Theoretical model for a periodically driven semiconductor laser subject to optical feedback from a microcantilever

We propose a theoretical model for analyzing the dynamics of a periodically driven semiconductor laser subject to optical feedback from a microcantilever. We numerically investigate the temporal evolution of the light intensity of the semiconductor laser, and we show the interspikes of the light intensity. These interspikes of light intensity are also demonstrated in our experiment. The validity of the theoretical model is verified. The observed phenomenon has a potential application for resonant sensing. (C) 2008 Optical Society of America.

Microwave generation in an electro-absorption modulator integrated with a DFB laser subject to optical injection

This paper presents a new technique to generate microwave signal using an electro-absorption modulator (EAM) integrated with a distributed feedback (DFB) laser subject to optical injection. Experiments show that the frequency of the generated microwave can be tuned by changing the wavelength of the external laser or adjusting the bias voltage of the EAM. The frequency response of the EAM is studied and found to be unsmooth due to packaging parasitic effects and four-wave mixing effect occurring in the active layer of the DFB laser. It is also demonstrated that an EA modulator integrated in between two DFB lasers can be used instead of the EML under optical injection. This integrated chip can be used to realize a monolithically integrated tunable microwave source. (C) 2009 Optical Society of America

Some Key Technics of Drop Tower Experiment Device of National Microgravity Laboratory (China) (NMLC)

Drop tower is an important ground based facility for microgravity science experiment. The technical performances of the drop tower NMLC are advanced compared with similar facilities in the US, Germany and Japan. The main components such as drop capsule, deceleration devices, release mechanism present its advantages and creativities.

Structures on sliding base subject to horizontal and vertical motions

In this paper particular investigation is directed towards the combined effects of horizontal and vertical motions of real earthquakes to structures resting on sliding base. A simplified method is presented to treat the nonlinear effects of time dependent frictional force of the sliding base as a function of the vertical reaction produced by the foundation. As an example, the El Centro 1940 earthquake record is used on a structural model to show the structural responses due to a sliding base with different frictional and stiffness characteristics. The study shows that vertical ground motion does affect both the superstructure response and the base sliding displacement. Nevertheless, the sliding base isolator is shown to be effective for the reduction of seismic response of a superstructure.

The dispersive properties of an excited-doublet four-level atomic system

We have investigated the dispersive properties of excited-doublet four-level atoms interacting with a weak probe field and an intense coupling laser field. We have derived an analytical expression of the dispersion relation for a general excited-doublet four-level atomic system subject to a one-photon detuning. The numerical results demonstrate that for a typical rubidium D1 line configuration, due to the unequal dipole moments for the transitions of each ground state to double excited states, generally there exists no exact dark state in the system. Close to the two-photon resonance, the probe light can be absorbed orgained and propagate in the so-called superluminal form. This system may be used as an optical switch.