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LLiST - a new star tracker camera for tip-tilt correction at IOTA

June 21, 2004
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Conference Paper
Author:
P. A. Schuller
…
Published in:
2004 SPIE Conf. on Astronomical Telescopes and Instrumentation, 21-26 June 2004.
Topic:
optics
R&D area:
R&D group:

Summary

The tip-tilt correction system at the Infrared Optical Telescope Array (IOTA) has been upgraded with a new star tracker camera. The camera features a backside-illuminated CCD chip offering doubled overall quantum efficiency and a four times higher system gain compared to the previous system. Tests carried out to characterize the new system showed a higher system gain with a lower read-out noise electron level. Shorter read-out cycle times now allow to compensate tip-tilt fluctuations so that their error imposed on visibility measurements becomes comparable to, and even smaller than, that of higher-order aberrations.
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Summary

The tip-tilt correction system at the Infrared Optical Telescope Array (IOTA) has been upgraded with a new star tracker camera. The camera features a backside-illuminated CCD chip offering doubled overall quantum efficiency and a four times higher system gain compared to the previous system. Tests carried out to characterize the...

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LLiST - a new star tracker camera for tip-tilt correction at IOTA

The orthogonal-transfer array: a new CCD architecture for astronomy

June 21, 2004
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Conference Paper
Author:
Barry E. Burke
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Published in:
SPIE Vol. 5499, Optical and Infrared Detectors for Astronomy, 21 June 2004, pp. 185-192.
Topic:
optics
R&D area:
R&D group:

Summary

The orthogonal-transfer array (OTA) is a new CCD architecture designed to provide wide-field tip-tilt correction of astronomical images. The device consists of an 8..8 array of small (~500x500 pixels) orthogonal-transfer CCDs (OTCCD) with independent addressing and readout of each OTCCD. This approach enables an optimum tip-tilt correction to be applied independently to each OTCCD across the focal plane. The first design of this device has been carried out at MIT Lincoln Laboratory in support of the Pan-STARRS program with a collaborative parallel effort at Semiconductor Technology Associates (STA) for the WIYN Observatory. The two versions of this device are functionally compatible and share a common pinout and package. The first wafer lots are complete at Lincoln and at Dalsa and are undergoing wafer probing.
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Summary

The orthogonal-transfer array (OTA) is a new CCD architecture designed to provide wide-field tip-tilt correction of astronomical images. The device consists of an 8..8 array of small (~500x500 pixels) orthogonal-transfer CCDs (OTCCD) with independent addressing and readout of each OTCCD. This approach enables an optimum tip-tilt correction to be applied...

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The orthogonal-transfer array: a new CCD architecture for astronomy

A high-power MEMS electric induction motor

June 1, 2004
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Journal Article
Author:
C. Livermore
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Published in:
J. Microelectromech. Syst., Vol. 13, No. 3, June 2004, pp. 465-471.
Topic:
microelectronics
R&D area:
R&D group:

Summary

An electric induction micromotor with a 4-mm-diameter rotor was designed and built for high-power operation. Operated at partial actuating voltage, the motor has demonstrated an air gap power in excess of 20 mWand torque of 3 5 Nmat speeds in excess of 55 000 rpm. Operation at higher power and speed was limited by bearing stability at higher rotational speeds. The device builds on an earlier micromotor demonstrated by Frechette et al. The high power of the present motor is enabled by its low-loss, high-voltage electric stator, which also offers improved efficiency. The development of this electromechanical device is an important enabling step not only for watt-scale micromotors, but also for the development of microelectric generators. This paper presents the motorαs design, the fabrication process that was created to meet its stringent design requirements, and its performance to date.
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Summary

An electric induction micromotor with a 4-mm-diameter rotor was designed and built for high-power operation. Operated at partial actuating voltage, the motor has demonstrated an air gap power in excess of 20 mWand torque of 3 5 Nmat speeds in excess of 55 000 rpm. Operation at higher power and...

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A high-power MEMS electric induction motor

Dynamic response of an electronically shuttered CCD imager

June 1, 2004
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Journal Article
Author:
Dennis D. Rathman
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Published in:
IEEE. Trans. Electron Devices, Vol. 51, No. 6, June 2004, pp. 864-869.
Topic:
sensors
R&D area:
R&D group:

Summary

The dynamic response of an electronically shuttered charge-coupled device (CCD) imager to nanosecond voltage pulses has been investigated. Measurements show that the shutter can be dynamically opened and closed in nanosecond times. For the shutter opening, simulations indicate that the collection of photoelectrons occurs in times much shorter than that needed to form the steady-state depletion region under the CCD well. In addition, the shutter closing occurs faster than the reconstitution of the p-buried (shutter) layer. Simulations further indicate that electric fields created in the neutral substrate by the shutter clocks enable photogenerated charge collection/rejection on nanosecond time scales despite the fact that the depletion-region formation and collapse take much longer times.
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Summary

The dynamic response of an electronically shuttered charge-coupled device (CCD) imager to nanosecond voltage pulses has been investigated. Measurements show that the shutter can be dynamically opened and closed in nanosecond times. For the shutter opening, simulations indicate that the collection of photoelectrons occurs in times much shorter than that...

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Dynamic response of an electronically shuttered CCD imager

A method for correcting Fourier transform spectrometer (FTS) dynamic alignment errors

April 12, 2004
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Conference Paper
Author:
Michael W. Kelly
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Published in:
SPIE Vol. 5425, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery X, 12-15 April 2004, pp. 443-455.
Topic:
image processing
R&D area:
R&D group:

Summary

The Cross-track Infrared Sounder (CrIS), like most Fourier Transform spectrometers, can be sensitive to mechanical disturbances during the time spectral data is collected. The Michelson interferometer within the spectrometer modulates input radiation at a frequency equal to the product of the wavenumber of the radiation and the constant optical path difference (OPD) velocity associated with the moving mirror. The modulation efficiency depends on the angular alignment of the two wavefronts exiting the spectrometer. Mechanical disturbances can cause errors in the alignment of the wavefronts which manifest as noise in the spectrum. To mitigate these affects CrIS will employ a laser to monitor alignment and dynamically correct the errors. Additionally, a vibration isolation system will damp disturbances imparted to the sensor from the spacecraft. Despite these efforts, residual noise may remain under certain conditions. Through simulation of CrIS data, we demonstrated an algorithmic technique to correct residual dynamic alignment errors. The technique requires only the time-dependent wavefront angle, sampled coincidentally with the interferogram, and the second derivative of the erroneous interferogram as inputs to compute the correction. The technique can function with raw interferograms on board the spacecraft, or with decimated interferograms on the ground. We were able to reduce the dynamic alignment noise by approximately a factor of ten in both cases. Performing the correction on the ground would require an increase in data rate of 1-2% over what is currently planned, in the form of 8-bit digitized angle data.
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Summary

The Cross-track Infrared Sounder (CrIS), like most Fourier Transform spectrometers, can be sensitive to mechanical disturbances during the time spectral data is collected. The Michelson interferometer within the spectrometer modulates input radiation at a frequency equal to the product of the wavenumber of the radiation and the constant optical path...

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A method for correcting Fourier transform spectrometer (FTS) dynamic alignment errors

Hyperspectral environmental suite for the Geostationary Operational Environmental Satellite (GOES)

April 12, 2004
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Conference Paper
Author:
Monica M. Coakley
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Published in:
SPIE Vol. 5425, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery X, 12-15 April 2004, pp. 329-340.
Topic:
satellites
R&D area:
R&D group:

Summary

The GOES satellites will fly a Hyperspectral Environmental Suite (HES) on GOES-R in the 2012 timeframe. The approximately 1500 spectral channels (technically ultraspectral), leading to improved vertical resolution, and approximately five times faster coverage rate planned for the sounder in this suite will greatly exceed the capabilities of the current GOES series instrument with its 18 spectral channels. In the GOES-R timeframe, frequent measurements afforded by geostationary orbits will be critical for numerical weather prediction models. Since the current GOES soundings are assimilated into numerical weather prediction models to improve the validity of model outputs, particularly in areas with little radiosonde coverage, this hyperspectral capability in the thermal infrared will significantly improve sounding performance for weather prediction in the western hemisphere, while providing and enhancing other products. Finer spatial resolution is planned for mesoscale observation of water vapor variations. The improvements over the previous GOES sounders and a primary difference from other planned instruments stem from two-dimensional focal plane array availability. These carry an additional set of challenges in terms of instrument specifications, which will be discussed. As a suite, HES is planned with new capabilities for coastal ocean coverage with the goal of including open ocean coverage. These new planned imaging applications, which will be either multispectral or hyperspectral, will also be discussed.
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Summary

The GOES satellites will fly a Hyperspectral Environmental Suite (HES) on GOES-R in the 2012 timeframe. The approximately 1500 spectral channels (technically ultraspectral), leading to improved vertical resolution, and approximately five times faster coverage rate planned for the sounder in this suite will greatly exceed the capabilities of the current...

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Hyperspectral environmental suite for the Geostationary Operational Environmental Satellite (GOES)

InGaAsP/InP quantum-well electrorefractive modulators with sub-volt V[pi]

April 12, 2004
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Conference Paper
Author:
Paul W. Juodawlkis
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Published in:
SPIE Vol. 5435, Enabling Photonic Technologies for Aerospace Applications VI, 12-16 April 2004, pp. 53-63.
Topic:
semiconductor (CMOS)
R&D area:

Summary

Advanced analog-optical sensor, signal processing and communication systems could benefit significantly from wideband (DC to > 50 GHz) optical modulators having both low half-wave voltage (V[pi]) and low optical insertion loss. An important figure-of-merit for modulators used in analog applications is TMAX/V[pi], where TMAX is the optical transmission of the modulator when biased for maximum transmission. Candidate electro-optic materials for realizing these modulators include lithium niobate (LiNbO3), polymers, and semiconductors, each of which has its own set of advantages and disadvantages. In this paper, we report the development of 1.5-um-wavelength Mach-Zehnder modulators utilizing the electrorefractive effect in InGaAsP/InP symmetric, uncoupled semiconductor quantum-wells. Modulators with 1-cm-long, lumped-element electrodes are found to have a push-pull V[pi] of 0.9V (V[pi]L = 9 V-mm) and 18-dB fiber-to-fiber insertion loss (TMAX/V[pi] = 0.018). Fabry-Perot cutback measurements reveal a waveguide propagation loss of 7 dB/cm and a waveguide-to-fiber coupling loss of 5 dB/facet. The relatively high propagation loss results from a combination of below-bandedge absorption and scattering due to waveguide-sidewall roughness. Analyses show that most of the coupling loss can be eliminated though the use of monolithically integrated invertedtaper optical-mode converters, thereby allowing these modulators to exceed the performance of commercial LiNbO3 modulators (TMAX/V[pi] ~ 0.1). We also report the analog modulation characteristics of these modulators.
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Summary

Advanced analog-optical sensor, signal processing and communication systems could benefit significantly from wideband (DC to > 50 GHz) optical modulators having both low half-wave voltage (V[pi]) and low optical insertion loss. An important figure-of-merit for modulators used in analog applications is TMAX/V[pi], where TMAX is the optical transmission of the...

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InGaAsP/InP quantum-well electrorefractive modulators with sub-volt V[pi]

Photoresist outgassing: a potential Achilles heel for short wavelength optical lithography?

February 22, 2004
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Conference Paper
Author:
Roderick R. Kunz
Published in:
SPIE Vol. 5376, Advances in Resist Technology and Processing XXI, 22-27 February 2004, pp. 1-15.
Topic:
optics
R&D area:
R&D group:

Summary

The outgassing of volatile organic compounds during photoresist exposure at short wavelengths (
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Summary

The outgassing of volatile organic compounds during photoresist exposure at short wavelengths (

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Photoresist outgassing: a potential Achilles heel for short wavelength optical lithography?

Optical down-sampling of wide-band microwave signals

December 1, 2003
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Journal Article
Author:
Paul W. Juodawlkis
…
Published in:
J. Lightwave Technol., Vol. 21, No. 12, December 2003, pp. 3116-3124.
Topic:
signal processing
R&D area:
R&D group:

Summary

Phase-encoded optical sampling allows radio-frequency and microwave signals to be directly down-converted and digitized with high linearity and greater than 60-dB (10-effective-bit) signal-to-noise ratio. Wide-band electrical signals can be processed using relatively low optical sampling rates provided that the instantaneous signal bandwidth is less than the Nyquist sampling bandwidth. We demonstrate the capabilities of this technique by using a 60-MS/s system to down-sample two different FM chirp signals: 1) a baseband (0-250 MHz) linear-chirp waveform and 2) a nonlinear-chirp waveform having a 10-GHz center frequency and a frequency excursion of 1 GHz. We characterize the frequency response of the technique and quantify the analog bandwidth limitation due to the optical pulse width. The 3-dB bandwidth imposed by a 30-ps sampling pulse is shown to be 10.4 GHz. We also investigate the impact of the pulse width on the linearity of the phase-encoded optical sampling technique when it is used to sample high-frequency signals.
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Summary

Phase-encoded optical sampling allows radio-frequency and microwave signals to be directly down-converted and digitized with high linearity and greater than 60-dB (10-effective-bit) signal-to-noise ratio. Wide-band electrical signals can be processed using relatively low optical sampling rates provided that the instantaneous signal bandwidth is less than the Nyquist sampling bandwidth. We...

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Optical down-sampling of wide-band microwave signals

High-fill-factor, burst-frame-rate charge-coupled device

August 3, 2003
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Conference Paper
Author:
Robert K. Reich
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Published in:
SPIE Vol. 5210, Ultrahigh- and High-Speed Photography, Photonics, and Videography, 3-8 August 2003, pp. 95-104.
Topic:
electronics
R&D area:
R&D group:

Summary

A 512x512-element, multi-frame charge-coupled device (CCD) has been developed for collecting four sequential image frames at megahertz rates. To operate at fast frame rates with high sensitivity, the imager uses an electronic shutter technology developed for back-illuminated CCDs. Device-level simulations were done to estimate the CCD collection well spaces for sub-microsecond photoelectron collection times. Also required for the high frame rates were process enhancements that included metal strapping of the polysilicon gate electrodes and a second metal layer. Tests on finished back-illuminated CCD imagers have demonstrated sequential multi-frame capture capability with integration intervals in the hundreds of nanoseconds range.
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Summary

A 512x512-element, multi-frame charge-coupled device (CCD) has been developed for collecting four sequential image frames at megahertz rates. To operate at fast frame rates with high sensitivity, the imager uses an electronic shutter technology developed for back-illuminated CCDs. Device-level simulations were done to estimate the CCD collection well spaces for...

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High-fill-factor, burst-frame-rate charge-coupled device
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