摘要:

The significant effect of fat emulsion intralipid‐10% mixing on lasing behaviors of liquid microdroplets was studied using rhodamine 6G dye. This highly scattering medium allows one to make the high‐gain laser dye‐soft scatterers microsystems that can provide well‐defined lasing threshold and one‐order or more magnitude enhancement of emission intensity with suitable (optimum) conditions of the mixing ratio, in comparison with original neat‐dye lasing microdroplets. We also present and discuss the measured results of input–output intensities for different dye concentrations and dye‐intralipid mixing ratios, and microscope images of spatial distribution of emission from both the microdroplets containing neat‐dye and dye‐intralipid mixture. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117869

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The mode behavior of symmetric air‐post vertical cavity surface emitting lasers is investigated using a unique tandem triple‐pass Fabry–Perot interferometer as well as standard characterization techniques. A series of high resolution spectra taken at various current levels demonstrates relaxation oscillations of the fundamental mode and the lifting of mode degeneracy by crystal birefringence and structural anisotropy. Near field images andL–Imeasurements identify the discontinuous jumps in mode number and polarization. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117870

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have investigated an antiferroelectric liquid crystal which is stabilized by a polymer network. The latter is formed byinsituphotopolymerization of a mesogenic diacrylate. The pure liquid crystalline monomer shows the well‐known tristable electro‐optic switching due to a field induced transition from the antiferroelectric to the ferroelectric state. The change of the optical transmittance due to this transition becomes more continuous if a polymer network is present. Thus, different gray shades can be easily achieved in polymer‐stabilized antiferroelectric liquid crystals. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117871

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present an experimental study of the photorefractive effect in a multifunctional carbazole trimer sensitized with 2,4,7‐trinitro‐9‐fluorenone. The trimer consists of a central carbazole ring which is conjugated with two 6‐dicyanovinylcarbazoles through ethynylene groups. It exhibits intrinsically photocarrier transporting, electro‐optic, film‐forming, and room‐temperature poling properties. Photorefractive effect at a wavelength of 633 nm was demonstrated by measuring the phase shift of refractive index and asymmetric energy transfer in a two‐beam coupling experiment. A large net photorefractive gain coefficient (&Ggr;‐&agr;) of 76/cm was obtained in a sensitizer‐optimized material. A four‐wave mixing experiment was carried out to measure the magnitude of index modulation and dynamics of the grating formation. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117872

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Phase‐matched second‐harmonic generation in the highly &khgr;(2)‐active layered semiconductor GaSe is demonstrated in the near‐infrared frequency region. Due to the high indices of refraction, the internal phase‐matching angle of about 30° is beyond the critical angle of total reflection for az‐cut crystal. This problem is overcome by sandwiching the crystal between two half‐cylindrical glass rods, which leads to a shift of the critical angle to larger values. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117873

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have realized a three‐layered multicolor organic electroluminescent device utilizing poly (9,9‐dihexylfluorene) and perylene derivatives as emission layers, with diamine derivatives as an electron blocking layer. Emission colors could be selected either blue or red by changing the polarity of the applied voltage. By driving with an ac biased electric field, both emission colors were observed and the intensity ratio of each emission color was modulated by the frequency of the applied ac field. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117874

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We analyze the effect of nonlinear loss on four‐wave mixing (FWM) conversion efficiency. Maximum conversion efficiency is geometry independent and equal toe−2|&khgr;(3)/Im{&khgr;(3)}|2when nonlinear loss dominates. Optimum device length and operating conditions are obtained and theoretical results are verified with a picosecond pulse FWM experiment. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117875

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We present the results of spectroscopic studies on GaN based epitaxial materials on SiC substrates by metalorganic chemical vapor deposition. A variety of techniques has been used to study the optical properties of GaN epilayers and GaN/AlGaN heterostructures. Sharp spectral structures associated with the intrinsic free excitons were observed by photoluminescence and reflectance measurements from GaN based materials grown on SiC substrates. The residual strain was found to have a strong influence in determining the energies of exciton transitions. Picosecond relaxation studies of exciton decay dynamics suggest that an AlGaN cladding layer with a small mole fraction of AlN can be relatively effective in enhancing the radiative recombination rate for excitons by reducing the density of dislocations and suppressing surface recombination velocity in the GaN active layer for the GaN/AlGaN heterostructure samples. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117876

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We have investigated the surface reflection properties of a layer‐by‐layer photonic crystal. By using a Fabry–Perot resonant cavity analogy along with the reflection‐phase information of the photonic crystal, we predicted defect frequencies of planar defect structures. Our predictions were in good agreement with the measured defect frequencies. Our simple model can also predict and explain double defect formation within the photonic band gap. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117877

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the application of optical second‐harmonic generation to the measurement of ultrafast electrical pulses. The technique relies on the sensitivity of the second‐harmonic response to electric fields in centrosymmetric materials. Electrical pulses propagating on a silicon‐based coplanar transmission line have been characterized with subpicosecond time resolution and 100 mV/&sqrt;Hz sensitivity. We have measured the bias dependence of the second harmonic intensity over a 20 V range and have used this data to calibrate the transient response. The observed full‐width at half maximum response time of the SHG waveform is ∼1 ps, which is consistent with the value obtained from an electronic cross‐correlation measurement. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117878

出版商:AIP    

年代:1996

数据来源: AIP