摘要:

Gain characteristics of an Er3+‐doped fiber are investigated with different pump wavelengths using a tunable Ti:sapphire laser in the 0.98 &mgr;m band. Maximum gain was obtained at a pump wavelength of 0.980 &mgr;m and the gain profile can be fully explained in terms of the pump absorption spectrum. The 3 dB gain bandwidth for the pump wavelength was 10–14 nm. A gain coefficient of 2.6 dB/mW was obtained for a 60 ppm Er3+‐doped fiber with an absorbed pump power of 9 mW.

ISSN:0003-6951    

DOI:10.1063/1.101982

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We report on the generation of widely tunable intense far‐infrared radiation pulses by stimulated Raman transitions in methylfluoride gas. Using a tunable high‐pressure CO2laser we achieved, byP‐branch tuning of stimulated Raman transitions in12CH3F and13CH3F gases, tunable generation of radiation in a series of intervals in the spectral range from 37 to 72 cm−1covering 20% of this range. Possibilities of further extension of the tuning regions are also discussed.

ISSN:0003-6951    

DOI:10.1063/1.101983

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Auger effects in undoped andp‐doped strained quantum wells (QWs) were evaluated taking the subband nonparabolicity of the valence band into account. The Auger lifetime is relatively short mainly due to the subband nonparabolicity. However, the Auger rates in a strained QW are lower, and the threshold current reduced to about 1/4 of that in a lattice‐matched QW is expected. It is concluded that a high‐speed laser with a relaxation oscillation frequency of near 70 GHz and with a relatively low threshold current 500 A/cm2will be realized in ap‐doped (∼5×1018cm−3) strained QW structure.

ISSN:0003-6951    

DOI:10.1063/1.101984

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We present some experimental results of ridge distributed feedback semiconductor lasers showing a linewidth broadening at high emission power which is due to the growth of transverse magnetic polarized radiation. We also show how the linewidth saturation can be ascribed to an increase in the low‐frequency content of the phase noise spectrum. This increase at low frequency is also linked to a deformation in the probability distribution of the instantaneous optical emission frequency.

ISSN:0003-6951    

DOI:10.1063/1.101985

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A series of separate confinement InxGa1−xAs‐GaAs (0.08<x<0.42) strained‐layer quantum well lasers with 70 A˚ well thickness has been grown by metalorganic chemical vapor deposition. Data are presented on emission wavelengths and threshold current densities (Jth) as a function of composition. A minimum inJthof 140 A/cm2was observed for devices with In0.24Ga0.76As wells. The dependence ofJthon well composition is explained by a balance between strain effects and carrier confinement in the quantum well.

ISSN:0003-6951    

DOI:10.1063/1.101986

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A high‐sensitivity fiber‐optic displacement sensor for atomic force microscopy is described. The sensor is based on the optical interference occurring in the micron‐sized cavity formed between the cleaved end of a single‐mode optical fiber and the microscope cantilever. As a result of using a diode laser light source and all‐fiber construction, the sensor is compact, mechanically robust, and exhibits good low‐frequency noise behavior. Peak‐to‐peak noise in a dc to 1 kHz bandwidth is less than 0.1 A˚. Images are presented demonstrating atomic resolution of graphite and magnetic force imaging of bits written on a magnetic disk.

ISSN:0003-6951    

DOI:10.1063/1.101987

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Device fabrication and basic experimental results obtained with a heterojunction bipolar transistor waveguide structure optical intensity modulator, whose device structure is particularly suitable for possible monolithic integrated circuits, are described for the first time. Common emitter dc current gainhFEobtained with a 0.25‐&mgr;m‐thick base/waveguide was 38, and the switching times have been determined as 1.5 ns. Free‐carrier injection modulates the absorption coefficient &agr; in the waveguide mainly by the band filling and plasma dispersion effects and consequently, the output light intensity can be modulated. The optical on/off modulation ratio of up to 2.1:1, corresponding to a modulation efficiency of &Dgr;&agr;/&agr;∼89%, has been demonstrated at a base current of 3 mA for a device with an emitter/waveguide width of 7 &mgr;m and a length of 190 &mgr;m.

ISSN:0003-6951    

DOI:10.1063/1.101988

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The complete set of elastic and photoelastic constants of 3‐methyl 4‐nitropyridine 1‐oxide (POM) organic single crystals is measured by Brillouin scattering. The acousto‐optic figures of merit are then derived and the anisotropy of the longitudinal and transverse acoustic wave velocity clearly evidenced from the knowledge of these constants. POM appears to be a promising material for acousto‐optical devices as light deflectors and modulators. It is shown that a Bragg cell using POM as an interaction medium would combine several favorable technical features.

ISSN:0003-6951    

DOI:10.1063/1.101989

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Experiments to study negative ion densities have been carried out using the photodetachment effect in a rf plasma in CF4. Electrons are detached from the negative ions under the influence of the pulse of a Nd:YAG laser. The induced increase of the electron density is measured as a function of time using the shift of the resonance frequency of a microwave cavity containing the plasma. The negative ion density [F−] is found to be about (4±1)×1015m−3, a factor 4±1 higher than the electron density.

ISSN:0003-6951    

DOI:10.1063/1.101990

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We have presented a novelinsitumethod which is simple and sensitive, to measure the micromass of the fuel layer in a cryogenic foam target. In this method, a foam shell is mounted on a flexible polyester fiber 7 &mgr;m in diameter and 800 &mgr;m in length. The fiber is suspended with a stalk which is mechanically vibrated at any given frequency. The resonant frequency of the elastic vibration of a foam‐fiber system is measured before and after fuel loading. The mass of the fuel can be determined from the change in the resonance frequency in the range from submicrograms to submilligrams. The resolution of this system, which is limited by theQfactor of the foam‐fiber system, is better than 0.2 &mgr;g corresponding to the measurement accuracy of 0.1%.

ISSN:0003-6951    

DOI:10.1063/1.101991

出版商:AIP    

年代:1989

数据来源: AIP