摘要:

The area of contactless characterization techniques for electronic applications is too wide a topic to be considered in full detail inside a single review article. On this line of argument, we considered only some contactless optoelectronic techniques paying particular attention to those optoelectronic techniques which can be easily employed for material diagnostics or to perform simple voltage or temperature measurements in electronic devices. In spite of their simplicity and reliability, some of these techniques are not well known by the electronic community. The considered techniques include: scanning electron, photoexcitation and force microscope, electro-optical sampling techniques, charge sensing probes, second harmonic generation, and photoacoustic and thermal wave microscopy. Applications to signal processing, detection and measurement of microcracks, temperature, lifetime, surface recombination velocity, diffusivity, and injection level are discussed. The article is, then, completed by a very rich bibliography and by three appendices describing some physical phenomena (electro-optic, plasma optic, and photoacoustic effect) instrumental for understanding most of the considered techniques. Most of the considered techniques can be mounted in almost each laboratory as they do not require particularly expensive and bulky instrumentation. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148752

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

An ultrafast time-resolved diffuse reflectance spectroscopic system has been developed as a potential instrument for analyzing photophysical and photochemical dynamics of light scattering materials such as powder and opaque suspension, using an amplified femtosecond Ti:sapphire laser as a light source. Transient absorption spectra of organic powder, covering the wavelength region from 400 to 760 nm, were precisely obtained by using a stable and bright femtosecond white-light continuum as a probe light. An ultrashort light pulse is temporally broadened owing to numerous times of refraction, reflection, and diffraction in scattering materials. This affects the temporal resolution of transient absorption measurements, which was examined and discussed in detail by using a simple numerical model with time-dependent light propagation of a short pulse. From the simulation and experimental results, it was shown that the temporal resolution of transient absorption measurement is less than a few ps under a certain measurement condition, although it strongly depends on the optical properties of the sample; scattering and absorption coefficients. Some applications to the analysis of excited dynamics of organic molecules in polymer latex and molecular microcrystalline powder are also demonstrated. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148668

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The different noise contributions in a coherent tunable far infrared spectrometer were measured. On the basis of this quantitative analysis, several experimental schemes to enhance the sensitivity for spectroscopy in this spectral region are proposed. In particular, a full theoretical analysis for differential detection is developed. A double-detector scheme is theoretically analyzed and it is shown that a noise reduction of up to 17 dB is achievable with this configuration. The present work should make possible quantitative forecasting of sensitivity enhancement for new, different experimental configurations. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148669

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A photospectrometer has been realized in a standard integrated circuit (IC) process. Only the masks, materials, and fabrication steps inherent to this IC process were used (i.e., no post processing to add mechanical or optical devices for filtering). The spectrometer was composed of a set of 18 photodetectors with independent spectral responses. The responses of these devices were weighted and summed to form outputs proportional to the input optical power in discrete wavelength bands in the region from∼400to∼1100 nm.With the solution space restricted to a 60 nm band, this instrument could resolve Gaussian input spectra(&sgr;=5 nm)with a peak-to-peak spacing of less than 15 nm. This device could easily be integrated with additional analog, digital, or wireless circuits to realize a true laboratory instrument on-a-chip. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148457

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have developed a fast detector using stacked avalanche photodiodes (APDs) for x-ray diffraction experiments with synchrotron radiation. This detector has four independent channels of APDs, and the detector efficiency has reached 55&percent; in all for 16.53 keV x rays. Since the dead time of the counting system is shorter than 4 ns, output rates of up to4.5×108 counts/shave been obtained for 16.53 keV x rays. The dynamic range is more than1010in the multibunch mode of a storage ring. Pulse-height measurements at output rates of up to108 counts/swere successfully carried out by sequential single-channel discrimination. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148670

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We present x-ray spectra obtained by a charge coupled device (CCD) from an electron impacting x-ray source using several kinds of electron targets: Au, Al–bronze, Al, and pure Al. The x rays from the source are dispersed by a grating and the dispersed x rays are focused on the CCD. Owing to the fine spatial and moderate energy resolutions of the CCD, fine spectra with 2 eV energy resolution up to 2.2 keV are obtained. X rays from the pure Al target (99.999&percent; purity) provide good continuum x rays except for AlKx rays. This continuum source is useful as a calibration source for low energy x-ray detectors. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148671

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A novel technique for measuring the instantaneous arrival times of a long series of consecutive photoevents effective at shorter intrapulse intervals up to 10 ns with an accuracy of better than 1 ns has been developed and tested experimentally and by simulations. It is based on linear processing without dead time effects of detector pulses by excitation of a resonant system, analog/digital sampling, deconvolution, and calculation of single pulse centers and electric charges. The maximum number of processed photoevents exceeds103at108pulse rate. In an accumulation regime the method can be used for temporal profiling of the number of photocounts with very high resolutions up to 0.1 ns. This method covers the intermediate range of photon rates, where the well known techniques are ineffective. It can be applied for high order photon statistics, in lidar sensing, time-resolved spectroscopy, as well as in typical electronic measurements of instantaneous frequencies, periods etc. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148672

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We were able to simplify the structure of the autocollimators and enhance the performance by using one- and two-axis PSDs (position-sensitive detectors) which have spatial resolution of 0.1 and 2.5 &mgr;m, respectively, with little dependence on the spot size of incident beam and the visible laser diodes as the light source. Two kinds of portable autocollimators which can measure angles with resolutions0.01″and0.1″,respectively, were made. They were calibrated by the reference angle generator which employed the laser interferometer. The characteristics of temporal stability were evaluated and the profile of a test surface was measured. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148673

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A pulsed slit-jet expansion source capable of generating moderate velocity-collimated pathlengths(∼1 cm)of rovibronically cooled target molecules for spectroscopic interrogation is described and characterized. Based upon the modification of a commercially available current loop-actuated design, this apparatus produces conductance-limited pulses of⩽50 &mgr;sduration at repetition rates of up to 20 pps. The short temporal length of the emerging gas pulse greatly alleviates the demands imposed upon vacuum pumping systems and enables the use of higher stagnation pressures in the expansion process. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148674

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A novel type of polarized3He ion source based on “electron pumping” was recently proposed. This ion source requires multiple electron capture and stripping collisions of3He+ions with polarized alkali atoms under a strong magnetic field (2–3 T). Since these processes may induce a serious increase in the emittance and reduction of polarized beam intensity, we investigated them in detail by using the Monte Carlo simulation. It was found that there is (1) increase in the emittance results not from angular broadening but from a beam size enlargement, (2) the phenomena under magnetic fieldBare simplified by a collisionless phenomenon under a weaker magnetic field (effective magnetic field)Beffdefined byBeff≃(&lgr;+0/(&lgr;+0+&lgr;0+))B,where&lgr;+0and&lgr;0+are mean free paths for3He+ions and3He0atoms traveling in the alkali vapor. ©1998 American Institute of Physics.

ISSN:0034-6748    

DOI:10.1063/1.1148719

出版商:AIP    

年代:1998

数据来源: AIP