Near-field optical detection of atoms with high sensitivity and high spatial resolution

HARUHIKO ITO

元一 大津, Motoichi Ohtsu

Hajime Ito, K. Totsuka, Tatsurou Kawamura +2 more

We describe an atom detector with two-color optical near fields designed for deflection experiments. The sensitivity is estimated to be about 10% for both photoionization and resonant excitation schemes using a slit-type probe.

U. Janicke, Martin Wilkens

K. Totsuka, Hajime Ito, Tatsurou Kawamura +2 more

Summary form only given. We have proposed deflection by an optical near field on a fiber probe to control atoms with high spatial accuracy. In this case, the deflection angle is estimated to be 0.1 degree for a Rb atom with an incident velocity of 10 m/s. It leads to the deviation of 10 /spl mu/m from the incident axis at 1 cm. in the downstream. To detect the deflected atoms with an accuracy of 1%, we need the spatial resolution of 100 nm. However, a commercial detector such as MCP has a low resolution of 50 /spl mu/m at most and the highest resolution that has been reported is 1 /spl mu/m to our knowledge. In addition, these are applied to metastable atoms and have less detection efficiency for the ground state atoms we manipulate. For drastic improvement, we present here a slit-type atom detector with a nanometric lateral resolution. Since the number of atoms deflected by the optical near field is very small, it is important to detect atoms with high efficiency. For this purpose, we use photoionization with two-color optical near fields.

Kenta Sagawa, Haruhiko Ito

We develop a nanoslit to detect a small number of neutral atoms in the ground state. The detection scheme of using two-step photoionization is very sensitive and the use of nanometric near-field lights leads to an ultrahigh spatial resolution. An edge-sharpened nanoslit is fabricated with FIB milling. Considering the case of detecting Rb atoms, the polarization-dependent spatial distribution of near-field light generated at the nanoslit by total-internal reflection of a 476.5-nm Ar-ion laser beam is obtained with a scanning near-field optical microscope. Based on the experimental results, the ionization efficiency is estimated for both s-polarization and p-polarization. We also discuss the discrepancy between the experimental value and the numerical one obtained from the finite difference time domain simulations in the p-polarization case.