Showing papers in "Progress in Optics in 1988"

V Phase-Measurement Interferometry Techniques

Abstract: Publisher Summary This chapter describes the phase-measurement interferometry techniques. For all techniques, a temporal phase modulation is introduced to perform the measurement. By measuring the interferogram intensity as the phase is shifted, the phase of the wavefront can be determined with the aid of electronics or a computer. Phase modulation in an interferometer can be induced by moving a mirror, tilting a glass plate, moving a grating, rotating a half-wave plate or analyzer, using an acousto-optic or electro-optic modulator, or using a Zeeman laser. Phase-measurement techniques using analytical means to determine phase all have some common denominators. There are different equations for calculating the phase of a wavefront from interference fringe intensity measurements. The precision of a phase-measuring interferometer system can be determined by taking two measurements, subtracting them, and looking at the root-meansquare of the difference wavefront. The chapter discusses the simulation results. The elimination of the errors that reduce the measurement accuracy depends on the type of measurement being performed. Phase-measurement interferometry (PMI) can be applied to any two-beam interferometer, including holographic interferometers. Applications can be divided into: surface figure, surface roughness, and metrology.

I Photon Bunching and Antibunching

Abstract: Publisher Summary This chapter describes photon bunching and antibunching The chapter reviews the theory pertaining to the generation of bunched and super-Poisson light within the semiclassical theory The quantum theory of light generation from superpositions of independent emissions is developed The implementation of physical mechanisms that lead to this kind of light is discussed The chapter demonstrates that the loss of photons randomizes the statistical properties of an anticorrelated stream of photons, converting it into random (Poisson) form The nonlinear optics mechanisms—atomic resonance fluorescence and parametric downconversion—that generate small clusters of conditionally sub-Poisson photons are discussed The use of excitation feedback for generating useful antibunched and cw unconditionally sub-Poisson light is also discussed The chapter discusses the use of sub-Poisson light for carrying information, such as in a direct-detection lightwave communication system Sources of light considered for use in direct-detection lightwave communications should (1) be strongly sub-Poisson, (2) exhibit a large photon flux, (3) be small in size, (4) be fast, and (5) produce a collimated output

I Dynamical Instabilities and Pulsations in Lasers

Abstract: Publisher Summary This chapter discuses the dynamical instabilities and pulsations in lasers. The laser instabilities are of interest in the research efforts. The characteristics of laser pulsations are in accord with the predictions of the early maser models. The chapter discuses the laser phenomena. The semiclassical theory of the laser was developed in response to the limited success of the rate equations in dealing with issues such as coherence, spectral purity, and the spiking phenomenon. The most analyzed laser model is a single-mode resonant system. The single-mode equations are the prototype example of an unstable laser model. The experimental realization of a single-mode, homogeneously broadened laser is attractive from the point of view of laser physics because the Lorenz model itself has no close realization in hydrodynamic systems. Neodymium glass lasers are inhomogeneously broadened because of differences in the local fields at the site of the active atoms. Most gas lasers operating in the visible and near-infrared regions of the spectrum are inhomogeneously broadened because of the Doppler shift suffered by the moving atoms. The combination of lasers and saturable absorbers has been proposed. Most experimental lasers are designed to operate as Fabry–Perot resonators.

III Principles and Design of Optical Arrays

Abstract: Publisher Summary This chapter discuses the principles and design of optical arrays. Arrays of optical elements can be found in nature, such as the compound eyes of insects, and in everyday life, such as the corner-cube arrays on cars and bicycles or on road signs. The chapter describes the most unusual new phenomena associated with arrays—that is, the non-Gaussian imaging property of GRIN (gradient index) rod arrays and the pseudo phase conjugation phenomenon of corner-cube arrays. The chapter reviews the essential features of the 2 × 2 ray transfer matrix method. The augmented 4 × 4 matrix introduced to describe the optical behavior of a misaligned optical element is derived. The chapter examines how an array may be treated in terms of a 2 × 2 matrix, which accounts for imaging properties, phase conjugation properties, and some other new properties of arrays. Some examples of arrays that possess interesting properties are given. The problem of the quality of synthesized images is treated by analyzing the additional aberrations of the arrays, and interference fringe formation, with particular regard to the conditions under which they can be eliminated.

II Nonlinear Optics of Liquid Crystals

Abstract: Publisher Summary This chapter discusses the nonlinear optics of the liquid crystals. The mechanisms for optically induced refractive index change in the nematic phase of liquid crystals, and related nonlinear optical processes such as optical wave mixings, self-focusing, and bistabilities are discussed. Liquid crystals are composed of large organic molecules with a typical chemical structure. As a result of intermolecular forces, the molecules tend to align themselves in some fixed direction. Most liquid crystal molecules are uniaxial, centrosymmetrical and nonpolar, although there is a class of liquid crystals that is ferroelectric and possesses large permanent dipole moments. The chapter focuses on selected nonlinear processes in which the extraordinarily large nonlinearity of liquid crystals has shed new light on the fundamental understanding of them, on processes that are on the threshold of being applicable to practical devices, and on special processes that can be obtained only with highly nonlinear materials.

II Coherence in Semiconductor Lasers

Abstract: Publisher Summary This chapter discuses the coherence in semiconductor lasers. Theoretical backgrounds and experimental results on temporal coherence in semiconductor lasers are described in the chapter. Techniques to improve coherence and applications to the field of optics are also reviewed. The semiconductor lasers presently available still have a primitive structure for obtaining high temporal coherence. Improvements in coherence require the fabrication of more sophisticated lasers, which are to be connected with external electronic and optical components. The reproducibility and reliability of semiconductor lasers also need improvement at the stage of laser fabrication. Close cooperation between device fabrication and system design is essential to obtain extremely high temporal coherence. Developments of external optical components, such as high-performance optical isolators, optical fibers, fiber couplers, and opto-electronic integrated circuits (OEIC), are required to support efforts to improve coherence. Ultrahigh coherence in semiconductor lasers can be achieved under these conditions, thus giving new applications and impact to optics.

IV Aspheric Surfaces

Abstract: Publisher Summary This chapter describes the aspheric surfaces. Aspheric surfaces, or “aspherics”, are optical surfaces that are neither spherical nor plane and are used in imaging and nonimaging systems. Mathematically an aspheric is generated by the rotation of an axisymmetrical plane curve about its axis. Spherical surfaces are a special case of aspherics in which the rotating curve is a circular arc. The chapter discusses the theoretical treatment and design methods, optically effective properties, and possibilities of application for the aspherics, with emphasis on methods and properties differing from those of spherical surfaces. The types of aspherics and their mathematical representations are surveyed. The methods for designing aspheric surfaces, and the manufacturing and testing methods for aspherics are summarized. The chapter discusses the applications of aspherics in a number of fields. The questions about fundamental possibilities and general limits of the performance of aspherics are also discussed in the chapter.

III Single-Longitudinal-Mode Semiconductor Lasers

Abstract: Publisher Summary This chapter discusses the single-longitudinal-mode (SLM) semiconductor lasers. The use of single-mode fibers has eliminated the problem of modal noise. The chapter reviews the recent progress in the field of SLM semiconductor lasers. The physics of semiconductor lasers is discussed and the material system and the structure commonly employed to make them is introduced in the chapter. The modes supported by a conventional Fabry–Perot (FP) type of semiconductor laser with particular attention paid to the longitudinal modes and their respective threshold gains are considered. The key to SLM operation of semiconductor lasers is to make the cavity loss wavelength dependent. Two mechanisms used for this are: (1) the distributed-feedback (DFB) mechanism, and (2) the coupled-cavity mechanism. As SLM lasers are modulated at high frequencies during their application in optical communication systems, the modulation performance through an analysis of the single-mode rate equations is discussed. The spectral linewidth of SLM lasers is described. The analysis is based on the single-mode rate equations modified to include fluctuations through Langevin noise sources. The chapter focuses on narrowlinewidth SLM lasers in view of their applications in coherent communication systems. The chapter also accounts for the current research in the field of SLM semiconductor lasers.