Search

We present three case studies focused on different types of feedback scenarios, each featuring a different technological tool. Results show greater student participation and engagement, and facilitation of teacher orchestration of active learning pedagogy.

Optical frequency combs (OFCs) play a key role in a variety of applications and have been implemented primarily using mode-locked lasers, Kerr resonators, and electro-optic (EO) modulation. EO modulation-based OFC generation may not yield as many comb lines nor span as broad a bandwidth as mode-locked lasers or Kerr resonators; however, it offers a high degree of tunability in central frequency and comb spacing. Integrated solutions are of interest as they significantly reduce device footprint and enable large scale system integration. In this paper, we demonstrate flexible on-chip OFC generation using two cascaded EO Mach-Zehnder modulators in silicon photonics. We demonstrate quasi-rectangular OFCs with 9 lines and a comb spacing of up to 10 GHz with an amplitude variation (comb flatness) within 6.5 dB. The corresponding time-domain waveforms have a good fit with sinc-shaped Nyquist pulses having a full-width at half maximum duration as short as 11.4 ps.

To engage students with EM waves and quantum physics, connecting it to their everyday lives and to promote “photonics awareness,” a five-part, twelve-week group research project on a photonics-based Nobel prize was developed.

We examine the design of error detection prompts which scaffold peer-feedback as a corrective process, rather than an error-identification task. After designing a series of these prompts, they were given to a class of students in an introductory physics course (treatment group). Students in the treatment group, in comparison to the control group, 1) were more successful at correctly identifying errors and providing more meaningful feedback to a fictional classmate, and 2) wrote more, and explained physics better on final exam questions. In addition, several students adopted a mentoring (tutor-tutee) identity when writing feedback.

We review the recent work on developing integrated microwave photonic subsystems in silicon photonics for performing radio-frequency spectral analysis, generating microwave waveforms, and filtering microwave signals.

Radio frequency (RF) spectrum analysis is an essential technique for monitoring signal quality in ultrahigh-speed optical transmission, broad bandwidth photonic RF arbitrary waveform generation, and for characterization of high repetition rate optical pulse sources. Whereas the intrinsic bandwidth of electronics limits its use for RF spectrum measurement of high-speed signals, a photonic approach based on ultrafast Kerr nonlinear effects can readily measure the RF spectrum of optical signals having a bandwidth beyond 1 THz. The majority of fiber-based or integrated photonic RF spectrum analyzers reported to date can monitor only one channel at a time. We demonstrate how to harness mode-selective excitation of nonlinear optical effects to perform simultaneous multichannel RF spectrum analysis using a single integrated silicon photonic device. This approach, which can be scaled to a higher number of channels, opens up a new degree of freedom for realizing multichannel signal characterization using a single integrated photonic device.

We demonstrate on-chip frequency comb generation using cascaded electro-optic Mach-Zehnder modulators in silicon photonics. Our on-chip frequency comb produces 9 lines with a frequency spacing of 6.67 GHz and an amplitude variation $\lt3$ dB.

We present the design and use of myDALITE, a web-based learning platform that provides students with asynchronous peer instruction that can be used in- and out-of-class. Supporting active learning pedagogy, myDALITE engages students in 1) written explanation (rationales for their answers); 2) comparison of these rationales to those of peers; and 3) reflection on the quality of the rationales. Furthermore, myDALITE assignments provide teachers with the opportunity to see what their students are thinking, before and/or after classroom instruction.

We show how Error-Detection Tasks (EDT) are an effective way for students to practice giving peer feedback. In EDT, students are presented with a solved physics problem, prepared by a fictional in-class peer, containing one or more errors - algebraic, procedural, or conceptual. Students must identify and explain how to correct the error(s), as though they were explaining it to the “peer” who wrote the solution. EDTs have been developed for a web-based learning platform (myDALITE.org) that provides students with asynchronous peer instruction such that students can provide feedback and evaluate feedback from other students. Results show that students trained with EDT significantly outperform a control group in correctly identifying errors and providing more meaningful feedback to their fictional in-class peer.

We demonstrate 1-to-6 wavelength multicasting of a 22-GBaud 16-QAM single polarization ( $6\times 88$ Gb/s) signal based on four-wave mixing in a dispersion engineered silicon nanowire. All six multicast signals perform below the bit error rate forward error correction threshold of $3.8\times 10^{-3}$ , with a worst case power penalty of 8 dB. We compare our wavelength multicasting performance against the theoretical power transfer during a three-wave mixing process and show that the average power of degenerate idlers agrees with the predicted 6 dB difference with respect to that of nondegenerate idlers. When distinguishing the nonlinear conversion efficiency from the absolute idlers power at the output of the silicon nanowire, we also show the importance of the output grating coupler’s loss and how it impacts the multicasting performance, in conjunction with the four-wave mixing efficiency.

As educators and researchers in the field of photonics, we find what we do to be very exciting, and sharing this passion and excitement to our university students is natural to us. Via outreach programs and college research funding, a new college and university collaboration has broadened our student audience: photonics is brought into the college classroom and research opportunities are provided to college students. Photonics-themed active learning activities are conducted in the college Waves and Modern Physics class, helping students forge relationships between course content and modern communications technologies. Presentations on photonics research are prepared and presented by the professor and past college student-researchers. The students are then given a full tour of the photonics university laboratories. Furthermore, funds are set aside to give college students a unique opportunity to assist the college professor with experiments during a paid summer research internship.

When implemented correctly, active learning pedagogies increase student engagement with discipline content. In addition, there is accumulating evidence that they also positively impact the learning of this content. This is particularly relevant for teaching science disciplines because many students perceive science as being difficult to fully understand. However, an ongoing problem is that instructors have difficulty implementing active learning pedagogies effectively and therefore see no benefit to it. Without persistence or guidance, instructors can become discouraged and return to a more traditional style of teaching. We report on how the Faculty of Science at Vanier College is getting more instructors to engage in active learning pedagogies through mentoring and activity co-design.

© 2009-2012 IEEE. We demonstrate RF arbitrary waveform generation based on microwave photonic filtering. We use four-wave mixing in a silicon nanowire to increase the number of taps in an N-tap microwave photonic filter (MPF). Using a programmable optical filter, we can control the tap weights and, hence, the MPF response and corresponding generated waveform. We show uniform and apodized waveforms with four taps and seven taps with tunable central frequencies.

We demonstrate how to harness mode-selective excitation of nonlinear optical effects to perform simultaneous multi-channel RF spectrum analysis for both 640 GHz and 160 GHz waveforms using a single integrated silicon photonic device.

[EN] An optical true time delay line (OTTDL) is a basic photonic building block that enables many microwave photonic and optical processing operations. The conventional design for an integrated OTTDL that is based on spatial diversity uses a length-variable waveguide array to create the optical time delays, which can introduce complexities in the integrated circuit design. Here we report the first ever demonstration of an integrated index-variable OTTDL that exploits spatial diversity in an equal length waveguide array. The approach uses subwavelength grating waveguides in silicon-on-insulator (SOI), which enables the realization of OTTDLs having a simple geometry and that occupy a compact chip area. Moreover, compared to conventional wavelength-variable delay lines with a few THz operation bandwidth, our index-variable OTTDL has an extremely broad operation bandwidth practically exceeding several tens of THz, which supports operation for various input optical signals with broad ranges of central wavelength and bandwidth., We thank Prof. Michael Hilke for lending the VNA used in this work and Prof. Thomas Szkopek for discussions. We also thank Richard Bojko for fabrication of our integrated silicon photonic OTTDLs at the University of Washington Nanofabrication Facility (WNF), a member of the NSF National Nanotechnology Infrastructure Network. This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC), Fonds de Recherche du Quebec - Nature et Technologies (FRQNT), and the Royal Society.

Microwave photonic (MWP) systems exploit the advantages of photonics, especially with regards to ultrabroad bandwidth and adaptability, features that are significantly more challenging to obtain in the electronic domain. Thus, MWP systems can be used to realize a number of microwave signal processing functions including, amongst others, waveform generation and radio-frequency spectrum analysis (RFSA). In this paper, we review recent results on fiber and integrated approaches for simultaneous generation of multiple chirped microwave waveforms as well as multi-channel RFSA of ultrahigh repetition optical rate pulse trains.

—We propose and demonstrate photonic arbitrary waveform generation based on microwave photonic filtering. We show uniform and apodized waveforms, as well as tuning of the RF spectrum. We discuss how the photonic structure can be fully integrated in silicon photonics. Keywords—Microwave photonics, arbitrary waveform generation, silicon photonics I. I NTRODUCTION The development of photonic approaches for RF arbitrary waveform generation (RF-AWG) are of interest due to advantages of being tunable, reconfigurable, and compatible with fiber optic transmission [1]. Indeed, a number of photonic structures and techniques for RF-AWG have been demonstrated, including those based on nonlinear optical effects in fiber or semiconductor optical amplifiers, optical frequency comb generation, phase modulation-to-intensity modulation using discrimination filters, and microwave photonic filtering [2-6]. The field of microwave photonic filters (MPFs) is extremely rich and the design of MPFs with reconfiguration and/or tuning capabilities has been the subject of intense research. Many structures have been proposed and important results have been demonstrated [6]. MPFs employ typically discrete components resulting in bulky, benchtop implementations. To address issues related to compactness, stability, power consumption, and ultimately mass production for reduced cost, the development of integrated (single chip) MPFs will be significant. There have been several integrated MPFs and MPF systems reported in chalcogenide and silicon (including silicon nitride) [7-10]. Those based in silicon are especially attractive for their compatibility with CMOS processing. In this paper, we demonstrate RF-AWG based on microwave photonic filtering. We also discuss the integration of the various building blocks and the possibility for a fully photonic integrated circuit (PIC) equivalent. II. G

We provide the first demonstration of encoding-decoding two-dimensional wavelength-time bipolar codes for optical code-division multiple access systems with differential detection, including a verification of multiaccess interference rejection. We implement the all-optical encoders and decoders using commercially available wavelength-division-multiplexing components.

We report the first multiuser optical code-division multiple-access (OCDMA) system demonstrator with full clock and data recovery using a novel OCDMA receiver. We achieve receiver sensitivities of -19.1, -16.3, and -9.2 dBm for one, two, and three users, respectively, at a BER/spl les/10/sup -10/ using a 2/sup 20/-1 pseudorandom binary sequence. Our results show the viability of OCDMA as a transport technology for access networks.

We describe the use of various silicon photonic device technologies to implement microwave photonic filters (MPFs). We demonstrate four-wave mixing in a silicon nanowire waveguide (SNW) to increase the number of taps for MPFs based on finite impulse response filter designs. Using a 12 mm long SNW reduces the footprint by five orders of magnitude compared to silica highly nonlinear fiber while only requiring approximately two times more input power. We also demonstrate optical delays based on serial sidewall Bragg grating arrays and step-chirped sidewall Bragg gratings in silicon waveguides. We obtain up to 63 ps delay in discrete steps from 15 ps to 32 ps over a wide bandwidth range from 33 nm to at least 62 nm. These components can be integrated with other silicon-based components such as integrated spectral shapers and modulators to realize a fully integrated MPF.

26th IEEE Photonics Conference (IPC) -- SEP 08-12, 2013 -- Bellevue, WA, WOS: 000369918000203, We compare using nonlinear fiber to a silicon nanophotonic waveguide in implementing a reconfigurable microwave photonic filter. Additional taps are generated via four wave mixing and tap levels are controlled by a programmable filter., IEEE, Amer Chem Soc, Multidisciplinary Digital Publishing Inst, IEEE Cloud Comp, LioniX

We demonstrate error-free wavelength conversion of 16-QAM 28-GBaud (112 Gb/s) signals and 1-to-6 wavelength multicasting of 16-QAM 22-GBaud (6×88 Gb/s) signals based on four wave mixing in a dispersion engineered silicon nanowire.

Canadian Photonics Industry Consortium (CPIC);CMC Microsystems;INRS, Photonics North 2013 Conference -- 3 June 2013 through 5 June 2013 -- Ottawa, ON -- 101241, We describe the design and characterization of a silicon nanophotonic waveguide (SNW) and its use in a reconfigurable microwave photonic filter (MPF). The SNW is dispersion tailored for efficient on-chip four-wave-mixing. We use the onchip four-wave-mixing to increase the number of taps in our multiple tap delay line MPF. The tap levels are controlled by a programmable filter. Using a 12 mm long SNW reduces the footprint by five orders of magnitude compared to silica highly nonlinear fiber while only requiring approximately two times more input power. © 2013 SPIE.

We report the demonstration of mechanically induced long-period gratings in ZBLAN fibers. We also show preliminary results of an all-fiber Mach-Zehnder interferometer based on cascading these gratings.

We report the first demonstration of a long period grating in single mode ZBLAN fibers. The grating structure is mechanically induced by pressing a threaded rod onto a section of the fiber. A notch filter response is observed both near 1365 nm and 1525 nm. The advantages of the approach include tunability, repeatability and erasability.

We investigate the operating characteristics of a semiconductor fiber laser mode-locked at 10 GHz using a nonlinear optical loop mirror. We discuss the potential application for performing all-optical clock recovery.

We investigate the performance of a multi-user OCDMA system demonstrator with full CDR using a novel OCDMA receiver. We achieve sensitivities (BER

We demonstrate error-free wavelength conversion of 28 GBaud 16-QAM single polarization (112 Gb/s) signals based on four-wave mixing in a dispersion engineered silicon nanowire (SNW). Wavelength conversion covering the entire C-band is achieved using a single pump. We characterize the performance of the wavelength converter subsystem through the electrical signal to noise ratio penalty as well as the bit error rate of the converted signal as a function of input signal power. Moreover, we evaluate the degradation of the optical signal to noise ratio due to wavelength conversion in the SNW.

We examine the effects of encoder and decoder mismatch due to wavelength and time chip misalignments on the bit-error rate (BER) performance of two-dimensional (2D) wavelength--time optical code-division multiple access systems. We investigate several instances of misalignment in the desired user encoder and decoder as well as in the interfering user encoders. Our simulation methodology can be used to analyze any type of 2D wavelength--time code family as well as probability distribution for misalignment. For illustration purposes, we consider codes generated by use of the depth-first search algorithm and a Gaussian distribution for the misalignment. Our simulation results show that, in the case of a misalignment in either wavelength or time chip, the variance of the distribution for the misalignment must be below 0.01 for the corresponding degradation in the BER system's performance to be less than 1 order of magnitude compared with that when there is no mismatch between the encoders and decoders. The tolerances become even more strict when misalignments in both wavelength and time chips are considered. Furthermore, our results show that the effect of misalignment in wavelength (time chips) is the same regardless of the number of wavelengths (time chips) used in the codes.

We review recent work on all-optical signal processing in silicon photonics. In particular, we describe the integration of a nonlinear optical loop mirror in silicon-on-insulator for applications including wavelength conversion, NRZ-to-RZ modulation format conversion, and optical time-division de-multiplexing.