摘要:

The high threshold current densities of single quantum well separate confinement heterostructure grating‐coupled surface‐emitting lasers are shown to result from a combination of inadequate gain in the lowest quantum state and the wavelength selective properties of the grating reflectors. The situation is aggravated by the saturable absorption loss in the grating sections and sizeable scattering losses at the etch step between gain and grating regions. Grating‐coupled surface‐emitting lasers with 50‐&mgr;m‐wide broad‐area double quantum well active regions are reported with threshold currents reduced by a factor of 3 and with improved differential efficiency. Measurements of gain saturation of single quantum wells are presented.

ISSN:0003-6951    

DOI:10.1063/1.101767

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Coherent operation of an array of AlGaAs diode lasers was obtained by placing the array in an external cavity which made use of the Talbot self‐imaging effect to couple the laser diodes together. A spatial filter was required to suppress oscillation of the highest order mode of the array. This filter introduced no significant loss to the cavity mode, and the mode was observed to be stable up to the maximum rated drive current for the device.

ISSN:0003-6951    

DOI:10.1063/1.101768

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

High quality single (SQW) and multiple (MQW) quantum well InGaAs/InP lasers have been realized for the first time utilizing a newly developed interlayer growth technique. The technique utilizes separate confinement SQW and MQW lasers grown by atmospheric pressure metalorganic vapor phase epitaxy (MOVPE) having 10–20 nm InGaAs well(s) cladded by 50‐nm‐thick InGaAsP (&lgr;g=1.46 &mgr;m) waveguide layers. Carrier confinement and interfacial layer perfection are improved by growth of a few monolayers (∼1 nm) of InP at the QW‐barrier interface and by using a novel flushing technique between growth of layers of different compositions. Both SQW and MQW lasers exhibit threshold current density of ∼2 kA/cm2. Buried‐heterostructure lasers grown entirely by MOVPE in a two‐growth step show threshold current of 18–40 mA and quantum efficiency as high as 21% facet with good linearity up to 15 mW.

ISSN:0003-6951    

DOI:10.1063/1.101769

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report on period doubling in a directly modulated InGaAsP semiconductor laser at 1.3 &mgr;m. This behavior is obtained for modulation frequencies betweenfrand 1.6fr, wherefris the laser resonant frequency measured under weak current modulation. The domain of period doubling as well as the time responses of the optical output is well interpreted using a rate equation model.

ISSN:0003-6951    

DOI:10.1063/1.101770

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The external efficiency &eegr;dof quantum well (QW) lasers is maximum at some characteristic laser length, which is dependent upon mirror reflectivities and the number of QWs in the active layer. The observed decrease in &eegr;din short lasers is caused by increased optical absorption associated with a high concentration of free carriers in the QW and the surrounding waveguide layer. The carriers spill into the waveguide because of QW subband filling in short cavity lasers with high threshold gains.

ISSN:0003-6951    

DOI:10.1063/1.101771

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A novel two‐wavelengthp‐i‐ndemultiplexer is proposed and fabricated using dopant‐free partial disordering of GaAs/AlAs quantum wells by rapid thermal annealing. A crosstalk attenuation of 41 dB and an interchannel spacing of 69 nm were achieved in the 0.8 &mgr;m wavelength region.

ISSN:0003-6951    

DOI:10.1063/1.101772

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A self‐pumped phase conjugate reflection induced by another mutually coherent incident beam has been observed and explained successfully for the first time in a photorefractive crystal BaTiO3. Other relevant phenomena, such as the destruction of the coupling channel when two incident beams are mutually coherent, have also been studied. Possible applications are pointed out.

ISSN:0003-6951    

DOI:10.1063/1.102444

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Acoustic phase conjugate waves were generated at a frequency of 50 MHz by nonlinear electroacoustic interaction in LiNbO3and their wave front reversal property was experimentally examined. The wave front of the incident acoustic wave was deformed by inserting a phase object in the beam path, but the phase conjugate wave after retracing the path showed little influence of deformation.

ISSN:0003-6951    

DOI:10.1063/1.102445

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Conventional ion plating theory assumes that the metal vapor arrives at the substrate in monatomic form. Our results suggest this is not the case, and that a large proportion of the metal arrives as clusters. This is based on measurements of the cathode fall distance before and during titanium deposition in a thermionically supported argon glow discharge. The results have been used to evaluate the charge‐to‐mass ratio of the metal species in accordance with the Child–Langmuir equation. This predicts that some titanium is present as atomic clusters which contain at least tens of atoms per unit charge. Also we show that at least 90% of the ion current arriving at the substrate is carried by the metallic species.

ISSN:0003-6951    

DOI:10.1063/1.101773

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Secondary ion‐energy distributions (SIEDs) emitted from Si under various conditions of targets (Si, SiO2) and primary ions (Ar+, O+) were measured and thin SiO2films were deposited by magnetron sputtering techniques under the corresponding conditions to the SIED experiments. The most probable energies of silicon oxygen cluster ions of SimO+n(m,n=1, 2,...) are equal to those of Al+thermal ions, while those of Si+l(l=1, 2,...) remain unchanged with the introduction of oxygen in chamber during Ar+ion bombardment. The current‐voltage plots of SiO2films are also measured and found to be influenced by the deposition conditions. It is concluded that the differences in current‐voltage characteristics of SiO2films prepared under various sputtering conditions can be reasonably explained in terms of the changes in the most probable energy of the sputtered particles.

ISSN:0003-6951    

DOI:10.1063/1.101575

出版商:AIP    

年代:1989

数据来源: AIP