摘要:

1.5 &mgr;m GaInAs/AlGaInAs multiquantum‐well (MQW) lasers with 1% compressively strained quantum wells were grown by molecular‐beam epitaxy. The effective differential gain (g0) determined from the squared relaxation oscillation frequency versus output power relations is a high value of 9.3×10−16cm2in long‐wavelength lasers. On the other hand, the effective transparent carrier density (n0) of strained‐layer MQW lasers determined from the measurement of the spontaneous carrier lifetime was found to be very high, which is different from the theory of strain effects. However, by taking the carrier transport effect into account, it was shown that (1) for the strained MQW lasers the intrinsic transparent carrier density is lower than that of the lattice‐matched MQW lasers, and (2) the intrinsic value ofg0is estimated to be 28–56×10−16cm2, which is close to the theoretically predicted value. By improving the laser structure to have better carrier transport, much higher effective differential gain and lower effective transparent carrier density can be expected. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114532

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We demonstrate a novel concept for a mode selection mechanism in surface emitting laser diodes. This concept is based on a strong coupling process between the laser mode and a surface mode on top of the laser diode. The mode selection mechanism is the result of a strong feedback from the surface mode into the laser diode. Nearly single‐modelike emission spectra are achieved from surface emitting GaAs/AlGaAs laser diodes and qualitatively explained by a model based on ray optics. The main advantage of this type of laser diode is its simple fabrication and the possibility of adjusting the desired wavelength independent of the growth process by external technological parameters. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114533

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The transient behavior of photorefractive gratings in the polymer composite poly(N‐vinyl carbazole) (PVK), 2,4,7‐trinitro‐9‐fluorenone (TNF), and N,N‐diethyl‐para‐nitroaniline (EPNA) doped with various amounts of 4‐(diethylamino)benzaldehyde diphenylhydrazone (DEH) is presented. The influence on the hole drift mobility due to the change in the trap density induced by DEH, was directly measured. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114534

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Two‐beam coupling gain coefficients of transmission and reflection gratings inBaTiO3:Ce crystals versus wavelength between 570 and 680 nm have been measured. The former decreases more quickly than predicted by theory. The latter was found to vary significantly with wavelength, while theory shows that it should vary little. In order to explain the experimental results we assumed that the effective carrier number densityNeffdepends on wavelength. By calculatingNefffrom the measured results we found thatNeffis approximately a linearly decreasing function of wavelength. The slopes and intercepts for the linear functions are given for the two crystals studied. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114535

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A novel mechanism for creating a periodic gain is presented which can be used in the design of complex‐coupled distributed feedback semiconductor lasers. A one‐dimensional longitudinal analysis shows that this gain‐coupling mechanism is characterized by negative differential coupling, which earlier reports have shown can offer the most significant reduction in the linewidth enhancement factor. A linewidth analysis predicts that the linewidth enhancement factor can be reduced by about a factor of 2 because of the negative differential coupling. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114536

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The dynamics of gain‐switched, low‐pressure photolytic iodine lasers were investigated experimentally and theoretically as a function of pressure and buffer gas. The behavior of the pulse shape, build‐up, and duration can be explained by relaxation from a nonthermalized to a thermalized velocity distribution of the gas. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.114537

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Recently, it has been shown that when a semiconductor laser is directly modulated at high frequencies, the modulation signals suffer substantial loss and phase shift propagating from the wire feed point along the length of the laser. It was suggested that these distributed microwave effects lead to a further bandwidth degradation in electrical current injection over the single‐pole roll‐off predicted by a lumped RC model. We show, however, that this degradation is significant only when the laser is driven directly by a voltage source. In contrast, when the laser is driven, commonly, through a 50 &OHgr; transmission line the degradation is minimal, and the total injection current is still RC limited. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114538

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have measured the complete 1.7 &mgr;m excited state absorption (ESA) spectrum in erbium‐doped glasses. The spectrum is obtained by measuring the gain of an erbium‐doped waveguide in the 1400–1800 nm region. Using the measured spectra, we estimate the 1.5 &mgr;m uniform upconversion rate by calculating the spectral overlap between the 1.5 &mgr;m emission and 1.7 &mgr;m ESA cross sections. The technique is applied to erbium‐doped, ion‐exchangeable silicate glasses yielding upconversion constants in the range of 1–10×10−18cm3/s. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114539

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Evidence is presented for a significant influence of electrode surface material and condition on the measurement of the kinetic energies of ions sampled from discharges through an orifice in the electrode. Significant differences in ion energy shifts and/or discrimination of low‐energy ions are found using aluminum and stainless‐steel electrodes in a radio‐frequency (rf) discharge cell. It is argued that the observed differences in energy shifts may be attributable in part to differences in charging of oxide layers on the electrode surface around the sampling orifice. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114540

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The atomic force microscope is used to measure dielectric polarization forces on surfaces induced by a charged tip. On insulators, the major contribution to the surface polarizability at low frequencies is from surface ions. The mobility of these ions depends strongly on the humidity. Using polarization forces we have been able to image liquid films, droplets, and other weakly adsorbed material. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114541

出版商:AIP    

年代:1995

数据来源: AIP