All-order dispersion cancellation and energy-time entangled state.

Dispersion cancellation with an energy-time entangled photon pair in Hong-Ou-Mandel (HOM) interference is one phenomenon that reveals the nonclassical nature of the entangled photon pair. This phenomenon has been observed in materials with very weak dispersions. If the higher-order dispersion coefficient is non-negligible, then the experiment must be modified to realize dispersion cancellation.

Enhancement of ultraviolet-beam generation through a double walk-off compensation.

We propose a novel walk-off-compensation method for ultraviolet-light-source development. A walk-off occurring in the frequency mixing of infrared and green beams is doubly compensated for using an external walk-off compensator and a nonlinear-material set with internal walk-off-compensation arrangement. We theoretically and experimentally verified that our method can improve the power and beam shape of the output ultraviolet beam.

Morphological and SERS Properties of Silver Nanorod Array Films Fabricated by Oblique Thermal Evaporation at Various Substrate Temperatures.

Aligned silver nanorod (AgNR) array films were fabricated by oblique thermal evaporation. The substrate temperature during evaporation was varied from 10 to 100 °C using a home-built water cooling system. Deposition angle and substrate temperature were found to be the most important parameters for the morphology of fabricated films.

Ultimate sensing resolution of water temperature by remote Raman spectroscopy.

The limit of sensing resolution of water temperature by remote Raman spectroscopy was investigated experimentally. A remote Raman spectrometer, which employed a telescope of 20 cm in pupil size and the second harmonic generation (SHG) of a Q-switched Nd:YAG laser, was used for the measurement. By analyzing the broad O-H stretching Raman band located near 3500  cm⁻¹, a parameter which is in second-order polynomial relation with water temperature from 13°C to 50°C could be obtained.

All-optical image switching in a double-Λ system.

The coherent control of optical images has garnered attention because all information embedded in optical images is expected to be controlled in a parallel way. One of the most important control processes is switch for information delivery. We experimentally demonstrated phase-controlled optical image switching in a double-Λ system where the transmission of the image through a medium was switched.

Phase-controlled switching by interference between incoherent fields in a double-Λ system.

We showed experimentally interference could be occurred between incoherent lights in a double-Λ lambda transition implemented with rubidium atomic vapor. Switching of probe transmission was controlled by the phases of two` independent probe lasers with low light intensity. More than 70% of the probe transmission could be switched by ultra-weak incoherent field.

Application of pulsed buffer gas jets for the signal enhancement of laser-induced breakdown spectroscopy.

We report a new simple method for the signal enhancement of laser-induced breakdown spectroscopy using a pulsed buffer gas jet. The signal is enhanced up to more than 10 fold by using argon gas jets, which are injected through a pulsed nozzle onto the sample area to be analyzed. By synchronizing the buffer gas pulse with the laser pulse and optimizing the spatial arrangements between the gas jet and the sample surface, we have successfully exploited the useful properties of the buffer gas in open atmosphere.

Electromagnetically induced transparency on GaAs quantum well to observe hole spin dephasing.

Electromagnetically induced transparency (EIT) was observed with transient optical response of exciton correlation in GaAs/AlGaAs quantum well structure. Decoherence of EIT was increased with temperature (12-60 K), which could be simulated by increasing non-radiation decay rate between coherently coupled ground states in Bloch equation for Lambda type three level. The non-radiation decay was mainly due to hole spin dephasing in the system for EIT via coulomb correlation.

Slow-light six-wave mixing at low light intensities.

We report an experimental study of resonant six-wave mixing in coherently prepared Rb atoms. Electromagnetically induced transparency in a four-level atomic system suppresses the linear susceptibility and enhances the nonlinear susceptibilities, which leads to the resonantly enhanced, slow-photon six-wave mixing at low light intensities. The light emission in the six-wave mixing process can be viewed as resulting from diffraction of slow light off a resonant nonlinear grating induced in the four-level system by a standing-wave pump field.

Observation of large Kerr nonlinearity at low light intensities.

We report an experimental observation of large Kerr nonlinearity with vanishing linear susceptibilities in coherently prepared four-level rubidium atoms. Quantum coherence and interference manifested by electromagnetically induced transparency suppress the linear susceptibilities and greatly enhance the nonlinear susceptibilities at low light intensities. The measured Kerr nonlinearity is comparable in magnitude to the linear dispersion in a simple two-level system and is several orders of magnitude greater than the Kerr nonlinearity of a conventional three-level scheme under similar conditions.