Changjiang Wei

Observation of Electromagnetically Induced Transparency Within an Electron Spin Resonance Transition

A sharp transparency feature is induced in an allowed electron spin resonance (ESR) transition by driving a nominally spin-forbidden transition. The width of the feature is narrower than the homogeneous linewidth of the ESR transition and is interpreted as being associated with electromagnetically induced transparency (EIT). Measurements are made for the nitrogen-vacancy centre in diamond and the signals are detected using a coherent optical technique.

Transient hole burning in N-V centre in diamond

Abstract The hole-burning spectrum associated with the 637 nm zero-phonon line in diamond is obtained using two CW lasers of equal intensity. Antiholes are observed at 2.88 and 0.8 GHz when burning on the low energy side of the zero-phonon line and at 2.88, 2.05 and 0.46 GHz when burning on the high energy side of the line. One sidehole is detected but only when the fastest sweep rates are used. The frequencies of the holes and antiholes are compared with frequencies obtained by other measurements and excited state energy levels are proposed.

A strongly driven two-level atom revisited: Bloch - Siegert shift versus dynamic Stark splitting

We calculate a probe response of a homogeneously broadened two-level transition in the presence of a strong pump. The derivation is carried out for a generalized interaction Hamiltonian, which gives a uniform account of both the Bloch - Siegert shift and dynamic Stark splitting. It is shown that the Bloch - Siegert shift can be viewed as an extreme situation of the dynamic Stark splitting, commonly known as light shift in the literature. Finally using a perturbative approach an analytical expression for the Bloch - Siegert shift is obtained, which is compared with the previous results.

Raman heterodyne detected magnetic resonance: I. CW and coherent transient measurements

We report cw and coherent transient studies on electronic and nuclear magnetic transitions of the nitrogen-vacancy centre in diamond using an optical-rf double resonance technique: Raman heterodyne detection. Emphasis is placed on the coherent transient measurements to illustrate the versatility of the detection technique, which is not only very sensitive but is also ideal in this case since it is based on a coherent process. In this paper we show that Raman heterodyne detection can be used to obtain a wide range of signals including nutation, spin echo, rotary echo and spin locking in a single system. Finally an example of using coherent transients to test the validity of the Bloch equation is given.

Probing a doubly driven two-level atom

A two-level system is driven by two strong fields, one on resonance and one close to resonance. There is a resonance-like response of the coupled atom-field system when the detuning of the second field is an integer fraction of the Rabi frequency of the resonant field. These subharmonic resonances are monitored by a transition to a third level and give a characteristic spectrum dominated by a series of doublets.

Effect of the Bloch-Siegert shift in a strongly driven transition: Asymmetric Autler-Townes profile

Under the conditions of the rotating wave approximation (RWA), a transition strongly driven by a resonant oscillating field displays the well known symmetric Autler - Townes doublet. However, if the counter-rotating component, neglected in the RWA, is taken into account, the Bloch - Siegert shift gives rise to an Autler - Townes doublet of unequal intensity even in the case of a resonant driving field. This effect is investigated theoretically in a V-shaped three-level double-resonance configuration and the results are presented in this paper. An interesting observation is that the level of asymmetry not only depends on the driving-field intensity but also on the characteristics of the driven system including relaxation rates and equilibrium population distributions.

Raman heterodyne detected magnetic resonance: II. Magnetic transitions of NV centre at level anticrossing region

In the preceding paper [1] we reported both cw and coherent transient measurements carried out in EPR and NMR transitions within the3A ground state of the nitrogen-vacancy centre in diamond using the Raman heterodyne detection technique. In this paper we use these measurements to characterise the nuclear magnetic transitions near a level anticrossing situation. The level anticrossing causes a mixing of the electronic spin and nuclear spin wave functions which results in a greatly enhanced NMR transition moment. The amount of mixing not only affects the dipole moment but, correspondingly, the characteristic relaxation times. In this paper we report the measurement of these parameters in the nitrogen-vacancy centre as a function of applied Zeeman field strength and analyse the results using the spin Hamiltonian formalism. Furthermore, combined with the particular features of the Raman heterodyne technique, such a system represents an ideal testing ground for the nonlinear behaviour of strongly driven transitions. Some results are illustrated, including dynamic Zeeman splitting and gain without inversion.

Strengths of Dressed States Transitions

We report on experimental measurements of transition strengths for spectral components associated with a driven two-level atom. The measurements involve time- and frequency-domain techniques and are performed in nuclear magnetic transitions of a nitrogen-vacancy colour centre in diamond using the optical Raman heterodyne method. The transition strengths are shown to depend on the characteristics of the driving field in a way readily accounted for by the dressed state formalism and the data provide an experimental confirmation of some elementary expressions frequently used for dressed states.

Control an electromagnetically induced transparence feature with a microwave field

In this paper we present a theoretical study of the effect of a microwave field on an EIT feature. The EIT feature is associated with the well-known three-level Λ type configuration where a pump and probe laser field couples two separate optical transitions. In addition to these two laser fields, there is a microwave field which drives one of the two lower levels of the Λ type three-level system to another hyperfine level. The EIT feature is studied as a function of microwave field frequency and intensity. Our results show that the presence of a microwave field can dramatically modify the EIT feature. When microwave is resonant with the hyperfine transition, the EIT feature can be split into two EIT features. When it is off resonant with the hyperfine transition, it causes a frequency shift of the EIT feature, reminiscent of the well-known light shift effect.

Coherent transients at the Rabi frequency

It is proposed to investigate the transition at the generalised Rabi frequency as a two-level system which is illustrated using a driven EPR transition in the nitrogen-vacancy centre in diamond. Various coherent transients signals of the driven and undriven Rabi transition are obtained including echoes, spin recovery, nutation and rotary echoes. The spin recovery measurements are found to be non-exponential which prohibits a satisfactory determination of the longitudinal relaxation rate and restricts the study. However, a reasonable account is given of each transient.