Publications by authors named "Po Dong"

46 Publications

Experimental demonstration of a 4,294,967,296-QAM-based Y-00 quantum stream cipher template carrying 160-Gb/s 16-QAM signals.

Opt Express 2021 Feb;29(4):5658-5664

We demonstrate a 4,294,967,296-quadrature amplitude modulation (QAM) based Y-00 quantum stream cipher system carrying a 160-Gb/s 16-QAM signal transmitted over 320-km SSMF. The ultra-dense QAM cipher template is realized by an integrated two-segment silicon photonics I/Q modulator.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.405390DOI Listing
February 2021

Broadly and finely tunable hybrid silicon laser with nanosecond-scale switching speed.

Opt Lett 2020 Nov;45(22):6198-6201

We demonstrate a hybrid silicon tunable laser with wide tunability and rapid switching speed for applications in sensing and optical networks. By implementing an optimized carrier injection phase shifter design, the filters of the silicon laser cavity may be efficiently controlled, enabling both fine and broad wavelength tuning across a 56 nm range, in addition to a rapid 10 ns switching time. The laser emits up to 10 dBm output power, and the linewidth is near 200 kHz. The fast wavelength switching demonstrated here may be employed in data center and access networks, while the potential for rapid wavelength sweeping is attractive for optical sensing and imaging applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.411115DOI Listing
November 2020

Device architectures for low voltage and ultrafast graphene integrated phase modulators.

IEEE J Sel Top Quantum Electron 2021 24;27(2):1-9. Epub 2020 Sep 24.

University of Delaware, Newark, DE 19716 USA.

The atomic layer thin geometry and semi-metallic band diagram of graphene can be utilized for significantly improving the performance matrix of integrated photonic devices. Its semiconductor-like behavior of Fermi-level tunability allows graphene to serve as an active layer for electro-optic modulation. As a low loss metal layer, graphene can be placed much closer to active layer for low voltage operation. In this work, we investigate hybrid device architectures utilizing semiconductor and metallic properties of the graphene for ultrafast and energy efficient electro-optic phase modulators on semiconductor and dielectric platforms. (1) Directly contacted graphene-silicon heterojunctions. Without oxide layer, the carrier density of graphene can be modulated by the directly contact to silicon layer, while silicon intrinsic region stays mostly depleted. With doped silicon as electrodes, carrier can be quickly injected and depleted from the active region in graphene. The ultrafast carrier transit time and small RC constant promise ultrafast modulation speed (3dB bandwidth of 67 GHz) with an estimated V·L of 1.19 V·mm. (2) Graphene integrated lithium niobite modulator. As a transparent electrode, graphene can be placed close to integrated lithium niobate waveguide for improving coupling coefficient between optical mode profile and electric field with minimal additional loss (4.6 dB/cm). Numerical simulation indicates 2.5× improvement of electro-optic field overlap coefficient, with estimated V of 0.2 V.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1109/jstqe.2020.3026357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7608027PMC
September 2020

Inter-polarization mixers for coherent detection of optical signals.

Opt Express 2018 Jul;26(14):18523-18531

Electro-magnetic (EM) mixers are fundamental building blocks in communication systems. They are used in frequency/wavelength filters, interferometric modulators, amplitude-phase receivers, to name a few. Traditional EM mixers have two or more input ports and work only for co-polarized signal and local-oscillator (LO) incident on its inputs. Here we report on novel designs, in silicon, of inter-polarization EM mixers operating at 1550 nm wavelength. The 180-degree optical mixer comprising a single input port is demonstrated to coherently mix orthogonally polarized signal and LO. Using the proposed 180-degree mixer, we report on a novel design for a 90-degree optical mixer on silicon with small footprint, broadband response, low loss and good fabrication tolerance. It exploits birefringence of a waveguide to achieve broadband and fabrication-tolerant 90° phase difference between the signal/LO relative phase in the in-phase and quadrature components. A monolithic silicon photonics coherent receiver is demonstrated using the reported 90-degree mixer, and its operation at 22 Gbaud and 44 Gbaud is shown. These mixers pave the way for novel coherent receiver architectures in long-haul, metro, passive optical networks and data-center interconnect applications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.26.018523DOI Listing
July 2018

Simultaneous four-channel thermal adaptation of polarization insensitive silicon photonics WDM receiver.

Opt Express 2017 Oct;25(22):27119-27126

We propose a novel approach to demonstrate simultaneous multi-wavelength locking during temperature changes in a silicon photonic polarization insensitive microring-based wavelength division multiplexing (WDM) receiver. The DC component of a single monitoring photodetector at the through port of the microring filter array is exploited as a feedback signal with no additional power consumption. This feedback signal is used in control circuitry to properly tune the microring filters using ohmic heating, thus creating a feedback loop for thermal adaptation. We describe the necessary information, specifically each microring filter's room temperature resonant wavelength and tunability, which can be used to calibrate and achieve proper wavelength configurability and locking. In addition, we describe a simple control algorithm based on an adaptive gradient method often used in machine learning, allowing the receiver to endlessly demultiplex at different temperatures. We successfully achieve thermal adaptation over a temperature range >37°C and demultiplex a 4 × 25 Gb/s on-off-keying signal of 150 GHz channel spacing, all while the polarization is scrambling.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.25.027119DOI Listing
October 2017

Simultaneous wavelength locking of microring modulator array with a single monitoring signal.

Opt Express 2017 Jul;25(14):16040-16046

A microring modulator array coupled to a common bus waveguide can be used to construct low power, compact and flexible wavelength-division-multiplexing (WDM) transmitters. However, due to extremely small working bandwidths of the rings, it is challenging to find the right resonant wavelength setting and locking the resonance to an external laser. In the paper, we propose a novel technique enabling simultaneous wavelength locking of a microring modulator array with a single monitor, together with automatically optimizing the wavelength setting. We experimentally demonstrate locking three rings over a temperature range >40 °C at 3x20 Gb/s on-off-keying (OOK) modulation and ~3x75 Gb/s discrete multi-tone (DMT) modulation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.25.016040DOI Listing
July 2017

Coplanar-waveguide-based silicon Mach-Zehnder modulator using a meandering optical waveguide and alternating-side PN junction loading.

Opt Lett 2016 Sep;41(18):4401-4

We demonstrate a silicon Mach-Zehnder modulator with a coplanar waveguide transmission-line electrode structure using a meandering optical waveguide and alternating-side PN junction loading of the electrodes, which helps suppress the signal distortion caused by the parasitic slot-line mode and improves the electro-optic (EO) bandwidth. The silicon MZM exhibits a π-phase-shift voltage (Vπ) of 4.5 V with an EO 3 dB bandwidth of ∼20  GHz for a 5 mm long phase shifter. This achieved Vπ is among the lowest for silicon-only modulators with a bandwidth of more than 20 GHz.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.41.004401DOI Listing
September 2016

128-Gb/s 100-km transmission with direct detection using silicon photonic Stokes vector receiver and I/Q modulator.

Opt Express 2016 Jun;24(13):14208-14

Recently, there is increasing interest in utilizing Stokes vector receiver, which is a direct-detection technique with the capability to digitally track the polarization changes in fibers and decode information in multiple dimensions. Here, we report a monolithically integrated silicon photonic Stokes vector receiver, which consists of one polarization beam splitter, two polarization rotators, one 90-degree optical hybrid, and six germanium photodetectors. Paired with a silicon in-phase/quadrature modulator incorporating a power-tunable carrier in the orthogonal polarization, transmission at 128-Gb/s over 100-km fiber is achieved with direct detection.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.24.014208DOI Listing
June 2016

Observation of nonreciprocal transmission in binary phase-shift keying modulation using traveling-wave Mach-Zehnder modulators.

Opt Lett 2016 Jun;41(12):2723-6

In coherent optical transmission, traveling-wave Mach-Zehnder modulators are commonly used to generate various advanced formats where the modulators are biased at the minimum transmission point. Here, we report that an optical isolation effect with lower backward transmission occurs under this condition. This concept is successfully demonstrated to achieve ∼7  dB isolation over a 90-nm wavelength span under binary phase-shift keying modulation using a commercial lithium niobate modulator.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.41.002723DOI Listing
June 2016

High-power dual-fed traveling wave photodetector circuits in silicon photonics.

Opt Express 2015 Aug;23(17):22857-66

We introduce the concept of dual-illuminated photodetectors for high-power applications. Illuminating the photodetector on both sides doubles the number of optical channels, boosting DC and RF power handling capability. This concept is demonstrated utilizing multiple-stage dual-illuminated traveling wave photodetector circuits in silicon photonics, showing a maximum DC photocurrent of 112 mA and a 3-dB bandwidth of 40 GHz at 0.3 mA. Peak continuous-wave RF power is generated up to 12.3 dBm at 2 GHz and 5.3 dBm at 40 GHz, at a DC photocurrent of 55 mA. High speed broadband data signals are detected with eye amplitudes of 2.2 V and 1.3 V at 10 Gb/s and 40 Gb/s, respectively. A theoretical analysis is presented illustrating design tradeoffs for the multiple-stage photodetector circuits based on the bandwidth and power requirements.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.23.022857DOI Listing
August 2015

Travelling-wave Mach-Zehnder modulators functioning as optical isolators.

Authors:
Po Dong

Opt Express 2015 Apr;23(8):10498-505

On-chip optical isolators not requiring the use of magneto-optical materials has become a long-standing challenge in integrated optics. Here, we demonstrate that a traditional travelling-wave modulator can effectively function as an optical isolator, when driven under a prescribed modulation condition. By using an off-shelve lithium niobate modulator, we achieve more than 12.5 dB isolation over an 11.3-THz bandwidth at telecommunication wavelengths with a fiber-to-fiber insertion loss of 5.5 dB, by employing only a single radio-frequency drive signal. We also verify that the proposed active isolator can be functional in a laser system to effectively prevent instability due to strong back reflections. Since travelling-wave modulators are common devices in III-V and silicon photonics, our simple but efficient architecture may provide a practical solution to non-reciprocal light routing in photonic integrated circuits.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.23.010498DOI Listing
April 2015

Novel integration technique for silicon/III-V hybrid laser.

Opt Express 2014 Nov;22(22):26854-61

Integrated semiconductor lasers on silicon are one of the most crucial devices to enable low-cost silicon photonic integrated circuits for high-bandwidth optic communications and interconnects. While optical amplifiers and lasers are typically realized in III-V waveguide structures, it is beneficial to have an integration approach which allows flexible and efficient coupling of light between III-V gain media and silicon waveguides. In this paper, we propose and demonstrate a novel fabrication technique and associated transition structure to realize integrated lasers without the constraints of other critical processing parameters such as the starting silicon layer thicknesses. This technique employs epitaxial growth of silicon in a pre-defined trench with taper structures. We fabricate and demonstrate a long-cavity hybrid laser with a narrow linewidth of 130 kHz and an output power of 1.5 mW using the proposed technique.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.22.026854DOI Listing
November 2014

Silicon optical modulator with shield coplanar waveguide electrodes.

Opt Express 2014 Sep;22(19):23724-31

A silicon Mach-Zehnder Interferometer (MZI) optical modulator with a shield coplanar waveguide (CPW) transmission line electrode design was demonstrated. This shield-CPW electrode suppresses the signal distortion caused by the parasitic slot-line (SL) mode and improves the electrical bandwidth and the electro-optical (EO) bandwidth. With the shield-CPW electrodes and 5.5 mm-long phase shifters, the silicon MZI optical modulator delivered an EO bandwidth of above 24 GHz and a V (π) = 3.0 V was achieved at λ = 1310 nm. When modulated at 28-Gb/s data rate, it achieved an extinction ratio of 5.66 dB under a driving voltage of V (pp) = 1.3 V, corresponding to a power consumption of 0.8 pJ/bit.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.22.023724DOI Listing
September 2014

Cascaded uncoupled dual-ring modulator.

Opt Lett 2014 Aug;39(16):4974-7

We demonstrate, by coherent driving two uncoupled rings in same direction, that the effective photon circulating time in the dual-ring modulator is reduced, with increased modulation quality. The inter-ring detuning-dependent photon dynamics, Q factor, extinction ratio, and optical modulation amplitude of two cascaded silicon ring resonators are studied and compared with that of a single-ring modulator. Experimentally measured eye diagrams, together with coupled mode theory simulations, demonstrate the enhancement of the dual-ring configuration at 20 Gbps with a Q∼20,000.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.39.004974DOI Listing
August 2014

Monolithic polarization diversity coherent receiver based on 120-degree optical hybrids on silicon.

Opt Express 2014 Jan;22(2):2119-25

We present a monolithic polarization diversity coherent receiver by employing 120-degree optical hybrids on a silicon photonic integrated circuit (PIC). This PIC monolithically integrates silicon inverse tapers for fiber coupling, silicon polarization splitters, germanium high-speed photo detectors, and 120-degree optical hybrids based on 3x3 multimode interferometers (MMI). We demonstrate that 112-Gb/s polarization-division-multiplexed quadrature phase-shift keyed signals are detected in the wavelength range of 1530-1580 nm with comparable performance to commercial receivers.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.22.002119DOI Listing
January 2014

960-km SSMF transmission of 105.7-Gb/s PDM 3-PAM using directly modulated VCSELs and coherent detection.

Opt Express 2013 May;21(9):11585-9

Bell Labs, Alcatel Lucent, 791 Holmdel-Keyport Road, Holmdel, NJ 07733, USA.

We generate a 105.7-Gb/s signal by directly modulating a 1.5-µm VCSEL with a 33.35-Gbaud 3-level signal and polarization multiplexing. By using digital coherent detection, we successfully transmit the 105.7-Gb/s line rate (88.10 Gb/s net bit rate) signal over 960-km standard single-mode-fiber (SSMF) at a 20% hard-decision forward-error correction (FEC) threshold, which is at bit-error ratio (BER) of 1.5 x 10(-2)
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.21.011585DOI Listing
May 2013

112-Gb/s monolithic PDM-QPSK modulator in silicon.

Opt Express 2012 Dec;20(26):B624-9

Bell Labs, Alcatel-Lucent, 791 Holmdel Road, Holmdel, New Jersey 07733, USA.

We present a monolithic dual-polarization quadrature phase-shift keying (QPSK) modulator based on a silicon photonic integrated circuit (PIC). This PIC consists of four high-speed silicon modulators, a polarization rotator, and a polarization beam combiner. A 112-Gb/s polarization-division-multiplexed (PDM) QPSK modulation is successfully demonstrated.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.20.00B624DOI Listing
December 2012

50-Gb/s silicon quadrature phase-shift keying modulator.

Opt Express 2012 Sep;20(19):21181-6

Bell Labs, Alcatel-Lucent, 791 Holmdel Road, Holmdel, NJ 07733, USA.

We report the first successful demonstration of quadrature phase-shift keying (QPSK) modulation using two nested silicon Mach-Zehnder modulators. 50-Gb/s QPSK signal is generated with only 2.7-dB optical signal-to-noise ratio penalties from the theoretical limit at a bit-error ratio of 10(-3). This result validates that silicon photonics could be a viable and powerful platform of photonic integrated circuits in coherent optical communications.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.20.021181DOI Listing
September 2012

Experimental demonstration of microring quadrature phase-shift keying modulators.

Opt Lett 2012 Apr;37(7):1178-80

Bell Labs, Alcatel-Lucent, Holmdel, New Jersey 07733, USA.

Advanced optical modulation formats are a key technology to increase the capacity of optical communication networks. Mach-Zehnder modulators are typically used to generate various modulation formats. Here, we report the first experimental demonstration of quadrature phase-shift keying (QPSK) modulation using compact microring modulators. Generation of 20 Gb/s QPSK signals is demonstrated with 30 μm radius silicon ring modulators with drive voltages of ~6 V. These compact QPSK modulators may be used in miniature optical transponders for high-capacity optical data links.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OL.37.001178DOI Listing
April 2012

High-speed low-voltage single-drive push-pull silicon Mach-Zehnder modulators.

Opt Express 2012 Mar;20(6):6163-9

Bell Labs, Alcatel-Lucent, 791 Holmdel Road, Holmdel, NJ 07733, USA.

We demonstrate a single-drive push-pull silicon Mach-Zehnder modulator (MZM) with a π-phase-shift voltage of 3.1 V and speed up to 30 Gb/s. The on-chip insertion loss is 9 dB due to the use of a 6 mm-long phase shifter. Higher switching speed up to 40-50 Gb/s is also demonstrated in devices with shorter phase shifters which require higher drive voltages but have lower insertion losses.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.20.006163DOI Listing
March 2012

Monolithic silicon chip with 10 modulator channels at 25 Gbps and 100-GHz spacing.

Opt Express 2011 Dec;19(26):B946-51

Alcatel-Lucent Bell Laboratories, 791 Holmdel Road, Holmdel, NJ 07733, USA. Long

We demonstrate a chip containing ten low-chirp silicon modulators, each operating at 25 Gbps, multiplexed by a SiN arrayed-waveguide grating with 100-GHz spacing, showing the potential for 250 Gbps aggregated capacity on a 5×8 mm(2) footprint.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.19.00B946DOI Listing
December 2011

36 GHz submicron silicon waveguide germanium photodetector.

Opt Express 2011 May;19(11):10967-72

Kotura Inc, 2630 Corporate Place, Monterey Park, CA 91754, USA.

We present two effective approaches to improve the responsivity of high speed waveguide-based Ge photodetectors integrated on a 0.25 μm silicon-on-insulator (SOI) platform. The main cause of poor responsivity is identified as metal absorption from the top contact to Ge. By optimizing Ge thickness and offsetting the contact window, we have demonstrated that the responsivity can be improved from 0.6A/W to 0.95 A/W at 1550 nm with 36 GHz 3 dB bandwidth. We also demonstrate that a wider device with double offset contacts can achieve 1.05 A/W responsivity at 1550 nm and 20 GHz 3 dB bandwidth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.19.010967DOI Listing
May 2011

Design and fabrication of 3μm silicon-on-insulator waveguide integrated Ge electro-absorption modulator.

Opt Express 2011 Apr;19(9):8715-20

Kotura Inc., Monterey Park, CA 91754, USA.

We present the design and fabrication of a waveguide-based Ge electro-absorption (EA) modulator integrated with a 3 µm silicon-on-isolator (SOI) waveguide. The proposed Ge EA modulator employs a butt-coupled horizontally-oriented p-i-n structure. The optical design achieves a low-loss transition from Ge to Si waveguides. The interaction between the optical mode of the waveguide and the bias induced electric field in the p-i-n structure was maximized to achieve high modulation efficiency. By balancing the trade-offs between the extinction ratio and the insertion loss of the device, an optimal working regime was identified. The measurement results from a fabricated device were used to verify the design. Under a -4Vpp reverse bias, the device demonstrates a total insertion loss (including the transition loss) of 2.7-5.2 dB and an extinction ratio of 4.9-8.2 dB over the wavelength range of 1610-1640 nm. Subtracting the contribution of the transition loss, the Δα/α value for the fabricated device was estimated to be between 2.2 and 3.2 with an electric field around 55 kV/cm.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.19.008715DOI Listing
April 2011

30GHz Ge electro-absorption modulator integrated with 3 μm silicon-on-insulator waveguide.

Opt Express 2011 Apr;19(8):7062-7

Kotura Inc., 2630 Corporate Place, Monterey Park, California 91754, USA.

We demonstrate a compact waveguide-based high-speed Ge electro-absorption (EA) modulator integrated with a single mode 3 µm silicon-on-isolator (SOI) waveguide. The Ge EA modulator is based on a horizontally-oriented p-i-n structure butt-coupled with a deep-etched silicon waveguide, which transitions adiabatically to a shallow-etched single mode large core SOI waveguide. The demonstrated device has a compact active region of 1.0 × 45 µm(2), a total insertion loss of 2.5-5 dB and an extinction ratio of 4-7.5 dB over a wavelength range of 1610-1640 nm with -4V(pp) bias. The estimated Δα/α value is in the range of 2-3.3. The 3 dB bandwidth measurements show that the device is capable of operating at more than 30 GHz. Clear eye-diagram openings at 12.5 Gbps demonstrates large signal modulation at high transmission rate.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.19.007062DOI Listing
April 2011

Ultra-efficient 10 Gb/s hybrid integrated silicon photonic transmitter and receiver.

Opt Express 2011 Mar;19(6):5172-86

Oracle Labs, San Diego, California 92121, USA.

Using low parasitic microsolder bumping, we hybrid integrated efficient photonic devices from different platforms with advanced 40 nm CMOS VLSI circuits to build ultra-low power silicon photonic transmitters and receivers for potential applications in high performance inter/intra-chip interconnects. We used a depletion racetrack ring modulator with improved electro-optic efficiency to allow stepper optical photo lithography for reduced fabrication complexity. Integrated with a low power cascode 2 V CMOS driver, the hybrid silicon photonic transmitter achieved better than 7 dB extinction ratio for 10 Gbps operation with a record low power consumption of 1.35 mW. A received power penalty of about 1 dB was measured for a BER of 10(-12) compared to an off-the-shelf lightwave LiNOb3 transmitter, which comes mostly from the non-perfect extinction ratio. Similarly, a Ge waveguide detector fabricated using 130 nm SOI CMOS process was integrated with low power VLSI circuits using hybrid bonding. The all CMOS hybrid silicon photonic receiver achieved sensitivity of -17 dBm for a BER of 10(-12) at 10 Gbps, consuming an ultra-low power of 3.95 mW (or 395 fJ/bit in energy efficiency). The scalable hybrid integration enables continued photonic device improvements by leveraging advanced CMOS technologies with maximum flexibility, which is critical for developing ultra-low power high performance photonic interconnects for future computing systems.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.19.005172DOI Listing
March 2011

Submilliwatt, ultrafast and broadband electro-optic silicon switches.

Opt Express 2010 Nov;18(24):25225-31

Kotura Inc., 2630 Corporate Place, Monterey Park, CA 91754, USA.

We present a broadband 2x2 electro-optic silicon switch with an ultralow switching power and fast switching time based on a Mach-Zehnder interferometer (MZI). Forward-biased p-i-n junctions are employed to tune the phase of silicon waveguides in the MZI, to achieve a π-phase switching power of 0.6 mW with a drive voltage 0.83 V with a MZI arm length of 4 mm. The 10%-90% switching time is demonstrated to be 6 ns. Optical crosstalk levels lower than -17 dB are obtained for an optical bandwidth of 60 nm. The free carrier induced silicon refractive index change is extracted from the experimental results for the concentration range from 10(16) to 10(17) cm(-3). We find that at the concentration of 10(16) cm(-3), the index change is about twice that calculated by the commonly used index change equation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.18.025225DOI Listing
November 2010

Thermally-efficient reconfigurable narrowband RF-photonic filter.

Opt Express 2010 Nov;18(24):24648-53

Kotura Inc., 2630 Corporate Place, Monterey Park, CA 91754, USA.

We present the design and fabrication of thermally-efficient tuning structures integrated into a narrowband reconfigurable radio-frequency (RF)-photonics filter using silicon-on-insulator waveguide optical delay lines. By introducing thermal isolation trenching, we are able to achieve IIR, FIR or arbitrary mixed response with less than 120 mW average tuning power in a single RF-photonic unit cell filter.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.18.024648DOI Listing
November 2010

1x4 reconfigurable demultiplexing filter based on free-standing silicon racetrack resonators.

Opt Express 2010 Nov;18(24):24504-9

Kotura Inc., 2630 Corporate Place, Monterey Park, California 91754, USA.

We present a 1x4 reconfigurable demultiplexing filter based on cascaded thermally tunable silicon racetrack resonators with ultralow tuning powers. The use of free-standing silicon resonators with undercut structures significantly reduces the tuning power, with a figure of ~2.9 mW per free spectral range. Even with the presence of thermal crosstalk between two adjacent resonators, we demonstrate multiplexing functionality for channel spacings of 200 GHz, 100 GHz, and 50 GHz, with channel wavelengths aligned to International Telecommunication Union (ITU) grid specifications. Crosstalk values for 200 GHz and 50 GHz channel spacings are less than -20 dB and -11.5 dB, respectively. The total power to achieve this performance is in the range of 1.84 mW to 2.4 mW. Such low-power, compact, and reconfigurable filters are particularly useful in chip-scale optical interconnects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.18.024504DOI Listing
November 2010

GHz-bandwidth optical filters based on high-order silicon ring resonators.

Opt Express 2010 Nov;18(23):23784-9

Kotura Inc., 2630 Corporate Place, Monterey Park, CA 91754, USA.

Previously demonstrated high-order silicon ring filters typically have bandwidths larger than 100 GHz. Here we demonstrate 1-2 GHz-bandwidth filters with very high extinction ratios (~50 dB). The silicon waveguides employed to construct these filters have propagation losses of ~0.5 dB/cm. Each ring of a filter is thermally controlled by metal heaters situated on the top of the ring. With a power dissipation of ~72 mW, the ring resonance can be tuned by one free spectral range, resulting in wavelength-tunable optical filters. Both second-order and fifth-order ring resonators are presented, which can find ready application in microwave/radio frequency signal processing.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.18.023784DOI Listing
November 2010

Thermally tunable silicon racetrack resonators with ultralow tuning power.

Opt Express 2010 Sep;18(19):20298-304

Kotura Inc., 2630 Corporate Place, Monterey Park, CA 91754, USA.

We present thermally tunable silicon racetrack resonators with an ultralow tuning power of 2.4 mW per free spectral range. The use of free-standing silicon racetrack resonators with undercut structures significantly enhances the tuning efficiency, with one order of magnitude improvement of that for previously demonstrated thermo-optic devices without undercuts. The 10%-90% switching time is demonstrated to be ~170 µs. Such low-power tunable micro-resonators are particularly useful as multiplexing devices and wavelength-tunable silicon microcavity modulators.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1364/OE.18.020298DOI Listing
September 2010