Optical bistability and set-reset operation of a Fabry-Perotsemiconductor laser amplifier with two detuned light injections

Optical bistability in a Fabry-Perot semiconductor laser amplifier when two optical inputs detuned from the resonant wavelength of a semiconductor laser amplifier are injected is discussed. A split branch is found in the optical output versus input characteristics in addition to conventional optical bistability behavior. It is shown analytically and experimentally that set and reset can be achieved in the optical output of the semiconductor laser amplifier for each wavelength by applying two detuned optical pulses and using the split branch     

A novel ferromagnetic thermo-stent for plaque stabilization that self-regulates the temperature

The purpose of this study is to investigate the vascular wall with a thermally self-regulating, cylindrical stent made of a low Curie temperature ferromagnetic alloy. Physiologic saline was circulated in the silicone model vessel implanted with the stent. The stent-temperature remained nearly constant for variable saline flows, saline temperatures, and magnetic flux densities. Stent implants of this type in human blood vessels could potentially enable thermotherapy and temperature determination without catheterization.     

Effects of AsH3 surface treatment for the improvement of ultra-shallow area-selective regrown GaAs sidewall tunnel junction

Low-temperature (290°C) area-selective regrowth by molecular layer epitaxy (MLE) was applied for the fabrication of an ultra-shallow sidewall (50 nm) GaAs tunnel junction. Fabricated tunnel junctions have shown a record peak current density up to 35,000 A/cm². It is shown that the tunnel junction characteristics are strongly dependent on the sidewall orientation and the AsH₃ surface treatment conditions just prior to regrowth. The effects of AsH₃ surface treatment are discussed in view of the control of surface stoichiometry.     

Synthesis and structures of iron nanoparticles coated with boron nitride nanomaterials

Iron (Fe) nanoparticles coated with boron nitride (BN) nanomaterials were synthesized by using Fe(4)N and B powders as raw materials. The Fe(4)N was reduced to alpha-Fe during annealing at 1000 degrees C for several hours with flowing 100 sccm N(2) gas. The reaction was predicted by Ellingham diagram. The atomic structure and magnetic properties were investigated by high-resolution electron microscopy and vibrating sample magnetometer system.     

Performance analysis of variable optical delay circuit using highly nonlinear fiber parametric wavelength converters

The performance of a variable optical delay circuit that employs a fiber loop with highly nonlinear fiber parametric wavelength converters is discussed using both experiments and simulations. In our optical delay circuit, the delay time is determined from the number of circulations, which is controlled by the initially selected wavelength of the optical signal. We discuss the factors that limit the number of circulations described in our previous paper, derive the parameters that provide good performance levels, and confirm the performance by simulation. The simulated results indicate that 100 wavelength conversions can be achieved, namely, 100 different delay times can be given to optical packets.     

Fibre Bragg grating compression-tuned over 110 nm

A fibre Bragg grating with a tuning range covering beyond the C- and L-bands has been realised, which represents the broadest tuning range reported of any Bragg grating. The device exhibits constant spectral response and polarisation mode dispersion within these bands.     

3D Micromolding of Arrayed Waveguide Gratings on Upconversion Luminescent Layers for Flexible Transparent Displays without Mirrors,Electrodes, and Electric Circuits

A new technique for the fabrication of arrayed waveguide gratings on upconversion luminescent layers for flexible transparent displays is reported. Ho³⁺‐ and Yb³⁺‐codoped NaYF₄ nanoparticles are synthesized by hydrothermal techniques. Transparent films consisting of two transparent polymers on the NaYF₄ nanoparticle films exhibit mechanical flexibility and high transparence in visible region. Patterned NaYF₄ nanoparticle films are fabricated by calcination‐free micromolding in capillaries. Arrayed waveguide gratings consisting of the two transparent polymers are formed on the patterned NaYF₄ nanoparticle films by micromolding in capillaries. Green and red luminescence is observed from the upconversion luminescent layers of the NaYF₄ nanoparticle films in the arrayed waveguide gratings under excitation at 980 nm laser light. Arrayed waveguide gratings on the upconversion luminescent layers are fabricated with Er³⁺‐doped NaYF₄ nanoparticles which can convert two photons at 850 and 1500 nm into single photon at 550 nm. These results demonstrate that flexible transparent displays can be fabricated by constructing arrayed waveguide gratings on upconversion luminescent layers, which can operate in nonprojection mode without mirrors, transparent electrodes, and electric circuits.     

Chaos control and noise suppression in external-cavitysemiconductor lasers

Feedback-induced chaos and intensity noise enhancement in a laser diode with external optical feedback are studied by computer simulations. The enhancement of relative intensity noise (RIN) that is often observed in experiments is considered as a result of the feedback-induced deterministic chaos and the intensity noise suppression is treated from the viewpoint of chaos control. Especially, the conventional noise suppressing technique known as a high-frequency injection modulation is turned into a problem of stabilizing chaos through parameter modulations. We developed an analytical method which allows to optimize the modulation frequency from the linear stability analysis of the dynamical model that describes the laser diode with external feedback. The robustness of the modulation with respect to the modulation frequency and depth is verified and the results suggest the feasibility of applying our method to actual noise suppression. The RIN in the low-frequency region (up to 100 MHz) is shown to be reduced to the solitary laser level when the feedback-induced chaos is effectively controlled with the optimized modulation frequency