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Joshi A.,Discovery Semiconductors, Inc. | Datta S.,Discovery Semiconductors, Inc.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

We present 16-element and 32-element lattice-mismatched InGaAs photodiode arrays having a cut-off wavelength of ~2.2 um. Each 100 um × 200 um large pixel of the 32-element array has a capacitance of 2.5 pF at 5 V reverse bias, thereby allowing a RC-limited bandwidth of ~1.3 GHz. At room temperature, each pixel demonstrates a dark current of 25 uA at 5 V reverse bias. Corresponding results for the 16-element array having 200 um × 200 um pixels are also reported. Cooling the photodiode array to 150K is expected to reduce its dark current to < 50 nA per pixel at 5 V reverse bias. Additionally, measurement results of 2-micron single photodiodes having 16 GHz bandwidth and corresponding PIN-TIA photoreceiver having 6 GHz bandwidth are also reported. © 2012 SPIE.


Joshi A.,Discovery Semiconductors, Inc. | Datta S.,Discovery Semiconductors, Inc.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2012

Broadband focal plane array sensors, operating in the 0.25 to 2.5 μm wavelength range, are an enabling technology for several imaging applications including atmospheric greenhouse gas monitoring. Currently, hyper-spectral imagers use separate image sensors for different spectral sub-bands, for example GaN for UV, Si for visible, and InGaAs for IR, thus requiring expensive component-level integration. Our approach is to manufacture a single image sensor with 0.25 to 2.5 μm spectral range using GaAs substrates, which are commercially available in diameters as large as 6 inches. The key challenges, namely achieving high UV efficiency, low dark current, and high speed operation, are addressed separately in a lattice-matched GaAs UV-to-Visible photodiode and a lattice-mismatched InGaAs NIR-to-SWIR photodiode. The method for monolithically combining the two structures into a single UV-to-SWIR photodiode / photodiode array is also presented. © 2012 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE).


Bhandare S.,Discovery Semiconductors, Inc. | Joshi A.,Discovery Semiconductors, Inc. | Becker D.,Discovery Semiconductors, Inc.
Journal of Lightwave Technology | Year: 2010

The purpose of this paper is to demonstrate the potential of an electrical signal processing technique to mitigate the effect of intersymbol interference in metro optical networks, using optical coherent detection. Intersymbol interference in fiber-optic systems can severely degrade the system performance and subsequently limit both the maximum transmission distance and data rate. The main sources of intersymbol interference include chromatic dispersion (CD) and polarization mode dispersion (PMD). The typical reach for 10 Gb/s metro optical systems is on the order of 300 km. To bridge this distance either with or without repeaters, we demonstrate the potential use of 10 Gb/s differential phase-shift keying (DPSK) modulation format in conjunction with an optical coherent receiver with a built-in switchable electrical dispersion compensator. The overall performance of the optical coherent receiver is compared with that of the corresponding direct detection (DD) receiver based on Mach-Zehnder delay interferometer. The optical signal-to-noise (OSNR) required to operate the optical coherent receiver at the enhanced forward error correction (EFEC) threshold of 2.1 × 10-3 is 6 dB/0.1 nm resolution bandwidth. The optical coherent receiver outperforms in absolute required OSNRby 0.5 dB at the EFEC threshold when compared to a DD receiver. A four position switchable CD compensator compensates up to ±5100 ps/nm of CD, using the method of heterodyne detection. The optical coherent receiver has a first-order PMD tolerance of 36.2 ps for 1 dB OSNR penalty. The utility of our optical coherent receiver is demonstrated by doing transmission experiments over 304 km of standard single-mode fiber (SSMF) in both repeatered (multiple spans) and repeaterless (single span) to measure the self-phase modulation (SPM) tolerance of 10 Gb/s nonreturn-to-zero (NRZ)-DPSK. The measured SPM tolerance of NRZ-DPSK over 304 km of SSMF in three spans of ̃100 km each is +8.8 dBm fiber launch power for 1.5 dB OSNR penalty. In addition, the best Q factor of ̃12 dB is obtained for the fiber launch power of +18 dBm over single repeaterless span of 304 km of SSMF, which gives ̃3 dB of system margin at the second generation EFEC threshold of 9.1 dB. © 2009 IEEE.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2009

Gravity wave detection using space-based long-baseline laser interferometric sensors imposes stringent noise requirements on the system components, including the large area photoreceiver front ends. The proposed innovation utilizes dual depletion region technology to produce a large area (1mm diameter) 2x2 quad p-i-n InGaAs photodiode array having ~2.1pF capacitance per quadrant. The small capacitance of the quad photodiode array is leveraged in combination with a low-noise JFET-input operational amplifier to manufacture ultra-low noise quad photoreceiver array. Each element (quadrant) of the photoreceiver array will have an input equivalent current noise


Grant
Agency: Department of Defense | Branch: Air Force | Program: SBIR | Phase: Phase I | Award Amount: 150.00K | Year: 2013

ABSTRACT: Discovery Semiconductors will assemble high power InGaAs/InP photodiodes with 50 ohm internal termination in a fiber-pigtailed, W1-connectorized microwave package having the following specifications: (a) Responsivity>0.7 A/W at 1550 nm wavelength; (b) -3 dB Bandwidth>60 GHz; (c) -9 dB Bandwidth>80 GHz; (d) 1 dB Compression Photocurrent>50 mA @ 60 GHz modulation frequency and>50% modulation depth; and (e) 1 dB Compression Photocurrent Density>0.64 mA/um^2. One packaged device will be delivered each to Lockheed Martin Space Systems Company and Air Force for system level testing. Additionally, packaging techniques for balanced and arrayed photodiodes will be investigated. BENEFIT: The anticipated benefits/applications of this work are :(1) 60 GHz cellular; (2) Hybrid fiber/wireless systems from X-Band to W-Band; (3)Optical phased array radar; and (4)Space systems fiber optic transponders.


Grant
Agency: Department of Defense | Branch: Navy | Program: SBIR | Phase: Phase I | Award Amount: 80.00K | Year: 2014

We will manufacture high current handling balanced photodiodes in a rugged 8-pin Kovar package having the following characteristics: (a) Small Package with height of 5 mm, and volume of 2.5 cubic cm; (b) Use 7 micron core, loose tube, SM fiber for tight bend radius; (c) Responsivity>0.7 A/W at 1310 and 1550 nm; (d) 20 GHz bandwidth with total 1dB saturation current of 100 mA (50 mA per photodiode); (e) 40 GHz bandwidth with total 1dB saturation current of 50 mA (25 mA per photodiode); (f) CMRR>20 dB for the entire frequency band; (g) Operating Temperature Range -40 to 100 degree Celcius; (h) OIP3 of minimum +40 dBm and, OIP2 +50 dBm per photodiode for 2 to 40 GHz frequency band. One packaged device of the high current handling balanced photodiode having a bandwidth of minimum 20 GHz will be delivered to NAVAIR.


Grant
Agency: Department of Defense | Branch: Defense Advanced Research Projects Agency | Program: SBIR | Phase: Phase I | Award Amount: 98.95K | Year: 2010

We propose to develop high-power, highly linear photodiodes having the following specifications at 1550 nm wavelength per photodiode: (1) 3 dB bandwidth > 20 GHz, (2) DC photocurrent > 200 mA, (3) maximum RF output power > 1 W, (4) two-tone OIP3 > 55 dBm, and (5) power-to-phase conversion factor < 3 rad/W. In conjunction with the significant advances in the state-of-the-art in individual photodiode performance, as mentioned above, we will demonstrate further ~ 6 dB enhancement in maximum RF output power and OIP3 by combining the RF outputs of an array of the proposed photodiodes with a RF Wilkinson combiner.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 600.00K | Year: 2011

Broadband focal plane arrays, operating in UV-to-SWIR wavelength range, are required for atmospheric monitoring of greenhouse gases. Currently, separate image sensors are used for different spectral sub-bands: GaN for UV, Si for visible, and InGaAs for SWIR, requiring expensive component-level integration for hyper-spectral imaging. Also, the size of the InGaAs focal plane arrays is currently limited by the InP substrate area.We propose to develop a 640 x 512 UV-to-SWIR focal plane array sensor using GaAs substrate having following photodiode performance: (1) Cut-on Wavelength = 0.25 micron; (2) Cut-off Wavelength = 2.5 micron; (3) RoA>35 Ohm-cm^2 at 300K; and (4) Quantum Eficiency>30% in UV (0.25 to 0.4 micron),>80% in Visible (0.4 to 0.9 micron), and>70% in IR (0.9 to 2.5 micron) subbands.Based on P.I.'s experience on SCIAMACHY, this project will enable one image sensor for 8 spectroscopic channels currently orbiting on European Space Agency's ENVISAT.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase I | Award Amount: 100.00K | Year: 2010

Broadband focal plane arrays, operating in UV-to-SWIR wavelength range, are required for atmospheric monitoring of greenhouse gases. Currently, separate image sensors are used for different spectral sub-bands: GaN for UV, Si for visible, and InGaAs for SWIR, requiring expensive component-level integration for hyper-spectral imaging. Also, the size of the InGaAs focal plane arrays is currently limited by the InP substrate area. We propose a GaAs/InGaP/InGaAs based photodiode on standard GaAs substrates for large-format (4096 x 4096) focal plane arrays with the following characteristics: (1) Wavelength = 0.25 to 2.5 micron; (2) Quantum Eficiency > 30% in UV (0.25 to 0.4 micron), > 80% in Visible (0.4 to 0.9 micron), and > 70% in IR (0.9 to 2.5 micron) subbands; (3) Photodiode Area (single element) = 15 x 15, 25 x 25, and 50 x 50 micron square; (4) RoA > 35 Ohm-cm^2 at 300K; and (5) Bandwidth > 1 GHz. Additionally, feasibility of UV-to-SWIR graded optical filters will be investigated. Based on P.I.'s experience on SCIAMACHY, this project will enable one image sensor for 8 spectroscopic channels currently orbiting on European Space Agency's ENVISAT. Also, feasibility of large-format image sensors on GaAs substrates will be demonstrated.


Grant
Agency: National Aeronautics and Space Administration | Branch: | Program: SBIR | Phase: Phase II | Award Amount: 600.00K | Year: 2010

We propose to design and develop 2x2 quad p-i-n InGaAs Photoreceivers having the following characteristics: (a) Active area diameter 0.75 mm; (b) Wavelength coverage 850 to 1700 nm, with responsivity of 0.7 A/W at 1064 nm; (c) Bandwidth up to 20 MHz for the individual quadrant; (d) Group Delay < 6 degrees/MHz; (e) Photodiode capacitance for individual quadrant of

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