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ABSTRACT: The authors report on a design and demonstration of a quartic-style optical true-time-delay device based on a White cell. This device is designed for 81 sequential time delays with an incremental delay of 243 ps and a maximum delay of 19.683 ns. The time delays are implemented by free-space translations, with lens trains as needed for beam containment. A digital microelectromechanical tilting micromirror array is used to send the light into different delay paths
Journal of Lightwave Technology 11/2006; · 2.78 Impact Factor
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ABSTRACT: We introduce two new designs for a spot displacement device (SDD) to be used in a White cell-based binary optical cross-connect system (OXC). We described in detail the implementation of an SDD based on a lens train configuration and a roof prism SDD. We discuss the aberrations associated with each design. We also show simulations for an eight-output OXC binary system using one of these designs
IEEE Journal of Selected Topics in Quantum Electronics 08/2006; · 3.78 Impact Factor
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ABSTRACT: An optical true-time delay device that uses a binary counting system in a modified White cell is demonstrated. The switching engine uses four spherical mirrors and a three-state digital micromirror array. The delay part, as designed, provides 6 bits of delay ranging from 78 ps to 5 ns, using a combination of dielectric blocks for short delays and lens trains for longer ones. Long lens trains are folded for compactness. The authors describe the design and demonstrate two of the 6 bits of delays experimentally. Delays were accurate to within the measurement resolution of 1.25 ps. The insertion loss varied from 3.1-5.2 dB, depending on delay. It was found that the micromirrors do not contribute significantly to the loss.
Journal of Lightwave Technology 05/2006; 24(4):1886- 1895. · 2.78 Impact Factor
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ABSTRACT: A methodology for designing an octic-style optical true-time-delay (TTD) device based on the White cell (WC) is investigated. The octic cell is a "polynomial" cell, one of the two classes of TTD White cells. This octic cell is designed to produce a maximum of 6399 delays in 17 bounces, with a unit delay of 3 ps. Glass blocks are used for short delays, white lens trains are used for the longer delays. The octic cell is designed to use a microelectromechanical tip/tilt micromirror array to direct light beams into various delay paths.
Journal of Lightwave Technology 03/2006; 24(2):982- 990. · 2.78 Impact Factor
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ABSTRACT: We demonstrate a 4×8 free-space 3D OXC architecture based on a White cell that uses a digital MEMS. We use manually reconfigurable mirrors for the MEMS. Experimental loss, redundancy and beam quality results are presented.
Lasers and Electro-Optics, 2005. (CLEO). Conference on; 06/2005
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ABSTRACT: We propose a true-time delay approach for steering optical beams over wide angles (approaching ±57°), without dispersion or sidelobes. A white cell with reflecting piston actuators provides delays from 1/500 to 3001.
Quantum Electronics and Laser Science Conference, 2005. QELS '05; 06/2005
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ABSTRACT: A White-cell-based binary optical true-time-delay device has two parts: the controller, or switching engine, and the delay elements. Here we discuss in detail the design of both glass blocks and lens trains as delay elements. Glass blocks can be used in our design for delays ranging from one to a few hundred picoseconds. Lens trains are suitable for longer delays. We also analyze the loss associated with each design and give design limits.
Applied Optics 01/2004; 42(35):6984-94. · 1.41 Impact Factor
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Antennas and Propagation Society International Symposium, 2003. IEEE; 07/2003
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ABSTRACT: We present a new approach to optical interconnections, based on microelectromechanical system tip/tilt mirror technology and the White cell. This is a free-space approach in which many beams circulate simultaneously in the device, each beam forming a unique spot pattern on the micromirror array. On each bounce, each beam can be switched to any of several White cells, each of which has a different effect on the spot pattern. By appropriate combinations of these White cells, any input beam can be directed to any output. A simple proof-of-concept prototype has been demonstrated, and output coupling loss addressed.
IEEE Journal of Selected Topics in Quantum Electronics 04/2003; · 3.78 Impact Factor
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ABSTRACT: We describe an N×N optical switch for use in cross-connects. It is a free-space device, based on multiple bounces in a pair of White cells sharing a spatial light modulator at one end. In a companion paper, we described various polynomial cells, in which the number of outputs was proportional to the number of bounces raised to some power. In the binary device described here, the number of possible outputs is proportional to the number two raised to the power of the number of bounces. It allows a 1024 × 1024 switch using a single digital two-state tip/tilt micromirror array, four spherical mirrors, and a spot displacement device. It is highly scalable and insensitive to micromirror pointing accuracy.
IEEE Journal of Selected Topics in Quantum Electronics 04/2003; · 3.78 Impact Factor
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ABSTRACT: We explain a technique that extracts both the structure and the modal weights of spatial modes of lasers by analyzing the spatial coherence of the beam. This is the first time, to our knowledge, that an experimental method is being used to measure arbitrary forms of the spatial modes. We applied this method to an edge-emitting Fabry-Perot semiconductor laser with a stripe width of 5 mum and extracted fundamental and first-order lateral modes with relative power weights of 96.2% and 3.8%. There was a single transverse mode.
Applied Optics 12/2000; 39(33):6109-17. · 1.41 Impact Factor
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ABSTRACT: We have shown a modified version of the binary white cell-based
true time delay (TTD) generator architecture to allow the use of a
deformable mirror device (DMD). If 10 bits of delay are required, then
each beam will make 20 bounces and use 20 pixels on the DMD. A
commercial DMD with 500,000 elements can thus in principle provide 10
bits of delay for 50,000 antenna elements
Lasers and Electro-Optics Society Annual Meeting, 1998. LEOS '98. IEEE; 01/1999
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ABSTRACT: We have shown that we can find the weights and shapes of spatial
modes in a semiconductor laser. The 5 μm stripe width laser tested
had two lateral spatial modes with approximate power weights of 96% and
4%. We are developing refinements that would be useful for detecting
even weaker modes
Lasers and Electro-Optics Society Annual Meeting, 1998. LEOS '98. IEEE; 01/1999
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ABSTRACT: The authors describe a recently developed laboratory course in
photonics aimed primarily at seniors in electrical engineering. Each
student performs four out of seven possible experiments during the
quarter in changing teams. The experiments were designed with the
following goals: to expose students to widest possible variety of
technologically important topics in optics; to allow students the
opportunity to use the widest possible variety of laboratory equipment;
to foster a healthy respect for potentially dangerous lasers; to
encourage individual thinking and self-reliance; and to provide a
significant technical writing experience. The experiments themselves are
in fiber-optic communication, optical sensing, laser physics, multiple
quantum-well detectors, liquid crystals, acoustooptic modulation and
solar cells. The authors describe here the experiments, the specific
equipment needed to perform them and the structure of their particular
course. They also have produced a detailed laboratory manual that is
available to other institutions
IEEE Transactions on Education 09/1998; · 1.02 Impact Factor
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ABSTRACT: It has been shown previously that the spatial coherence of a source can be modulated and demodulated; hence it can be used as the basis for a new dimension of multiplexing in high-speed optical communication links. We address the sensitivity of such a system to misalignments of the receiver with respect to the beam and examine how changing transverse modes affect the spatial coherence in the lateral direction. Specifically, we show that such a system is surprisingly robust for both lateral offsets, in which the receiver is not properly aligned on the beam center, and rotational offsets, in which the receiver is tilted with respect to the plane of the spatial coherence modulation. The presence of higher-order transverse modes or changes in the transverse-mode structure are also shown to have little effect on the system operation.
Applied Optics 03/1998; 37(5):815-20. · 1.41 Impact Factor
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ABSTRACT: A device is described for generating true-time delays optically for microwave signals used in beam steering and beam shaping in phased-array antennas. The device can be adapted to provide delays from picoseconds to nanoseconds. A single, compact unit should provide parallel delays for more than 64 independent antenna elements with a greater than 6-bit resolution. The time delays are produced by multiple reflections in a mirror configuration with continuous refocusing. A single spatial light modulator selects independent optical path lengths for each of the parallel antenna elements. Amplitude control for beam shaping can be integrated into the device. The unit can be made rugged for harsh environments by use of solid-block construction. The operation of the true-time delay device is described, along with the overall system configuration. Preliminary experimental data are given.
Applied Optics 12/1997; 36(32):8493-503. · 1.41 Impact Factor
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ABSTRACT: The effects of gamma radiation on high-power semiconductor laser
diodes were measured. While operating, five commercial near-infrared
(785 nm, 60 mW) and six visible laser diodes (670 nm, 30 mW) were
exposed to approximately 10 kGy at a relatively high dose rate (≈5
kGy/h). The far-field, output beam patterns were monitored during
radiation and recovery, as well as the overall intensity (constant
current mode) and the internal monitor photodiode current. The linear
dimensions of the far-field beam patterns shrank in size by the end of
radiation by 3%-20% for the IR lasers and 15%-20% for the visible. The
ellipticity of the beams changed by -16% for the IR and +8% for the
visible case. The intensity, as measured with an external camera,
decreased during irradiation by a maximum of 2.7 dB for the visible
laser and 2.5 dB for the infrared; however, the photodiode photocurrents
changed by less than 1 dB. Both types of lasers recovered completely
over several days. The near- and far-field patterns were examined both
below and above threshold before and after radiation/recovery, with no
evidence of defects or other gross changes
IEEE Transactions on Nuclear Science 07/1996; · 1.45 Impact Factor
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ABSTRACT: A new channel for optical communication is described, in which the
energy distribution among the spatial modes of a laser beam is
modulated. The number and strength of the modes directly influences the
spatial coherence of a beam, which can then be detected with a simple
interferometer. The transmitter is an electric-optic device that allows
one or two modes to propagate depending on the logic state. The
distribution of the energy among the allowed modes is independent of the
overall intensity, thereby giving another depth of multiplexing in
addition to common schemes such as intensify and frequency modulation,
polarization, and wavelength-division multiplexing, etc. We present an
optical interconnection scheme by which the intensity carries the data
and the spatial coherence conveys the address information on the same
beam
Devices, Circuits and Systems, 1995. Proceedings of the 1995 First IEEE International Caracas Conference on; 01/1996
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ABSTRACT: The spatial coherence of a laser beam depends on the number and the relative weights of the spatial modes supported by the laser waveguide. By electro-optic modulation of the cavity geometry, the spatial-coherence function can be modulated between zero and one at predictable locations across the beam and thus carry information. A simple integrated-optic interferometer is used to decode the signal. Spatial coherence can be modulated independently of the beam intensity and can be used as another level of multiplexing in addition to amplitude modulation, wavelength-division modulation, etc. One can implement a free-space optical interconnection scheme by carrying data on the intensity and address information on the spatial coherence.
Applied Optics 11/1995; 34(32):7443-50. · 1.41 Impact Factor
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ABSTRACT: A novel optical interconnection is introduced for a multistage optical switching network that uses orthogonally polarized data and address information. The network is unique in that the data information is never regenerated and remains in optical form throughout (i.e., it is never converted into electrical information). This has two main consequences: (1) the bandwidth of the data is not restricted by electrical circuit considerations, and (2) the optical interconnections from one stage of the network to the next must be highly efficient. The interconnection meets several goals: high efficiency, preservation of cross polarization of data and address, low cross talk between polarizations, good manufacturability, resistance to misalignment caused by thermal expansion, and absence of significant aberrations. In addition, sychronization of the signals is maintained, as the optical path lengths for all routes through the system are equal.
Applied Optics 04/1995; 34(11):1788-800. · 1.41 Impact Factor
