John B. Hayes

Modern approaches in phase measuring metrology (Invited Paper)

The measurement accuracy of an interferometric optical test is generally limited by the environment. This paper discusses two single-shot interferometric techniques for reducing the sensitivity of an optical test to vibration; simultaneous phase-shifting interferometry and a special form of spatial carrier interferometry utilizing a micropolarizer phase-shifting array. In both techniques averaging can be used to reduce the effects of turbulence and the normal double frequency errors generally associated with phase-shifting interferometry.

Phase-shifting multiwavelength dynamic interferometer

The benefits of using two-wavelength measurements to extend the dynamic range of an interferometric measurement are well known. We present a new multi-wavelength interferometer that uses two successive single frame measurements obtained rapidly in time to significantly reduce sensitivity to vibration. At each wavelength, four phase-shifted interferograms are captured in a single image. The total acquisition time for both wavelengths is 100 microseconds, over three orders of magnitude shorter than conventional interferometers. Consequently, the measurements do not suffer from the fringe contrast reduction and measurement errors that plague temporal phase-shifting interferometers in the presence of vibration. In this paper we will discuss the basic operating principle of the interferometer, analyze its performance and show some interesting measurements.

Testing of nonlinear diamond-turned reflaxicons

The extreme alignment sensitivity of nonlinear diamond-turned reflaxicons makes them difficult to test and analyze. To evaluate the wave front it is necessary to know what portion results from alignment errors. This paper describes the setup, alignment, and testing of a nonlinear diamond-turned independent-element reflaxicon manufactured at the Union Carbide, Oak Ridge Y-12 plant. Interferograms taken with the center cone misaligned a known amount are analyzed using the axicon preprocessing option in FRINGE [J. S. Loomis (ASTM Report STP 666 and Proc. Soc. Photo-Opt. Instrum. Eng. 171, 64 (1979)]. The results show that FRINGE correctly removes the cone and decenter errors introduced by the misalignments. It is also shown how the resulting interferograms are unfolded to give the OPD errors as seen on the outer cone.

A Heterodyne Interferometer For Testing Laser Diodes

A heterodyne, Mach-Zehnder interferometer system has been developed for testing the wavefront quality of laser diode collimator pens. The testing system is described and the problems associated with testing laser diodes are discussed.

Interferometric measurement of the vibrational characteristics of light-weight mirrors

We present a technique to characterize and quantitatively measure the vibrational mode shapes and amplitudes of mirrors concurrently with surface figure testing. The technique utilizes a fast interferometer that does not introduce any mass loading to the test structure. We present the fundamentals of the technique, discuss sevral modes of operation, such as resonant and transient response, and analyze the operational limits. The performance of the measurement system is characterized using a small ambient test mirror.

An origin for pulsar kicks in supernova hydrodynamics

It is now believed that pulsars comprise the fastest population of stars in the galaxy. With inferred mean, root‐mean‐square, and maximum 3‐D pulsar speeds of ∼300–500 km/s, ∼500 km/s, and ∼2000 km/s, respectively, the question of the origin of such singular proper motions becomes acute. What mechanism can account for speeds that range from zero to twice the galactic escape velocity? We speculate that a major vector component of a neutron star’s proper motion comes from the hydrodynamic recoil of the nascent neutron star during the supernova explosion in which it is born. Recently, theorists have shown that asymmetries and instabilities are a natural aspect of supernova dynamics. In this paper, we highlight two phenomena: 1) the ‘‘Brownian‐like’’ stochastic motion of the core in response to the convective ‘‘boiling’’ of the mantle of the protoneutron star during the post‐bounce, pre‐explosion accretion phase, and 2) the asymmetrical bounce and explosion of an aspherically collapsing Chandrasekhar core. In...

Scatterplate Interferometry: A Diffraction Theory

The Burch scatterplate interferometer is an extremely precise, equal path interferometer that provides direct wavefront information without the use of any precision optical components. This paper describes the use of Fourier transform techniques to provide a straightforward scalar diffraction theory of the interferometer. The results show the characteristic hot spot and speckle pattern seen in scatterplate interferograms. Practical applications of the theory are also discussed.

Instantaneous phase-shift, point-diffraction interferometer

We demonstrate a phase-shift, point diffraction interferometer that achieves high accuracy and is capable of measuring a single pulse of light. Results of measuring transient phenomena and numerical apertures as high as NA 0.8 are presented. The operational limits and accuracies of the technique are discussed.

The Physics of Core‐Collapse Supernova Explosionsa

Fresh insights and powerful numerical tools are revitalizing the theoretical exploration of the supernova mechanism. The realization that the protoneutron star is Rayleigh-Taylor unstable at various times and radii and, hence, that a multi-dimensional perspective is required is one agent of this revolution. However, a new physical understanding of the nature of explosions (even spherical explosions) that are driven by neutrino heating and that escape from deep within a gravitational potential well is also emerging. This, together with the new multi-dimensional approach, promises to establish a paradigm within which supernova explosions and their consequences can be studied in the future.