摘要:

The effect of through‐thickness temperature gradients in thin films irradiated by short laser pulses is described, together with its application to direct overwrite. We found by simulation that through‐thickness temperature gradients become substantial when a medium is irradiated by short laser pulses of the order of 1 ns which is the characteristic time of heat diffusivity. This effect qualitatively explains why in writing experiments on a double‐layered medium short pulses expand the laser power range for a writing process.

ISSN:0003-6951    

DOI:10.1063/1.103957

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Drastic changes in index of refraction and volume shrinkage of spin‐on‐glass films induced by P+implantation are reported. An increase in refraction index (n) as large as 20% (from 1.38 to 1.79) has been measured following 1.6×1016cm−2implantations. The changes innare accompanied by a volume shrinkage of similar magnitude. However, at doses exceeding ≊1015cm−2the shrinkage saturates while the index of refraction continues to increase indicating that material changes other than simple densification must be responsible for the observed rise in refractive index.

ISSN:0003-6951    

DOI:10.1063/1.103958

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The optical characteristics of the new nonlinear crystal lithium triborate (LiB3O5) are evaluated for second‐harmonic generation (SHG) in the femtosecond regime. Using crystals grown in our laboratory, we demonstrate the use of LiB3O5for autocorrelation measurements of ultrashort optical pulses. We find that pulse widths down to 40 fs can be measured accurately with crystal thicknesses varying from 0.195 to 4.165 mm. The effect of crystal length on the autocorrelation shape is also investigated.

ISSN:0003-6951    

DOI:10.1063/1.104211

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Electrically controllable optical waveguides have been created by using only the increase in refractive index from linear and quadratic electro‐optic effects in GaAs/AlGaAs multiple quantum well substrates for the first time. Unlike conventional fixed waveguides, lateral guiding of this field‐induced guide (FIG) can be turned on and off, so that the confinement factor, propagation constant, and net loss can be adjusted over wide ranges electrically. This special property plus a very simple fabrication process suggest that the FIG could be an important base technology for photonic integrated circuits.

ISSN:0003-6951    

DOI:10.1063/1.103959

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Continuous‐wave room‐temperature operation is reported for the first time of vertical cavity current injection semiconductor lasers with a metallic reflector. The GaAs/(AlGa)As lasers have low‐threshold currents of 8 mA for 8‐&mgr;m‐diam contacts and threshold current densities of 9.5 kA/cm2. Single longitudinal mode and bimodal operation are obtained for short and long Fabry–Perot e´talons, respectively. The spectral width of the single‐mode laser line is 0.1 A˚. The laser structures have a very small series resistance which results in a voltage drop of 1.8 V along the diodes at lasing threshold.

ISSN:0003-6951    

DOI:10.1063/1.103960

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

The interfacial‐gel copolymerization of 3/1, or 4/1 (wt/wt) methyl methacrylate‐vinyl benzoate monomer mixture followed by heat drawing results in graded‐index plastic optical fibers with attenuation loss of 212 and 134 dB/km at 652 nm, respectively, and with bandwidths of 170 and 260 MHz km, respectively, in comparison with 6 MHz km of the current step‐index plastic optical fiber. Now, it has been confirmed experimentally that graded‐index fibers are tremendously superior to step‐index fibers for data‐carrying capacity, while attenuation losses of both fibers are comparable.

ISSN:0003-6951    

DOI:10.1063/1.103961

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Spontaneous emission and gain measurements in GaAlAs single quantum well lasers are presented. The gain is derived from the spontaneous emission detected through an opening in the top metallic contact of the lasers. Excitonic effects are seen in the gain (absorption) spectra for low carrier densities, and the step‐like nature of the two‐dimensional density of states is evident. From the gain spectra, refractive index changes are derived via a Kramers–Kronig transformation, and this is used to evaluate the linewidth enhancement factor as a function of photon energy.

ISSN:0003-6951    

DOI:10.1063/1.103962

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Large second hyperpolarizabilities, ⟨&ggr;xxxx⟩, have been measured in solutions of two recently prepared organic polymer superlattices. These compounds have period aromatic and quinoidal structures and differ from each other by a side group substituent. The values observed are 1.6×10−29esu for the parent copolymer and 3.7×10−30esu for its acetoxy derivative. The corresponding values of &khgr;(3)xxxxfor the solid phase are estimated to be 2.7×10−7and 4.5×10−8esu. Time‐resolved degenerate four‐wave mixing measurements, made at 532 nm, showed that the dynamics of the parent copolymer were faster than the 25 ps resolution of the instrument while the derivative exhibited an additional slower response component.

ISSN:0003-6951    

DOI:10.1063/1.104116

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

In this letter we report the first femtosecond measurements of gain and loss dynamics in InGaAsP diode laser amplifiers using optically induced changes in diode junction voltage. Our results confirm that previously observed optical pump‐probe signals are related to carrier dynamics in the active region of the amplifiers.

ISSN:0003-6951    

DOI:10.1063/1.103963

出版商:AIP    

年代:1990

数据来源: AIP

摘要:

Gigahertz surface acoustic waves have been optically generated and detected on aluminum metallic films and silicon wafers using the laser‐induced grating technique. The acoustic velocities were in good agreement with those of Rayleigh waves. Photothermal surface gratings could also be detected as a nonpropagating component of the thermoelastic waves. The relaxation time of the grating was related to the thermal diffusivity of the material. A simplified theory for the generation of surface transient gratings containing acoustic waves is presented in addition to the experimental results.

ISSN:0003-6951    

DOI:10.1063/1.103964

出版商:AIP    

年代:1990

数据来源: AIP