Zhi-Hui Kang

SHG phase matching in GaSe and mixed GaSe 1-x S x , x≤0.412, crystals at room temperature

The optical properties of p-type GaSe and mixed GaSe(1-x)S(x), x=0.04, 0.023, 0.090, 0.133, 0.175, 0.216, 0.256, 0.362, 0.369, and 0.412, crystals were studied to reveal the potentials for phase matching and frequency conversion. Comparative experiment on Er3+:YSGG and CO2 laser SHG at identical experimental conditions is carried out at room temperature. Any change in polytype structure of GaSe1(1-x)S(x) was not found.

Gold nanorod saturable absorber for passive mode-locking at 1 μm wavelength

Gold nanorods (GNRs) were used as a saturable absorber (SA) for passive mode-locking at 1 μm wavelength. The GNR-SA film was fabricated by mixing GNRs with sodium carboxymethylcellulose. The longitudinal surface plasmon resonance absorption of GNRs was used to induce mode-locking. By using the GNR-SA film, stable passive mode-locking at 1039 nm was experimentally demonstrated in an ytterbium-doped fiber laser cavity pumped by a 980 nm laser diode. The laser produced ~440 ps pulses with a repetition rate of 36.6 MHz and an average output power of ~1.25 mW for a pump power of ~82 mW.

Mode-locked thulium-doped fiber laser at 1982 nm by using a gold nanorods saturable absorber

We demonstrated a passively mode-locked fiber laser operating at 1982 nm by using a gold nanorods (GNRs) saturable absorber (SA). The GNRs SA was fabricated by mixing GNRs with sodium carbonxymethyl cellulose. By inserting the GNRs SA into a Tm-doped fiber laser cavity pumped by a 1570 nm fiber laser, stable passively mode-locking was achieved with a threshold pump power of 224 mW, ~4.02 ps pulses at 1982 nm with a repetition rate of ~37.49 MHz, and a maximum average power of ~6 mW was obtained for a pump power of ~265 mW.

Investigation of spontaneously generated coherence in dressed states of 85 Rb atoms

We investigate the effects of spontaneously generated coherence (SGC) on the electromagnetically induced transparency features in a four-level Lambda-type system. We show that double-transparency windows and a controllable narrow absorption peak can be obtained with the presence of SGC. We present an equivalent system without the rigorous requirement of close-lying levels to observe the phenomena. We also experimentally demonstrate the corresponding features in a rubidium atomic beam.

All-optical routing by light storage in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an all-optical routing based on light storage in a Pr3+:Y2SiO5 crystal. Under electromagnetically induced transparency, the optical information of the probe light pulse can be stored in the crystal. By simultaneously switching on two retrieve control fields in the release process, the stored optical information from one light channel can be distributed into two light channels. Such an all-optical routing in solids may have practical applications in quantum information and all-optical network.

Erasure of stored optical information in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an erasure of stored optical information in a Pr3+:Y2SiO5 crystal by applying an erasing pulse to destroy atomic spin coherence. We observed an erasing efficiency of about 85%. Such an erasing operation of stored optical information may have practical applications in the field of information processing and all-optical network.

Wide-tunable, high-energy AgGaS 2 optical parametric oscillator

Nanosecond AgGaS(2) type-I singly resonant optical parametric oscillator pumped by a Q-switched 1.064 mum Nd:YAG laser is demonstrated experimentally. Continuously tunable 2.6-5.3 mum radiation and output pulse energy up to 0.6 mJ at 4 mum are achieved in a single-stage conversion process. The analysis of pump threshold is investigated both theoretically and experimentally.

EIT-assisted large cross-Kerr nonlinearity in a four-level inverted-Y atomic system

A four-level inverted-Y scheme with an electromagnetically induced transparency (EIT) core is investigated for the enhancement of cross-Kerr effect in rubidium atoms. When detunings of the coupling and control fields are appropriately set, an enhanced EIT window is observed, and the induced phase shift of the probe field due to cross-phase modulation (XPM) is obtained by measuring the dispersive property of the probe transition. The maximal XPM phase shift is about 12° under the current experimental conditions. The experimental measurements agree well with the theoretical calculations. The enhanced XPM phase shift in such an atomic system has applications in quantum nonlinear optics and quantum information science.

Enhanced four-wave mixing by atomic coherence in a Pr3+:Y2SiO5 crystal

We experimentally demonstrate an enhanced four-wave mixing (FWM) based on atomic coherence in a Pr3+:Y2SiO5 crystal. By employing coherent population return and fractional stimulated Raman adiabatic passage to prepare maximum atomic coherence in the crystal, an efficient FWM signal can be generated. By measuring the generated FWM signal, the time-dependent atomic coherence is monitored. Such an enhanced FWM in solids may have practical applications in nonlinear optics and laser spectroscopy.

Slowing and storage of double light pulses in a Pr3+:Y2SiO5 crystal.

We experimentally demonstrate the slowing and storage of double light pulses in a Pr(3+):Y(2)SiO(5) crystal using a multilevel-tripod scheme. Owing to double dark-state polaritons of the tripod-type system, two signal pulses can be simultaneously slowed. Also, we realize the simultaneous storage (and retrieval) of double light pulses by switching off (and back on) the control field. Slowing and storage of double light pulses in solids may have practical applications in quantum information and quantum networks.