Mustafa Hammood | The University of British Columbia (original) (raw)

Papers by Mustafa Hammood

Conference on Lasers and Electro-Optics, May 5, 2019

We use long, spiral contra-directional couplers (contra-DCs) to make optical add-drop filters wit... more We use long, spiral contra-directional couplers (contra-DCs) to make optical add-drop filters with 30 dB extinction ratios and 12.2 nm bandwidths, and avoid some of the effects caused by fabrication non-uniformities in long, straight contra-DCs. © 2019 The Author(s)

We experimentally demonstrate and compare contra-directional-coupler-based filters in a compact s... more We experimentally demonstrate and compare contra-directional-coupler-based filters in a compact series cascaded configuration and an ultra-compact, fabrication variation tolerant, parallel stacked configuration. Both filters are shown to be similar in performance as regards their sidelobe suppression ratios and bandwidths.

Vernier effect, series-coupled microring resonators (MRRs) are used to extend the free-spectral-r... more Vernier effect, series-coupled microring resonators (MRRs) are used to extend the free-spectral-range (FSR) of MRRs. In this work we demonstrate integrating two MRRs in a compact Vernier configuration (compact as compared to previously demonstrated Vernier effect devices). our design was realized by using two waveguide crossings to form a major, outer ring that was coupled to a minor ring nested within the major ring. The ratio of the path length of the major ring to the path length of minor ring was 5:2. The spectral response of the device had an FSR of 27.94 nm, a drop port 3 dB bandwidth of 0.87 nm, a minimum extinction ratio of 16.1 dB, a minimum interstitial peak suppression of 10.6 dB, and a footprint of only 540 μm2 .

We propose and demonstrate compact, add-drop filters using cladding-modulated, sub-wavelength gra... more We propose and demonstrate compact, add-drop filters using cladding-modulated, sub-wavelength grating (SWG), contra-directional couplers (CDCs) on a silicon-on-insulator platform. In our device, two asymmetric SWG waveguides, integrated with periodically loaded Bragg segments along the sides of the waveguides, are used to achieve contra-directional coupling between the fundamental and next higher-order transverse electric modes of the two-SWG-waveguide system. We present results for a 286.8-µm-long CDC that has a 3 dB bandwidth of 13.4 nm at the drop-port with a low excess loss of 0.8 dB. This device also has an 11.5-nm region at the through-port over which the extinction ratio is greater than 40 dB.

Optics Letters, Dec 11, 2018

A silicon-on-insulator (SOI), bandwidth (BW)-tunable, free-spectral-range (FSR)-free, microring r... more A silicon-on-insulator (SOI), bandwidth (BW)-tunable, free-spectral-range (FSR)-free, microring resonator (MRR)-based filter is experimentally demonstrated. The device achieves an FSR-free response at its through and drop ports by using a grating-assisted coupler in one coupling region of the MRR and achieves a non-adjacent channel isolation, (nAi), for 400 GHz WDM, greater than 26.7 dB. A thermally tunable Mach-Zehnder Interferometer-based coupling scheme is also utilized to compensate for fabrication variations and enable the BW tunability of the filter. The BW of the filter can be continuously tuned from 25 to 60 GHz while maintaining an nAi greater than 26.7 dB.

Optics Letters, Oct 2, 2019

We report on broadband, flat-top, optical add-drop filters using apodized, sub-wavelength grating... more We report on broadband, flat-top, optical add-drop filters using apodized, sub-wavelength grating contradirectional couplers (SWG CDCs) on a silicon-on-insulator platform. In our device, two asymmetric SWG waveguides, having corrugation-apodized Bragg gratings, are used to couple light contradirectionally between the fundamental and next higher-order transverse electric modes of a two-waveguide system. We demonstrate an apodized, SWG CDC that has a flat-top, drop-port response with a 3 dB bandwidth of 32.6 nm, a sidelobe suppression ratio of 19 dB, and a low excess loss of 0.26 dB. We also demonstrate series-cascaded, apodized, SWG CDCs that have square-shaped, drop-port responses with 3 dB bandwidths >30 nm, sidelobe suppressions >50 dB, and low excess losses <0.85 dB.

In this work, we experimentally demonstrate a FSR-free, MRR-based, coupling modulator that integr... more In this work, we experimentally demonstrate a FSR-free, MRR-based, coupling modulator that integrates a bent, grating-based contra-directional-coupler (contra-DC) into a microring cavity to achieve an FSR-free response at its through port. Our modulator suppresses the amplitude response at all but one resonance, operating mode (hence, has an FSR-free response). In our modulator, coupling modulation is used and is achieved by modulating a relatively short, 210 μm long, p-n junction phase-shifter in a two-point coupler (which forms the drop-port coupler of the MRR). We demonstrate open eyes at 2.5 Gbps and discuss how the effects of DUV lithography on the contra-DC limited the electro-optic bandwidth of the fabricated modulator to 2.6 GHz. In these proceedings, we also cover details of the device design and the small and large signal characterization of the device, including an analysis of the effect of lithography on the “as-fabricated" device performance. We also discuss how to significantly improve the electro-optic bandwidth in future implementations by accounting for these lithographic effects in the device design flow and layout.

IEEE Journal of Selected Topics in Quantum Electronics, Mar 1, 2020

We demonstrate a method to predict the photolithography effects of a 193 nm deep ultraviolet (DUV... more We demonstrate a method to predict the photolithography effects of a 193 nm deep ultraviolet (DUV) process, and we build a lithography model using physical measurements on a fabricated test pattern. Our model accurately predicts the proximity and smoothing effects that are characteristic of DUV lithography. We verify the accuracy of the model by visually inspecting the fabricated test patterns and comparing them to the predicted ones. Additionally, using predicted shapes, we compare experimental measurements on a benchmark device (the contra-directional coupler) against those of our predicted, computed responses. Our predictions show good agreement with the fabricated results using both verification methods. Lastly, we illustrate the design-formanufacturability enabled by our model by demonstrating a design correction method for the contra-directional coupler that improves its compatibility with the DUV process.

Optics Letters, Jan 15, 2019

In this work, we present optical add/drop multiplexer (OADM) filters for coarse wavelength-divisi... more In this work, we present optical add/drop multiplexer (OADM) filters for coarse wavelength-division-multiplexing (CWDM) systems with high sidelobe suppressions that result in high adjacent channel isolations (Ai). The filters are realized by using a compact, series-cascaded configuration of apodized, contradirectional-coupling-based filters. We experimentally demonstrate a device with a measured Ai of 53 dB (these devices hold the promise of achieving even higher Ais). While having large Ais, our devices have the wide bandwidths and low insertion losses required for CWDM applications. In addition, our demonstrated OADM has a nearly constant group delay, which results in low dispersion in the passband.

We propose a microring modulator in which the free spectral range is eliminated by using a bent, ... more We propose a microring modulator in which the free spectral range is eliminated by using a bent, contra-directional-coupler to couple light into and out of the ring and in which the extinction ratio and bandwidth are tuned using a secondary, two-point coupler.

2022 IEEE Photonics Conference (IPC), Nov 1, 2022

We demonstrate an optical add-drop multiplexer on the silicon-on-insulator platform with a 3 dB b... more We demonstrate an optical add-drop multiplexer on the silicon-on-insulator platform with a 3 dB bandwidth of 6.3 nm, an ultra-high adjacent channel isolation of 58 dB, an insertion loss of 0.8 dB, and a footprint of only 1882 μm2.

We present a wideband, flat-top, optical add-drop filter using an apodized sub-wavelength-grating... more We present a wideband, flat-top, optical add-drop filter using an apodized sub-wavelength-grating contra-directional coupler on a silicon-on-insulator platform. Our device achieves a >30 nm wide, flat-top drop-port response, centered at 1545 nm, with an extinction ratio >20 dB.

Contra-directional couplers are proposed as optical pump reject filters with the potential to ach... more Contra-directional couplers are proposed as optical pump reject filters with the potential to achieve over 100 dB extinction ratios for on chip photon-pair sources. A scheme for these filters to enable reusing the pump laser for multiple microring resonator, photon-pair sources is presented.

We present a four-channel, silicon-photonic, wavelength multiplexer-demultiplexer made using casc... more We present a four-channel, silicon-photonic, wavelength multiplexer-demultiplexer made using cascaded contra-directional couplers with adjacent and nonadjacent channel isolations of at least 37 dB and 45 dB, respectively. The device’s maximum insertion-loss is 0.72 dB.

Optics Letters, Jul 23, 2021

We present the designs, theory, and experimental demonstrations of ultra-broadband, optical add–d... more We present the designs, theory, and experimental demonstrations of ultra-broadband, optical add–drop filters on the silicon-on-insulator platform, realized using period-chirped contra-directional couplers. Our fabricated devices have ultra-broad 3 dB bandwidths of up to 11 THz (88.1 nm), with flat-top responses at their drop ports. All of our devices were fabricated using a commercial, CMOS-compatible, 193 nm deep-ultraviolet lithography process. By using lithography-prediction models, the measured bandwidths, insertion losses, central wavelengths, and extinction ratios of our devices are all in good agreement with our predicted, simulated results. Such filters are necessary for photonic integrated circuits to operate over multiple optical bands.

We propose a Mach-Zehnder interferometer-assisted coupling-based, microring modulator that achiev... more We propose a Mach-Zehnder interferometer-assisted coupling-based, microring modulator that achieves a free spectral range free response by integrating a bent, contra-directional-coupler into the ring cavity. This design enables high capacity microring-based dense wavelength division multiplexing transmitter systems.

Optics Letters, May 25, 2021

Seventeenth Conference on Education and Training in Optics and Photonics: ETOP 2023

Optics Letters

We demonstrate a method to emulate the optical performance of silicon photonic devices fabricated... more We demonstrate a method to emulate the optical performance of silicon photonic devices fabricated using advanced deep-ultraviolet lithography (DUV) processes on a rapid-prototyping electron-beam lithography process. The method is enabled by a computational lithography predictive model generated by processing SEM image data of the DUV lithography process. We experimentally demonstrate the emulation method’s accuracy on integrated silicon Bragg grating waveguides and grating-based, add-drop filter devices, two devices that are particularly susceptible to DUV lithography effects. The emulation method allows silicon photonic device and system designers to experimentally observe the effects of DUV lithography on device performance in a low-cost, rapid-prototyping, electron-beam lithography process to enable a first-time-right design flow.