Chen Jing-Biao

Magic Wavelengths for a Lattice Trapped Rubidium Four-Level Active Optical Clock

After pumped from5s1/2 ground state to6p1/2 state, the population inversion between 6s1/2 and 5p1/2,3/2 will be established for Rubidium four-level active optical lock. In this paper, we calculate AC Stark shift due to lattice trapping laser which dominates th e frequency shift of clock transition in lattice trapped Rubidium four-level active optical clock. Several magic wavelengths are found that can form desired optical lattice trapping potential. By choosing a p roper intensity and linewidth of trapping laser, the fractional frequency uncertainty of clock transition d ue to AC Stark shift of trapping laser, is estimated to be below 10.After being pumped from the 5s1/2 ground state to the 6p1/2 state, the population inversion between 6s1/2 and 5p1/2,3/2 can be established for a rubidium four-level active optical clock. We calculate the ac Stark shift due to lattice trapping laser which dominates the frequency shift of clock transition in a lattice trapped rubidium four-level active optical clock. Several magic wavelengths are found, which can form desired optical lattice trapping potential. By choosing a proper intensity and linewidth of the trapping laser, the fractional frequency uncertainty of clock transition due to the ac Stark shift of the trapping laser, is estimated to be below 10−18.

Application of Electron-Shelving Detection via 423 nm Transition in Calcium-Beam Optical Frequency Standard

A new scheme of small compact optical frequency standard based on thermal calcium beam with application of 423 nm shelving detection and sharp-angle velocity selection detection is proposed. Combining these presented techniques, we conclude that a small compact optical frequency standard based on thermal calcium beam will outperform the commercial caesium-beam microwave clock, like the 5071 Cs clock (from HP to Agilent, now Symmetricom company), both in accuracy and stability.

A Potassium Atom Four-Level Active Optical Clock Scheme

We present an active optical clock scheme with a four-level quantum potassium system. We calculate the population probabilities of each state using the density matrix. At the steady state, ρ33 and ρ55 are equal to 8.3% and 3.5%, respectively, and the population inversion between the 5S1/2 and 4P3/2 states is built up in the thermal potassium cell with a 404.7 nm pumping laser. According to the mechanism of the active optical clock, under the action of the 404.7 nm pumping laser, the scheme can output a 1252.2 nm quantum-limited-linewidth laser, which can be directly used as an active optical frequency standard.

Feasibility of Extreme Ultraviolet Active Optical Clock

We propose an experimental scheme of vacuum ultraviolet (VUV) and extreme ultraviolet (XUV) optical frequency standards with noble gas atoms. Considering metastable state 3P2 noble atoms pumped by a conventional discharging method, the atomic beam is collimated with transverse laser cooling at the metastable state and enters into the laser cavity in the proposed setup. Due to stimulated emission from the metasable state to the ground state inside the laser cavity consisting of VUV reflection coating mirrors, our calculations show that with enough population inversion to compensate for the cavity loss, an active optical frequency standard at VUV and XUV is feasible.

Microwave Atomic Clock in the Optical Lattice with Specific Frequency

A scheme for a microwave atomic clock is proposed for Cs or Rb atoms trapped in a blue detuned optical lattice. The ac Stark shift of the clock transition due to a trapping laser is calculated. We analyze it at some specific laser wavelength. Compared with the case of the fountain clock, the cavity related shifts, the collision shift and the Doppler effect are eliminated or suppressed dramatically in an atomic lattice clock. By analyzing various sources of clock uncertainty, a microwave atomic lattice clock with a high accuracy and small volume is feasible.

The near-infrared spectra and distribution of excited states of electrodeless discharge rubidium vapour lamps

The population ratio between the excited states of rubidium in the electrodeless discharge rubidium vapour lamp is calculated according to the near-infrared spectra in the region of 780-1550 nm. By using a 1529 nm laser, we measure the density of natural rubidium atoms at the 5P(3/2) level. The populations of different excited states are then clarified.

Adiabatic Passage Based on the Calcium Active Optical Clock

We propose a new application of the optical adiabatic passage effect for the excitation of a thermal atomic beam, which will be used in the calcium active optical clock to produce population inversion. A comparison between the optical adiabatic passage effect and the Rabi π pulse is investigated, 99% of the calcium atoms in the atomic beam that has a wide velocity distribution will be excited to the upper state for population inversion using the adiabatic passage, while 76% at most will be excited to the excited state using the π pulse with suitable parameters.

Alternating Current Zeeman and Stark Interference Effect in Ramsey Separated Oscillating Fields

Analytic expressions have been derived of the alternating current (ac) Zeeman and ac Stark effect in an atomic beam magnetic resonance method using Ramsey separated oscillating fields. An interesting feature which will affect the normal Ramsey pattern is that an interference fringe is superimposed on the dispersion lineshapes of the normal ac Zeeman or ac Stark effect. We point out that this new character of ac Zeeman (ac Stark) effect generally exists in all kinds of Ramsey method, for example, in the optical Ramsey atomic interferometer and atomic beam frequency standard. An important implication is that, particularly in an atomic beam frequency standard using Ramsey method, this effect has an influence on the evaluation of the second-order Doppler frequency shift.

Magic Wavelength for Caesium Transition Line 6S1/2 – 6P3/2

We investigate the magic wavelengths of the trapping laser for 6S1/2 – 6P3/2 of the Cs atom in a region where the optical shift between two different states can be eliminated. For fine levels and linear polarized laser they are 930.4 nm and 937.2 nm. The magic wavelengths range from 927.7 nm to 945.0 nm for circle-polarized perturbing laser. Effects of nuclear spin, the hyper-fine Zeeman levels, and the polarization of the light, which generate different magic wavelengths, are further discussed.

Dual-Wavelength Bad Cavity Laser as Potential Active Optical Frequency Standard*

We experimentally realize the dual-wavelength bad cavity laser for the first time. As the Cs cell temperature is kept between 118°C and 144°C, both the 1359 nm and 1470 nm lasing outputs of dual-wavelength bad cavity laser are detected. The laser output power of dual-wavelength bad cavity laser is measured when changing the 455 nm pumping laser frequency and power at 127°C Cs cell temperature. Both the 1359 nm laser and the 1470 nm laser are working at the deep bad cavity regime, and the ratio between the linewidth of cavity mode and the laser gain bandwidth a ≈ 40 for 1359 nm and 1470 nm lasers. The 1470 nm laser linewidth is measured to be 407.3 Hz. The dual-wavelength bad cavity laser operating on atomic transitions demonstrated here has a potential in the application as a stable optical local oscillator, even an active optical frequency standard directly in the future.