_____________________________________________________ THEMEARTICLES WILLIAM J. TROPF OPTICS AT THE APPLIED PHYSICS LABORATORY Work in optics at the Applied Physics Laboratory has described in the following paragraphs. References 1 to steadily grown over the past decade, and has become 24 are articles on optics from previous issues of the Tech­ a major discipline that rivals the traditional APL special­ nical Digest. Those past articles, along with the articles ties in microwaves and acoustics. Optical activities at in this issue, present examples of APL work in optics. APL include areas as diverse as research, sensor evalu­ ation, and optical techniques as applied to medical, Fleet Systems Department space, military, and oceanographic tasks. Optical work in the Fleet Systems Department focuses This issue of the Johns Hopkins APL Technical Di­ primarily on performance of detection, tracking, I guid­ gest reviews current and recent tasks in optics at APL. ance, 7 and communication4 systems for the Navy, as Harris begins with an introductory article on optical de­ well as basic research in propagation, 23 material prop­ sign that is intended to acquaint the nonspecialist with erties, 24 device characterization, mensuration, and re­ the optical design process, available tools, and typical mote sensing. Research activities in the department in­ APL products. clude optical signal processing, property measurements, Several articles look at different facets of optical tech­ remote sensing, and biomedical instrumentation develop­ nology. Thomas and Joseph describe a process for char­ ment. The department has a complete optical design and acterizing the optical properties of transparent materials measurement capability that supports instrument devel­ through a combination of theory, models, and measure­ opment and performance evaluation throughout APL. ments. Gearhart and Thomas show the feasibility of a Optical methods have been applied to many sensor- and spectroscopic remote-sensing technique for measuring the instrument-development tasks (Fig. 1), and instruments temperature of gases. and systems are used in the field for precise measure­ The remaining papers review APL optical instrument ments. development and the resulting data. The article by Rust, The department maintains an optical sensor laboratory O'Byrne, and Harris describes an imaging polametric op­ for testing visible- and infrared-light sensors, a signal­ tical instrument that measures the solar magnetic field. and image-processing laboratory for superconducting­ Duncan reports on two optical instruments for medical detector and optical-processing work, and an infrared applications: an interferometer to measure inner-ear mo­ laboratory for measurements in the ultraviolet to sub­ tion and a laser Doppler velocimeter to determine shear millimeter spectral regions. Special instrumentation in­ in blood flow. Mayr and Warren recount the design and cludes a high-resolution Fourier transform spectrometer, development of an optical position-measuring system cryogenic systems for detectors and laser diodes, high­ that gathered pointing and tracking data to characterize power argon and carbon dioxide lasers, and a heterodyne a precision laser director system. The final theme article laser interferometer. of this issue is a description of the APL laser machine tool by Blum and Charles. Space Department The theme of optics will continue in the next issue of Optical programs of the Space Department concen­ the Digest. Articles for the next issue will describe the trate on spacecraft instruments operating at ultraviolet, development of new semiconductors as optical sources optical, and near-infrared wavelengths, as well as optical and detectors, technology allowing improved light­ systems for ground-based astronomical observations. gathering and optical resolution in astronomical tele­ Several groups design, build, and use optical instruments. scopes, signal processing, ocean optical properties, and Work in space optics began with radiative-transfer space measurements of ultraviolet and visible back­ measurements for thermal control. In 1967, the fitst grounds. APL imager was flown on the DODGE spacecraft. Op­ tical instrumentation was used also in the SAS and Mag­ CAPABILITIES AND ACTIVITIES IN OPTICS sat2 satellites. More recently, APL has built ultraviolet­ Three APL departments, along with the Eisenhower and visible-light imaging and spectrographic instruments I2 Research Center and the Biomedical Program, conduct for auroral observation from space (HILAT ,13 arid 21 a significant number of optical projects. The capabilities, Polar BEAR ,22 ) and for Strategic Defense Initiative facilities, and typical tasks of these APL divisions are experiments (Delta 180 and 181). f ohns Hopkins A PL Technical Digest, Volume 9, Number 4 (1988) 315 Tropf - Optics at the Applied Physics Laboratory Figure 2-Donald Duncan (left) and F. Fausten Mark making laser Doppler velocimeter measurements of simulated blood Figure 1-Roger Lapp inspecting lightweight, 1.8-m-diameter flow. The crossed laser beams of the velocimeter are seen mirror made for the U.S. Navy by REOSe (France). APL assist­ emerging from the model of a segment of artery. Further infor­ ed the Navy in holding, mounting, and transporting the mirror. mation is given in the article by Duncan . The Space Department has also worked on several as­ laser deposition methods for making thin-film high-Tc tronomical telescopes (the Hopkins Ultraviolet Tele­ superconductors, development of molecular electronics l6 l7 scope and the Space Telescope ) and maintains an and nonlinear organic optical devices, thermal wave im­ active program in solar astronomy. The Center for Ap­ aging for nondestructive testing,19 and the development plied Solar Physics, funded by a University Research Ini­ of optical switches and III-V semiconductors for optical tiative, is located at APL. Several ground-based instru­ emitters and detectors. Extensive biomedical research is ments have been built for solar astronomy,20 including conducted on optical properties of the corona 10,18 (laser seismology and magnetic field measurements, and a effects and scattering), laser fluorescence, spectroscopy, 5 small observatory is maintained at APL as a test site fo"r and the role of singlet oxygen 6 in biological systems. their development. The Research Center makes extensive use of optical Submarine Technology Department systems and techniques in most of its laboratories. Staff This department uses optical instruments for oceano­ members have experience in Raman, coherent anti­ graphic measurement and remote sensing, including op­ Stokes Raman spectroscopy (CARS), and laser Doppler tical measurements of wave structure,3,9 radiometry of velocimeter techniques. The center has many medium­ the ocean surface, 8 and modeling and measurement of to high-power laser systems, including excimer, ruby, underwater optical propagation, reflection, and scatter­ Nd:YAG, dye, and carbon dioxide systems. Property ing at the air/ sea interface. The department also develops measurements are made with FTIR and UV /visible spec­ and tests charged-coupled-device imaging systems for trometers and an ellipsometer. ocean remote-sensing investigations. A facility is main­ Biomedical Programs tained for the characterization and calibration of the im­ The biomedical programs at APL began in 1964 with aging systems. five projects in ophthalmology; since then, this work has Research Center been characerized by a large proportion of optical tasks The center carries out research in optical techniques, (Fig. 2). Early work included development of optical materials, and devices. Early optical work included de­ methods for evaluation of the retina, optical systems for velopment of chemical lasers, advances in photochemical eye geometry and dye movement measurements, and la­ and photoacoustic techniques, and studies in laser-in­ ser systems for photocoagulation. Biomedical activities duced decomposition. Current work includes the use of are managed by a program office that uses primarily the 316 fohns Hopkins APL Technical Digest, Volume 9, Number 4 (1988) Tropf - Optics at the Applied Physics Laboratory capabilities and resources of the departments as described the Department of Materials Science and Engineering; above. The biomedical program has a biodynamics lab­ Peacock worked on design problems of the Magellan oratory and an imaging laboratory that support measure­ telescope project at the Center for Astrophysical Sci­ ments, data analysis, and system development activities. ences. Peacock will report on the status of large-telescope Biomedical work is extensively reported in the Technical technology in his article in the next issue. Digest. 6,10, 18 APL also offers employment opportunities for stu­ dents. Educational assistance is available to staff mem­ Other Departments bers through the APL part-time study program. Sum­ The Aeronautics Department has long been a user of mer and cooperative appointments are available for un­ sophisticated optical instrumentation 11 to support their dergraduates. Graduate students can conduct thesis and work in aerodynamics, propulsion, and structures. Its dissertation work under temporary appointments, and staff makes extensive use of flow-visualization methods post-doctoral research fellowships are also available. such as shadowgraph and Schlieren techniques (Fig. 3), video recording, and laser Doppler velocimetry. PARTICIPATION IN The Technical Services Department maintains