Applied Physics began as the Division of Applied Physics in 1962 in response to a recognition of the expanding boundaries of physics as applied to particle accelerators, condensed matter, and devices. Early motivation for the division’s mission came from the desire of the particle physics community to develop new accelerator designs. In response, the Physics Department started the Microwave Laboratory in the 1940’s. Working in the Microwave Laboratory, Edward Ginzton and Marvin Chodorow developed the world's first high-power klystrons, and in a project led by William Hansen, this technology lead to the first electron linear accelerator and, eventually, to SLAC. Indeed, Ginzton later wrote the proposal and first budget for SLAC. Recognizing the need for an applied physics faculty to pursue work in this laboratory (and others to come), they helped start the Division of Applied Physics. Chodorow led the movement to create a separate department in 1968.
Meanwhile, the Microwave Laboratory became the first independent laboratory (independent of both the Physics and Applied Physics departments) before splitting into the Ginzton and Hansen Experimental Physics Laboratories. These successful independent labs became the model for several others at Stanford. They include School of Humanities and Sciences faculty beyond the Applied Physics and Physics departments as well as include faculty from other Schools at Stanford, especially the School of Engineering. Applied Physics faculty continue to populate and play leadership roles in these labs.
Early leadership of the Department of Applied Physics was provided by Chodorow, and Hu Heffner. Soon, interests in laser physics, condensed matter, and astrophysics spurred hiring in each of these fields. Cal Quate and Ted Geballe were among the first professors recruited by Applied Physics when still a division. Leadership in Applied Physics drove Stanford’s growth in condensed matter physics, starting with the hire of Geballe from Bell Labs. The hiring in 1969 of Vehe Petrosian launched astrophysics efforts, and Bob Byer, also arriving in 1969, solidified the department’s world-renowned efforts in photonics and lasers. Later, interest in ultracold atomic physics led to the recruitment of Steve Chu (Nobel Prize 1997) as a professor in both the Applied Physics and Physics Departments.
Our department has been chaired by many distinguished faculty whose names appear at the bottom of this page, along with a complete list of AP faculty through the ages. Paula Perron was the administrative glue and encyclopedia for the department throughout most of its history, from her arrival at Stanford in 1971 till her retirement as departmental administrator in 2017.
We now recount a select number of departmental milestones:
Contributions to LIGO
Researchers in the groups of Byer and Fejer in Applied Physics developed key components of the LIGO gravitational wave detector, which made headlines by detecting the coalescence of two massive black holes a billion years ago. This manifested as the change in separation by 10-18 m of mirrors spaced 4 km apart. The ultrastable laser that serves as the master “clock” for the detector was one of the key Stanford contributions. Our tradition of tool-building enabled a key element of one of the most precise measurements made in mankind’s history.
Legacy of Cal Quate, inventor or advanced microscopes
Calvin Quate (Image credit: L.A. Cicero)
Cal Quate, who spent much of his career developing ultrasonic imaging methods (now, of course, omnipresent as a medical diagnostic tool), conceived the atomic force microscope. The AFM enabled atomic-scale imaging of surfaces and helped launch the field of nanotechnology. For this work, he was awarded the Kavli prize in nanoscience.
Herman Winick, together with a colleague at UCLA, initiated the development of the Linac Coherent Light Source (LCLS), which converted the SLAC linac from a tool for particle physics into an X-ray free electron laser (xFEL). The LCLS produces femtosecond pulses of coherent X-rays that are many orders of magnitude brighter than any previous X-ray source. It is revolutionizing fields from atomic physics to molecular biology. One can now take time-resolved “movies” of the vibrations of the atoms in a molecule. Seb Doniach, who was founding director of SSRL, in collaboration with Bill Spicer of EE and Herman Winick of AP, has recently demonstrated the application of xFELs to determine molecular structure on atomic length scales, pointing the way to capturing movies of biological molecules in action on biological time scales and under physiological conditions.
X-Ray Source Development
When Burton Richter conceived of and later built the SPEAR ring for electron/positron colliding beams, which led to the discovery of the psi particle, he was approached by Seb Doniach of AP and Bill Spicer of EE to add a window to allow X-rays to be accessed. Richter confirmed that this was compatible with the vacuum in the ring and added the X-ray window. This led to the brightest X-ray source on the planet at that time and to the application of X-rays to condensed matter physics. The leadership of the SSRL synchrotron source by Artie Bienenstock---AP, joint with Materials Science---led to a user facility with multiple ports and a wide range of applications. Later, in 1992, SSRL built its own electron accelerator for injections.
Revolutions in Biophysics
Optically tweezing biomolecules (Steve Block group)
Steve Block’s group has developed a system based on applying pico-Newton forces to individual macromolecules with “optical tweezers.” One can now observe nanometer steps taken by molecular motors, such as kinesin “walking” along microtubules. This enables the observation of phenomena such as motors backing up a few nanometers at a time to correct errors made during DNA transcription.
New Frontiers in Neuroscience
Mark Schnitzer combined concepts from micro-optics, fiber optics, MEMS, and ultrafast laser technology to develop a microscope that can be mounted on the head of a mouse, and can image, through a fiber optic cable, activity deep within in a mouse’s brain at the scale of individual neurons while the mouse is active during complex behaviors such as navigating a maze. Observation of the operation of the neurons operating as a network, rather than just in vitro studies of individual neurons, has become an essential tool in the burgeoning field of systems neuroscience.
New Tools to Study New Materials
The late John Shaw made seminal contributions to the development of fiber-optic gyroscopes, now widely commercialized for inertial navigation systems. Marty Fejer and Aharon Kapitulnik recognized this instrument could be modified to optically detect tiny magnetic signals in complex materials, inaccessible by other methods, and they worked with the Shaw group to develop such a system. This tool has been playing an important role in understanding modern quantum materials exhibiting unusual superconducting and subtle magnetic states.
Interfering Atoms to Study Gravity
Atom interferometer (Kasevich Group)
Another take on precision navigation emerged from the work Mark Kasevich did in his Ph.D. project with Nobel laureate Steve Chu 25 years ago, the first demonstration of interference between matter waves over millimeter distances (“atom interferometry”). This field, with continued fundamental contributions from Kasevich, has evolved from an exploration of fundamental quantum physics to commercialization of important tools for measurement of time, gravity, and position, including GPS-free inertial navigation systems.
This small selection of examples illustrates how our agile interdisciplinary approach has lead to significant successes across many disparate fields, often creating tools which fundamentally alter the course of research worldwide. We aim to foster and enhance this intellectual culture within our department going forward, pushing science, technology and society forward in the 21st century.