Sayan D. Mukherjee

Switched time-delay elements based on AlGaAs/GaAs optical waveguide technology at 1.32 μm for optically controlled phased-array antennas

Integrated optical time-shift networks consisting of cascaded pairs of 2 x 2 linear electrooptic switches and optical delay lines in GaAs waveguides at 1.32 micron are investigated for true-time optical beam forming in phased array antennas. We report new state-of-the-art results in curved waveguide and corner bend insertion loss, and preliminary results from 2-bit time delay generators (TDGs) constructed in the form of GaAs-based photonic integrated circuits utilizing these components. These results represent significant progress in our longer-term goal of demonstrating a 7-bit TDG with a loss matching monolithic microwave integrated circuit (MMIC) delay line techniques, while providing very wide bandwidth unmatched by MMIC technology.

Polymeric optical spot-size transformer with vertical and lateral tapers

The design, fabrication, and characterization of a polymeric optical spot-size transformer with vertical and lateral tapers is reported. The vertical taper is formed by utilizing the planarization properties of a polymer, while the lateral taper is defined by photolithography. An optimization method for the taper shape is described based on fundamental results from coupled local mode theory. A total fiber to waveguide insertion loss of 0.6 dB has been measured with the integration of the transformer, an improvement of 2.1 dB. The spatial alignment tolerance for 1 dB excess loss was measured to ±2.7μm, consistent with theory.

Progress and status of guided-wave optical interconnection technology

Optical interconnects at the cabinet-to-cabinet, board-to-board, and multichip module-to- multichip module levels will enable future avionics systems requirements to be met by eliminating undesirable compromises associated with electrical interconnects. Fiber optics is the well established medium of choice for cabinet-to-cabinet applications, while planar polymeric interconnects are required at the backplane level. Significant advances have been made in demonstrating practical polymer interconnects compatible with existing board fabrication principles, however both waveguide loss and interfaces to optoelectronic components require further improvement before the technology is broadly applicable.

Design, fabrication, and performance of an integrated optoelectronic cellular array

SUMMARY AND CONCLUSIONS An integrated optoelectronic chip has been designed and fabricated with a cellular architecture which providesoptical input and output, via LEDs and photoconducting detectors, from each cell in the array, and electricalinput and output to the array one row at a time. Each cell in the array can perform memory, thresholding and amplification functions.A fabrication process was developed for the integration of optoelectronic devices and GaAs enhancement-mode MESFET integrated circuits. The integrated process, which included the epitaxial deposition of layers for theLED, did not have any measurable effect on the performance of FETs and photodetectors fabricated on thesame substrate. LED efficiency and series resistance were degraded somewhat by the integrated process. Alloptical devices and electronic circuits functioned as designed when tested separately. However, a feedbackmechanism was observed between the LED and LED driver. The source of the problem was found to be

High Density Waveguide Modulator Arrays for Parallel Interconnection

AbstractA new design of GaAs/AlGaAs waveguide amplitude modulator intended for array applications at 830nm wavelength is reported. The device is based on polarization rotation, and has bandwidths in excess of 1 GHz, andan extinction ratio of 1 7dB. Mach-Zehnder modulators with 23dB have also been fabricated, and arrays with 20 microns device separation fabricated. The arrays have crosstalk less than -20dB, and feature electrical interconnection compatible with standard packaging techniques. Introduction Increases in the speed, bandwidth and size of computers places progressively higher demands on backplanebased board-to-board interconnects. In current machines, great effort is expended in using existing technology toimplement the required connectivity. The bottleneck associated with the connection will prevent the potentialadvantages of multiprocessors from being realized as clock speeds and message widths increase. While opticalinterconnection media have been predicted to offer a solution (1), their ability to eliminate the bottleneck will onlybe realized if optical source arrays can be developed with spacings comparable to those of the interconnectionchannels. Implementation using existing discrete devices will suffer from excessive amounts of space being

Packaged AlGaAs waveguide modulator array at 830 nm wavelength

We report a fully packaged AlGaAs waveguide modulator array with four individually addressable elements operating at approximately 830 nm wavelength and a clock speed of 1 GHz. The modulators rely largely on the linear electro-optic effect for operation, and have been packaged with an E/D MESFET driver with complementary 3.5 V outputs, and a thick-film ceramic bias network. The device is compact, using multimode interference devices for on-chip splitters and combiners and has a 4 mm electrode length. Extinction ratios in excess of 10 dB have been demonstrated over a temperature range from room temperature to 143/spl deg/C. The modulator array has been packaged with a remote high power (100 mW) diode laser using stable single mode input coupling, while the modulator output is packaged with a multimode fiber array of 52.5 /spl mu/m core diameter. >

OEICs for Optical Interconnects

Optical interconnect (OI) is used for functionally connecting components and subsystems over short distances by incorporating the superior transmission and other characteristics of optical media over electrical lines. These are: (i) High bandwidth, useful for microwave and millimeter wave (MMW) systems, and time division and wavelength division multiplexing (TDM and WDM) in digital systems, (ii) Superior confinement, resulting in lower cross-talk, enables the realization of high path-densities needed for parallel interconnects, and of cross-over circuits used in crossbars and shuffles, (iii) Far superior immunity against EMP and EMI (electromagnetic pulse, and interference, respectively), (iv) Two times reduction in the number of information carrying paths, eliminates the return path required in electrical equivalents. Two times power compression, achieved through energy conversion processes (electrical to optical and back to electrical), (v) Elimination of line impedance matching at transmitter output, and of required compliance with electrical potential and impedance matching at receiver input.

Linear AlGaAs/GaAs waveguide modulator at lambda = 1.32μm utilizing lateral mode interference

Optical modulators based on electrooptically-induced lateral mode interference in multimode AlGaAs/GaAs waveguides at lambda = 1.32 micron are investigated for high-frequency linear applications. The key design issue is achieving higher slope efficiency while maintaining significant linearity improvements over sinusoidal interference-based modulator designs. We report experimental results which demonstrate indirectly a reduction in intermodulation distortion of 48 dB compared to an ideal Mach-Zehnder interferometer.

Final Report on LDRD Project: Heterogeneous Integration of Optoelectronic Arrays and Microelectronics

Integrated microsystems provide the benefits of small size, low power consumption, robustness, and potentially inexpensive manufacture. However, multifunctional advanced microsystems often require a combination of microelectronic and photonic technologies, For example, high-density 2-dimensional integrated optoelectronic arrays are the basic components necessary to construct real-time electro-optical signal processing and analog information processing microsystems. In corresponding *no longer at Sandia **L&M Technologies, Inc.

GaAs optoelectronic smart pixel arrays

In summary, our long term directions will involve the monolithic integration of vertical cavity surface emitting lasers (VCSELs), either p-i-n or photoconducting detectors, and the complementary heterostructure field effect transistor LC technology. An approach to the monolithic integration of these structures is illustrated.<<ETX>>