Optical bistablility in six-wave mixing parametrical amplification.

We investigate the nonreciprocity "∞"-shape optical bistability (OB) induced by the feedback dressing effect of six-wave mixing parametrically amplified process in a four-level atomic system. Compared to the traditional OB by scanning power, the "∞"-shape OB is scanning probe frequency and demonstrated by "∞"-shape non-overlapping region. More, this non-overlapping region in the x direction (frequency difference) and in the y direction (intensity difference) could demonstrate the degree of this OB phenomenon of dressed probe and conjugate signals, which can be changed by the intensity of feedback dressing. Further, we find the feedback intensity can be controlled by experimental parameters include powers of external-dressing, frequency detuning, incident phase and the nonlinear phase shift of internal-dressing beam. As a result, the nonreciprocity "∞"-shape OB is more sensitive and multiple than traditional OB. These outcomes have potential applications in logic-gate devices and quantum information processing.

Fabrication of diamond microlenses by chemical reflow method.

We introduce a chemical reflow method to fabricate diamond microlenses. First, photoresist pillars developed by photolithography are reflowed in organic solvent vapor atmosphere at 20 °C to form spherical segment patterns on diamond substrate. The effects of chemical solvent type and reflow time on photoresist pattern profiles are investigated. Second, via dry etching, diamond microlenses are fabricated by transferring the spherical segment pattern into substrate. Furthermore, these diamond microlenses demonstrate low numerical aperture, well-controllable curvature, and good imaging performance with projecting experiment.

Fabrication of monolithic diamond photodetector with microlenses.

A monolithic diamond photodetector with microlenses is fabricated by etching microlens arrays (MLAs) on single crystal diamond surface and patterning tungsten electrode strips on the edge of these arrays. Firstly, compact MLAs are etched on half of diamond sample surface by thermal reflow method. Secondly, via magnetron sputtering technique, two sets of interdigitated tungsten electrodes are patterned on the sample surface, one set is on the edge of MLAs, the other set is on the planar area. The optoelectronic performances of photodetectors have been investigated and indicated that the photocurrent of microlens photodetector increases by 74.8 percent at 10 V under 220 nm UV light illumination by comparing with that in planar case. Simulations of photodetectors' electrical and optical properties have been carried out, illustrating an improvement of charge collection ability and light absorption efficiency in microlens case. Furthermore, the present device structure can be extended to other semiconductor photodetectors.

HfAlOx/Al2O3 Bilayer Dielectrics for a Field Effect Transistor on a Hydrogen-Terminated Diamond.

In this work, a hydrogen-terminated (H-terminated) diamond field effect transistor (FET) with HfAlOx/Al2O3 bilayer dielectrics is fabricated and characterized. The HfAlOx/Al2O3 bilayer dielectrics are deposited by the atomic layer deposition (ALD) technique, which can protect the H-terminated diamond two-dimensional hole gas (2DHG) channel. The device demonstrates normally-on characteristics, whose threshold voltage (VTH) is 8.3 V. The maximum drain source current density (IDSmax), transconductance (Gm), capacitance (COX) and carrier density (ρ) are -6.3 mA/mm, 0.73 mS/mm, 0.22 µF/cm2 and 1.53 × 1013 cm-2, respectively.

Hydrogen-terminated diamond field-effect transistor with AlOx dielectric layer formed by autoxidation.

Fabrication of hydrogen-terminated diamond (H-diamond) field-effect transistor (FET) with AlOx dielectric layer has been successfully carried out. The AlOx layer was formed by auto-oxidizing 6 nm Al film in the air at room temperature, and a FET without AlOx dielectric layer has also been fabricated for comparison. For both FETs, 100 nm Al layers were deposited as the gate electrodes, respectively. The leakage current density in FET with AlOx dielectric layer was four magnitude orders lower than that without AlOx dielectric layer at VGS = -5 V, indicating that AlOx dielectric layer could effectively reduce leakage current and prevent reverse ID in ID - VDS caused by defects on diamond surface. Distinct pinch-off characteristic with p-type channel was observed in ID - VDS measurement. The threshold voltage was -0.4 V at VDS = -15 V.

Flip-flop Converter of Dual-bistability Using Cavity and Parametric Amplified Four-Wave Mixing.

We study the realization of dual-bistability flip-flop converter in cavity and parametrically amplified four-wave mixing (FWM) process at a four-level cavity atomic system. Using the effect of nonreciprocity optical dual-bistability, we can obtain different output multi-mode states of probe transmission signal and FWM signal. We find the channel equalization ratio and optical contrast between multi-mode states is related to the degree of dual-bistability. Besides, the degree of dual-bistability can be controlled by the input parameters (frequency detuning and powers of the dressing beams). More, using electro-optical modulator and acoustic optical modulator to modulate the powers and frequency detuning, respectively, we can realize the fast conversion between different output states. And the switch speed of this flip-flop converter is about 16 ns. These outcomes may provide foundation for the development of all-optical devices and quantum information processing.

Ohmic contact between iridium film and hydrogen-terminated single crystal diamond.

Investigation of ohmic contact between iridium (Ir) film and hydrogen-terminated single crystal diamond has been carried out with annealing temperature from 300 to 600 °C in argon (Ar) and hydrogen ambient. Electrodes were deposited on hydrogen-terminated single crystal diamond by electron beam evaporation technique, and specific contact resistivity has been measured by transmission line model. The interface between Ir film and hydrogen-terminated single crystal diamond was characterized by transmission electron microscopy and energy dispersive X-ray spectroscopy. Theoretical calculation value of barrier height between Ir film and hydrogen-terminated single crystal diamond was around -1.1 eV. All results indicate that an excellent ohmic contact could be formed between Ir film and hydrogen-terminated single diamond.