Over the last five years NASA has supported ranging on the lunar surface with a ruby laser. l'2 The laser was constructed by the KORAD Corporation and is installed at the McDonald Observatory in Texas. The laser emits a 20 joule 30 nanosecond pulse. Of the returning signal, collected by the McDonald telescope, approximately on: photoelectron is produced. The photomultiplier on the telescope is range gated to reduce the background. Signal averaging techniques are used. With this whole system one can measure distance from McDonald Observatory to the moon to an accuracy of A,10 centimeters. Experiments are aimed at determining more precisely the orbit of the moon. Better knowledge of the orbit of the moon can be used to determine more accurately the shape of the earth. Future experi-ments were described in which laser ranging would be done simul-taneously from different points on the earth, i. e. , different stations. These measurements would afford a means of predicting continental drifts and early prediction of earthquakes. Ideally, it would be better to have a more intense laser and a laser which emitted in the green where photomultipliers are more sensitive. Funding for these necessary improvements have not been forthcoming.

The production of fusion energy from a pellet of thermonuclear fuel can be achieved on a level useful for power production only if the pellet is highly compressed with efficient energy transfer from the external , energy source into the pellet. The simple model of a uniformly compressed DT sphere can be used to determine the fusion energy production. Figure (1) gives the ratio of fusion energy out-put to initial thermal energy for a uniform initial temperature of 5 kev. The energy multiplication, for an initial thermal energy of one kilo-joule, is 5 at a density of 300 gm/cm3, 16 at 600, 40 at 1000, and 80 at 2000. For high energy input on high compres-sion, the energy multiplication levels off at about 200 corresponding to about 35% burnup of the DT. The energy multiplication can be increased if thefuel is only centrally heated to the ignition point of 5 kev, with the rest of the fuel ignited by an expanding supersonic burning front propagating outward from the fuel center. Figure (2) shows a typical example of the propagation of a supersonic burning front. Figure (3) shows the energy multiplication with the fuel center heated to 5 kev over a few micron radius and the rest of the fuel at 500 ev. With an initial thermal energy of one kilojoule, the energy multiplication is 130 at p= 600 gm/cm3, 400 at p= 1000 gm/cm3, and 700 at p = 2000 gm/cm3 . The energy multipli-cation reaches a maximum of about 1200 for initial thermal energy of 5-10 kilojoules, independent of initial density, corresponding to about 35% fuel burnup. The effect of the centrally-initiated burning wave increases the energy multiplication by about a factor of ten over the uniformly heated case.

The design of a neodymium glass laffr system for irradiation of targets of 10 -1012 watt pulses in a high brightness beam requires simultaneous solution of a number of technical problems. These problems can be separated into two areas relating to self focusing and to target and interstage isolation in the system.

Cleaning is usually the first step involved in the various processes employed to restore a work of art. It is also one of the most delicate and difficult operations undertaken to preserve a deteriorating art object. Generally, the criteria governing the cleaning of a work of art in stone or metal are concerned with a maximum respect and care for the original materials, the eventual irreversible alterations undergone through centuries (formation of patinas, changes of color, etc.) as well as the removal or isolation of parts that may, during later periods, have been added. Difficulties involved in cleaning works of art in marble and stone change according to the different materials involved, and their varying exposures to exterior elements. Particularly complicated are the problems arising from outdoor exposure where destructive elements such as air pollution, biological attacks, etc., are superimposed on natural weathering effects. Natural or artificial degradation almost always reveals itself as a bulk degradation that begins on the surface of these materials. The presence of varying extraneous substances on the surface often encourage the introduction and propagation of exceedingly harmful forms of degradation to the interior. Consequently, surface cleaning not only improves appearance, but preserves materials as well. Many bibliographical examples exist of statues and monuments in which superficial modifications. have strongly encouraged the advance of a degradation process towards the interior. The cleaning of works of art protected by an indoor location, though as important in every way, tends to be a generally easier affair.

The concept of the laser may be attributed to a number of scientists beginning with Tolman and ending with Townes, Basov and Prokorov. Who, actually, could be credited with having a clear enough conception of the physics involved to allow the implementation of the principle could be argued ad infinitum. There is no argument about the first demonstration of the laser by Maiman in 1959. The subsequent explosion in this technology and its associated physics is a matter of record.

The peak power that can be produced by 01-switching a law pressure continuously excited CO, laser is limited to about 100 watts per centimeter length of discharge because of the slow, inefficient pumping of the molecular vibrational levels by the relatively high velocity discharge electrons. Much higher powers can be produced by gain switching the CO laser. This is obtained by pulsing the electrical discharge at pressures considerably higher than the 20 torr pressure typical of the conventional dc-excited CO, laser. The resulting relatively slow plectrons produce more efficient pumping of the (001), (002) and (003) upper lasing vibrational levels of the carbon dioxide molecule and there is no bottleneck in depopulating the lower (100) laser level as is the case with conventional lasers because the low duty cycle permits the gas to return to the ground state between excitation pulses.

The cold-cathode, e-beam gun is now well established as a source for ionizing large-volume CO2 lasers (Ref. 1-3). High pumping rates have been achieved with e-beam densities >1 A/cm2 for periods of a few ,is. The beauty of the cold cathode gun lies in its essential simplicity, ruggedness and efficiency.

There are several pumping mechanisms occuring in electron beam excited lasers. The importance of each depends upon the range of the electrons in the gaseous medium.

Heat release in a laser with subsonic or supersonic flow of the lasing medium causes variation in gas density. Variations in gas density result in phase differences at the exit aperture of the laser beam. Beam quality is degraded. Using the linearized solutions for a line source of heat in subsonic, planar flow, equations are derived for the density perturbation Lip p. Lasers having subsonic flow in the cavity include electroaerodynamic lasers. The equations permit assessment of Mach number effects and wall shape. As Mach number increases, the influence of the heat source wakes becomes less important. A wall shape equivalent to operation in a flow of infinite extent gives smaller Lp/p than par-allel walls. To apply the aforementioned equations, it is necessary to know the heat release function, h(x,y). A simplified vibra-tional relaxation model is developed and coupled with Joule heating to arrive at estimates for h(x,y). The model predicts populations with and without laser power extraction.

Recent advances in high power lasers with their optically active media at supersonic flow conditions require experimental gain measurements to be performed under difficult conditions. The spatial inhomogeneities and their rapid temporal variations cannot be prescribed analytically; their effect on the accuracy of measured gain values can only be estimated. In the cases of media with low gain values (typically in the order of 0.1 to 1.0 percent per cm) inaccuracies resulting from time varying optical inhomogeneities may completely mask the data when conventional gain measuring techniques are used. The present paper describes a method that was developed at Atlantic Research Corporation with IR&D funds to eliminate the problem as described above. The system has several unique features: 1. By appropriate design of the optical train, the influence of rapid variations of inhomogeneities of the optically active medium on roundtrip gain measurements are effectively eliminated. This feature is maintained throughout a wide range of inhomogeneities such as is experienced in well-designed gas dynamic and chemical lasers. 2. A single detector sequentially monitors a ref-erence level, the signal itself, and an off condition. High frequency noise components of the probe laser are eliminated by a synchronous detector with variable RC constant; the low frequency noise components are elimi-nated by ratio taking. 3. A unique optical arrangement allows complete elimination of laser radiation feedback into the probe laser allowing quiet laser operation. The above system can be operated in any portion of the optical spectrum. It has been operating at Atlantic Research Corporation at 10 microns with a total resolution of roundtrip gain of better than 1 percent.

Of the two principal areas in which laser and nuclear technology may interact - laser-induced fusion and nuclear-pumped lasers - this paper concerns the latter. The concept involves direct conversion of fission energy, mostly kinetic energy of charged particles (fission fragments), into coherent radiation of optical frequencies. Papers dealing with this subject began to appear around 1961. A review of this earlier work is given in Reference (1).

A dye-switched TEM:00 ruby laser has been employed for two types of diagnostic studies of short, unstable, high-pressure dc arcs in noble gases. Holographic interferometry mea-sures gas density distributions, and a simple fringe-projection technique gives time-resolved contours of the agitated molten anode surface. A recently-developed mathematical technique permits avoidance of speckle problems in the holography by use of collimated scene beams, while greatly reducing the labor involved in gathering experimentally and analyzing numerically the data needed to determine asymmetric density distributions. Because fringe projection revealed intriguing unexpected details of arc-anode interface behavior, ideas are presented for further elaboration of the technique.

With the low priority for R and D, research and development, for laser applications in medicine, it is surprising that any current report of progress could be developed. However, still in an all too limited phase, laser medicine continues in this country both for diagnosis and treatment other than for diseases of the eye. (Ref. 1, 2). Fortunately,there is increased activity both in laser biology and medicine in Europe and Russia at the present time. A laser cancer treatment institute has been established in Kiev, Russia. West Germany has plans to develop a laser institute of biology and medicine through the Gesllschaft fur Strahlen and Umweltforschung. So progress in this important field of laser applications will be continued at least, if not here. It is not recognized by those who have withdrawn funding for basic research that research in biology and medicine helps to develop programs for laser safety. With effective programs of laser safety, the field of applications of the laser has expanded and will continue to expand. Work in laser biology is necessary for progress in laser medicine.

In 1965 the first model of a laser cane for the blind was produced for the Veterans Administration (VA)* by Bionic Instruments, Inc. Since then, development has proceeded through three more models (Ref. 1) to the present C-5 cane (Ref. 2)-- the final "production" model to be described here.

The selective damage of cell structures by partial irradiation is a technique employed by biologists since the early 1900's. (See reviews: Refs. 1, 2, 3, 4) The approach is simple: expose a specific cellular region or structure to a non-lethal dose of radiation, and then examine the cell with respect to altered structure and function. In this way, much can be learned about various subcellular struc-tures (organelles) and general cell function. In theory, this approach to the study of organelle function could be most productive. Indeed, several hundred studies have been published. However, of these only a few have resulted in substantial progress in understanding the cell. The types of radiation have included par-ticulate (protons, electrons, alpha particles, etc.) and electromagnetic (ultra-violet, X-ray, gamma ray). It is probable that the general damaging properties of these types of radiation have resulted in much secondary cell damage, thus making strict interpretation of the results difficult. It was not until the early 1960's that successful partial cell irradiation was performed with visible wavelengths. The intensity attainable at a single or few wavelengths with laser light has permitted the selective damage of numerous cell organelles. Surprisingly, secondary effects to non-target structures appear to be minimal, if not non-existent. Though a coherent explanation of this capability cannot be given at this time, the fact remains that numerous cell structures can be affected selectively without apparent damage to nearby organelles. These results have been confirmed by assaying subsequent cell function as well as cell ultrastructure. In fact, it has been possible to demonstrate that the unirradiated regions of an otherwise irradiated organelle are structurally (and apparently functionally) unaffected.

The laser is unique in its capacity to deliver very high heat energy in a short time. This paper will describe the aleration of the carious process in vitro and in vivo by laser induced physical changes of the surface enamel. It will also broadly consider future laser application in dentistry.

A holographic image projection and tracking system has been developed which can automatically map a surface with high precision. To illustrate the potential usefulness of this technique to bio-medical applications, point coordinate data for preselected points and automatically scanned surface profile data has been taken of a skull geometry model. The model is representative of the average American male. System design studies on this holographic technique show that 1) dimensions of objects of the order of 1 meter in size can be produced from their image to an accuracy of 1 part in 10⁴ and 2) the precise location of the image surface can unambiguously be determined for even matte, featureless surfaces without the need for surface preparation. The skull model data and suggestions for other biomedical applications are presented.

Holographic interferometry is firmly established as a versatile tool for the research scientist and the practical engineer. The principal applications of the method up to now have been in the general area of non-destructive testing of various mechanical structures. The purpose of this paper is to review the recent advances in the state-of-the-art of holographic interferometry and to discuss the potential of the technique for biomedical applications.

This paper reexamines laser-excited pulsed dye lasers since they may be advantageous over other types of pulsed lasers in some holographic applications. Of particular interest is the capability of dye lasers to generate sufficient energy per pulse and with sufficient coherence to record holograms. This capability was demonstrated just recently (Ref. 1) and will be discussed in more detail in this paper. The additional capabilities of the dye laser to be frequency tuned throughout the entire visible spectrum and to operate at two or more frequencies have potential importance in holographic contouring and underwater holography. (Dyes can be selected and tuned to match the optimum transmissivity of the working medium.) The selective interaction of dye laser light with living organisms may permit minute dimensional changes to be observed and measured. The low intrinsic cost of the active materials and operational reliability of dye lasers are other desirable features.

Radiographic diagnostic evaluation of numerous specific pathogenic entities in medicine and dentistry can be significantly enhanced through the use of recently developed mathematical data processing techniques. A method is described to non-destructively section a human organ, at any desired angle of orientation, using computer processed data derived from a series of ordinary radiographs.

This paper provides a summary of various known techniques for generating holograms by means of a digital computer and associated display devices, and discusses a recently invented method which is some cases offers distinct advantages over alternate approaches.

Under monochromatic illumination, objects with a scale of roughness or texture grossly on the order of the wavelength appear to a viewer to be speckled. The occurrence of these speckles, which are rapid intensity variations in the image, often leads to a substantial reduction in the apparent resolution of the imaging system. While the exact speckle structure is, in principle, deterministically related to the specific textural detail of a particular object, still its effect is often deleterous since other feature details are often greatly obscured in the speckled image. The distinction between textural and feature details is rather subjective, and so it may be helpful to describe some specific cases. Thus, holograms of typical biological specimens of microscopic size are usually so speckled in reconstruction as to render them impractical. Boundaries, cell walls and the like, are completely lost in the speckle. And one almost never uses a laser illuminator in a microscope due to the attendant speckle and interference fringes, unless there is an overriding need for the mono-chromaticity, e.g., as in flourescence systems. Some feeling for the effect of speckle can be gained if the reader will glance ahead to the illustrations in Figs. 1, 2, and 3. So for many purposes speckle is troublesome and unwanted, that is the position we take in this paper; however, it is worth noting, as an aside, that others have reported useful applications of speckle in metrology and in surface texture analysis.

A camera having a lens with two apertures and equipped with a shearing mechanism is employed to image a specimen which is illuminated by coherent light. With this arrangement, the speckle from one point on the surface is allowed to interfere with the speckle from a neighboring point so that a speckle-grid pattern may be detected in the image plane. By double-exposure or real-time techniques, the speckle-grid pattern corresponding to the deformed state of the specimen is added to the speckle-grid pattern corresponding to the undeformed state of the specimen. The resulting mechanical interference produces a moire-fringe pattern which depicts derivatives of surface-displacements. The camera will be referred to as "Speckle-shearing Interferometric Camera". Three applications of the speckle-shearing interferometric camera are described: (1) mea-surement of slopes of structural deflections, (2) in-plane strain measurement, (3) vibration analy-sis. Experimental demonstrations for each case of the applications are presented. Although the speckle-shearing interferometric camera is based on interferometric principles, it overcomes several of the limitations associated with holographic and speckle interferometries, namely: (1) the setup is simple and does not re-quire laborous alignment of optical components, (2) it does not require stringent mechanical and ambient atmospheric stabilities, (3) coherent requirements of light are greatly relaxed, (4) the sensitivity is greatly reduced, and (5) it does not require differentiation to obtain strains.

The numerous problems involved in making a hologram of a moving object are well known. Chief among them is the lack of coherence be-tween the reference wave and the light scattered from the moving object. This incoherence arises because the scattered light suffers a Doppler frequency shift due to the motion of the scattering object. At optical frequencies, this shift is so great that no available detector can perceive interference between object and reference waves, and hence they are effectively incoherent.

The biological populations contained in the Earth's oceans are a current focal point for intense scientific study aimed at describ-ing and understanding the complexity of interactions between and among the various component parts of the living system and with their physical and chemical environments. Any possible utilization of marine aquaculture in the future on an economically-practical basis to augment man's food supply depends upon the gaining of this knowledge. Attainment of such a goal presents a great challenge because of the dynamic and variable nature of many of these interactions. As a part of the quest for this understanding, new means for the study of marine populations must be developed because of shortcomings in our present methodology. Successful application of holographic techniques to the study of planktonic populations (i.e. the populations of small organisms living unattached within the water column, either passively moving or possessing very limited powers of locomotion) could provide a major contribution towards furthering our knowledge of the behavior of this important component of the total biological community in the sea. While, in general, the plankton organisms are not directly exploited as a commercial product, they are an integral part in the overall production of marketable fish and other marine biological products.

During the future exploration and exploitation of the ocean, most of the underwater television, photography, and direct viewing from sub-mersibles or by divers, will utilize submerged non-or low-coherent light sources. However, at the present there are no valid procedures to follow in designing underwater lighting installations. This lack of knowledge is due to the fact that no one at the present time knows how to calculate the distribution of light underwater by any given type of lamp.

An extensive literature exists concerning the phenomena that occur when laser radiation interacts with solids or fluids. The nature of the interaction depends greatly on the optical, mechanical, and thermal properties of these materials. There can be such things as plasma generation if the radiation is absorbed in short distances or nonlinear optical behavior leading to "filamenting, " "banana peeling, " or harmonic generation in the more transparent materials (Ref. 1, 2).

Molecular association lasers are characterized by laser molecules having a repulsive ground state with stable excited states formed by association of the constituent atoms. These lasers have the potential for high power operation with high efficiency in the visible and shorter wavelength region. The recent achievement of a xenon molecular laser has demonstrated the feasibility of this class of lasers.

Integrated optical circuits are now the subject of research and de-velopment at a number of laboratories. The long-range goal of integrated optics research is to provide arrays of circuit elements capable of combining various discrete operations on guided light beams into sophisticated signal processing and communication devices and systems. It is expected that these devices and systems will take advantage of the inherently wide band-widths available at optical frequencies. They would also be compact, lightweight, economical, and immune to environmental and electromagnetic disturbances. The potentials and advantages of integrated optics are analogous to those realized by integrated electronics technology of the lower frequency spectrum. Considerable amount of work remains to be done, however, before the above ultimate goals are realized. At the present time the approaches taken by the different researchers in the field vary depending on the time frame in which they are working. The most immediately practically realizable systems will probably involve fiber optic communication links with discrete sources (most commonly LED's), direct electrical modulation, existing. detectors, a small number of terminals, and modest bandwidths on the order of tens of megahertz. Such systems have already been demonstrated and are being developed for practical applications. The next generation of systems will most likely involve the so-called "hybrid" approach where information transmission is done in the optical domain and some of the, func-tions are performed in a true integrated optical circuit while others involve discrete components or electronic circuits. In such systems interface elements are of great importance. Finally, the ultimate systems would involve truly integrated optical circuits with integrated and miniaturized components and most of the functions performed in the optical domain. The practical realization of such systems is, however, several years in the future. In the meantime, most of the current research effort is directed toward development of components and technologies compatible with the long-range goals outlined above. This paper reviews the objectives and motivations of the present day integrated optics research and then goes on to discuss recent progress in component and technology development relevant to integrated optics. Special emphasis is placed on the work performed by the several investigators at Hughes Research Laboratories, some of it in collaboration with the Cali-fornia Institute of Technology. Work on fabrication of optical waveguides by various methods such as ion implantation, electron beam lithography, ion beam micromachining, and vapor and liquid epitaxial techniques will be reviewed. Work on various materials such as GaAs, Gai-xAlxAs, GaP, glasses, PMM, etc. will be summarized. Experiments dealing with guide-to-guide coupling (using ion implanted as well as micro-machined three-dimensional guides), gratings for distributed feedback lasers, modulators, and integrated detectors will be discussed.

The operation, application, and work-ing theory of an ultra stable laser as a length digitizer is summarized. The two projects presently under way, a 1.6 KM (1 mile) long laser earth strain seis-mometer and a 1-cm pendulum tilt meter, each with a range of 10-12 to 10-5 strain units and radians (or acceleration g units), respectively, are detailed as examples of application. Concepts in angular measurement and servo-controlled physical dimension are reviewed. The perfection of ultra stable lasers has opened the door for a host of even more precise electro-optical mensuration applica-tions. Compact lasers whose absolute frequency stability is measured in kilohertz make possible in practice the use of digital techniques and heterodyne of optical frequencies. This in turn allows the engineering of a "length" digitizer with dynamic range and precision many orders of magnitude beyond the presently accepted state of the art. A dynamic measurement system of dimension of very small (1 cm) to very large (1 km) sized objects is presently under way using this technology. In each case the target recision is 1 in 10¹² in dimension and 10⁹:1 in instantaneous dynamic range. The combination of both sensitivity and range represents an advance in the state of the art by about a factor of 10⁴.

Since the commercial introduction of the gas Laser in the early 1960's, various industries (not including pure scientific research) have attempted to adopt the coherent light source as a standard tool. By far, the most successful attempt to date has been the use of the low powered He-Ne Laser in the construction industry for alignment purposes. The properties of the He-Ne Laser makes it ideal for the construction industry: Relative Low Cost High Single-Mode Stability Portability--low input power requirement from 12 VDC source Ruggedness of Design of Internal Mirror Plasma Tube In turn, the construction industry needs are ideal for low-powered He-Ne Lasers: Stable, Long Distance Reference Line Reference Line Not Requiring Operator Improved Accuracy Improved Efficiency