Brent E. Little

Micro-Resonator Frequency Comb Source based Time Domain Hilbert Transform

We demonstrate a temporal Hilbert transformer based on an integrated microresonator optical frequency comb source, and perform a temporal transform of a Gaussian pulse with a full-width half maximum of 0.12ns.

A Radio Frequency Channelizer based on Cascaded Integrated Micro-ring Resonator Optical Comb Sources and Filters

We report a broadband RF channelizer based on an integrated optical frequency Kerr micro-comb source, with an RF channelizing bandwidth of 90 GHz, a high RF spectral slice resolution of 1.04 GHz, and experimentally verify the RF performance up to 19 GHz. This approach to realizing RF channelizers offers reduced complexity, size, and potential cost for a wide range of applications to microwave signal detection.

High-order Radio Frequency Differentiation via Photonic Signal Processing with an Integrated Micro-resonator Kerr Optical Frequency Comb Source

We demonstrate the use of integrated micro-resonator based optical frequency comb sources as the basis for transversal filtering functions for microwave and radio frequency photonic filtering and advanced functions. Keywords—frequency comb, microwave, micro-resonator

Integrated Kerr comb-based reconfigurable transversal differentiator for microwave photonic signal processing

An arbitrary-order intensity differentiator for high-order microwave signal differentiation is proposed and experimentally demonstrated on a versatile transversal microwave photonic signal processing platform based on integrated Kerr combs. With a CMOS-compatible nonlinear micro-ring resonator, high quality Kerr combs with broad bandwidth and large frequency spacings are generated, enabling a larger number of taps and an increased Nyquist zone. By programming and shaping individual comb lines’ power, calculated tap weights are realized, thus achieving a versatile microwave photonic signal processing platform. Arbitrary-order intensity differentiation is demonstrated on the platform. The RF responses are experimentally characterized, and systems demonstrations for Gaussian input signals are also performed.

Optical square waves from a nonlinear amplifying loop mirror laser (Conference Presentation)

Optical square wave sources are particularly important for applications inxa0high speedxa0signal processing and optical communications. In most realizations, optical square waves are generated by electro-optic modulation,xa0dispersion engineering of mode-locked lasers,xa0polarizationxa0switching, or by exploiting opticalxa0bi-stabilityxa0and/or optical delayed feedback in semiconductor diode lasers, as well asxa0vertical-cavityxa0surface-emitting lasers (VCSELs). All such configurations are bulky andxa0cause significant timing jitters.xa0Here we demonstratexa0the direct generation of optical square waves from a polarization-maintaining figure-eight nonlinear amplifying loop mirror (NALM) configuration that uses an embedded high index glass micro-cavity as the nonlinear element.xa0Suchxa0a NALMxa0mimics the behavior of a saturable absorber and has been used to reach passivexa0mode-lockingxa0of pico- and even nano-second pulses.xa0In our method, the NALM, including a high-Qxa0micro-ringxa0resonator,xa0acts as an ultra-narrowband spectral filter and at the same time provides a large nonlinear phase-shift. Previously we have demonstratedxa0that such a configuration enables sufficient nonlinear phase-shifts for low-power narrow-bandwidth (~100 MHz FWHM) passive mode-locked laser operation.xa0Here we demonstrate the switching of stable optical square wave pulses from conventional mode-locked pulses by adjusting thexa0cavity properties.xa0In addition, the square wave signal characteristics, such as repetition rate andxa0pulse duration, can be also modified in a similar fashion. The source typically produces nanosecond optical square wave pulses with a repetition ratexa0of ~ 120 MHz atxa01550nm. In order to verify the reach of our approach, we compare our experimental results with numerical simulations using a delay differential equation model tailored for a figure-eight laser.

Invited Article: Enhanced four-wave mixing in waveguides integrated with graphene oxide

We demonstrate enhanced four-wave mixing (FWM) in doped silica waveguides integrated with graphene oxide (GO) layers. Owing to strong mode overlap between the integrated waveguides and GO films that have a high Kerr nonlinearity and low loss, the FWM efficiency of the hybrid integrated waveguides is significantly improved. We perform FWM measurements for different pump powers, wavelength detuning, GO coating lengths, and number of GO layers. Our experimental results show good agreement with theory, achieving up to ∼9.5-dB enhancement in the FWM conversion efficiency for a 1.5-cm-long waveguide integrated with 2 layers of GO. We show theoretically that for different waveguide geometries an enhancement in FWM efficiency of ∼20 dB can be obtained in the doped silica waveguides and more than 30 dB in silicon nanowires and slot waveguides. This demonstrates the effectiveness of introducing GO films into integrated photonic devices in order to enhance the performance of nonlinear optical processes.We demonstrate enhanced four-wave mixing (FWM) in doped silica waveguides integrated with graphene oxide (GO) layers. Owing to strong mode overlap between the integrated waveguides and GO films that have a high Kerr nonlinearity and low loss, the FWM efficiency of the hybrid integrated waveguides is significantly improved. We perform FWM measurements for different pump powers, wavelength detuning, GO coating lengths, and number of GO layers. Our experimental results show good agreement with theory, achieving up to ∼9.5-dB enhancement in the FWM conversion efficiency for a 1.5-cm-long waveguide integrated with 2 layers of GO. We show theoretically that for different waveguide geometries an enhancement in FWM efficiency of ∼20 dB can be obtained in the doped silica waveguides and more than 30 dB in silicon nanowires and slot waveguides. This demonstrates the effectiveness of introducing GO films into integrated photonic devices in order to enhance the performance of nonlinear optical processes.Yunyi Yang, Jiayang Wu, Xingyuan Xu, Yao Liang, Sai T. Chu, Brent E. Little, Roberto Morandotti, Baohua Jia, and David J. Moss Centre for Micro-Photonics, Swinburne University of Technology, Hawthorn, VIC 3122, Australia Department of Physics and Material Science, City University of Hong Kong, Tat Chee Avenue, Hong Kong, China. Xi’an Institute of Optics and Precision Mechanics Precision Mechanics of CAS, Xi’an, 710119, China. INSR-Énergie, Matériaux et Télécommunications, 1650 Boulevard Lionel-Boulet, Varennes, Québec, J3X 1S2, Canada. National Research University of Information Technologies, Mechanics and Optics, St. Petersburg, 197101, Russia. Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, China.

Integrated Kerr Comb-based Reconfigurable Transversal Differentiator for Microwave Photonic Signal Processing

An integrated reconfigurable transversal differentiator is achieved based on a microring resonator. The RF responses of different orders of differentiation are experimentally characterized. Systems demonstrations for Gaussian pulses are performed.

Optical intensity square root differentiator based on an integrated Kerr frequency comb source

We propose and experimentally demonstrate an optical intensity square root differentiator based on an integrated comb source. The proposed differentiator features full reconfigurablity and compact structure. Transmission responses and temporal characterization are also experimentally demonstrated.

Photonic microwave and RF signal processing based on optical micro-combs

We demonstrate the use of integrated micro-resonator based optical frequency comb sources as the basis for transversal filtering functions for microwave and radio frequency photonic filtering and advanced functions.

Four-Photon Entanglement Generation with Integrated Optical Frequency Combs

We demonstrate the generation of four-photon entangled quantum states with integrated optical frequency comb sources. We measure four-photon quantum interference with a visibility above 89%, and perform quantum state tomography revealing a fidelity above 64%.