摘要:

Optical nonlinearities of PbSe are studied in picosecond pump‐probe experiments at wavelengths from 4 to 8 &mgr;m. Excitation of an electron‐hole plasma leads to a shift of the absorption edge to higher energies and to large changes of the refractive index by up to −0.1 for a carrier density of 4×1017cm−3. The optical nonlinearities result from band filling by both electrons and holes. The time‐dependent absorption change shows a partial recovery within 100 ps, giving evidence of enhanced recombination rates. Theoretical calculations of the absorption change are in agreement with the experimental data.

ISSN:0003-6951    

DOI:10.1063/1.106381

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Theoretical and experimental work shows that electroabsorption improves and the quantum‐confined Stark effect becomes stronger in In0.2Ga0.8As/AlxGa1−xAs quantum wells as the aluminum concentration (x) is increased in the barriers. This improved electroabsorption was used in a reflection modulator that exhibited the largest reported reflectivity change of 77%.

ISSN:0003-6951    

DOI:10.1063/1.105266

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A pulsed iodine laser driven by a chemical oxygen generator was developed. The energy deposition on I(2P3/2) was made by a high‐pressure pulsed O2(a1&Dgr;g) generator. Although this scheme is the same as the conventional chemically pumped oxygen‐iodine laser (COIL), it is unique in that the pulsed laser was extracted by the high‐energy density pulsed pumping scheme. The pulse energy obtained was 1.34 J, the pulse width was 1.5 ms, and the peak power was 900 W. The specific energy was estimated to be 3.6 J/l.

ISSN:0003-6951    

DOI:10.1063/1.105267

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report the first interferometric characterization of freely propagating, subpicosecond, far‐infrared (FIR) light pulses. FIR light was generated via short pulse photoexcitation of a semi‐insulating InP wafer. The half width of the intensity interferogram was 230 fs. The FIR light contained frequency components from 3 to 150 cm−1.

ISSN:0003-6951    

DOI:10.1063/1.105268

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Passive devices capable of generating coherent blue‐green light radiated in a surface emitting geometry is realized on (111)BGaAs substrates. This substrate orientation is required by the symmetry of the III–V crystals for the particular nonlinear counterpropagating interaction under consideration. The visible light output power versus the fundamental optical power is measured and shown to agree with the theory. This result demonstrates the feasibility of active visible surface emitting generators in the milliwatt output power range on (111)Bsubstrate.

ISSN:0003-6951    

DOI:10.1063/1.105269

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A novel type of optical beam scanning device based on the same principle as a phased array radar has been made and demonstrated. This phased array optical scanning device consisted of a uniformly illuminated array of ten closely spaced, single mode GaAs/AlGaAs electrooptic waveguides, each of which was individually addressed to give more than 2&pgr; radians of optical phase control. This gave a line of ten point sources of light on a 3 &mgr;m pitch at the output face of the array. By independently phase shifting these light sources the output wavefront was controlled to scan a 2° wide beam through 20° in the far field.

ISSN:0003-6951    

DOI:10.1063/1.105270

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We report on the fabrication of poly(methyl methacrylate) (PMMA) nonlinear optical fibers with dye‐doped cores. The dye‐doped cores have an elevated refractive index that defines a waveguiding region with a large third‐order susceptibility and with single‐mode dimensions. The measured third‐order susceptibility of a squarylium‐doped PMMA film material and the measured optical loss of the dye‐doped fiber core results in a figure of merit that is suitable for all‐optical device applications at &lgr;=1.3 &mgr;m. The impact of further improvements in PMMA loss and chromophore nonlinearity are also discussed.

ISSN:0003-6951    

DOI:10.1063/1.105271

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

An analysis of the luminescence quenching of4F3/2level of Nd3+in YAG is presented in terms of two models: uniform random distribution and nonuniform placement of activators. It is shown that the correlated placement model for Nd3+ions, assuming the absence, based on ionic size arguments, of Nd3+ions in nearest‐neighbor sites, is in contradiction with high resolution absorption spectra as well as quantum yield data. The anomalous decay can be described by energy transfer theory for a uniform distribution with a short‐range interaction connecting the nearest‐neighbor pairs and with dipolar interaction inside the other donor‐acceptor pairs.  

ISSN:0003-6951    

DOI:10.1063/1.106420

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We observed the input power dependence of the second‐harmonic generation of a 370‐MHz focused acoustic beam in pressurized superfluid4He at about 300 mK. We also measured the resolving power of a reflection mode acoustic microscope using pressurized superfluid4He as a coupling liquid under 11 atm (anomalous dispersion region) and 21 atm (normal dispersion region). At the nonlinear power region of each pressure, the resolution was improved beyond the diffraction limit. Results of these two experiments confirmed that the higher harmonics are generated and they are converted to the fundamental as the wave propagates through the focal point. The higher harmonics play an important role in recently observed exotic nonlinear phenomenon in pressurized superfluid4He.

ISSN:0003-6951    

DOI:10.1063/1.106297

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Microcrystalline diamonds were successfully deposited on an abraded molybdenum surface under a magnetic field using a combustion flame of acetylene (C2H2) and oxygen (O2) gases. The deposition rate was about 1 &mgr;m/min, which is an order larger than that obtained by conventional chemical‐vapor‐deposition methods. The magnetic field led to an increase of the deposited area and of the microcrystal diameter. The microcrystals show good crystallinity as observed from scanning electron microscopy, reflective electron diffraction, and x‐ray diffraction measurements.

ISSN:0003-6951    

DOI:10.1063/1.106298

出版商:AIP    

年代:1991

数据来源: AIP