Polarization-dependent Phase Shift Research Articles

Spectrally resolved polarization angle across the motional Stark effect spectrum.

A new diagnostic technique has been developed that couples a spectrometer and an image-intensified camera into the traditional motional Stark effect (MSE) system on DIII-D. The image-intensified camera syncs with the photo-elastic modulators to spectrally resolve the Stokes parameters across the Stark multiplet. Polarization dependent phase shift, likely from a plasma facing mirror, leads to the spectropolarimeter measuring a variation in the polarization angle across the MSE spectrum of ∼8°.

Effect of inhomogeneous Dzyaloshinskii-Moriya interaction on antiferromagnetic spin-wave propagation

We investigate the effect of inhomogeneous Dzyaloshinskii-Moriya interaction (DMI) on antiferromagnetic spin-wave propagation theoretically and numerically. We find that antiferromagnetic spin waves can be amplified at a boundary where the DMI varies. The inhomogeneous DMI also provides a way to construct a magnonic crystal with forbidden and allowed antiferromagnetic spin-wave bands in terahertz frequency ranges. In contrast to ferromagnetic spin waves, antiferromagnetic spin waves experience a polarization-dependent phase shift when passing through the inhomogeneous DMI, offering a magnonic crystal that also serves as a spin-wave polarizer.

Adjustable dispersion reduction in low-coherent techniques by a system of tilted metallic mirrors with dielectric coating

In this paper a new method for adjustable reduction of a dispersive drop in axial resolution during low-coherent measurements is presented. This method is based on multiple reflections of a light beam from dielectric coated metallic mirrors and is intended for reducing dispersion in full-field systems. The tilted metallic mirror with a dielectric coating works like an adjustable Gires–Tournois interferometer. The concept of adjustability is based on a polarization dependent phase shift upon reflection from metallic surfaces at incidence angles different from θi=0°. The dispersion compensation was simulated numerically with the use of Fresnel equations for a silver mirror based compensator. The possibility of dispersion reduction was then verified experimentally in a Twyman–Green interferometer showing over 40% improvement in the axial resolution.

Analysis of experimental error sources in a linear-optics quantum gate

Possible error sources in an experimentally realized linear-optics controlled-Z gate (Okamoto et al 2005 Phys. Rev. Lett. 95 210506) are analyzed by considering the deviations of the beam splitting ratios from the ideal values (δRH, δRV), the polarization-dependent phase shift (birefringence) of the optical components (δϕ) and the mode mismatch of input photons (δξ). It is found that the error rate is linearly dependent on δRV and δξ, while the dependence on δRH and δϕ is approximately quadratic. As a practical result, the gate is much more sensitive to small errors in RV than in RH. Specifically, the reflectivity error for vertical polarization must be less than 0.1% to realize a gate with an error of less than 0.1%, whereas the reflectivity error for horizontal polarization can be up to 1%. It is also shown that the effects of different error sources are not independent of each other (linear error model). Under certain conditions, the deviation from the linear error model exceeds 10% of the total error. The method of analysis used illustrates the basic features of errors in general linear optics quantum gates and circuits, and can easily be adapted to any other device of this type.

Compact and Athermal DQPSK Demodulator with Silica-Based Planar Lightwave Circuit

We present a full description of a polarization-independent athermal differential quadrature phase shift keying (DQPSK) demodulator that employs silica-based planar lightwave circuit (PLC) technology. Silica-based PLC DQPSK demodulator has good characteristics including low polarization dependence, mass producibility, etc. However delay line interferometer (DLI) of demodulator had the large temperature dependence of its optical characteristics, so it required large power consumption to stabilize the chip temperature by the thermo-electric cooler (TEC). We previously made a quick report about an athermal DLI to reduce a power consumption by removing the TEC. In this paper, we focus on the details of the design and the fabrication method we used to achieve the athermal characteristics, and we describe the thermal stability of the signal demodulation and the reliability of our demodulator. We described two athermalization methods; the athermalization of the transmission spectrum and the athermalization of the polarization property. These methods were successfully demonstrated with keeping a high extinction ratio and a small footprint by introducing a novel interwoven DLI configuration. This configuration can also limit the degradation of the polarization dependent phase shift (PDf) to less than 1/10 that with the conventional configuration when the phase shifters on the waveguide are driven. We used our demodulator and examined its demodulation performance for a 43Gbit/s DQPSK signal. We also verified its long-term reliability and thermal stability against the rapid temperature change. As a result, we confirmed that our athermal demodulator performed sufficiently well for use in DQPSK systems.

Poincare Sphere Method for Optimizing the Wavelength Converter Based on Nonlinear Polarization Rotation in Semiconductor Optical Amplifiers

We present a Poincare sphere (PS) model to optimize the wavelength converter (WC) based on nonlinear polarization rotation (NPR) in semiconductor optical amplifiers (SOA). The PS method is applied to describe the variations of ellipticipy angle and azimuth of SOA output state of polarization (SOP) induced by polarization-dependent gain (PDG) and polarization-dependent phase shift, respectively. The theoretical results reveal that the polarization dependence of the linewidth enhancement factor (LEF) and the variation of SOA gain are significant factors for the NPR. The evolutions of output SOP on the PS under quasi-continuum condition have been demonstrated experimentally. The experimental results agree well with our analysis.

Polarization-dependent reflective dispersion relations of photonic crystals for waveplate mirror construction

We have measured the polarization-dependent phase shift imparted to the radiation reflected by a two-dimensional photonic crystal within the band gap spectral region. We show that the relative phase between retroreflected basis polarizations can be large, reaching and exceeding a quarter of a wave in spectral regions of extremely high reflectivity for certain crystals. Using this property, we have directly experimentally demonstrated the operation of a reflective quarter-waveplate. All-dielectric, reflective waveplates could generate new applications involving polarization control

Demonstration of feed-forward control for linear optics quantum computation

One of the main requirements in linear optics quantum computing is the ability to perform single-qubit operations that are controlled by classical information fed forward from the output of single-photon detectors. These operations correspond to predetermined combinations of phase corrections and bit flips that are applied to the postselected output modes of nondeterministic quantum logic devices. Corrections of this kind are required in order to obtain the correct logical output for certain detection events, and their use can increase the overall success probability of the devices. In this paper, we report on the experimental demonstration of the use of this type of feed-forward system to increase the probability of success of a simple nondeterministic quantum logic operation from approximately $\frac{1}{4}$ to $\frac{1}{2}.$ This logic operation involves the use of one target qubit and one ancilla qubit which, in this experiment, are derived from a parametric down-conversion photon pair. Classical information describing the detection of the ancilla photon is fed forward in real time and used to alter the quantum state of the output photon. A fiber-optic delay line is used to store the output photon until a polarization-dependent phase shift can be applied using a high-speed Pockels cell.