Rahul Mhaskar

A low-power, high-sensitivity micromachined optical magnetometer

We demonstrate an optical magnetometer based on a microfabricated 87Rb vapor cell in a micromachined silicon sensor head. The alkali atom density in the vapor cell is increased by heating the cell with light brought to the sensor through an optical fiber, and absorbed by colored filters attached to the cell windows. A second fiber-optically coupled beam optically pumps and interrogates the atoms. The magnetometer operates on 140 mW of heating power and achieves a sensitivity below 20 fT/√Hz throughout most of the frequency band from 15 Hz to 100 Hz. Such a sensor can measure magnetic fields from the human heart and brain.

Time averaging of multimode optical fiber output for a magneto-optical trap

We demonstrate a method for increasing the amount of power available for laser cooling applications by using a multimode optical fiber. Through randomization of phase shifts of modes within the fiber on time scales faster than the center-of-mass response time of the atoms, a smooth time-averaged trapping beam is generated. The principle has been demonstrated in a pyramidal magneto-optical trap. The method is particularly suitable for the harnessing of the high output power of broad-area diode lasers for laser cooling.

Atoms and plasmas in a high-magnetic-field trap

We investigate cold rubidium plasmas in a particle trap that has the unique capability to simultaneously laser‐cool and trap neutral atoms as well as to confine plasmas in magnetic fields of about three Tesla. The atom trap is a high‐field Ioffe‐Pritchard laser trap, while the plasma trap is a Ioffe‐Penning trap that traps electrons and ions in separate wells. The observed plasma dynamics is characterized by a breathing‐mode oscillation of the positive (ionic) plasma component, which feeds back on the behavior of the negative (electron) component of the plasma. At higher densities, the observed oscillations become nonlinear. The electron component has been found to undergo rapid cooling. We further report on the recombination of magnetized plasmas into Rydberg atoms in transient traps and quasi‐steady‐state traps. In transient traps, large numbers of recombined Rydberg atoms in high‐lying states are observed. In quasi‐steady‐state traps, the measured numbers of recombined atoms are lower and the binding e...

Ion imaging in a high-gradient magnetic guide

We study a photoionization method to detect and image a narrow beam of cold atoms traveling along a high-gradient two-wire magnetic guide that is continuously on. Ions are accelerated in a compact acceleration region, directed through a drift region several centimeters in length, and detected using a position-sensitive ion detector. The potentials of several electrodes can be varied to adjust the imaging properties. Using ion trajectory simulations as well as experiments, we study the passage of the ions through the detection system, the magnification of the detection system, and the time-of-flight characteristics.

Role of the Mean-field in Bloch Oscillations of a Bose-Einstein Condensate in an Optical Lattice and Harmonic Trap

Using the Crank-Nicholson method, we study the evolution of a Bose-Einstein condensate in an optical lattice and harmonic trap. The condensate is excited by displacing it from the center of the harmonic trap. The mean field plays an important role in the Bloch-like oscillations that occur after sufficiently large initial displacement. We find that a moderate mean field significantly suppresses the dispersion of the condensate in momentum space. When the mean field becomes large, soliton and vortex structures appear in the condensate wavefunction.