Barry Behnken - Academia.edu (original) (raw)
Papers by Barry Behnken
SPIE Proceedings, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum casc... more Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum cascade laser (QCL) and an uncooled, 160x120 pixel microbolometer camera fitted with a picarin lens. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was calculated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. After evaluating the effects of various operating parameters on laser performance, the QCL found to perform optimally at 1.9 A in pulsed mode with a 300 kHz repetition rate and 10-20% duty cycle; average output power was approximately 1 mW. Under this scheme, a series of metallic objects were imaged while wrapped in various obscurants. Single-frame and extended video recordings demonstrate strong contrast between metallic materials and those of plastic, cloth, and paper-supporting the viability of this imaging technology in security screening applications. Thermal effects arising from Joule heating of the laser were found to be the dominant issue affecting output power and image quality; these effects were mitigated by limiting laser pulse widths to 670 ns and operating the system under closed-cycle refrigeration at a temperature of 10 K.
SPIE Proceedings, 2008
We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-sca... more We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-scale 3.6 THz quantum cascade laser, for real-time imaging of materials which are exclusively nonmetallic in character. By minimizing diffraction effects suffered by the camera system and operating the laser at bias currents approaching saturation values, an imaging scheme was developed in which overlapping samples of nonmetallic materials can be imaged with high fidelity and long persistence times. Furthermore, an examination of various security features embedded within domestic and foreign currency notes suggests that this imaging scheme could serve a future role in detection of assorted counterfeiting practices.
SPIE Proceedings, 2007
The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Curren... more The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Currently, detection of THz radiation is carried out using either antenna-coupled semiconductor detectors or superconducting bolometers. Imaging of objects using these detection schemes requires complex scanning mechanisms which limits the applications involving real time imaging. For imaging applications it is desirable to employ focal plane arrays (FPAs) which leads to more compact systems. The FPAs based on photon detectors commonly used in infrared require cooling which becomes stringent as the detection extends to THz wavelengths. On the other hand, microbolometer FPAs using thermal detectors based on temperature change due to infrared absorption have a broad wavelength response and can be operated at room temperature. The advances of microbolometer technology allow real time imaging in the 7-13 µm wavelength range with relatively high sensitivity. However, their ability to detect THz radiation is relatively unknown. In this paper, imaging of a 3.4 THz (88 µm) laser beam using an uncooled microbolometer camera is described.
Optics Letters, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8... more Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160ϫ 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications.
Approved for public release, distribution unlimited.
: A kinetic model of the directly solar-pumped, atomic bromine laser-operating on the Br (4 (2)P ... more : A kinetic model of the directly solar-pumped, atomic bromine laser-operating on the Br (4 (2)P 1/2 --> (2)P 3/2) transition under IBr photolysis-was developed, executed, and interpreted. In recognition of an evolving national interest in space-based laser development, the model presumed operation on a space station platform. Results indicate that a well-engineered IBr laser is capable of generating 1.2 kilowatts of continuous-wave (CW) power under a pumping concentration of 20,000 solar units. Such performance translates to an efficiency of roughly 0.29%, appreciably better than the 0.1% ascribed to the heretofore leading solar-pumped competitor. An extensive analysis of kinetic data suggests the unanticipated conclusion that, under proper parameter selection, sustained CW oscillation can be achieved absent any flow mechanism whatsoever. This result seems most strongly predicated upon proper bandpass discrimination: a 457-545 nm range of incidence produced optimal results. Sens...
: Real-time imaging in the terahertz (THz) spectral range was achieved using an uncooled, 160 120... more : Real-time imaging in the terahertz (THz) spectral range was achieved using an uncooled, 160 120 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 securit...
... Professor Karunasiri's and Dr. Chamberlin's novel (and rather radical) idea to usem... more ... Professor Karunasiri's and Dr. Chamberlin's novel (and rather radical) idea to usemicrobolometers to detect radiation at wavelengths that are a full order of magnitude ... system can be designed for terahertz frequencies. Microbolometer arrayscomprised of ...
spie.org
Dendrimer is a workhorse nanomaterial for a number of important photonic devices. The electro-opt... more Dendrimer is a workhorse nanomaterial for a number of important photonic devices. The electro-optic (EO) properties of a chromophore doped and poled dendrimer film exhibits higher electro-optic coefficient r 33 . Measured refractive index shows significant difference ...
<p> This conference providesa technical forum for increased... more <p> This conference providesa technical forum for increased awareness of enabling component technology developments, new and novel sensors, signal and image processing, and specific applications in.
The US Army Night Vision and Electronic Sensors Directorate (NVESD) and the US Army Research Labo... more The US Army Night Vision and Electronic Sensors Directorate (NVESD) and the US Army Research Laboratory (ARL) have developed a terahertz-band imaging system performance model for detection and identification of concealed weaponry. The details of this MATLAB-based model which accounts for the effects of all critical sensor and display components, and for the effects of atmospheric attenuation, concealment material attenuation, and active illumination, were reported on at the 2005 SPIE Europe Security and Defence Symposium ...
We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-sca... more We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-scale 3.6 THz quantum cascade laser, for real-time imaging of materials which are exclusively nonmetallic in character. By minimizing diffraction effects suffered by the camera system and operating the laser at bias currents approaching saturation values, an imaging scheme was developed in which overlapping samples of nonmetallic materials can be imaged with high fidelity and long persistence times. Furthermore, an examination of various security features embedded within domestic and foreign currency notes suggests that this imaging scheme could serve a future role in detection of assorted counterfeiting practices.
Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum casc... more Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum cascade laser (QCL) and an uncooled, 160×120 pixel microbolometer camera fitted with a picarin lens. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was calculated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. After evaluating the effects of various operating parameters on laser performance, the QCL found to perform optimally at 1.9 A in pulsed mode with a 300 kHz repetition rate and 10-20% duty cycle; average output power was approximately 1 mW. Under this scheme, a series of metallic objects were imaged while wrapped in various obscurants. Single-frame and extended video recordings demonstrate strong contrast between metallic materials and those of plastic, cloth, and paper - supporting the viability of this imaging technology in security screening applications. Thermal effects arising from Joule heating of the laser were found to be the dominant issue affecting output power and image quality; these effects were mitigated by limiting laser pulse widths to 670 ns and operating the system under closed-cycle refrigeration at a temperature of 10 K.
Optics Letters, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8... more Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160ϫ 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications.
Optics Letters, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8... more Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160ϫ 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications.
The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Curren... more The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Currently, detection of THz radiation is carried out using either antenna-coupled semiconductor detectors or superconducting bolometers. Imaging of objects using these detection schemes requires complex scanning mechanisms which limits the applications involving real time imaging. For imaging applications it is desirable to employ focal plane arrays (FPAs) which leads to more compact systems. The FPAs based on photon detectors commonly used in infrared require cooling which becomes stringent as the detection extends to THz wavelengths. On the other hand, microbolometer FPAs using thermal detectors based on temperature change due to infrared absorption have a broad wavelength response and can be operated at room temperature. The advances of microbolometer technology allow real time imaging in the 7-13 µm wavelength range with relatively high sensitivity. However, their ability to detect THz radiation is relatively unknown. In this paper, imaging of a 3.4 THz (88 µm) laser beam using an uncooled microbolometer camera is described.
SPIE Proceedings, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum casc... more Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum cascade laser (QCL) and an uncooled, 160x120 pixel microbolometer camera fitted with a picarin lens. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was calculated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. After evaluating the effects of various operating parameters on laser performance, the QCL found to perform optimally at 1.9 A in pulsed mode with a 300 kHz repetition rate and 10-20% duty cycle; average output power was approximately 1 mW. Under this scheme, a series of metallic objects were imaged while wrapped in various obscurants. Single-frame and extended video recordings demonstrate strong contrast between metallic materials and those of plastic, cloth, and paper-supporting the viability of this imaging technology in security screening applications. Thermal effects arising from Joule heating of the laser were found to be the dominant issue affecting output power and image quality; these effects were mitigated by limiting laser pulse widths to 670 ns and operating the system under closed-cycle refrigeration at a temperature of 10 K.
SPIE Proceedings, 2008
We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-sca... more We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-scale 3.6 THz quantum cascade laser, for real-time imaging of materials which are exclusively nonmetallic in character. By minimizing diffraction effects suffered by the camera system and operating the laser at bias currents approaching saturation values, an imaging scheme was developed in which overlapping samples of nonmetallic materials can be imaged with high fidelity and long persistence times. Furthermore, an examination of various security features embedded within domestic and foreign currency notes suggests that this imaging scheme could serve a future role in detection of assorted counterfeiting practices.
SPIE Proceedings, 2007
The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Curren... more The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Currently, detection of THz radiation is carried out using either antenna-coupled semiconductor detectors or superconducting bolometers. Imaging of objects using these detection schemes requires complex scanning mechanisms which limits the applications involving real time imaging. For imaging applications it is desirable to employ focal plane arrays (FPAs) which leads to more compact systems. The FPAs based on photon detectors commonly used in infrared require cooling which becomes stringent as the detection extends to THz wavelengths. On the other hand, microbolometer FPAs using thermal detectors based on temperature change due to infrared absorption have a broad wavelength response and can be operated at room temperature. The advances of microbolometer technology allow real time imaging in the 7-13 µm wavelength range with relatively high sensitivity. However, their ability to detect THz radiation is relatively unknown. In this paper, imaging of a 3.4 THz (88 µm) laser beam using an uncooled microbolometer camera is described.
Optics Letters, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8... more Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160ϫ 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications.
Approved for public release, distribution unlimited.
: A kinetic model of the directly solar-pumped, atomic bromine laser-operating on the Br (4 (2)P ... more : A kinetic model of the directly solar-pumped, atomic bromine laser-operating on the Br (4 (2)P 1/2 --> (2)P 3/2) transition under IBr photolysis-was developed, executed, and interpreted. In recognition of an evolving national interest in space-based laser development, the model presumed operation on a space station platform. Results indicate that a well-engineered IBr laser is capable of generating 1.2 kilowatts of continuous-wave (CW) power under a pumping concentration of 20,000 solar units. Such performance translates to an efficiency of roughly 0.29%, appreciably better than the 0.1% ascribed to the heretofore leading solar-pumped competitor. An extensive analysis of kinetic data suggests the unanticipated conclusion that, under proper parameter selection, sustained CW oscillation can be achieved absent any flow mechanism whatsoever. This result seems most strongly predicated upon proper bandpass discrimination: a 457-545 nm range of incidence produced optimal results. Sens...
: Real-time imaging in the terahertz (THz) spectral range was achieved using an uncooled, 160 120... more : Real-time imaging in the terahertz (THz) spectral range was achieved using an uncooled, 160 120 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 securit...
... Professor Karunasiri's and Dr. Chamberlin's novel (and rather radical) idea to usem... more ... Professor Karunasiri's and Dr. Chamberlin's novel (and rather radical) idea to usemicrobolometers to detect radiation at wavelengths that are a full order of magnitude ... system can be designed for terahertz frequencies. Microbolometer arrayscomprised of ...
spie.org
Dendrimer is a workhorse nanomaterial for a number of important photonic devices. The electro-opt... more Dendrimer is a workhorse nanomaterial for a number of important photonic devices. The electro-optic (EO) properties of a chromophore doped and poled dendrimer film exhibits higher electro-optic coefficient r 33 . Measured refractive index shows significant difference ...
<p> This conference providesa technical forum for increased... more <p> This conference providesa technical forum for increased awareness of enabling component technology developments, new and novel sensors, signal and image processing, and specific applications in.
The US Army Night Vision and Electronic Sensors Directorate (NVESD) and the US Army Research Labo... more The US Army Night Vision and Electronic Sensors Directorate (NVESD) and the US Army Research Laboratory (ARL) have developed a terahertz-band imaging system performance model for detection and identification of concealed weaponry. The details of this MATLAB-based model which accounts for the effects of all critical sensor and display components, and for the effects of atmospheric attenuation, concealment material attenuation, and active illumination, were reported on at the 2005 SPIE Europe Security and Defence Symposium ...
We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-sca... more We report the use of a 160×120 pixel microbolometer camera, under illumination by a milliwatt-scale 3.6 THz quantum cascade laser, for real-time imaging of materials which are exclusively nonmetallic in character. By minimizing diffraction effects suffered by the camera system and operating the laser at bias currents approaching saturation values, an imaging scheme was developed in which overlapping samples of nonmetallic materials can be imaged with high fidelity and long persistence times. Furthermore, an examination of various security features embedded within domestic and foreign currency notes suggests that this imaging scheme could serve a future role in detection of assorted counterfeiting practices.
Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum casc... more Real-time imaging in the terahertz (THz) spectral range was achieved using a 3.6-THz quantum cascade laser (QCL) and an uncooled, 160×120 pixel microbolometer camera fitted with a picarin lens. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was calculated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. After evaluating the effects of various operating parameters on laser performance, the QCL found to perform optimally at 1.9 A in pulsed mode with a 300 kHz repetition rate and 10-20% duty cycle; average output power was approximately 1 mW. Under this scheme, a series of metallic objects were imaged while wrapped in various obscurants. Single-frame and extended video recordings demonstrate strong contrast between metallic materials and those of plastic, cloth, and paper - supporting the viability of this imaging technology in security screening applications. Thermal effects arising from Joule heating of the laser were found to be the dominant issue affecting output power and image quality; these effects were mitigated by limiting laser pulse widths to 670 ns and operating the system under closed-cycle refrigeration at a temperature of 10 K.
Optics Letters, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8... more Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160ϫ 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications.
Optics Letters, 2008
Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8... more Real-time imaging in the terahertz (THz) spectral range was achieved using a milliwatt-scale, 2.8 THz quantum cascade laser and an uncooled, 160ϫ 120 pixel microbolometer camera modified with Picarin optics. Noise equivalent temperature difference of the camera in the 1-5 THz frequency range was estimated to be at least 3 K, confirming the need for external THz illumination when imaging in this frequency regime. Despite the appearance of fringe patterns produced by multiple diffraction effects, single-frame and extended video imaging of obscured objects show high-contrast differentiation between metallic and plastic materials, supporting the viability of this imaging approach for use in future security screening applications.
The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Curren... more The THz wavelengths cover the frequency range of 0.1-10 THz or 30-3000 µm wavelength band. Currently, detection of THz radiation is carried out using either antenna-coupled semiconductor detectors or superconducting bolometers. Imaging of objects using these detection schemes requires complex scanning mechanisms which limits the applications involving real time imaging. For imaging applications it is desirable to employ focal plane arrays (FPAs) which leads to more compact systems. The FPAs based on photon detectors commonly used in infrared require cooling which becomes stringent as the detection extends to THz wavelengths. On the other hand, microbolometer FPAs using thermal detectors based on temperature change due to infrared absorption have a broad wavelength response and can be operated at room temperature. The advances of microbolometer technology allow real time imaging in the 7-13 µm wavelength range with relatively high sensitivity. However, their ability to detect THz radiation is relatively unknown. In this paper, imaging of a 3.4 THz (88 µm) laser beam using an uncooled microbolometer camera is described.