW CW) extracted from klystron is dissipated on water cooled DLs. The unspent dc power ( ~800-kW CW) is dissipated in the collector that is heavily cooled with water flowing at ~1300 L/min. The power loss in the klystron body remained within 15 kW. The cavity temperature, measured using J-type thermocouple, remained below 150 °C. The output RF power, sampled through directional couplers and measured by RF detectors shows good agreement with calorimetric measurements. A detailed description of the klystron test setup and the test results obtained during its commissioning is presented in this paper.

A 94-GHz planar orthogonal mode transducer

The orthogonal LSM10and TE10modes that are supported by the image SINRD (iSINRD) guide andsubstrate integrated waveguide(SIW) is exploited to develop a planar millimeter-wave hybrid orthogonal-mode transducer (OMT) within the same dielectric substrate. The two output arms are iSINRD guide and an SIW. The proposed co-layered planar OMT belongs to a narrowband acute angle class. The design process is explained and measurements at 94 GHz are presented. No septa or step changes in thickness are required. Both modes are excited using WR10 transitions, where the transition of one mode is orthogonal to the other. Therefore, the OMT is fabricated as a back-to-back 4-port OMT; two inputs and two outputs for each mode respectively. The lateral dimensions of all guiding arms are 0.6 × 0.635 mm2. An insertion loss of around 1.2 dB is obtained for both LSM10and TE10modes, while isolation better than 17 dB is obtained for both modes (30 dB for the LSM10mode).

Correlations, indistinguishability and entanglement in Hong–Ou–Mandel experiments at microwave frequencies

Interference at a beam splitter reveals both classical and quantum properties of electromagnetic radiation. When two indistinguishable single photons impinge at the two inputs of a beam splitter they coalesce into a pair of photons appearing in either one of its two outputs. This effect is due to the bosonic nature of photons and was first experimentally observed by Hong, Ou, and Mandel (HOM) [1]. Here, we present the observation of the HOM effect with two independent single-photon sources in the microwave frequency domain. We probe the indistinguishability of single photons, created with a controllable delay, in time-resolved second-order cross- and auto-correlation function measurements. Using quadrature amplitude detection we are able to resolve different photon numbers and detect coherence in and between the output arms. This measurement scheme allows us to observe the HOM effect and, in addition, to fully characterize the two-mode entanglement of the spatially separated beam splitter output modes. Our experiments constitute a first step towards using two-photon interference at microwave frequencies for quantum communication and information processing, e.g. for distributing entanglement between nodes of a quantum network [2, 3] and for linear optics quantum computation [4, 5].

Design of mode-sorting asymmetric Y-junctions

The theory of mode-sorting in bimodal asymmetric Y-junctions is extended to multimode asymmetric Y-junctions with multiple output arms. This theory allows for the optimization of these mode-sorting planar structures. Asymmetric Y-junctions provide unique opportunities for spatial mode division multiplexing (MDM) of optical fiber. Spatial MDM is considered paramount to overcoming the bandwidth limitations of single-mode fiber. The design criteria presented in this paper facilitate their design.