摘要:

Tunable wavelength filters are demonstrated based on the thermo-optic refractive index change of the polymer waveguide with Bragg reflection grating. For the low-loss waveguide operating around 1.55 &mgr;m, fluorinated polymers are incorporated. Bragg reflection gratings are fabricated using a phase mask and a high-index polymer. The Bragg reflector exhibits a narrow bandwidth of less than 1.0 nm, a crosstalk of −20 dB, an insertion loss of 3.2 dB, and a flat-top passband. The peak wavelength of Bragg reflection is shifted over 11 nm with a slight insertion loss change. The thermo-optic tuning efficiency is 22 nm/W and the peak shift is linearly proportional to the heating power. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122527

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The effect of a local electric field upon photogeneration efficiency was investigated through analyses of the dependence of photocurrent, photorefractive gain, diffraction efficiency, and birefringence on the applied field of a novel photorefractive polymer containing an ionic tri(bispyridyl) ruthenium complex. It was found that since this polymer system possesses a low glass transition temperature, the dipole moments formed between the counter ions are readily aligned and generate ionic dipole field which screen photogeneration sites from the applied field. This local field lowers the photogeneration efficiency and results in the saturation of photocurrent and photorefractive gain at high applied field. This local field’s effect on an ionic polymer is further confirmed experimentally by comparing the photoconduction of a similar nonionic polymer. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122528

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the preliminary experimental results obtained from an annular radio-frequency excitedCO2laser with a Talbot cavity and a phase correcting mirror external to the cavity. The Talbot cavity is adopted in order to reduce the number of oscillating azimuthal modes. The use of the external profile-modulated mirror is aimed at reducing the beam phase modulation and thus increasing the amount of fundamental annular mode energy content. The beam quality results to be sensibly increased. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122529

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

With the collinear model forH2+,we have numerically investigated the photoelectron spectrum of hydrogen molecular ions exposed to an ultrashort intense laser pulse. Above-threshold ionization (ATI) peaks and their temporal evolution are carefully analyzed. We find that once the photon-energy-spaced photoelectron peaks appear, their positions will not shift during the interaction. The stability of ATI spectrum is attributed to the fact that the Stark-shifted ionization potential ofH2+exhibits a minimum plateau during the internuclear distanceRc=3.6–6 bohrin which the stretchingH2+is significantly ionized. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122530

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The effect of silanol content on the grating buildup dynamics was examined by preparing two different lots of polymethylphenylsilane (PMPS). While the high silanol-containing PMPS showed very sluggish grating formation time, the lower silanol-containing PMPS exhibited very rapid grating formation in a diffraction efficiency measurement. The diffraction efficiency, on the other hand, was found to be unaffected. The results suggest that the silanol is acting as hole trap and a reduction of its content is a key to improving the response characteristics of polysilane-based photoconducting electro-optic polymer composite for photorefractive applications. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122531

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Patterning characteristics of indium tin oxide thin films using different wavelengths of a diode-pumpedQ-switched Nd:YLF and a flashlamp-pumped Nd:YAG laser have been studied. While a ripplelike structure in the etched line was formed due to incomplete material removal when the first harmonic of the Nd:YLF or Nd:YAG laser was used, a residue-free line could be obtained using the fourth harmonic of the Nd:YLF laser even at higher scan speeds. The observed differences in the morphology could be attributed to different absorption characteristics at the infrared and ultraviolet wavelengths. High process speeds in excess of 1 m/s could be achieved. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122532

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A hybrid inkjet printing (HIJP) technology, which combines a pin-hole free polymer buffer layer and an inkjet printed polymer layer, allows the patterning of high quality polymer light-emitting devices. In this letter, we present a successful demonstration of controllable patterning of dual-color polymer light-emitting pixels using this HIJP technique. In this demonstration, the polymer buffer layer is a wide band gap, blue emitting semiconducting polymer prepared by the spin-casting technique. The inkjet printed layer is a red-orange semiconducting polymer which was printed onto the buffer layer. When a proper solvent was selected, the printed polymer diffused into the buffer layer and efficient energy transfer took place generating a red-orange photoluminescence and electroluminescence from the inkjet printed sites. Based on this principle, blue and orange-red dual-color polymer light-emitting pixels were fabricated on the same substrate. The use of this concept represents an entirely new technology for fabricating polymer multicolor displays with high-resolution, lateral patterning capability. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122533

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Room-temperature lasing at the wavelength of 1.31 &mgr;m is achieved from the ground state of an InGaAs/GaAs quantum-dot ensemble. At 79 K, a very low threshold current density of 11.5 A/cm2is obtained at a wavelength of 1.23 &mgr;m. The room-temperature lasing at 1.31 &mgr;m is obtained with a threshold current density of 270 A/cm2using high-reflectivity facet coatings. The temperature-dependent threshold with and without high-reflectivity end mirrors is studied, and ground-state lasing is obtained up to the highest temperature investigated of 324 K. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122534

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Catastrophic optical damage (COD) in Al-free InGaAs/InGaP 0.98 &mgr;m lasers has been investigated using real-time electroluminescence (EL) and transmission electron microscopy (TEM). From EL images, we observed that multiple bright spots initiated from one of the facets and then propagated to the center of the cavity during the COD process. It is clarified by the TEM analysis that the propagation of bright spots resulted in 60-nm-wide Moire´ fringe along the cavity and the crystalline phase of the active area became polycrystalline. Highly nonradiative polycrystalline phase of the active area is the major cause of COD failure in the Al-free 0.98 &mgr;m lasers. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122557

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

In situphotoluminescence (PL), Raman, and infrared (IR) spectra of porous Si (PS) duringF2/D2Oexposures were investigated.F2exposure at 298 K resulted in a peak shift of PL band from 750 to 670 nm with an intensity reduction. IR spectra revealed that the surface hydrogenated Si of the PS was displaced by fluorinated one. By subsequentD2Oexposure, the PL band further shifted to a shorter wavelength with a significant intensity increase: IR bands due to surface oxides as well as SiD and SiOD bonds were observed after the exposure. On the contrary, the average size of the Si crystallites in the PS evaluated from Raman spectra remained almost unchanged throughout the exposures. These results suggest that surface chemistry plays a crucial role in the PL of the PS. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122508

出版商:AIP    

年代:1998

数据来源: AIP