Real-time terahertz imaging using a quantum cascade laser and uncooled microbolometer focal plane array
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Authors
Behnken, Barry N.
Subjects
THz
terahertz
real-time
microbolometer
uncooled
QCL
quantum cascade laser
imaging
detection
camera
focal plane array
Tsurupica
NETD
NEP
vanadium oxide
silicon nitride
terahertz
real-time
microbolometer
uncooled
QCL
quantum cascade laser
imaging
detection
camera
focal plane array
Tsurupica
NETD
NEP
vanadium oxide
silicon nitride
Advisors
Karunasiri, Gamani
Date of Issue
2008-06
Date
June 2008
Publisher
Monterey, CA; Naval Postgraduate School
Language
Abstract
Real-time imaging in the terahertz (THz) spectral range was achieved using an uncooled, 160x120 pixel infrared microbolometer camera and a milliwatt-scale quantum cascade laser (QCL). By replacing the camera's original focusing optics with a Tsurupica-based lens and minimizing diffraction effects incurred by the QCL output beam, an imaging scheme was developed in which the camera's focal plane array successfully detected wavelengths that are more than an order of magnitude longer than those for which the system is designed. Moreover, the incorporation of parabolic reflecting optics yielded a capability to produce high-resolution images of objects placed within the beam path. Despite the low laser powers employed, this scheme allows high-contrast imaging of various objects concealed by a wide range of nonmetallic materials-confirming the suitability of this technology for homeland security screening applications. Furthermore, the identification of relatively obscure security features in British currency notes suggests that Terahertz imaging could serve a future role as a detection mechanism against assorted counterfeiting practices. An extensive comparative analysis of experimental data produced using two QCLs (resonating at 2.8 and 3.6 THz) provides additional insight into the physics underlying these results, and suggests methods by which this imaging technology could be further improved.
Type
Thesis
Description
Series/Report No
Department
Physics (PH)
Organization
Identifiers
NPS Report Number
Sponsors
Funding
Format
xviii, 81 p. : ill. (chiefly col.) ; 28 cm.
Citation
Distribution Statement
Approved for public release; distribution is unlimited.