We have developed a first generation of electro-optic polymer modulators, designed specifically for passive millimeter-wave
detection. The advantages of utilizing electro-optic polymers for modulator fabrication are their economical and
simple fabrication, potential for large scale array fabrication, and well matched RF and optical indices, which provide
the potential for an excellent high-frequency response. The current drawbacks of these devices include long term device
stability due to oxidation and the relative immaturity of the RF designs for the modulator and interconnects, which lead
to unacceptable internal losses and low sensitivity. These are both items we expect remedied in the upcoming year. We
provide a brief overview on the opto-electronic method of detecting millimeter waves and our design and fabrication of
the polymer modulator. Current measured results for the modulator response at 95GHz are presented and an analysis of
the required performance for imaging is presented.
We have developed a mm wave/terahertz imaging simulation package from COTS graphic software and custom
MATLAB code. In this scheme, a commercial ray-tracing package was used to simulate the emission and reflections of
radiation from scenes incorporating highly realistic imagery. Accurate material properties were assigned to objects in the
scenes, with values obtained from the literature, and from our own terahertz spectroscopy measurements. The images
were then post-processed with custom Matlab code to include the blur introduced by the imaging system and noise levels
arising from system electronics and detector noise. The Matlab code was also used to simulate the effect of fog, an
important aspect for mm wave imaging systems. Several types of image scenes were evaluated, including bar targets,
contrast detail targets, a person in a portal screening situation, and a sailboat on the open ocean. The images produced by
this simulation are currently being used as guidance for a 94 GHz passive mm wave imaging system, but have broad
applicability for frequencies extending into the terahertz region.
We describe the use of non-focal interferometric cameras for reconstruction of the 4D power spectral density of incoherent sources. We develop a 4D version of the generalized van Cittert-Zernike theorem to establish the Fourier transform relationship between the mutual coherence function and the power spectral density. We present experimental demonstrations of 4D imaging using a rotational shearing interferometer. We discuss limitations of interferometric imaging systems and consider how sensor systems might evolve to combine the stability of focal systems with the algorithmic sophistication and multidimensional capacity of interferometry.
Optical wavelength domain code-division multiplexing access (WD-CDMA) using an AOM-based ultrafast optical pulse shaping approach is proposed and demonstrated experimentally at 1550 nm. This new multiplexing technique utilizes wavelength domain codes that are essentially different optical spectral patterns in order to achieve CDMA. In addition to the advantages of the conventional CDMA technique, WD-CDMA can make full use of the entire optical bandwidth without requiring faster optical switches or modulators. This approach also drastically reduces sensitivity to fiber dispersion. Experimentally, we demonstrate an optical spectral encoder using ultrafast optical pulse shaping with 16 wavelength bits over an optical bandwidth of 5 THz. The spectrally-encoded optical pulse generated with the spectral encoder is then decoded with different WD-CDMA codes in the spectral domain. Different code-division channels can thus extract their own bit information while sharing the same spectral-encoded laser pulse as their common carrier. These spectral-encoded pulses are shown using the cross- correlation technique to be confined within a time slot of 15 ps. A larger number of WD bits is also achievable with our system.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.