摘要:

A new method for obtaining cross‐linked second‐order nonlinear optical polymer by photochemical reaction has been described. An active dye was processed and poled in a photoreactive polymer in a manner similar to doped polymer system, and photo‐cross‐linked in the poled phase by ultraviolet irradiation. The dye doped (20% by weight) cross‐linked polymer has a nonlinear optical coefficientd33of 5.1 pm/V at 1.540 &mgr;m and shows no relaxation after being subjected to thermal treatment at 60 °C for 0.5 h.

ISSN:0003-6951    

DOI:10.1063/1.104843

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Silver bromide nanoparticles exposed briefly to intense UV light in the presence of ethylenediaminetetraacetic acid (EDTA) have optical extinction spectra similar to those computed for distributions of silver‐coated silver bromide nanoparticles. With longer exposure times the plasmon resonance maximum is shifted to shorter wavelengths, a result consistent with theory so long as the coat thickness increases with exposure to light. The resonance maximum of the distribution of coated particles can be controllably shifted from 400 up to 700 nm.

ISSN:0003-6951    

DOI:10.1063/1.104844

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Visible light (665 nm) laser diodes employing a strained‐layer, single quantum well, graded index separate confinement heterostructure were fabricated from epitaxial wafers grown by metalorganic chemical vapor deposition. Threshold current densities for single element, uncoated, broad‐area diodes operated cw as low as 425 A/cm2, cw power outputs of 340 mW per facet, and pulsed outputs (100 &mgr;s pulse width) of slightly under 1 W per facet were achieved. These power output values are believed to be the highest reported to date for visible light diode lasers, and this cw threshold current density is believed to be, by far, the lowest.

ISSN:0003-6951    

DOI:10.1063/1.104845

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

This letter describes some Monte Carlo simulations of electron transport in quantum well infrared photodetectors designed to operate in the 10 &mgr;m wavelength range. These GaAs/AlGaAs superlattice photodetectors absorb radiation between a bound state in the wells and the continuum of states above the wells. We have studied the collection efficiency of the photoexcited electrons at 70 K as a function of bias across the device, as well as the response time. It is concluded that the quantum mechanical well capture transition rate through interaction with LO phonons, between the extended states in the continuum and the bound state, has to be considered for agreement with the experimental results.

ISSN:0003-6951    

DOI:10.1063/1.104846

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A Michelson interferometer containing a nonlinear fiber in one arm and dispersion control in the other arm has been used for passive mode locking of a continuous wave Nd:glass laser. We discuss scaling issues and demonstrate the usefulness of this technique by generating ≊300 fs pulses with onlyPf≊15 mW of average power in the fiber and ≊100 fs pulses with a self‐starting threshold ofPf≊100 mW.  

ISSN:0003-6951    

DOI:10.1063/1.104847

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Optical emission measurements of the Doppler broadening of argon (549.6 nm) and helium (501.6 nm) neutral lines in the unmagnetized regions of an electron cyclotron resonance plasma show that the gas temperature ranges from 300 to 900 K. After compensation for Zeeman splitting, Doppler widths are found to be constant across the radius of the plasma. Plasma heating of the argon gas (0.77 mTorr) is shown to increase from 300 to 500 K as microwave power absorption increases from 80 to 330 W. Long neutral residence times are observed to increase the argon gas temperature to ≊900 K. Helium and argon neutral temperatures decrease as the neutral mean free path increases indicating that the gas may be heated by ion‐neutral collisions including charge exchange.

ISSN:0003-6951    

DOI:10.1063/1.105232

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Silicon oxynitride films of controlled composition have been deposited on silicon by dual ion beam sputtering (DIBS) making simultaneous use of an energetic argon ion beam to sputter silicon nitride from a target and a low‐energy oxygen ion beam to react with the sputtered film on the substrate. The correspondence between film properties and oxygen beam parameters has been studied from measurements of refractive index, chemical etch rate, infrared absorption, and x‐ray photoelectron spectroscopy spectra.Insituion beam oxidation of silicon prior to oxynitride deposition results in a film with a low insulator charge density (3.5×1011cm−2) and interface trap density (4×1011cm−2 eV−1).

ISSN:0003-6951    

DOI:10.1063/1.104848

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The preparation of epitaxial potassium‐tantalate‐niobate (KTa0.7Nb0.3O3, KTN) films on strontium‐titanate substrates by means of pulsed excimer laser evaporation in vacuum is reported. In the most successful deposition experiments, a segmented evaporation target consisting of a semicircular KTN single crystal and a semicircular potassium nitrate pellet was utilized−to our knowledge for the first time; it was thus possible to overcome the otherwise observed partial loss of the volatile potassium and to avoid potassium deficiency in the KTN films. Rutherford backscattering spectrometry and x ray diffraction results indicate that the samples have the desired stoichiometric composition as well as the orientation prescribed by the substrate crystal.

ISSN:0003-6951    

DOI:10.1063/1.104849

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The nucleation and growth of cubic boron nitride (c‐BN) onto diamond powder using solid NaBH4in low pressure gas mixtures of NH3and H2by microwave plasma enhanced chemical vapor deposition has been studied. Boron nitride was deposited on submicron diamond seed crystals scattered on (100) silicon single crystal wafers and evidence was found for the formation of the cubic phase. Diamond powder surfaces appear to preferentially nucleatec‐BN. In addition it was found that the ratio ofc‐BN to turbostratic structure boron nitride (t‐BN) deposited increases with decreasing NH3concentration in H2. It is suggested that this may be due to an increased etching rate fort‐BN by atomic hydrogen whose partial pressure may vary with NH3concentration.

ISSN:0003-6951    

DOI:10.1063/1.104850

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The seeding for large‐area mosaic diamond films approaching single‐crystal quality is described. The technique includes patterned etching of relief structures in Si substrates, deposition from a slurry and orientation of macroscopic diamond seed crystals in the structures, and chemical vapor deposition overgrowth of the diamond seeds to form a continuous film. The film comprises ∼100 &mgr;m single crystals, which are separated by low‐angle grain boundaries of a few degrees or less. We believe that these low‐angle grain boundaries will not affect the electrical properties of majority‐carrier devices.

ISSN:0003-6951    

DOI:10.1063/1.104851

出版商:AIP    

年代:1991

数据来源: AIP