| Cranbury, N.J., January 2, 2008 Princeton Lightwave, Inc. (PLI), a manufacturer of high-performance optical semiconductor
components and sub-systems, has been awarded a two-year $3.5M contract for the
development of focal plane arrays (FPAs) with single photon sensitivity for use in threedimensional
(3-D) imaging systems at 1.06 μm. For this program, sponsored by the Defense
Advanced Research Projects Agency (DARPA), PLI will develop FPA modules which employ
InP-based Geiger-mode avalanche photodiodes (GmAPDs) to achieve single photon sensitivity
and perform time-of-flight ranging measurements on a per-pixel basis. These modules are
intended for use as the optical engines at the core of 3-D imaging flash ladar systems such as
those demonstrated in DARPA’s Jigsaw program.
The key component that enables the end performance of the 3-D imaging FPA is an
InGaAsP/InP GmAPD photodiode array (PDA) optimized for detection of single photons at 1.06
μm. PLI is leveraging its best-in-class GmAPD device technology for the design and fabrication
of this PDA. The company’s commercially deployed single-element GmAPD detector is based
on a highly reliable planar-passivated, diffused-junction photodiode structure that has
demonstrated the highest performance to date utilizing this structure for critical single photon
detection parameters such as dark count rate, photon detection efficiency, and timing jitter.
The GmAPD, also commonly referred to as a single photon avalanche diode (SPAD), is an
avalanche photodiode structure that, when operated above its breakdown voltage, can generate
a macroscopic current pulse in response to the absorption of just a single photon. The
operation and readout of this PDA requires a specialized readout integrated circuit (ROIC)
designed for the 3-D imaging application. On a per-pixel basis, this ROIC senses the GmAPD
output current pulse corresponding to the absorption of a single photon and assigns a time
stamp indicating the time-of-flight between the launching of a short-duration ranging laser pulse
and the photon detection event. The per-pixel time-of-flight information is translated to distance,
as in conventional ladar measurements, and provides the third spatial dimension to complement
the two-dimensional image provided by pixel location in the detector array. PLI will hybridize the
GmAPD PDAs and ROICs using flip-chip bonding, and a high optical fill factor will be achieved
using an array of microlenses mated to the back-illuminated PDA chip.
“We are very excited to be a key contributor to the development of 3-D imaging systems,” says
Mark Itzler, PLI’s CTO and principal investigator for the program. “We’ve been developing
single photon counting technology for several years, and 3-D imaging is an excellent application
for it since we can leverage our expertise in both semiconductor device design and module
packaging. By the time we complete this two-year development program, we expect to see
product-scale demand for these sensors to provide 3-D imaging capability in a variety of
defense systems.”
The GmAPD FPA technology, initially demonstrated by MIT Lincoln Laboratory under DARPA
sponsorship of the Jigsaw program, has a number of highly desirable features. Since single
photon detection in a GmAPD provides a macroscopic current pulse that can be sensed using
digital thresholding circuitry, this device technology provides a direct―and noiseless―“photonsto-
bits” conversion process. Among the benefits of single photon sensitivity is the ability to
obtain 3-D image data using low-power pulsed sources and the collection of 3-D images even in
situations involving very large source attenuation. In particular, the Jigsaw program demonstrated the feasibility of using the GmAPD FPA technology to create 3-D images of
objects obscured by forest canopy and camouflage netting.
About Princeton Lightwave:
Headquartered in Cranbury, NJ, Princeton Lightwave provides leading-edge semiconductor
detectors and lasers for defense, industrial, and communications applications. PLI's rich product
capability is based upon unique InP and GaAs optical chip design, optoelectronic packaging,
and integration technology. For more information, visit www.princetonlightwave.com.
Contact:
Sales@Princetonlightwave.com
PR@princetonlightwave.com |
