摘要:

A new technique for the continuously variable linear attenuation of high‐power transversely excited atmospheric (TEA) CO2laser pulses is reported. The use of a binary gas mixture comprising SF6as the absorber and helium or argon as the buffer gas causes a significant enhancement in the saturation intensity, thereby allowing saturation‐free attenuation of TEA CO2laser pulses up to 1 MW/cm2. A linearly variable dynamic attenuation range of 0–30 dB, and continuously variable attenuation up to 60 dB in a 10‐cm cell length, without spatial or temporal distortion in the attenuated beam is demonstrated.

ISSN:0034-6748    

DOI:10.1063/1.1143442

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A laser microprobe and resonance ionization mass spectrometer (LAM/RIMS) has been designed and constructed by combining a newly designed simple laser microprobe (LAM) with a continuous‐wave (cw) resonance ionization mass spectrometer, for the direct analysis of trace elements in solids. The LAM/RIMS has achieved a simultaneous record of the complete mass spectrum of a solid sample, and a three orders of magnitude enhancement in the detection signal of the selected trace elements in the solid, with precise spatial information, and without the need of sample preparation. An‐type silicon wafer containing an impurity of sodium in parts per billion order has been easily detected by applying a single shot of an ablation laser pulse and a cw resonance ionization laser. The result has also shown that the sensitivity of the LAM/RIMS for the analysis of selected trace elements is better than the Auger electron spectroscopy and is comparable to neutron activation analysis.

ISSN:0034-6748    

DOI:10.1063/1.1143443

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

Detection of spherical acoustic waves by the laser beam deflection probe is examined. The probe is modeled as a linear system transforming acoustic wave form into transient angular deflection of the probe beam. Transfer and step response functions are derived assuming thin Gaussian laser beam and small deflection angle. It is demonstrated that the probe behaves as a half‐order differentiator when short acoustic transients are detected far from the source. Theoretical predictions are compared to the results of frequency analysis of optoacoustic signals detected by the deflection probe. Good agreement is found.

ISSN:0034-6748    

DOI:10.1063/1.1143444

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A simple method for estimating the collection efficiency of a nearly ideal optical system is described. Calculation of spatial response functions for the analysis and absolute calibration of optical emission data is emphasized. The simple geometric algorithm presented is several orders of magnitude faster than algorithms based on ray tracing. The method is applied to the case of a radially uniform cylindrical source between parallel plates and the results are in excellent agreement with ray tracing calculations.

ISSN:0034-6748    

DOI:10.1063/1.1143445

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A two‐dimensional microchannel plate photomultiplier with a position sensitive resistive anode has been integrated with time‐correlated single photon counting circuitry. The result is a very powerful spectroscopic system which combines the very low dark count and parallel collection capabilities of the imaging tube with simultaneous timing information about the individual photon events. The digitalx,yand timing information for each photon event is directly stored onto a hard‐disk in real time. When the detector is placed at the output of a spectrometer, the system provides software‐controllable arbitrary time windowing of complete spectra. When used as an image recorder, the system provides software‐controllable time windowing of entire two‐dimensional images, with ∼100‐ps effective frame times.

ISSN:0034-6748    

DOI:10.1063/1.1143446

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A new interferometer has been developed for the accurate determination of the density of a silicon crystal, in which a single‐crystal silicon sphere of nearly perfect geometry is placed in a Fabry–Perot etalon of accurately known plate distance, and the diameters are obtained by measuring the two gaps between the etalon and the adjacent surface of the sphere. A new method is used to measure the sum of the length of the two gaps by scanning the etalon against the sphere. Two wavelengths, 633 nm from a frequency‐stabilized He–Ne laser and 441 nm from a free‐running He–Cd laser, are used to determine the order of interference by applying the method of exact fractions. The diameter of about 94 mm has been measured with a resolution of 0.5 nm. Diameter measurements from uniformly distributed directions have shown that the mean diameter has been determined with a standard deviation of 8.6 nm, corresponding to 0.28 ppm in the volume determination. The total uncertainty of the volume is estimated to be 0.34 ppm. Effects of a thin oxide layer and impurities on the bulk density are discussed.

ISSN:0034-6748    

DOI:10.1063/1.1143447

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

For the small angle scattering of coherent plane waves from inhomogeneous random media, the three‐dimensional mean square distribution of random fluctuations may be recovered from the interferometric detection of the nonstationary modulational structure of the scattered field. Modulational properties of coherent waves scattered from random media are related to nonlocal correlations in the double sideband structure of the scattered field. To second order, such correlations may be expressed in terms of a suitably generalized spectral coherence function for analytic fields.

ISSN:0034-6748    

DOI:10.1063/1.1143448

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A new reflectance anisotropy (RA) spectrometer, in the 0.23–0.83‐&mgr;m range, is presented. The numerous similarities with phase‐modulated ellipsometry (PME) are emphasized. In particular, the RA spectrometer takes advantage of the high‐frequency modulation (50 kHz) provided by a photoelastic modulator. The use of optical fibers in both optical arms allows an increase of the compactness of the spectrometer. Four detectors can be used simultaneously providing the real‐time spectroscopic capability. The numerical data acquisition system of the detected signal is based on the use of a high precision analog‐digital converter and a fast Fourier transform processor. However, as compared to ellipsometry, RA can be only sensitive to the crystal surface. The adaptation of RA to a III‐V growth reactor by metalorganic chemical vapor deposition is described in detail. The high sensitivity of the RA spectrometer is emphasized. In particular real‐time variations of the RA signal ranging from 10−4to 10−3are reported. Then, the various RA techniques are compared. In particular, it is shown that this RA spectrometer allows the determination of both the real and the imaginary part of the signal. Finally the origin of the RA signal is discussed.

ISSN:0034-6748    

DOI:10.1063/1.1143398

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

A KTiOPO4crystal block was used as a Fizeau interferometer. We modulated the interference pattern formed by the primary reflections from the front and rear surfaces of the crystal by the application of an electric field. The modulation is detected via a Faraday cell. In this way we measured the unclamped linear electro‐optic tensor with high precision.

ISSN:0034-6748    

DOI:10.1063/1.1143399

出版商:AIP    

年代:1992

数据来源: AIP

摘要:

We demonstrate that x‐ray reflectivity data covering eight decades of intensity can be obtained from a rotating anode source. Our moderate resolution configuration uses a bent graphite monochromator in contrast to the usual high resolution measurement which uses a silicon or germanium monochromator. Illustrative data show that moderate resolution is appropriate for probing a wide variety of surfaces and films. The availability in our configuration of roughly 100 times the incident intensity of a high resolution experiment using a laboratory source allows measurements over a broader angular range which in turn allows us to probe short length scale details of interface structure and tightens the constraints on models of interface structure. Both specular and diffuse scattering signals are accessible. A discussion of reciprocal space resolution explains why there is almost no difference in effective resolutions in the measurement of diffuse scattering.

ISSN:0034-6748    

DOI:10.1063/1.1143400

出版商:AIP    

年代:1992

数据来源: AIP