法拉第镜旋转角的偏振分束测量法

提出了基于偏振分束法的法拉第镜偏振旋转角的测量方法.利用非偏振分束器改变法拉第镜出射光的方向,偏振分束器将该出射光分为p光和s光,分别测量其光强,应用后续"差除和"信号处理方案消除光源波动的影响,推导出法拉第镜偏振旋转角的理论表达式.分析了起偏器的消光比非0及起偏角误差对输出结果的影响,分别是0.057 29°和-0.100 0°.实验验证了该方法的可行性,重复测量结果为89.68°,均方值为0.014 93.     

Implications of mirror dark matter kinetic mixing for CMB anisotropies

Mirror dark matter is a dissipative and self-interacting multiparticle dark matter candidate which can explain the DAMA, CoGeNT and CRESST-II direct detection experiments. This explanation requires photon–mirror photon kinetic mixing of strength ?∼10⁻⁹$?\sim {10}^{-9}$. Mirror dark matter with such kinetic mixing can potentially leave distinctive signatures on the CMB anisotropy spectrum. We show that the most important effect of kinetic mixing on the CMB anisotropies is the suppression of the height of the third and higher odd peaks. If ??10⁻⁹$??{10}^{-9}$ then this feature can be observed by the PLANCK mission in the near future.     

Short optical pulse profile characterization using a nonlinear optical loop mirror

We propose in this work a technique for short pulse profile retrieval based on the Kerr effect in a fiber nonlinear optical loop mirror (NOLM). Under some assumptions, the profile can be determined from the energy transfer characteristic of the pulses through the NOLM, which can be measured with a low-frequency detection setup. Two numerical approaches are considered, both relying on the resolution of a system of nonlinear algebraic equations, and which differ in the way that the profiles are discretized. We show numerically that both approaches allow proper profile retrieval for a wide variety of pulse shapes. The two techniques are compared, and their advantages and drawbacks are discussed. The effect of the amplitude noise of the pulses is assessed, as well as the impact of an inaccurate knowledge of the NOLM transfer function, or of the energy transfer characteristic. The technique is demonstrated in the frame of the characterization of both ns and ps pulses.     

Demonstration of a simple entangling optical gate and its use in bell-state analysis

We demonstrate a new architecture for an optical entangling gate that is significantly simpler than previous realizations, using partially polarizing beam splitters so that only a single optical mode-matching condition is required. We demonstrate operation of a controlled-z gate in both continuous-wave and pulsed regimes of operation, fully characterizing it in each case using quantum process tomography. We also demonstrate a fully resolving, nondeterministic optical Bell-state analyzer based on this controlled-z gate. This new architecture is ideally suited to guided optics implementations of optical gates.     

Single atom as a mirror of an optical cavity

By tightly focusing a laser field onto a single cold ion trapped in front of a far-distant dielectric mirror, we could observe a quantum electrodynamic effect whereby the ion behaves as the optical mirror of a Fabry-Pérot cavity. We show that the amplitude of the laser field is significantly altered due to a modification of the electromagnetic mode structure around the atom in a novel regime in which the laser intensity is already changed by the atom alone. We propose a direct application of this system as a quantum memory for single photons.     

The filtering behavior of cesium Faraday optical filter

In this paper we investigated cesium Faraday filter at 852 nm in the relatively weak and strong magnetic field theoretically and experimentally. With a cesium cell of 0.02 m in length in an axial magnetic field of 0.06 T, the line-center operation has been achieved. The calculated peak transmission has reached 98.6% with a FWHM bandwidth of only 3.9 GHz, the measured FWHM bandwidth of the filter is 3.29 GHz, which is general agreement with the theoretical result.     

Endoscopic optical coherence tomography based on a microelectromechanical mirror

An endoscopic optical coherence tomography (OCT) system based on a microelectromechanical mirror to facilitate lateral light scanning is described. The front-view OCT scope, adapted to the instrument channel of a commercial endoscopic sheath, allows real-time cross-sectional imaging of living biological tissue via direct endoscopic visual guidance. The transverse and axial resolutions of the OCT scope are roughly 20 and 10.2mum, respectively. Cross-sectional images of 500x1000 pixels covering an area of 2.9 mmx2.8 mm can be acquired at ~5 frames/s and with nearly 100-dB dynamic range. Applications in thickness measurement and bladder tissue imaging are demonstrated.     

Microfabricated surface ion trap on a high-finesse optical mirror

A novel approach to optics integration in ion traps is demonstrated based on a surface electrode ion trap that is microfabricated on top of a dielectric mirror. Additional optical losses due to fabrication are found to be as low as 80 ppm for light at 422 nm. The integrated mirror is used to demonstrate light collection from, and imaging of, a single Sr88(+) ion trapped 169±4 μm above the mirror.     

Multiple optical Tamm states at a metal-dielectric mirror interface

The reflectivity map is theoretically investigated by applying the transfer matrix method in a metal-dielectric mirror structure at normal incidence. The existence of multiple optical Tamm states (OTSs) is demonstrated in this structure. It is found that an OTS is periodic resonance with the variation of the top-layer thickness of the dielectric mirror for a given wavelength. The energy for the corresponding OTS mainly depends on the thickness of the top layer. The appropriate thicknesses of metal film are proposed for the convenient observation of OTSs. This work may be useful in designing a new type of multichannel filter in optical communication systems.     

利用离轴三反镜光学系统确定各镜的装调公差

利用条纹泽尼克系数与赛德尔像差的关系,在三反镜光学系统的出瞳面上,用条纹泽尼克系数来表示系统的波像差。通过光学设计软件Zemax计算得到三反镜光学系统各镜的装调公差,以公差要求高的镜面作为装调基面,从而减少要调整的自由度。通过分析泽尼克(Zernike)系数在公差范围内的变化幅度来确定光学系统在出瞳面上各个像差的变化幅度,用该幅度的变化量来决定主次三镜各自由度在各个方向上的敏感度,最终确定各个自由度的优化调整级别。对一大口径无遮拦离轴三反镜光学系统进行了装调,在波长λ=632.8nm的条件下进行了检测。结果表明:整个光学系统全视场波前误差的均方根值RMS=0.108λ。     

Signal-to-noise ratio improvement of a supercontinuum continuous-wave optical source using a dispersion-imbalanced nonlinear optical loop mirror

A multiwavelength continuous-wave (cw) optical source is based on supercontinuum (sc) produced in a highly nonlinear fiber. Noise properties of this optical source are studied through numerical simulations based on the nonlinear Schrödinger equation. The numerical simulations show that the amplified spontaneous emission (ASE) generation in an erbium-doped fiber amplifier and the ASE amplification during the sc generation result in a serious degradation of the signal-to-noise ratio (SNR). A novel scheme for improvement of the SNR of the multiwavelength cw optical source based on sc by using a dispersion-imbalanced nonlinear optical loop mirror is presented and the numerical simulation results are given. As a result, the average level of the SNR improvement is 11 dB and the eye-opening penalty is reduced by 0.91 dB due to the SNR improvement. In addition, the scheme can also be applied for improvement of the SNR of a pulse-type multiwavelength light source. PACS 42.50.Lc; 42.65.Re; 42.79.Sz; 02.60.Cb     

Multiwavelength erbium-doped fiber laser employing a nonlinear optical loop mirror

A stable and broad bandwidth multiwavelength erbium-doped fiber laser is proposed and demonstrated successfully. A nonlinear optical loop mirror which induces wavelength-dependent cavity loss and behaves as an amplitude equalizer is employed to ensure stable room-temperature multiwavelength operation. Up to 50 wavelengths lasing oscillations with wavelength spacing of 0.8 nm within a 3-dB spectral range of 1562-1605 nm has been achieved. The measured power fluctuation of each wavelength is about 0.1 dB within a 2-h period.     

Soliton squeezing in a highly transmissive nonlinear optical loop mirror

A perturbation approach is used to study the quantum noise of optical solitons in an asymmetric fiber Sagnac interferometer (a highly transmissive nonlinear optical loop mirror). Analytical expressions for the three second-order quadrature correlators are derived and used to predict the amount of detectable amplitude squeezing along with the optimum power-splitting ratio of the Sagnac interferometer. We find that it is the number-phase correlation owing to the Kerr nonlinearity that is primarily responsible for the observable noise reduction. The group-velocity dispersion affecting the field in the nonsoliton arm of the fiber interferometer is shown to limit the minimum achievable Fano factor.     

Scanning mirror on a vibrating membrane for dynamic optical trapping

A study of the variation of the spectral shape and the harmonic distribution of the high-order harmonics generated from silver plasma on the frequency chirp of the driving laser radiation (793 nm 48 fs) is reported. The results of the systematic study of the harmonic generation from the 21st order up to the 61st order (λ=13 nm) are presented. A tuning of the harmonic wavelength up to 0.8 nm can be accomplished by variation of the laser chirp. PACS 42.65.Ky; 42.79.Nv; 52.38.Mf     

Hexagonal optical structures in photorefractive crystals with a feedback mirror

A nonlinear theory is presented for the formation of hexagonal optical structures in a photorefractive medium equipped with a feedback mirror. Oppositely directed beams in photorefractive crystals are unstable against the excitation of sideband waves. It is shown here that as this instability evolves to its nonlinear stage, the three-wave interaction between weak sideband beams does not stabilize it, but rather leads to explosive growth of the amplitudes of beams whose transverse wave vectors form angles that are multiples of π/3. As a result, sideband beams at these angles are found to be correlated. A range of parameters is found in which four-wave interactions saturate the explosive instability, which explains the appearance of stable hexagons in the experiment. Outside this region, nonlinearities of higher order saturate the explosive instability, and the process of hexagon generation must be studied numerically. Matrix elements are obtained for the three-and four-wave interactions as functions of the distance to the feedback mirror, and an equation for the time evolution of the sideband wave amplitudes is derived that describes the hexagon generation. A comparison is made with experimental results for the photorefractive crystals KNbO₃ and BaTiO₃. Zh. éksp. Teor. Fiz. 113, 1122–1146 (March 1998)     

Cancellation of laser dither modulation from optical frequency standards

We demonstrate the removal of the dither modulation from an iodine-stabilized He-Ne laser by using a frequency-modulated acousto-optic modulator and feed-forward techniques. This procedure reduces the linewidth of the beat between this laser and a flywheel He-Ne laser from 6 MHz to 8 kHz, the undithered beat linewidth being ~7 kHz. Dither suppression greatly reduces counter errors during beat measurements from stroboscopic effects between the counter's gate and the frequency of the dither modulation and increases the utility of the already formidable array of dithered laser frequency standards by making locking to them an easier task.     

Anisotropy of optical activity and Faraday effect in TeO2

The tensor of optical activity of TeO₂ was derived with the aid of measurements of the Faraday effect. This technique allows the separation of gyrative effects in crystals having a large birefringence. The natural activity of TeO₂ perpendicular to the fourfold axis is by about a factor two larger than along this axis. The sign of the tensorial components is related to structural details.Dedicated to Prof. Dr. S. Haussühl on his 65th birthday     

Common-path double-pass optical interferometry using a wire-grid polarizer as a reference mirror

A novel common-path double-pass optical interferometer that employs a wire-grid polarizer (WGP) as a reference mirror is presented. When a laser beam polarized at 45° relative to the wire grid is incident on the WGP, the polarization component parallel to the grid direction (s-polarized beam) is reflected and is used as a reference beam. The perpendicular component (p-polarized beam) passes through the WGP coupled with a quarter-wave plate and serves as a probe beam, with its polarization transformed as p, right-circular, s, left-circular, and p, to irradiate the sample surface twice in order to double the phase change due to displacement of the sample. This beam is then retransmitted through the WGP, where it recombines and interferes with the reference beam. Preliminary experiments demonstrate that the WGP performs successfully as a reference mirror, and that the interferometer has a potential displacement sensitivity as low as 0.1 nm.     

Cancellation of stark shifts in optical lattice clocks by use of pulsed Raman and electromagnetically induced transparency techniques

We propose a combination of electromagnetically induced transparency-Raman and pulsed spectroscopy techniques to accurately cancel frequency shifts arising from electromagnetically induced transparency fields in forbidden optical clock transitions of alkaline earth atoms. At appropriate detunings, time-separated laser pulses are designed to trap atoms in coherent superpositions while eliminating off-resonance ac Stark contributions, achieving efficient population transfer up to 60% with inaccuracy <10(-17). Results from the wave-function formalism are confirmed by the density matrix approach.