Obtaining temperature, pressure, and composition profiles along with wind velocities in the Earth’s
thermosphere/ionosphere system is a key NASA goal for understanding our planet. We report on the status of a
technology development effort to build an all-solid-state heterodyne receiver at 2.06 THz that will allow the
measurement of the 2.06 THz [OI] line for altitudes greater than 100 km. The receiver front end features low-parasitic
Schottky diode mixer chips that are driven by a local oscillator (LO) source using Schottky diode based multipliers. The
multiplier chain consists of a 38 GHz oscillator followed by a set of three cascaded triplers at 114 GHz, 343 GHz and
We report on the first room-temperature modular multi-pixel Schottky diode-based, tunable, frequency-multiplied local
oscillator sub-system at 1.9 THz. This source has been developed to enable efficient high-resolution mapping of the C+
line using suborbital platforms such as the SOFIA aircraft and balloons, as well as space instruments. This compact LO
source features four multipliers (X3X2X3X3) to up-convert Ka-band power to 1.9 THz. Preliminary results at 300 K
demonstrate more than 5 μW per pixel at 1.9 THz. The source is designed to provide a large output power dynamic
range and can be expanded to larger array receivers.
The Jet Propulsion Laboratory (JPL) is developing compact transceiver arrays housing discrete GaAs Schottky diodes with integrated waveguides in order to increase the frame rate and lower the cost of active submillimeter-wave imaging radar systems. As part of this effort, high performance diode frequency multiplier and mixer devices optimized for a 30 GHz bandwidth centered near 340 GHz have been fabricated using JPL’s MoMeD process. A two-element array unit cell was designed using a layered architecture with three-dimensional waveguide routing for maximum scalability to multiple array elements. Prototype two-element arrays have been built using both conventionally machined metal blocks as well as gold-plated micromachined silicon substrates. Preliminary performance characterization has been accomplished in terms of transmit power, and conversion loss, and promising 3D radar images of concealed weapons have been acquired using the array.
Compact, room temperature terahertz sources are much needed in the 1 to 3 THz band for developing multi-pixel heterodyne receivers for astrophysics and planetary science or for building short-range high spatial resolution THz imaging systems able to see through low water content and non metallic materials, smoke or dust for a variety of applications ranging from the inspection of art artifacts to the detection of masked or concealed objects. All solid-sate electronic sources based on a W-band synthesizer followed by a high-power W-band amplifier and a cascade of Schottky diode based THz frequency multipliers are now capable of producing more than 1 mW at 0.9THz, 50 μW at 2 THz and 18 μW at 2.6 THz without the need of any cryogenic system. These sources are frequency agile and have a relative bandwidth of 10 to 15%, limited by the high power W-band amplifiers. The paper will present the latest developments of this technology and its perspective in terms of frequency range, bandwidth and power.
Recent results from the Heterodyne Instrument for the Far-Infrared (HIFI) on the Herschel Space Telescope have
confirmed the usefulness of high resolution spectroscopic data for a better understanding of our Universe. This paper
will explore the current status of tunable local oscillator sources with emphasis on building a multi-pixel LO subsystem
for the scientifically important CII line around 1908 GHz. Recent results have shown that over 50 microwatts of output
power at 1.9 THz are possible with an optimized single pixel LO chain. These power levels are now sufficient to pump
array receivers in this frequency range. Further power enhancement can be obtained by cooling the chain to 120 K or by
utilizing in-phase power combining technology.
Heterodyne terahertz (0.3 - 3THz) imaging systems are currently limited to single or a low number of pixels. Drastic
improvements in imaging sensitivity and speed can be achieved by replacing single pixel systems with an array of
detectors. This paper presents an array topology that is being developed at the Jet Propulsion Laboratory based on the
micromachining of silicon. This technique fabricates the array's package and waveguide components by plasma etching
of silicon, resulting in devices with precision surpassing that of current metal machining techniques. Using silicon
increases the versatility of the packaging, enabling a variety of orientations of circuitry within the device which increases
circuit density and design options. The design of a two-pixel transceiver utilizing a stacked architecture is presented that
achieves a pixel spacing of 10mm. By only allowing coupling from the top and bottom of the package the design can
readily be arrayed in two dimensions with a spacing of 10mm x 18mm.
Recent results from the Heterodyne Instrument for Far-Infrared (HIFI) on the Herschel Space Telescope have confirmed
the usefulness of high resolution spectroscopic data for a better understanding of our Universe. This paper will explore
the current status of tunable local oscillator sources beyond HIFI and provide demonstration of how power combining of
GaAs Schottky diodes can be used to increase both power and upper operating frequency for heterodyne receivers.
Availability of power levels greater than 1 watt in the W-band now makes it possible to design a 1900 GHz source with
more than 100 microwatts of expected output power.
A novel approach for submillimeter-wave heterodyne imaging arrays is presented in this paper. By utilizing diverse
technologies such as GaAs membrane based terahertz diodes, wafer bonding, bulk Si micromachining, micro-lens optics,
and CMOS 3-D chip architectures, a super-compact low-mass submillimeter-wave imaging array is envisioned. A fourwafer
based silicon block for a working W-band power amplifier MMIC is demonstrated. This module drastically
reduces mass and volume associated with metal block implementations without sacrificing performance. A path towards
super compact array receivers in the 500-600 GHz range is described in detail.
The motivation for the work reported is portable NMR spectroscopy of liquids and solids with higher sensitivity than
inductive detection and without the need for tuned elements specific to the frequency of each isotope observed. The
fabrication and assembly of a BOOMERANG force-detected nuclear magnetic resonance (NMR) spectrometer is
reported. The design is optimal for samples of ~ 50 micron diameter and realizes tolerances of ~1 micron in the Si and
ferromagnetic parts. Optical lithography, electrodeposition, reactive ion etching, and release of the moving part by
solution etching are key methods used. Resistance to delamination of the ferromagnetic material was achieved by Cr/Au
deposition prior to electrodeposition of 85/15 Co:Ni.
NASA's planetary exploration strategy is primarily targeted to the detection of extant or extinct signs of life. Thus, the agency is moving towards more in-situ landed missions as evidenced by the recent, successful demonstration of twin Mars Exploration Rovers. Also, future robotic exploration platforms are expected to evolve towards sophisticated analytical laboratories composed of multi-instrument suites. MEMS technology is very attractive for in-situ planetary exploration because of the promise of a diverse and capable set of advanced, low mass and low-power devices and instruments. At JPL, we are exploiting this diversity of MEMS for the development of a new class of miniaturized instruments for planetary exploration. In particular, two examples of this approach are the development of an Electron Luminescence X-ray Spectrometer (ELXS), and a Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer. The ELXS is a compact (< 1 kg) electron-beam based microinstrument that can determine the chemical composition of samples in air via electron-excited x-ray fluorescence and cathodoluminescence. The enabling technology is a 200-nm-thick, MEMS-fabricated silicon nitride membrane that encapsulates the evacuated electron column while yet being thin enough to allow electron transmission into the ambient atmosphere. The MEMS FDNMR spectrometer, at 2-mm diameter, will be the smallest NMR spectrometer in the world. The significant innovation in this technology is the ability to immerse the sample in a homogenous, uniform magnetic field required for high-resolution NMR spectroscopy. The NMR signal is detected using the principle of modulated dipole-dipole interaction between the sample's nuclear magnetic moment and a 60-micron-diameter detector magnet. Finally, the future development path for both of these technologies, culminating ultimately in infusion into space missions, is discussed.
We report a fabrication technique that is potentially capable of producing arrays of individually addressable nanowire sensors with controlled dimensions, positions, alignments, and chemical compositions. The concept has been demonstrated with electrodeposition of palladium wires with 75 nm to 350 nm widths. We have also fabricated single and double conducting polymer nanowires (polyaniline and polypyrrole) with 100nm and 200nm widths using electrochemical direct growth. Using single Pd nanowires, we have also demonstrated hydrogen sensing. It is envisioned that these are the first steps towards nanowire sensor arrays capable of simultaneously detecting multiple chemical species.