Peter H. Siegel

Visiting Associate: Engineering and Applied Science
Senior Scientist: Division of Biology (11 years)
Senior Research Scientist:
Jet Propulsion Laboratory (26 years)
Founder: JPL Submillimeter Wave Advanced Technology (SWAT)

Founder/CEO of THz Global, an international collaborative research consulting team working on a wide variety of THz research and applications

Founder, International Society of
Infrared, Millimeter, and Terahertz Waves

Founding Editor-in-Chief, IEEE Transactions on
Terahertz Science and Technology

B.A. Astronomy, 1976, Colgate University, Hamilton, NY
M.S. Physics, 1978, Columbia University, NY
Ph.D. Electrical Engineering, 1983, Columbia University, NY

Email contact phs AT caltech DOT edu

Research in Terahertz Technology and Applications: Earth and Space Science, Biology, Medicine, Defense and related Civilian opportunities

To view Dr. Siegel's current research and his former research group .

Link to the International Society of Infrared, Millimeter and Terahertz Waves

Link to 39th International Conference on Infrared, Millimeter and Terahertz Waves held at University of Arizona, Tucson from September 14th-19th, 2014.

Link to 33rd International Conference on Infrared, Millimeter and Terahertz Waves held at Caltech from September 15-19, 2008.

Link to IEEE Transactions on Terahertz Science and Technology   THZ Journal
Download flyer for the new journal: THz Journal Flyer
If you wish to be considered for review board membership or to help out with the new journal in any way please email Peter Siegel

Background and Philosophy: Dr. Siegel’s research specializes in the invention, development and delivery of a wide range of specialized sensor and source devices, components, and instruments spanning the frequency range between 100 and 10,000 GHz which includes the millimeter, submillimeter and far infrared wavelength regimes: the terahertz bands. Emphasis is placed on a cross disciplinary approach which brings together a diverse range of backgrounds and skills that can be directly applied towards progress in bridging the electronic and optical regimes, one of the last remaining technology gaps in the electromagnetic spectrum. Students and staff working with Dr. Siegel include electrical engineers, physicists, biologists and chemists from a wide range of backgrounds and countries. Research work is conducted both at Caltech and at the nearby Jet Propulsion Laboratory, where the emphasis is on Earth, space science and planetary applications of THz technology. Dr. Siegel has recently founded a small international consulting company, THz Global, through which he is continuing his THz research work in collaboration with an international team of colleagues with expertise that spans the full range of millimeter and submillimeter wave applications.

Over the past 26 years Dr. Siegel and his Submillimeter Wave Advanced Technology team at JPL and Caltech have developed and delivered critical sensor hardware for four space flight missions: NASA’s Upper Atmospheric Research Satellite Microwave Limb Sounder, the first instrument to directly measure the anti-correlation between chlorine monoxide build up and ozone depletion on a global scale; NASA’s Earth Observing System Aura Microwave Limb Sounder currently measuring a wide range of stratospheric molecular species involved in ozone depletion, global water distribution, climate change and pollution monitoring across the Earth; European Space Agency’s Microwave Instrument on the Rosetta Orbiter (MIRO), scheduled to rendezvous with comet Churyumov-Gerasimenko in 2014 and measure nuclear temperature and out gassing rates of carbon monoxide, water, ammonia and methanol; and most recently the Heterodyne Instrument for the Far Infrared (HIFI) on the European Space Agency’s Herschel Space Telescope, an ambitious astrophysics mission to record thousands of molecular signatures between 300 and 1900 GHz in and around star forming regions and in external galaxies, as a means of understanding the composition and evolution of the universe. Future mission opportunities include a Discovery class instrument for Venutian cloud measurements, Vesper; a Mars orbiter searching for volcanic emission and life signatures, Marvel/SIGNAL (Submillimeter Investigation of Geothermal Networks and Life); and a Europa orbiter previewing a new technique, Terahertz Radar Absorption Chemistry Experiment (TRACE) being pioneered in the SWAT group, to detect signatures from chemicals sputtered off the Europan surface by the high intensity radiation environment around Jupiter. Third generation Earth science and several new astrophysics missions are also in the near and long term planning and proposal phases.

In addition to Earth, planetary and space science, Dr. Siegel is interested in terrestrial applications of terahertz imaging and spectroscopy and has been actively pursuing several related initiatives in the health and biological sciences at Caltech as well as defense and security applications at both Caltech and JPL. The very first National Institute of Health program in the terahertz field, granted to Dr. Siegel in 2002, had the goal of developing high signal-to-noise imaging and spectroscopy instruments for disease diagnostics. A second THz NIH program to develop low loss terahertz waveguide for endoscopy applications has also been completed. A consortium proposal with Stanford University School of Medicine and ZOmega Inc. to apply this newly established terahertz frequency and time domain instrumentation to skin cancer, in the first US health science application of terahertz in a clinical environment is currently pending. Additional work has also just begun on the thermal and non- thermal effects of millimeter and submillimeter-wave radiation on cellular systems. This work is being undertaken in conjunction with the Caltech biology division and a neurophysiologist, Dr. Victor Pikov, at the Huntington Medical Research Institute. Significant expansion of the biological science work at Caltech is planned for 2013/14 through US NIH initiatives. Emphasis is being placed on affecting and monitoring cell processes under high frequency, low power, RF exposure. A major goal is to use millimeter waves to stimulate cell membrane depolarization thereby allowing direct, non-contact control of chemical transport. Initial results have now provided the first definitive measurements of significant change in membrane permeability and action potential firing rates on ex vivo cortical neurons from rat pups and neural ganglia in the medicinal leech. Additional RF-bio work in 2014 will include millimeter wave monitoring and diagnosis for health applicaitons. Work has already begun with animal experiments at 40 GHz and will continue under a Caltech patent in 2014. .

After successful responses to DoD research calls, Dr. Siegel's group at JPL began applying submillimeter wave imaging to security and defense. In this application, novel radar imaging and ranging techniques were applied in the submillimeter wave frequency regime for the very first time. A new class of phenomenology and instrumentation has now emerged that shows great promise for undergarment and threat detection imaging. This application is expected to expand dramatically over the next few years with growing involvement at JPL.

Finally, Dr. Siegel and his research team have been dedicated to the long term development of novel devices and components that can push terahertz instruments into mainstream applications. This includes in-house design and fabrication of THz superconductor and semiconductor devices, new single-photon detectors, carbon nanotube based electron tube sources (high efficiency cathodes) and detectors (CNT Schottky diodes), planar array antennas and monolithic GaAs circuits as well as similar programs involving collaborations with research groups and commercial enterprises around the world.

Current Research:

THz Imaging for Biomedical Applications (Caltech): This research was funded under several prior NIH and internal grants and involves the application of terahertz imaging and spectroscopy techniques to problems in the biomedical sciences. Specifically Dr. Siegel has been developing and utilizing the RF instrumentation that was pioneered under his former NASA programs for disease diagnosis, measurements of tissue properties, enhancing contrast through common biomedical staining techniques, and most recently to the impact of THz radiation on cellular processes and real time monitoring of metabolic processes in the body.

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THz Effects on Cellular Systems (Caltech/HMRI): This program attempts to quantitatively examine THz (and millimeter wave) radiation impact on cells and cellular processes. It blends biological, optical and RF instrumentation in a novel way to examine RF dosimetry effects while directly monitoring cell lines and will establish one of the first IR Raman/optical/RF test instruments for microscopic evaluation of thermal and chemical processes at the cellular level. A proposal to continue the work is currently awaiting review at the NIH with collaborator Dr. Victor Pikov, a neurophysiologist at the Huntington Medical Research Institutes. Additional work on non-invasive millimeter wave monitoring of metabolic processes is awaiting final patent filing and will be pursued through NIH funding in 2014.

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THz Detection of BC & SC Carcinoma (Caltech/Stanford/RPI): THz imaging has already been proven to be effective in delineating tumor margins on areas of the body that are near the surface, i.e. skin or surgically exposed regions. Our efforts involve establishing real time video imaging instruments in the THz bands (using pulsed time domain techniques  developed at ZOmega – Renssalaer Polytechnic Institute) and then applying these in an actual clinical environment – Stanford University Medical Center – to establish efficacy for diagnosing, and perhaps someday thermally treating, skin lesions, specifically basal and squamous cell carcinoma. This work has been proposed through NIH but has not yet received funding. The work has been ongoing at a low level in the hopes of acquiring sufficient data to bolster future proposal efforts. Collaborators include Dr. David Peng, a clinical dermatologist at Stanford Medical Center and Tom Tongue, CEO of ZOmega Inc.

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THz Radar Imaging (JPL): Using our NASA developed source and sensor technologies we have started the first work on THz FMCW radar. In this very exciting program we have designed, fabricating and begun testing a 670 GHz FMCW radar imager that can mechanically scan and 3D reconstruct (using radar ranging) objects between 1 and 25 meters distance with cm resolution in all three dimensions. Since THz waves can pass through many dielectrics, the system is being applied to undergarment threat detection. However significant phenomenologic breakthroughs have already been established through the use of this established technique in this new frequency range. The ultimate goal of the program is to demonstrate near video rate imaging over a modest angular scene scale. The work is being supported by the DoD and most of the instrumentation resides at JPL. Program participants include a number of JPL SWAT team members, particularly Dr. Ken Cooper and Mr. Robert Dengler. Other contributors are Dr. Nuria Llombart and Dr. Tomas Bryllert, as well as JPL’s Dr. Imran Mehdi, Dr. Choonsup Lee, Dr. Anders Skalare, Dr. Goutam Chattopadhyay, Dr. Cecile Jung, Dr. Theodore Reck, Dr. Jose Siles, and Dr. Erich Schlecht. This work is ongoing in Dr. Siegel's former SWAT group at JPL but no longer directly involves Dr. Siegel.

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THz Radar Imaging using Integrated Planar Arrays (Caltech/JPL): Just recently funded, this program is intended as a follow-on to the radar imaging program already described. In this approach, novel planar array architectures combined with GaAs MMIC transceiver circuitry are envisioned for the realization of phased array transceivers at 300 GHz. Applications go well beyond the security screening field and spill over into multipixel spectrometers for both the space science and biomedical areas. A low level design effort is ongoing as a precursor to future proposal opportunities that may materialize in the coming year. Primary collaborators include the JPL SWAT group and submillimeter wave engineers at Nothrop Grumman, Redondo Beach. Dr. Siegel is no longer directly involved in this work.

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 Source and Sensor Development: This ongoing set of tasks has been the core of the JPL SWAT team work for more than 20 years and represents the major thrust of the Earth, planetary and space science applications. A continually evolving set of technical goals and spectroscopic techniques and applications derive from the devices and components that are being developed. These span the frequency range from 100 GHz to 5 THz and include two and three terminal semiconductor devices, passive waveguide and quasi optical components, novel planar and planar array antennas, superconducting detectors, carbon nanotube based sensors and sources, many varieties of upconverter and downconverter circuits and any components that might be critical for achieving a particular instrument goal. The work spans both development and actual delivered flight components, subsystems and instruments. The team works with scientists, engineers and flight systems people to propose, plan, and implement NASA missions and collaborates with space agencies and institutions world wide. The team has so far delivered flight hardware for four major programs including two Earth science, one planetary and one space science mission. Major participants include JPL’s Dr. Imran Mehdi, Dr. Lorene Samoska, Dr. Jonathon Kawamura, Dr. Erich Schlecht, Dr. Goutam Chattopadhyay, Dr. Anders Skalare, Dr. Ken Cooper, Dr. Boris Karasik, Dr. Hamid Javadi, Dr. Andy Fung, Dr. Choonsup Lee, Dr. Cecile Jung, Dr. Theodore Reck, Dr. Jose Stiles, Mr. Robert Dengler, Mr. Robert Lin, Mr. Alex Peralta, Mr. David Pukala, and Mr. Seth Sin.

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Dr. Siegel's team operates nine separate laboratory facilities at JPL containing a large range of terahertz test and measurement equipment. These include microwave, millimeter, submillimeter and optical components and instruments as well as sophisticated microassembly and inspection equipment and some biologic processing equipment. They also heavily utilize the JPL Micro Device Laboratory (MDL) with a 100,000+ square foot clean room housing direct write e-beam, wet and dry etching, sputter and thermal coating, bonding, MBE and a wide variety of chemical and optical processing equipment. At Caltech Dr. Siegel is working in the millimeter wave MMIC lab in 362 Moore where he has epi-fluorescence inverted and upright microscopes, an incubator, and an RF exposure system for studying cell level responses and processes. Dr. Siegel also regularly accesses the Huntington Medical Research Institute animal facilities across from Huntington Hopsital, Pasadena, where he works with Dr. Victor Pikov on the millimeter wave bio applications.

Recent and review papers describing current work: