Jung Bog Kim

Amplification without Inversion in the Four-level N-Type 87Rb D1-Line

We demonstrate amplification without inversion in the 87Rb D1-line pumped by an incoherent light. A closed N-type, four-level atomic system has been considered to obtain an insight into the origin of the gain as well as the conditions under which the system exhibits gain without population inversion in bare states. We investigate the gain as a function of the incoherent pumping rate, the coupling laser detuning, and Rabi frequency. The experimental results are in good agreement with the numerical calculations considering the velocity distribution of atoms.

Controllable asymmetric double well and ring potential on an atom chip

We have constructed an asymmetric matter-wave beam splitter and a ring potential on an atom chip by applying rf-field parallel to the quantization axis added to perpendicular rf-fields. Versatile controllability on the potentials can be obtained.

Controllable asymmetric matter-wave beam splitter and ring potential on an atom chip

We have constructed an asymmetric matter-wave beam splitter and a ring potential on an atom chip by applying rf-field parallel to the quantization axis added to perpendicular rf-fields. Versatile controllability on the potentials can be obtained.

Velocity Selective Polarization Spectroscopy for Modulation-Free Dispersion Signals at Detuned Frequencies

We present a simple technique to obtain modulation-free locking signals at the detuned frequency from an atom transition between hyperfine structures. Polarization spectroscopy allows us to obtain the dispersion signals that are suitable for frequency locking. Velocity selective optical pumping using another laser beam also allows us to obtain signals at the detuned frequency and to shift crossover signal away. By combining these two techniques, we were able to obtain the velocity selective birefringence signal only at the principle transition in an Rb vapor cell and compare the birefringence signal with the theoretical spectrum predicted by using Nakayama’s model.

The non-paradox of superluminal tunneling, and a planned experiment to study the real mystery

Although the now well-established fact of superluminal tunneling may be somewhat surprising, we maintain that as in previous cases of quantum nonlocality, there is in fact no paradox. No signal, in the sense of previously unpredictable information, may be transmitted faster than c by making use of anomalously fast tunneling. On the other hand, we believe that mysteries persist about where a particle is while it is tunneling, how long it spends there, and whether (in a carefully defined sense, but less restricted than that of the familiar two-slit discussions) it can be in two places at the same time. We are setting up a series of atom optics experiments which we believe will provide direct experimental evidence about some of these issues.

Large Capacitance Measurement by Multiple Uses of MBL Charge Sensor

A recent article by Morse1 described interesting electrostatics experiments using an MBL charge sensor. In this application, the charge sensor has a large capacitance compared to the charged test object, so nearly all charges can be transferred to the sensor capacitor from the capacitor to be measured. However, the typical capacitance of commercial charge sensors is 10 nF, which is quite small compared to general capacitances for electric circuit experiments. In this paper, we will describe how to use the commercial charge sensor to measure a large capacitance.

Classical and quantum analysis of one-dimensional velocity selection for ultracold atoms

We discuss a velocity selection technique for obtaining cold atoms, in which all atoms below a certain energy are spatially selected from the surrounding atom cloud. Velocity selection can in some cases be more efficient than other cooling techniques for the preparation of ultracold atom clouds in one dimension. With quantum mechanical and classical simulations and theory we present a scheme using a dipole force barrier to select the coldest atoms from a magnetically trapped atom cloud. The dipole and magnetic potentials create a local minimum which traps the coldest atoms. A unique advantage of this technique is the sharp cut-off in the velocity distribution of the sample of selected atoms. Such a non-thermal distribution should prove useful for a variety of experiments, including proposed studies of atomic tunnelling and scattering from quantum potentials. We show that when the rms size of the atom cloud is smaller than the local minimum in which the selected atoms are trapped, the velocity selection technique can be more efficient in one dimension than some common techniques such as evaporative cooling. For example, one simulation shows nearly 6% of the atoms retained at a temperature 100 times lower than the starting condition.

Atomic coherence in laser spectroscopy and atom optics

In order to investigate effects of coherent population trapping (CPT) on electromagnetically induced transparency (EIT), we added an external weak magnetic field to identify a quantization axis. The laser beam whose polarization is parallel to the direction of the external magnetic field and the perpendicular laser are coupled to different transitions. CPT generated by two circular polarization components of the strong coupling beam when the polarization was perpendicular to the quantization axis, was competed with (EIT) so that absorption reduction could be larger than the case without CPT. We investigated the mechanism of steady-state light amplification without inversion using an incoherent pumping laser.