85Rb灯对87Rb原子的光抽运

本文对用⁸⁵Rb灯不经滤光泡直接对⁸⁷Rb吸收泡的光抽运作了观测,得到了比传统的用⁸⁷Rb灯经⁸⁵Rb滤光泡对⁸⁷Rb吸收泡进行光抽运更强的基态0—0跃迁共振讯号。并在一定温度下观察到负的共振讯号。到目前为止,还不能对这种负的共振讯号作出解释。同时还测量了共振线宽和光频移。对在⁸⁷Rb原子频标中应用的可能性作了评述。 关键词：     

光抽运实验中的拍频现象

我们用两个频率相近的微波同时作用在⁸⁷Rb气泡中的原子上,在⁸⁵Rb灯的抽运下,观察到了⁸⁷Rb原子基态0—0跃迁共振谱线中的拍频现象,并给予了理论解释。 关键词：     

40K-87Rb原子冷却的半导体激光系统

对⁴⁰K-⁸⁷Rb原子冷却的半导体激光系统提出了一种实验方案，并进行了初步实验.采用三台外腔光栅反馈半导体激光器(ECDL)、四台注入锁定从激光器和一台半导体激光放大器组成激光系统.三台ECDL通过声光调制器产生四束光，分别作为⁴⁰K和⁸⁷Rb原子的冷却光和再抽运光，四束不同频率成分的激光分别注入锁定四台从激光器，然后Rb 冷却光、K冷却光和K再抽运光再同时注入半导体激光放大器进行放大.该装置可同时产生冷却⁴⁰K和⁸⁷Rb原子的冷却光和再抽运光，结构紧凑、工作稳定. 关键词： 简并费米气体 激光器系统 外腔光栅反馈半导体激光器 半导体激光放大器     

强光谱灯抽运87Rb激射器

提出在光谱灯中采用蘑菇形和圆饼形灯泡代替传统的球形灯,运用高功率射频源成功地点燃了这两种灯,并进行了光抽运⁸⁷Rb激射器实验。它们的发射光强分别为球形灯的2.3和2倍,对应激射器最高输出功率的最佳共振泡温度分别升高5和4℃,激射器最高输出功率由-67.5dBm分别提高到-60和-62dBm。实测⁸⁷Rb激射器的短期频率稳定度的改善与输出功率的提高相符合。 关键词：     

39K-87Rb双组分|F=1,mF=-1>态玻色-爱因斯坦凝聚体的实验制备

本文在³⁹K-⁸⁷Rb混合气体的|F=1,mF=-1>态上获得了双组分玻色-爱因斯坦凝聚体(Bose-Einstein condensates,BECs)。由于³⁹K原子气体的背景散射长度是负值,必须利用磁场调节Feshbach共振技术来操控其散射长度,从而实现³⁹K原子气体的有效蒸发冷却。在0～200 G磁场强度范围内,我们分别测量了³⁹K-⁸⁷Rb混合气体的同核和异核Feshbach共振,并确定了它们在|1,-1>态中的散射长度与磁场的对应关系。通过优化³⁹K-⁸⁷Rb混合气体中原子种内和种间的相互作用,进一步比较了在不同磁场区域³⁹K-⁸⁷Rb混合气体的协同蒸发冷却效率。最后,实验上制备出³⁹K-⁸⁷Rb混合气体|1,-1>态的双组分BECs,同时为接下来进一步研究量子液滴等相互作用体系提供了理想的平台...     

一种基于非标准矩形微波腔的铷频标腔泡系统

针对超薄型铷频标应用需求,本文研制了一种基于开槽管腔原理的非标准矩形微波腔.它的厚度仅为12 mm,仿真结果显示其微波场方向因子约为0.9.测量了基于该微波腔设计的腔泡系统的⁸⁷Rb原子双共振跃迁信号,并通过外推法得到铷原子吸收泡内双共振谱线的本征线宽约为452 Hz.在优化后的实验参数下,该腔泡系统散弹噪声对铷频标短期频率稳定度的限制可达到5.2×10^-13τ^-1/2.     

实现玻色-费米混合气体量子简并的四极Ioffe组合磁阱设计

四极Ioffe组合磁阱(QUIC磁阱)是由一对四极线圈和一个Ioffe线圈组合构成的一种Ioffe-Pritchard磁阱,它已广泛应用在囚禁中性原子和实现蒸发冷却原子的实验中.设计了两种不同结构的四极线圈和Ioffe线圈,并对其进行了相应的数值模拟和测试.通过比较获得了一种参数优化的QUIC磁阱,这为QUIC磁阱线圈的优化设计提供了参考.最后在优化的QUIC磁阱中,采用射频蒸发冷却俘获⁸⁷Rb原子,实现了⁸⁷Rb原子气体的玻色-爱因斯坦凝聚,同时采用“共同冷却 关键词： 四极线圈 Ioffe线圈 四极Ioffe线圈组合磁阱 原子冷却     

积分球内的铷原子激光冷却

研究了积分球内激光冷却原理,设计积分球时对积分球的反射率、尺寸及球上开孔大小对于激光冷却的影响进行了讨论. 进行了积分球冷却⁸⁷Rb实验,实验结果表明积分球有效的冷却了球腔中的铷原子,获得了积分球内冷原子的吸收信号以及冷原子随冷却光失谐的变化曲线. 关键词： 漫反射光场 积分球 全光冷却     

多微管阵列结构腔-原子吸收光谱测量Rb同位素比

Rb同位素分析在地质探索和环境监测中具有重要应用价值.本文基于可调谐激光吸收光谱技术,通过热分解的样品处理方式,搭建了一套Rb同位素吸收光谱测量装置,实现了Rb同位素比稳定测量.并通过新型多微管阵列结构设计原子发生器,增强了其原子束准直能力,有效抑制了光谱的多普勒效应,提高Rb同位素光谱分辨率.装置选用钽金属制作6 mm口径的高温原子发生器,内部堆叠1 mm口径微管阵列,发生器经电阻加热最高可达3000℃.实验通过高温(600℃)催化Rb₂CO₃样品释放气态Rb原子,同步利用探测激光通过Rb原子进行测量,获得高分辨率Rb原子吸收光谱,结合谱线参数反演获得自然丰度Rb₂CO₃样品中Rb同位素比(⁸⁵Rb:⁸⁷Rb)为2.441±0.02,探测误差为5.9%,⁸⁷Rb检测极限达1.76‰(3σ).实验结果表明,相较于传统的单管结构,采用多微管阵列结构进行测量时,Rb原子谱线展宽降低了约450 MHz (半高全宽),可有效区分Rb同位素的吸...     

冷原子系综的光学厚度对腔增强量子存储读出效率的影响

本文在⁸⁷Rb冷原子系综中开展了腔增强量子存储,研究了光学厚度对读出效率的影响。我们通过改变冷却光的失谐量得到了原子系综不同的Optical Depth(OD),测量了读出效率随着原子系综光学厚度的变化。结果显示：当冷却光处于负失谐18.5 MHz的情况时,可使冷原子系综的OD达到最大值14,读出效率的增强倍数为1.6倍,本质恢复效率最大可达43.2%。     

Acousto-optic amplitude modulation and demodulation of electromagnetic wave in magnetised diffusive semiconductors

Using hydrodynamical model of semiconductor plasma analytical investigations are made for the amplitude modulation as well as demodulation of an electromagnetic wave in a transversely magnetised acousto-optic semiconducting plasma. The inclusion of carriers diffusion adds new dimension in the analysis presented here. Analysis are made under different wave number regions over a wide range of cyclotron frequency. It has been seen that diffusion of charge carriers modifies amplitude modulation and demodulation processes effectively. Numerical estimations are made for n-InSb crystal irradiated by pump wave of frequency 1.6 T s^-1. Complete absorption of the waves takes place in all the possible wave lengths regimes when the cyclotron frequency becomes exactly equal to (v ² + )^1/2. Received 28 February 2002 Published online 19 July 2002     

Excitation of ion acoustic waves at the difference frequency of two microwave beams in a semiconductor

This letter presents an investigation of the resonant excitation of the electrostatic ion acoustic wave at the difference frequency of two microwave beams in a semiconductor, viz., n-type InSb. The ponderomotive force at the difference frequency on electrons drives the ion acoustic wave at the difference frequency. The resonance conditions are satisfied over a wide range of semiconductor parameters. For typical plasma parameters of n-InSb and microwave beams of power densities 1 MW cm^?2, the power density of the excited ion acoustic wave is ≈ 1.76 kW cm^?2.     

Confinement of massless particles: Photon

Confinement of massless particles in a suitably chosen dielectric medium is considered. Light waves of selected frequencies are shown to be confined in a medium with dielectric constantε(r)=a/r−b ². A wave theoretical analysis gives equispaced frequency spectrum for the confined light, the radial dependence of its electric wave vector resembling that of hydrogen atom wave functions. In the large frequency limit an eikonal approximation of the problem gives elliptic orbits for the confined rays. Higher frequency orbits are shown to be closer to the centre of the medium than the lower frequency ones.     

Parametric transformation of the amplitude and frequency of a whistler wave in a magnetoactive plasma

The results of experiments studying the propagation of a high-frequency whistler wave in a magnetized plasma duct in the presence of an intense low-frequency wave also related to the whistler frequency range are reported. Amplitude-frequency modulation of the high-frequency whistler wave trapped in the duct was observed. A deep amplitude modulation of the signal that can lead to its splitting into separate wave packets is observed. It is shown that an increase in the wave propagation path leads to a broadening of the wave frequency spectrum and to a shift of the signal spectrum predominantly toward the red side. The transformation of the frequency of the high-frequency wave is related with the time-dependent perturbation of the external magnetic field by the field of the low-frequency whistler wave (the relative perturbation of the magnetic field δB/B≤5×10^?2).     

Amplitude modulation and demodulation of an electromagnetic wave in magnetised acousto-optic diffusive semiconductor plasmas: Hot carrier effects

In communication processes, amplitude modulation is very helpful to save power using a single band transmission. Using the hydrodynamical model of semiconductor plasma analytical investigations are made for the amplitude modulation as well as demodulation of an electromagnetic wave incorporating carrier heating (CH) effects in acousto-optic magnetised semiconductor plasma. The CH effects add new dimensions in the present analysis. Analysis are made under different wave number regions over a wide range of cyclotron frequencies. It is found that incorporation of CH effects modifies the amplitude modulation and demodulation processes effectively. Numerical estimations are made for III–V semiconductor crystal irradiated by pump wave of frequency 1.6×10¹³ s^?1. Complete absorption of the waves takes place in all the possible wavelength regimes when the cyclotron frequency ω_c becomes nearly equal to ω₀, the pump frequency on neglecting the collision term in modulation/ demodulation indices.     

Influence of Negative Ions on Drift Waves in a Low‐Density Ar/O2‐Plasma

The effect of negative ions on the drift wave instability has been studied in detail in a linear device by means of Langmuir probes and cross‐correlation analysis. Drift waves are excited in low‐density (5 × 10¹⁴ m^–3) and strongly magnetized (0.5 T) pure argon plasmas and in the presence of an oxygen admixture. The radial density profile of negative ions is hollow. For increasing concentration of negative ions the wave frequency decreases by about 25%. Despite of an axial density gradient, a global wave frequency is established for the entire column length. While for the noble gas case the drift wave frequency is given by the equilibrium plasma parameters in the mid‐plane, there is no such relationship for the argon plasma with oxygen admixture. This different finding is attributed to the inhomogeneous distribution of the negative ions (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Laser wiggler beat wave in a plasma

It is shown that by combining a laser wave and an electron beam propagating through a plasma inside a wiggler: (i) Electrons can be accelerated to high energies. For usual laser frequencies and wiggler wavelengths, plasma densities are in the range 10¹⁵–10¹⁶ cm^-3. The plasma density fluctuation in the longitudinal wave suffices to obtain electron energies of several hundred MeV over short distances. (ii) High frequency radiation can be amplified.     

The turbulence of capillary waves on the surface of liquid hydrogen

It is experimentally demonstrated that the surface excitation of liquid hydrogen at a low frequency results in the turbulent mode in a system of capillary waves. The experimental results are in good agreement with the theory of weak wave turbulence. The pair correlation function of the surface deviations is described by the exponential function ω^m. The exponent m decreases in magnitude from m=?3.7±0.3 to ?2.8±0.2 when the pumping at a single resonant frequency changes to broadband noise excitation. Measurements are made of the dependence of the boundary frequency ω_b of the upper edge of the inertial range in which the Kolmogorov spectrum is formed on the wave amplitude η_p at the pumping frequency. It is demonstrated that the obtained data are well described by a function of the form ω_b∝η _p ^4/3 ω _p ^23/9 .     

A technique for frequency stabilization of an internal mirror He-Ne laser

A technique for frequency stabilization of an internal mirror He-Ne laser using phase sensitive detection without cavity length modulation is suggested. The orthogonally plane polarized modes are separated and then convered into two photoelectric signals using two photodetectors. The photoelectric signals are switched alternately so as to generate a square wave, whose amplitude is proportional to the intensity difference between the two orthogonal polarizations. A lock-in amplifier is used to detect this square wave, with the switching frequency as reference. The phase detected signal is used for thermal stabilization of the laser. The frequency stability of 5 × 10⁻⁹ was obtained with an integration time of 1 s.     

The possibility of detecting gravitational waves from a shift in the resonance frequency of an optical resonator

Under the action of the gravitational wave, the length of an optical resonator and, therefore, its resonance frequency change. In conventional resonators, this frequency shift is too small to be detected. We propose a method that provides a very high resonance frequency-versus-resonator length slope. As a result, a gravitational wave with an intensity of 10⁻²¹ can shift the resonance frequency by more than 10 kHz, which can easily be detected.