摘要:

In this letter the first demonstration of low‐crosstalk passive polarization splitters based on Ti: LiNbO3single‐mode waveguide crossings is reported. Polarization crosstalk of less than −20 dB for both polarizations and total insertion loss figures of −2.5 dB (TE) and −3.0 dB (TM) at &lgr;=1.3 &mgr;m have been achieved by optimizing the design and the fabrication of the intersection area. The devices operated nearly wavelength independent (±0.3 dB) over a range of 100 nm.

ISSN:0003-6951    

DOI:10.1063/1.102452

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report the effect of well profile on the performance of absorptive electro‐optic spatial light modulators based on multiquantum well structures. In particular we calculate the variation in exciton oscillator strength and the absorption coefficient at the signal wavelength as a function of applied electric field. For a monochromatic source at 1572 meV, for example, we consider modulators based on square, parabolic, and asymmetric triangular GaAs‐AlxGa1−xAs quantum wells and find that at zero field the exciton oscillator strengths are comparable but that superior performance is obtained using asymmetric triangular wells. These conclusions hold even assuming fairly large exciton linewidths in triangular wells.

ISSN:0003-6951    

DOI:10.1063/1.101727

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have performed picosecond time‐resolved measurements on In0.53Ga0.47As/InP quantum wells with varying barrier thicknesses using 10 ps Nd:YAG excitation. For this excitation, holes and electrons are created in the In0.53Ga0.47As layers. Due to momentum conservation the Nd:YAG excitation accelerates the electrons above the InP barrier where they can diffuse but cannot recombine. By examining the rise time of the quantum well emission, we can show that for samples with thick barriers, the barrier geometry largely controls the dynamic properties of the carriers after Nd:YAG excitation.

ISSN:0003-6951    

DOI:10.1063/1.101728

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We show theoretically and experimentally that enhancements of up to 40 dB in the efficiency of optical transmission of microwave signals can be obtained by using a single quantum well laser transmitter whose contact is segmented into two sections, and modulation is applied to one of the sections. The improvement is dependent fundamentally on the relaxation oscillation frequency of the device, with the improvement factor dropping to around 15 dB at relaxation oscillation frequencies approaching 10 GHz.

ISSN:0003-6951    

DOI:10.1063/1.101729

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The room‐temperature modulation response of a GaAs/GaAlAs semiconductor laser (relaxation resonance frequency, &ngr;R=6.5 GHz) is measured to 37 GHz using the active‐layer photomixing technique. The measured response function agrees with the theoretical ideal, and there is no indication of device parasitic effects. An ultrahigh‐finesse Fabry–Perot interferometer is used to detect the optical modulation, which appears as sidebands in the laser field spectrum. With a moderately faster laser diode (i.e., &ngr;R∼10 GHz), the modulation response should be measurable beyond 100 GHz.

ISSN:0003-6951    

DOI:10.1063/1.101730

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We describe a new type of optical low‐reflectivity coating and its application to GaAs/AlGaAs power lasers. The low‐reflectivity region of this coating extends over a broad wavelength range, therefore making the overall reflectivity much less sensitive to thickness variations as compared to single‐layer coatings. In addition, only two materials (SiO2anda‐Si:H) are required, thus making it very easy to fabricate such coatings with standard deposition techniques such as plasma‐enhanced chemical vapor deposition (PECVD) or ion beam sputtering. Finally, the optical quality of coatings deposited by PECVD was confirmed by measurements on power lasers, showing optical power outputs in excess of 60 W/mm, among the highest reported value for coated mirrors.

ISSN:0003-6951    

DOI:10.1063/1.102453

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Thermonuclear burn time and burn duration in ablatively driven high‐aspect‐ratio targets have been measured. While the observed burn times were in agreement with results of a one‐dimensional hydrodynamic simulation, the observed burn durations were excessively long.

ISSN:0003-6951    

DOI:10.1063/1.101731

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Dielectric liquids for possible use as (opening/closing) switching materials in pulsed power technology are identified. A concept for a dielectric‐liquid‐pulsed‐power switch employing flashlamps is outlined.

ISSN:0003-6951    

DOI:10.1063/1.101732

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Low‐temperature partially ionized plasmas, as used in plasma processing reactors and gas lasers, are often contaminated by gas phase particulates (1–10’s &mgr;m radius) resulting from electrode sputtering or gas phase chemical reactions. Particles having sizes comparable to or greater than the Debye length will negatively charge in the plasma and form a sheath at their surfaces. These particles thereby become a Coulomb‐like scatterer of electrons. A hybrid Monte Carlo/molecular dynamics computer simulation has been developed to study the effect of such particulate contamination on electron transport in glow discharges and this letter presents results for argon. The dominant effect of particulate contamination is to shift the electron energy distribution to lower energies, thereby reducing electron impact rate coefficients for processes which have high threshold energies, particularly ionization. The self‐sustainingE/Nof discharges having dusty plasmas is therefore increased. The effect, proportional to particle density, begins to become important at a density of 103–105cm−3for gas pressures of 0.1–3 Torr.

ISSN:0003-6951    

DOI:10.1063/1.101733

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

In‐doped HgCdTe films have been grown by molecular beam epitaxy (MBE) on CdTe substrates in the (100) crystallographic orientation. They were characterized by Hall and secondary‐ion mass spectroscopy measurements. The results are compared with those of In‐doped HgCdTe layers grown in the (111)Borientation. In the (111)Borientation indium is incorporated in the metal site whereas in the (100) orientation it appears that indium is mainly incorporated interstitially. The results agree with a Te antisite model as a possibility for explaining the electrical behavior of (100) HgCdTe grown by MBE.

ISSN:0003-6951    

DOI:10.1063/1.101734

出版商:AIP    

年代:1989

数据来源: AIP