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Silicon photonics devices for integrated analog signal processing and sampling

Published in:
Nanophotonics, Vol. 3, No. 4-5, 1 August 2014, pp. 313-27.

Summary

Silicon photonics offers the possibility of a reduction in size weight and power for many optical systems, and could open up the ability to build optical systems with complexities that would otherwise be impossible to achieve. Silicon photonics is an emerging technology that has already been inserted into commercial communication products. This technology has also been applied to analog signal processing applications. MIT Lincoln Laboratory in collaboration with groups at MIT has developed a toolkit of silicon photonic devices with a focus on the needs of analog systems. This toolkit includes low-loss waveguides, a high-speed modulator, ring resonator based filter bank, and all-silicon photodiodes. The components are integrated together for a hybrid photonic and electronic analog-to-digital converter. The development and performance of these devices will be discussed. Additionally, the linear performance of these devices, which is important for analog systems, is also investigated.
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Summary

Silicon photonics offers the possibility of a reduction in size weight and power for many optical systems, and could open up the ability to build optical systems with complexities that would otherwise be impossible to achieve. Silicon photonics is an emerging technology that has already been inserted into commercial communication...

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Waveguide engineering for hybrid Si/III-V lasers and amplifiers

Published in:
CLEO: Conf. on Lasers and Electro-Optics, 6-11 June 2012.

Summary

Using adiabatic tapers, hybrid silicon / III-V lasers and amplifiers are integrated with conventional thin (t = 0.25 um) silicon waveguides. Amplifiers have ~12 dB intrachip gain, and similar lasers have thresholds of 35 mA.
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Summary

Using adiabatic tapers, hybrid silicon / III-V lasers and amplifiers are integrated with conventional thin (t = 0.25 um) silicon waveguides. Amplifiers have ~12 dB intrachip gain, and similar lasers have thresholds of 35 mA.

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Driven dynamics and rotary echo of a qubit tunably coupled to a harmonic oscillator

Summary

We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel, and we find that low-frequency noise in the coupling parameter causes a reduction of the coherence time during driven evolution. The noise can be mitigated with the rotary-echo pulse sequence, which, for driven systems, is analogous to the Hahn-echo sequence.
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Summary

We have investigated the driven dynamics of a superconducting flux qubit that is tunably coupled to a microwave resonator. We find that the qubit experiences an oscillating field mediated by off-resonant driving of the resonator, leading to strong modifications of the qubit Rabi frequency. This opens an additional noise channel...

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Photonic ADC: overcoming the bottleneck of electronic jitter

Summary

Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy. Photonic ADCs, which perform sampling using ultra-stable optical pulse trains generated by mode-locked lasers, have been investigated for many years as a promising approach to overcome the jitter problem and bring ADC performance to new levels. This work demonstrates that the photonic approach can deliver on its promise by digitizing a 41 GHz signal with 7.0 effective bits using a photonic ADC built from discrete components. This accuracy corresponds to a timing jitter of 15 fs - a 4-5 times improvement over the performance of the best electronic ADCs which exist today. On the way towards an integrated photonic ADC, a silicon photonic chip with core photonic components was fabricated and used to digitize a 10 GHz signal with 3.5 effective bits. In these experiments, two wavelength channels were implemented, providing the overall sampling rate of 2.1 GSa/s. To show that photonic ADCs with larger channel counts are possible, a dual 20- channel silicon filter bank has been demonstrated.
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Summary

Accurate conversion of wideband multi-GHz analog signals into the digital domain has long been a target of analog-to-digital converter (ADC) developers, driven by applications in radar systems, software radio, medical imaging, and communication systems. Aperture jitter has been a major bottleneck on the way towards higher speeds and better accuracy...

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Thermally tuned dual 20-channel ring resonator filter bank in SOI (silicon-on-insulator)

Published in:
CLEO 2011, Conf. on Lasers and Electro-Optics, 1 May 2011.

Summary

Two 20-channel second-order optical filter banks have been fabricated. With tuning, the requirements for a wavelength multiplexed photonic AD-converter (insertion loss 1-3 dB, extinction >30 dB and optical bandwidth 22-27 GHz) are met.
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Summary

Two 20-channel second-order optical filter banks have been fabricated. With tuning, the requirements for a wavelength multiplexed photonic AD-converter (insertion loss 1-3 dB, extinction >30 dB and optical bandwidth 22-27 GHz) are met.

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Operation and optimization of silicon-diode-based optical modulators

Published in:
IEEE J. Sel. Top. in Quantum Electron., Vol. 16, No. 1, January/February 2010, pp. 165-172.

Summary

An optical modulator in silicon based on a diode structure has been operated in both forward and reverse bias. This modulator achieves near state-of-the-art performance in both modes, thereby making this device idea for comparing the two modes of operation. In reverse bias, the device has a V[pi]L of 4.9 V-cm and a bandwidth of 26GHz. In forward bias, the device is very sensitive, a V[pi]L a slow as 0.0025 V-cm has been achieved, but the bandwidth is only 100 MHz. A ndw geometyr for a reverse-bias device is proposed, and it is predicted to achieve a V[pi]L of 0.5V.cm.
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Summary

An optical modulator in silicon based on a diode structure has been operated in both forward and reverse bias. This modulator achieves near state-of-the-art performance in both modes, thereby making this device idea for comparing the two modes of operation. In reverse bias, the device has a V[pi]L of 4.9...

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CMOS-compatible dual-output silicon modulator for analog signal processing

Summary

A broadband, Mach-Zehnder-interferometer based silicon optical modulator is demonstrated, with an electrical bandwidth of 26 GHz and V[pi]L of 4 V·cm. The design of this modulator does not require epitaxial overgrowth and is therefore simpler to fabricate than previous devices with similar performance.
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Summary

A broadband, Mach-Zehnder-interferometer based silicon optical modulator is demonstrated, with an electrical bandwidth of 26 GHz and V[pi]L of 4 V·cm. The design of this modulator does not require epitaxial overgrowth and is therefore simpler to fabricate than previous devices with similar performance.

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Effect of carrier lifetime on forward-biased silicon Mach-Zehnder modulators

Summary

We present a systematic study of Mach-Zehnder silicon optical modulators based on carrier-injection. Detailed comparisons between modeling and measurement results are made with good agreement obtained for both DC and AC characteristics. A figure of merit, static VpiL, as low as 0.24Vmm is achieved. The effect of carrier lifetime variation with doping concentration is explored and found to be important for the modulator characteristics.
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Summary

We present a systematic study of Mach-Zehnder silicon optical modulators based on carrier-injection. Detailed comparisons between modeling and measurement results are made with good agreement obtained for both DC and AC characteristics. A figure of merit, static VpiL, as low as 0.24Vmm is achieved. The effect of carrier lifetime variation...

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All silicon infrared photodiodes: photo response and effects of processing temperature

Summary

CMOS compatible infrared waveguide Si photodiodes are made responsive from 1100 to 1750 nm by Si+ implantation and annealing. This article compares diodes fabricated using two annealing temperatures, 300 and 475C. 0.25-mm-long diodes annealed to 300C have a response to 1539 nm radiation of 0.1 A W-1 at a reverse bias of 5 V and 1.2 A W-1 at 20 V. 3-mm-long diodes processed to 475C exhibited two states, L1 and L2, with photo responses of 0.3 +/-0.1 A W-1 at 5 V and 0.7 +/-10.2 A W-1 at 20 V for the L1 state and 0.5 +/-0.2 A W-1 at 5 V and 4 to 20 A W-1 at 20 V for the L2 state. The diodes can be switched between L1 and L2. The bandwidths vary from 10 to 20 GHz. These diodes will generate electrical power from the incident radiation with efficiencies from 4 to 10 %.
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Summary

CMOS compatible infrared waveguide Si photodiodes are made responsive from 1100 to 1750 nm by Si+ implantation and annealing. This article compares diodes fabricated using two annealing temperatures, 300 and 475C. 0.25-mm-long diodes annealed to 300C have a response to 1539 nm radiation of 0.1 A W-1 at a reverse...

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Infrared frequency selective surfaces fabricated using optical lithography and phase-shift masks

Published in:
J. Vac. Sci. Technol. B, Vol. 19, No. 6, November/December 2001, pp. 2757-2760. (45th Int. Conf. on Electron, Ion, and Photon Beam Technology and Nanofabrication (EIPBN), 29 May-1 June 2001.)

Summary

A frequency selective surface (FSS) structure has been fabricated for use in a thermophotovoltaic system. The FSS provides a means for reflecting the unusable light below the band gap of the thermophotovoltaic cell while transmitting the usable light above the band gap. This behavior is relatively independent of the light's incident angle. The fabrication of the FSS was done using optical lithography and a phase-shift mask. The FSS cell consisted of circular slits spaced by 1100 nm. The diameter and width of the circular slits were 870 and 120 nm, respectively. The FSS was predicted to pass wavelengths near 7 um and reflect wavelengths outside of this pass band. The FSSs fabricated performed as expected with a pass band centered near 5 um.
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Summary

A frequency selective surface (FSS) structure has been fabricated for use in a thermophotovoltaic system. The FSS provides a means for reflecting the unusable light below the band gap of the thermophotovoltaic cell while transmitting the usable light above the band gap. This behavior is relatively independent of the light's...

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