Propagation Loss Effects Research Articles

Phase-insensitive amplifier gain estimation at Cramér-Rao bound for two-mode squeezed state of light.

Phase-insensitive amplifiers (PIAs), as a class of important quantum devices, have found significant applications in the subtle manipulation of multiple quantum correlation and multipartite quantum entanglement. Gain is a very important parameter for quantifying the performance of a PIA. Its absolute value can be defined as the ratio of the output light beam power to the input light beam power, while its estimation precision has not been extensively investigated yet. Therefore, in this work, we theoretically study the estimation precision from the vacuum two-mode squeezed state (TMSS), the estimation precision of the coherent state, and the bright TMSS scenario, which has the following two advantages: it has more probe photons than the vacuum TMSS and higher estimation precision than the coherent state. The advantage in terms of estimation precision of the bright TMSS compared with the coherent state is researched. We first simulate the effect of noise from another PIA with gain M on the estimation precision of the bright TMSS, and we find that a scheme in which the PIA is placed in the auxiliary light beam path is more robust than two other schemes. Then, a fictitious beam splitter with transmission T is used to simulate the noise effects of propagation loss and imperfect detection, and the results show that a scheme in which the fictitious beam splitter is placed before the original PIA in the probe light beam path is the most robust. Finally, optimal intensity difference measurement is confirmed to be an accessible experimental technique to saturate estimation precision of the bright TMSS. Therefore, our present study opens a new avenue for quantum metrology based on PIAs.

Photon-pair generation in a lossy waveguide

Abstract An on-chip quantum light source based on spontaneous four-wave mixing is an essential element for developing quantum photonic integrated circuit technology, which has the advantage of no connection loss owing to the integration of the source into photonic circuits. The waveguide-based quantum light source inevitably causes propagation loss owing to imperfections in the fabrication process, but the propagation loss effects on photon-pair generation have not been extensively studied. In this study, propagation loss effects were examined using theoretical and experimental methods. In theory, the performance of quantum light sources, such as brightness, heralding efficiency, and coincidence-to-accidental ratio, strongly depend on propagation loss. We fabricate several waveguides with a moderate propagation loss of 2.2 dB/cm to investigate the loss dependence and ascertain that the brightness, heralding efficiency, and coincidence-to-accident ratio strongly correlate with the length of the optical waveguide. The maximum coincidence-count brightness occurred at an optimization length of 1/α, where α is the absorption coefficient. In contrast, the single-count brightness shows slightly different waveguide length dependence owing to loss-induced one-photon states. We expect that the results obtained in this study will greatly assist in determining the proper waveguide length for photon-pair generation according to the source’s application fields. The results will be helpful in the development of a quantum light source suitable for practical and quantum optical integrated circuits and will lead to the development of high-fidelity quantum technologies.

Spin angular momentum of surface modes from the perspective of optical power flow.

We show that the spin angular momentum (SAM) carried by a surface mode can be linked to the expectation value, with respect to the distribution of optical power flow, of its decay constant by itself or divided by the product of permittivity and permeability of the medium. Rewriting the formulas for the SAM of a surface mode using the relation between the SAM density and the Poynting vector and then normalizing the light field so that the surface mode carries unit power, we derive novel formulas that show the linear relation between the SAM and those expectation values. The effect of propagation loss is also discussed briefly.

Rigorous evaluation of propagation losses in arbitrarily shaped waveguide structures using boundary integral – resonant mode expansion and perturbation of boundary conditions

The accurate consideration of propagation losses in arbitrarily shaped waveguide-based structures is studied in this paper. For such a purpose, a software tool based on the perturbation of the boundary conditions on the waveguide metallic walls and on the boundary integral – resonant mode expansion method has been developed. To show the advantages of the proposed technique with respect to the classic power-loss method, the complex propagation wavenumbers of a double ridge and an elliptical waveguide have been first computed and compared with results of a commercial software based on the finite element technique. Next a circular, a sectorial shaped and a triangular shaped waveguide have been considered. Then, a computer-aided design software package based on this modal analysis tool has been applied to predict the propagation loss effects in complex waveguide structures, such as an evanescent mode ridge waveguide filter, a traditional dual mode filter with circular cavities and a twist component for K-band applications.

Improved Computation of Propagation Losses in Waveguide Structures Using Perturbation of Boundary Conditions

In this letter, a method for the improved consideration of propagation losses in metallic waveguide structures is presented. The method relies on the perturbation of the boundary conditions on the metallic walls of the waveguides. Following this advanced technique, we are able to compute a complex modal propagation constant, thus avoiding the drawbacks of the classical power-loss method where losses associated to evanescent modes were not taken into account. A Computer Aided Design (CAD) software package based on such a modal analysis tool has been applied to predict the propagation loss effects in a Ka-Band rectangular waveguide filter.

亚毫米尺度对称金属包覆波导中传输损耗的抑制

亚毫米尺度对称金属包覆波导中传输损耗的抑制

Sensor based on extending the concept of fidelity to classical waves

We propose and demonstrate a remote sensor scheme by applying the quantum mechanical concept of fidelity loss to classical waves. The sensor makes explicit use of time-reversal invariance and spatial reciprocity in a wave chaotic system to sensitively and remotely measure the presence of small perturbations. The loss of fidelity is measured through a classical wave analog of the Loschmidt echo by employing a single-channel time-reversal mirror to rebroadcast a probe signal into the perturbed system. We also introduce the use of exponential amplification of the probe signal to partially overcome the effects of propagation losses and to vary the sensitivity.

Quality factor and finesse optimization in buried InGaAsP/InP ring resonators

Quality factor and finesse of buried In1-xGaxAsyP1-y / InP ring resonators have been optimized in this paper by a very general modelling technique. Limiting effect of propagation loss within the ring has been investigated using a three-dimensional (3D) highly accurate complex mode solver based on mode matching method to analyze bending loss dependence on ring radius and wavelength. Coupling between straight input/output (I/O) bus waveguides and ring resonator has been studied by 3D Beam Propagation Method (BPM), deriving coupling loss and coupling coefficient for a large range of ring radius and bus waveguides-ring distance values (for both polarizations). Ring resonator has been modelled by the transfer-matrix approach, while finesse and quality factor dependence on radius has been estimated for two resonator architectures (including one or two I/O bus waveguides) and for quasi-TE and quasi-TM modes. Guiding structure has been optimized to enhance resonator performance. The modelling approach has been validated by comparing results obtained by our algorithm with experimental data reported in literature. Influence of rejection (at resonance wavelength) at through port on quality factor and finesse has been widely discussed. A quality factor larger than 8 x 105 has been predicted for the ring resonator employing only one I/O bus waveguide and having a radius of 400 μm. This resonator exhibits a rejection of -8 dB at through port.

Performance Analysis of Wireless Networks With Directional Antennas

In this paper, we consider wireless networks with directional antennas using slotted ALOHA medium access control. The channel model incorporates the effects of propagation loss and shadowing with Rayleigh fading. By deriving the cumulative distribution function of the signal-to-interference-and-noise ratio (SINR) of a certain link in the network, the outage probability of the link is analyzed. In particular, the analysis works for the arbitrary beam patterns of the directional antennas used in the networks. Moreover, we propose a new parameter, i.e., the array interference factor, which can characterize the average performance of an arbitrary beam pattern in random wireless networks. This provides an efficient way for designers to evaluate the system performance under different beam patterns. The network throughput and the transport capacity of a random wireless network with directional antennas are also analyzed. It is shown that the network transport capacity is of the same order as the square root of the node density, which conforms with the well-known capacity of wireless networks. The analysis is useful for designers to optimize the system performance of wireless networks with directional antennas.

Analysis of the frequency response of a dispersive IDT/ZnO/sapphire SAW filter using effective permittivity and the coupling of modes model

In this paper, we propose a modified coupling of modes (COM) approach, which can be used in the practical design of a layered surface acoustic wave (SAW) filter. Unlike the half-space SAW filter, frequency dependences of the COM parameters are included by using the effective permittivity approach of surface waves. Owing to the introduction of the COM model, the effects of propagation loss, electrode reflections, electrical transduction, acoustic reception, thin film loss and the distributed finger capacitance can be taken into accounts in the frequency analysis of the layered SAW filter. The frequency response of a two-port 440 MHz IDT/ZnO/R-plane sapphire layered SAW filter is analysed and compared with the existing experimental results. Results have shown good agreement between the calculated and experimental frequency responses.

Optical frequency conversions in nonlinear medium with periodically modulated linear and nonlinear optical parameters

A new method considering both linear and nonlinear optical parameter modulation and propagation loss is proposed to treat second-order nonlinear optical interactions in nonlinear media having periodic structures. Mathematical expressions are derived for difference frequency generation (DFG) and compared with those for second-harmonic generation (SHG). Wavelength conversions around 1.55 /spl mu/m, which are very interesting in optical communication systems, are studied for semiconductor DFG devices with periodic structures. Semiconductor (e.g., AlGaAs) DFG devices of standard device lengths (several mm) and pump light intensities (10/sup 5/ kW/cm/sup 2/) are shown capable of practical level conversion efficiencies (/spl sim/10%) and extremely wide bandwidths (/spl ges/100 nm). Effects of propagation loss in DFG devices are also examined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Pressure ridging spectrum level and a proposed origin of the infrasonic peak in arctic ambient noise spectra

Evidence is presented that the infrasonic peak observed in the 10- to 20-Hz region in Arctic ambient noise spectra may result from a combination of the source spectrum of pressure ridging and the effects of propagation loss on this spectrum. This peak has been attributed to a hypothetical source spectrum but may also be explained by a minimum in the propagation loss. The received spectral level of a nearby active pressure ridge was measured to be monotonously decreasing (from 2–200 Hz), while both measurements and modeling studies indicate a minimum in propagation loss versus frequency near 30 Hz. When the propagation loss effects are included, the resulting spectra of either a single event at a range of tens of kilometers or a distribution of events separated by tens of kilometers resembles the broad infrasonic peak found in the ambient noise.

Pressure ridging source spectrum level and a proposed origin of the 20-Hz peak in Arctic ambient noise spectra.

This paper presents evidence that the origin of the low-frequency peak (10–20 Hz) observed in Arctic ambient noise spectra may result from a combination of the source spectrum of pressure ridging and the effects of propagation loss on this spectrum. This peak is often attributed to a hypothetical source spectrum but may also be explained by a minimum in the propagation loss. This paper shows that both measurements and modeling studies indicate a minimum in propagation loss versus frequency near 30 Hz. When combined with the measured spectrum of a nearby forming pressure ridge, a ridging event at 60-km range results in a broadband peak at approximately 20 Hz. a)Also at Defense Research Establishment Pacific.

A planar waveguide analysis of the mode extinction modulator in LiNbO&amp;lt;inf&amp;gt;3&amp;lt;/inf&amp;gt;

An analysis of the mode extinction modulator is reported based on a step index planar waveguide model. Three modulation mechanisms, the propagation loss, the coupling loss, and the radiative transfer, have been shown to have a significant influence on the transfer function shape and the performance characteristics of the device. The propagation loss effect is shown to play a dominant role in device efficiency and linearity. The operating point of the device can be selected by the choice of physical parameters without the use of a dc bias voltage. Verification of the modulation mechanisms has been demonstrated experimentally.

Investigation of an Equivalent Circuit Including Propagation Loss for an Interdigital Surface-Acoustic-Wave Transducer

An equivalent circuit for an interdigital surface-acoustic-wave transducer (IDT), in which the propagation loss is taken into account, is investigated. From this circuit, the three-port admittance parameter Yij for the IDT having N-pair electrodes is derived in closed form. In the derivation, the image parameter theory is applied. Using this Yij in explicit expression, the driving-point admittance for an IDT is analyzed, and the effect of propagation loss on the radiation admittance is investigated.

Improved mode extinction modulator using a Ti in-diffused LiNbO3 channel waveguide

An efficient, linear mode extinction modulator has been demonstrated using a weakly guided, near cutoff, channel waveguide. Modulation slopes as high as 16% per volt have been measured. Deviation from a linear voltage-intensity relationship of less than 1% has been observed over a 77% modulation range. Over 97% modulation has been achieved with ±4 V applied. An optical bias is also demonstrated. A coupled mode analysis for the modulator is reported which includes propagation loss effects.

Fundamental Performance Characteristics That Influence EHF MILSATCOM Systems

As technology advances, satellite communications traffic is required to support both civil and military, current, and projected needs. These needs can sometimes be better satisfied if the communication system operates in the EHF band as opposed to the SHF or lower frequency bands. This paper addresses those factors that are of considerable interest to the system designer. In particular, the candidate frequency bands are placed in evidence; then the effects of propagation losses, orbit parameters, terminal antenna gain limitations, EIRP, and low probability of intercept are considered.

A Method for Selection of an Optimum Communication Link

A method is presented for the selection of a communication system based upon optimization of both frequency-dependent and frequency independent parameters. The indicator of quality used is the effective radiated power per cycle per second of information bandwidth. The method involves consideration of the frequency-dependent qualities such as system temperature and propagation losses independently from the frequency-independent quantities such as modulation loss, signal-to-noise ratio, performance margin, etc. Except for temperature and propagation loss effects, the method is made frequency-independent by considering the spacecraft antenna in terms of area while the ground terminal antenna is treated in terms of gain, thus removing wavelength from the transmission equation. An example is presented of the application of the method to the selection of a system for transmission of wide-band video signals over a satellite to earth link. The example illustrates the exchanges that can be made between the frequency-dependent and -independent quantities in order to arrive at an optimum system.