Celebrating Holography after 60 years of successful application

The invention of Holography by Dennis Gabor¹ goes back to the year 1948. Gabor could show that the complete original wavefront of the object both with its amplitude and phase can be reconstructed by adding a coherent background to a wave coming from an object while recording in a storage medium. However, because no adequate source of coherent light was available at this time, the small coherence length of the mercury lamp forced him to arrange everything along one axis. This setup, known as in-line holography, has the disadvantage that the desired reconstruction is in line with disturbing diffraction orders, and can be separated from these disturbances only by focusing. Gabor finally gave up his investigations and mentioned in 1955 to his collaborator Michael W. Haine, “It was a very ill wind which I let out now almost eight years ago which blew nobody any good, least of all to myself.”

The holographic principle, on which Gabor had set his high hopes, especially with respect to the enhancement of the resolution of the electronic microscope, seemed to retain only the status of a scientific curiosity. But the breakthrough would be achieved a couple of years later. In the early 1960s, Emmett Leith and Juris Upatnieks, two physicists at the University of Michigan, implemented their off-axis scheme as a smart combination of Gabor’s holographic principle with the carrier frequency technique known from side-looking radar. Their famous publication came out 61 years ago in 1961². In this way the twin image problem could be effectively eliminated. However, it resulted in the requirement of increased temporal coherence which could be satisfied using a powerful coherent light source only. Such a source was soon available. In 1958, Charles Townes at the Columbia University, and a Russian research group led by Nicolay Basov and Aleksandr Prokhorov at the Lebedev Institute for Physics, Moscow, simultaneously and independently analyzed the possibilities of applying the principle of the Microwave Amplification by Stimulated Emission of Radiation (MASER) for the optical region of the electromagnetic spectrum.

The first operating optical MASER, now known as the laser, was constructed by Maiman and was demonstrated at the Hughes Research Laboratories in Malibu, California, in 1960³. The symbiosis of the holographic and laser principle opened the door for a large variety of new technologies and applications in optical imaging, information processing, and metrology. The 1960s were filled with a variety of successful practical applications and innovations such as display or volume holography⁴, computer generated holography⁵, holographic interferometry⁶, holographic nondestructive testing, holographic pattern recognition, and holographic storage technology. Gabor took an active part in this development. 50 years ago, on the occasion of his Nobel lecture at the Imperial Colleges in 1971, he also tried to take a look into the future of holography⁷. Gabor mentioned “However, there are important areas in which we can do much more, and where an improvement is badly needed. This is the area of microholograms for storing and for display. An even more ambitious scheme, probably even farther in the future, is three-dimensional cinematography, without viewing aids such as Polaroids”. The basics for such a technological leap like digital storage, reconstruction, and synthesis of holograms were already on the way^{8, 9} when Gabor made this prediction.

Holography also established the basis for new measurement technologies that play an important role in manufacturing. 1966 Karl A. Stetson and Robert L. Powell published their groundbreaking article “Holographic Interferometry” ⁶. A.J. McGovern and J.C. Wyant proposed 1971 a new method for testing optical elements based on computer generated holograms¹⁰. Later Karl Stetson correctly mentioned “The novelty of Holography is Speckle”. This astonishing effect because of the interaction of coherent light with scattering media was observed already many years ago. But to use Speckle as an outstanding tool for non-destructive testing goes back to the early 70^th11 and was also stimulated by holography. The application of video tubes instead of photo plates and electronic recording was a further major step in 1971 to make Speckle metrology called ESPI (Electronic Speckle Pattern Interferometry) to a mature technology¹².

In 2021, 60 years after the publication of the seminal article by Leith and Upatnieks, 55 years after the invention of Holographic Interferometry by Stetson and Powell, and 50 years after Gabor’s remarkable Nobel lecture, the editors took the opportunity to celebrate these groundbreaking contributions to modern optics with a special edition of “Light – Advanced Manufacturing”. Our call for papers found an impressive echo in the international community. We received 45 contributions from well-known experts in the field who reported about the history, state of the art and perspectives of holographic technologies. Finally, we could accept 39 papers and present this impressive collection in that special issue. Because these contributions address many different issues, we decided on a structure into 5 main topics:

- 6 papers^13-18 “Celebrating Holography and its Impact over 60 Years”

- 8 papers^19-26 dealing with the “Digital Transition of Holography”

- 8 papers^27-34 describing the Potential of Holography for the “Making of New Optical Components”

- 10 papers^35-44 addressing the “Wide Field of Applications” opened by holography

- 7 papers^45-51 discussing “Perspectives of Holographic Technologies”.

Our thanks go to all authors who joined our journey through 60 years of a meanwhile traditional but even young discipline of modern optics. All these contributions express the conviction that this journey has just started and that we can still expect many remarkable innovations in the coming years. Further thanks go to all reviewers who helped us with their comments and proposals to keep the high quality of our LAM journal. We know about the large workload that we transfer to the colleagues with the request for careful assessment of all submissions. Finally, we thank all members of the editorial office of LAM who made it possible to publish that extensive collection of papers in a relatively short time after the acceptance of all submitted papers. Special thanks go to Shuai Ding and Siqiu Guo for their careful assistance and support.

The editors hope that this issue will find an interested audience and will be a welcome contribution to another successful 60 years of holography.