摘要:

We report on the coherent detection of ultra-broadband mid-infrared electromagnetic pulses using a 30-&mgr;m-thick ZnTe electro-optic sensor. The detected frequency spectrum exceeds 37 THz, extending from microwave to the mid-infrared. The frequency response can be further improved by reducing the sensor thickness to 10 &mgr;m. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119873

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Shock waves generated by rear- and front-side infrared(&lgr;=1.064 &mgr;m)laser irradiation of calcite were measured using time-resolved surface-plasmon resonance spectroscopy. The shock waves generated in the two cases are found to be distinctly different: Rear-side ablation gives rise to planar shock waves, while the front-side ablation is more nearly spherical. The observed differences are related to differing material-removal mechanisms at the two surfaces. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119930

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A model for the current–voltage characteristics and the quantum efficiency of single-layer organic light emitting diodes is presented. With variables such as the electric field, the hole, and electron carrier densities, a set of coupled nonlinear differential equations is derived by using classical electrostatics and by assuming Fowler–Nordheim injection. Numerical calculations for different carrier mobility and barrier height conditions show that low barrier height at both electrodes leads to higher efficiency and higher carrier mobility leads to higher brightness. We find that for applications that require high current injection such as lasers, materials with high mobility are desired to reduce space charge effects. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119874

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Thep-i-njunction in a polymer light-emitting electrochemical cell (LEC) is stabilized by cooling the device below the glass transition temperature of the ion-transport polymer. LECs with frozenp-i-njunctions exhibit typical light emitting diode (LED) behavior including diode rectification, unipolar light emission (same polarity as that used for generating the junction), and fast response. The freezeout of ion motion allows polymer LECs to be driven at bias voltages well beyond the electrochemical stability window, and thereby extends the potential applications of polymer LECs to high pixel density, column-row addressable displays. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119875

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report on grating-tuned tapered lasers that oscillate on a single external-cavity mode at powers as high as 720 mW. Frequency stabilization and side-mode discrimination are achieved through the use of an intracavity etalon. The emission frequency was stabilized against mode hops for a period of>2000 sand exhibited a short term jitter of∼85 MHzover a period of 300 s. The single-frequency emission was tunable over a 17 nm range centered at 783 nm. Furthermore, the far-field emission remained near-diffraction limited throughout the measured current range(<2 A).©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119876

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Stimulated emission was observed from optically pumped GaN quantum dots in anAlxGa1−xNseparate confinement heterostructure fabricated on 6H-SiC(0001) substrate by metal organic chemical vapor deposition. Nanostructural GaN quantum dots, with an average size of ∼10 nm width, ∼1–2 nm height, and density of ∼1011 cm−2, were self-assembled on theAlxGa1−xNcladding layer surface. The stimulated emission peak was observed at ∼3.48 eV, which is ∼50 meV lower than that of spontaneous emission. The excitation power dependence on the emission intensity clearly indicates threshold pump power density of 0.75 MW/cm2for the onset of stimulated emission. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119877

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A novel method is presented herein regarding the preparation of a single-layer organic electroluminescent (EL) polymer thin film device. The device was made by simultaneously co-depositing two polymer thin film forming monomers, a hole-transporting molecule triphenyldiamine derivative (TPD) and an EL active molecule 1,1,4,4-tetraphenyl-1,3-butadiene (TPB) on an indium-tin-oxide (ITO) glass substrate. The device structure was composed of the ITO glass, the TPD, and TPB co-doped polymer thin film, and a thermally evaporated aluminum electrode. Carrier injection from the two electrodes was significantly observed and the blue light in EL spectra, with an emission maximum at 435 nm, was triggered at a driving voltage of 17 V. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119878

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A simultaneous generation of multiwavelength short pulses is demonstrated by self-injection seeding of a laser diode. The wavelengths are selected by the use of multiple optical paths in an external cavity consisting of a grating, a beam splitter, and two mirrors. By adjusting the grating and either one of the mirrors, the wavelengths and their spacings can be readily tuned in a flexible manner. The system is simple, robust, and is of low cost. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119879

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present an analytic theory of the transmission of electromagnetic waves through a structure “two-dimensional electron system with a flowing current – grating coupler.” The transmission coefficientT(&ohgr;,vdr)is calculated as a function of frequency, drift velocityvdr,and other physical and geometrical parameters of the structure. Threshold conditions for amplification[T(&ohgr;,vdr)>1] are analyzed. A number of ideas for a reduction of the threshold velocity and an enhancement of the amplification are proposed. Our results can be used for designing tunable solid-state terahertz wave amplifiers (generators), based on the grating coupled low-dimensional electron systems. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119880

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

High angle hollow cone darkfield orZ-contrast imaging is used to supress dynamical contributions like bend or extinction contours to electron imaging. Using a multiple scattering model it is possible to interpret image intensities quantitatively and to analyze specimen composition on a nanometer scale without specialized detectors like energy-energy-loss spectroscopy or energy dispersive spectroscopy. This method is practically tested on the interdiffusion of Cu-Au couples. Measured thin film interdiffusion coefficents, are comparable to literature data of the bulk diffusion coefficent in this system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119881

出版商:AIP    

年代:1997

数据来源: AIP