摘要:

Submicron spatial resolution photoluminescence is used to assess radiative efficiency and spatial uniformity of GaN/InGaN heterojunctions. Room temperature photoluminescence of multiple InGaN quantum wells with GaN barriers fabricated by electron-cyclotron resonance assisted molecular beam epitaxy was measured as a function of position on a facet perpendicular to the layer structure. Our high resolution studies reveal that the radiative recombination for the InGaN quantum wells is 50–60 times more efficient than for the underlying GaN film. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118600

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Direct evidence for the multiphoton ionization with subsequent fragmentation of the chromate ions(CrO42−)adsorbed on a disperseSiO2surface is provided by luminescence measurements using the Nd-doped yttrium aluminum garnet pulsed laser as a source of excitation. Experiments were done with the fundamental laser frequency (&lgr;=1.064 &mgr;m;&tgr;p=20 ns). The multiphoton absorption proceeds through an intermediate three-photon resonance state. The luminescence response results from recombination of photoelectrons with ionizedCrO42−ions and ionized surface oxygendeficient centers. The dynamics of this process include autoionization, which is stimulated by intermolecular perturbation in overexcited states, fragmentation of chromate ions, and annealing of the oxygen-deficient centers. ©1997 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.118572

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report observations of photorefractive grating fixing in potassium niobate at room temperature by means of ferroelectric domains. A grating is recorded while the crystal is simultaneously depoled. By repoling the crystal, the presence of a latent grating is revealed. This fixed grating diffracts light with an efficiency which increases when an electric field is subsequently applied and when it is uniformly illuminated. We explain these observations qualitatively using a previously developed model that involves charge compensation by domain walls, and a new aspect that invokes the creation of new trap sites at the ferroelectric domain walls. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118573

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Integrated Mach–Zehnder and straight channel electro-optic modulators have been fabricated with a double-end crosslinked polymer containing amino-sulfone chromophores. The optical power handling capability of these modulators was tested at 1.32 &mgr;m wavelength and at input optical power levels compatible with commercial analog transmitters. At a cw peak intensity of 0.9MW/cm2inside the waveguide, the double-end crosslinked polymer waveguide modulators exhibited no observable increase in optical loss or degradation of nonlinearity during the experiment period. The poled polymer showed a long-term thermal stability of the electro-optic coefficient at 100 °C and photochemical stability at 633 nm wavelength. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118574

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We have observed mid-infrared photoluminescence at &lgr;≈10 &mgr;m between conduction subbands in GaAs quantum wells. As for regular band-to-band interband photoluminescence spectroscopy, carriers are optically generated in the quantum wells using an interband optical pumping. At room temperature, the excited subbands of the quantum wells are thermally populated. Most of the carriers recombine nonradiatively through electron–phonon interactions, but a fraction of the carriers in the excited subbands recombine radiatively and give rise to the intersubband spontaneous emission in the 10 &mgr;m wavelength region. The intersubband photoluminescence is polarized along the growth axis of the quantum wells as expected from intersubband polarization selection rules. The emitted optical power is in the nW range and the quantum efficiency is found in agreement with calculations taking into account the radiative subband lifetimes. The emission is analyzed in terms of a blackbody emission of an electron gas in a two-dimensional confined system. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118601

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate the improvement of an indium tin oxide anode contact to an organic light emitting device via oxygen plasma treatment. Enhanced hole-injection efficiency improves dramatically the performance of single-layer doped-polymer devices: the drive voltage drops from >20 to <10 V, the external electroluminescence quantum efficiency (backside emission only) increases by a factor of 4 (from 0.28&percent; to 1&percent;), a much higher drive current can be applied to achieve a much higher brightness (maximum brightness ∼10,000cd/m2at 1000mA/cm2),and the forward-to-reverse bias rectification ratio increases by orders of magnitude (from102to106–107).The lifetime of the device is also enhanced by two orders of magnitude. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118575

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We report the operation of new photo-pumped blue-green ZnCdSe/ZnCdMgSe graded-index separate confinement heterostructure single quantum well lasers grown lattice matched on InP substrates. Laser emission at 512 nm was observed. TheT0value is 150 K at room temperature. These materials are proposed as alternative materials for the fabrication of visible semiconductor lasers. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118576

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We demonstrate that an antenna can be used to realize a near-field optical probe that combines spatial resolution well below the diffraction limit with transmission efficiency approaching unity. The probe consists of a planar bow-tie antenna with an open-circuited gap at its apex. We present proof-of-principle measurements using microwave radiation and discuss scaling the antenna to the visible optical spectrum. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118577

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Masked signal communication between two chaotic lasers, described by rate equations, was implemented using analog circuits. Digital modulation of the gain parameter in the master circuit generated the messages. It is shown that there is a level of modulation for which the receiver circuit decodes the signal by on-off synchronization while the Poincare´ sections, the first return maps and the time of return maps recovered directly from the master signal could not distinguish the bits. The circuits simulate the dynamics of two optically coupledCO2lasers with intracavity saturable absorber. The signal appears to be unbreakable in such low dimensional systems because they operate at homoclinic chaos which corresponds to multibranched one-dimensional return maps. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118578

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present a detailed study of four-wave mixing in a long-wavelength distributed-feedback (DFB) laser for both nearly degenerate and nondegenerate pump-probe detunings. We characterize scaling laws of the power dependence of multiple conjugate waves on the pump and probe power levels for the nearly degenerate case. We also measure the output ratio of the probe and conjugate waves up to a detuning of 500 GHz and report the cavity enhancement of the DFB laser on this output ratio. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.118579

出版商:AIP    

年代:1997

数据来源: AIP