Microwave and RF Applications for Micro-resonator based Frequency Combs

Photonic integrated circuits that exploit nonlinear optics in order to generate and process signals all-optically have achieved performance far superior to that possible electronically - particularly with respect to speed. We review the recent achievements based in new CMOS-compatible platforms that are better suited than SOI for nonlinear optics, focusing on radio frequency (RF) and microwave based applications that exploit micro-resonator based frequency combs. We highlight their potential as well as the challenges to achieving practical solutions for many key applications. These material systems have opened up many new capabilities such as on-chip optical frequency comb generation and ultrafast optical pulse generation and measurement. We review recent work on a photonic RF Hilbert transformer for broadband microwave in-phase and quadrature-phase generation based on an integrated frequency optical comb. The comb is generated using a nonlinear microring resonator based on a CMOS compatible, high-index contrast, doped-silica glass platform. The high quality and large frequency spacing of the comb enables filters with up to 20 taps, allowing us to demonstrate a quadrature filter with more than a 5-octave (3 dB) bandwidth and an almost uniform phase response.Comment: 10 pages, 6 figures, 68 references. arXiv admin note: substantial text overlap with arXiv:1512.0174

Half-panda ring resonator used to generate 100 MHZ repetition rate femtosecond soliton

Interferometric measurement techniques have been employed in research and industry for investigations into propagation behavior aspects of the optical solitons within semiconductor lasers. The half-PANDA ring resonator system introduced in this paper consists of an add/drop multiplex connected to a microring resonator on the right side, where the output powers can be controlled by specific parameters. The collision of dark and bright solitons occurs inside the system in which femtosecond (fs) optical solitons with 100 MHz repetition rate form the through and drop port outputs of the system. A trapping force is produced via the add port signals that constitute the input powers; thus the femtosecond optical soliton are generated and controlled within the half-PANDA ring resonator. The results of the soliton signals are obtained based on the iterative method technique in which a number of experimental and practical parameters are employed. These circumstances allow for manipulation of the trapping bandwidth by means of system parameter alterations. The input powers of the dark and bright solitons are 5.12 mW and 4 mW respectively. The full width at half maximum (FWHM) of the through and drop port output signals are 35 and 76 femtoseconds respectively correspond to 0.76 and 1.56 terahertz (THz) in frequency domain, where the repetition rate of the solitons is 100 MHz

Harnessing optical micro-combs for microwave photonics

In the past decade, optical frequency combs generated by high-Q micro-resonators, or micro-combs, which feature compact device footprints, high energy efficiency, and high-repetition-rates in broad optical bandwidths, have led to a revolution in a wide range of fields including metrology, mode-locked lasers, telecommunications, RF photonics, spectroscopy, sensing, and quantum optics. Among these, an application that has attracted great interest is the use of micro-combs for RF photonics, where they offer enhanced functionalities as well as reduced size and power consumption over other approaches. This article reviews the recent advances in this emerging field. We provide an overview of the main achievements that have been obtained to date, and highlight the strong potential of micro-combs for RF photonics applications. We also discuss some of the open challenges and limitations that need to be met for practical applications.Comment: 32 Pages, 13 Figures, 172 Reference

Ultra-high-linearity integrated lithium niobate electro-optic modulators

Integrated lithium niobate (LN) photonics is a promising platform for future chip-scale microwave photonics systems owing to its unique electro-optic properties, low optical loss and excellent scalability. A key enabler for such systems is a highly linear electro-optic modulator that could faithfully covert analog electrical signals into optical signals. In this work, we demonstrate a monolithic integrated LN modulator with an ultrahigh spurious-free dynamic range (SFDR) of 120.04 dB Hz4/5 at 1 GHz, using a ring-assisted Mach-Zehnder interferometer configuration. The excellent synergy between the intrinsically linear electro-optic response of LN and an optimized linearization strategy allows us to fully suppress the cubic terms of third-order intermodulation distortions (IMD3) without active feedback controls, leading to ~ 20 dB improvement over previous results in the thin-film LN platform. Our ultra-high-linearity LN modulators could become a core building block for future large-scale functional microwave photonic integrated circuits, by further integration with other high-performance components like low-loss delay lines, tunable filters and phase shifters available on the LN platform

Cavity-enhanced second harmonic generation via nonlinear-overlap optimization

We describe an approach based on topology optimization that enables automatic discovery of wavelength-scale photonic structures for achieving high-efficiency second-harmonic generation (SHG). A key distinction from previous formulation and designs that seek to maximize Purcell factors at individual frequencies is that our method not only aims to achieve frequency matching (across an entire octave) and large radiative lifetimes, but also optimizes the equally important nonlinear--coupling figure of merit $\bar{\beta}$, involving a complicated spatial overlap-integral between modes. We apply this method to the particular problem of optimizing micropost and grating-slab cavities (one-dimensional multilayered structures) and demonstrate that a variety of material platforms can support modes with the requisite frequencies, large lifetimes $Q > 10^4$, small modal volumes $\sim (\lambda/n)^3$, and extremely large $\bar{\beta} \gtrsim 10^{-2}$, leading to orders of magnitude enhancements in SHG efficiency compared to state of the art photonic designs. Such giant $\bar{\beta}$ alleviate the need for ultra-narrow linewidths and thus pave the way for wavelength-scale SHG devices with faster operating timescales and higher tolerance to fabrication imperfections

Graphene-Enhanced Optical Signal Processing

Graphene has emerged as an attractive material for a myriad of optoelectronic applications due to its variety of remarkable optical, electronic, thermal and mechanical properties. So far, the main focus has been on graphene based photonics and optoelectronics devices. Due to the linear band structure allowing interband optical transitions at all photon energies, graphene has remarkably large third-order optical susceptibility χ(3), which is only weakly dependent on the wavelength in the near-infrared frequency range. Graphene possesses the properties of the enhancement four-wave mixing (FWM) of conversion efficiency. So, we believe that the potential applications of graphene also lies in nonlinear optical signal processing, where the combination of its unique large χ(3) nonlinearities and dispersionless over the wavelength can be fully exploited. In this chapter, we give a brief overview of our recent progress in graphene-assisted nonlinear optical device which is graphene-coated optical fiber and graphene-silicon microring resonator and their applications, including degenerate FWM based tunable wavelength conversion of quadrature phase-shift keying (QPSK) signal, two-input optical computing, three-input high-base optical computing, graphene-silicon microring resonator enhanced nonlinear optical device for on-chip optical signal processing, and nonlinearity enhanced graphene-silicon microring for selective conversion of flexible grid multi-channel multi-level signal

The analysis of phase, dispersion and group delay in InGaAsP/InP microring resonator

The Vernier operation with signal flow graph (SFG) is a graphical approach for analyzing the intricate photonic circuits mathematically and quick calculation of optical transfer function. Analysis of a cascaded microring resonators (CMRR) made of InGaAsP/InP semiconductor is presented using the signal flow graph (SFG) method which enables modelling the transfer function of the passive CMRR. These passive filters are mostly characterized by their frequency response. The theoretical calculations of the system is performed by the Vernier effects analysis. Two MRRs with radius of 100 μm which are vertically coupled together are used to generate resonant peaks. Here, the phase, dispersion and group delay of the generated signals are analyzed

Ultrafast all-optical ALU operation using a soliton control within the cascaded InGaAsP/InP microring circuits

A dark-bright soliton conversion is used to perform the two arithmetic logic unit operations namely adder and subtractor operations. The advantage of the system such as power stability, non-dispersion and the dark-bright soliton phase conversion control can be obtained. The input source into the circuit is the bright soliton pulse, with the pulse width of 35 ps, the peak power at 1.55 µm is 1 mW. By using the dark-bright soliton conversion pair, the generated logic bits can be controlled, and the secure bits can be achieved. The simulation results show the output signal with a minimum loss of only 0.1% with respect to a low input power of 1 mW, and ultra-fast response time of about 1 ps can be achieved. It gives the ultra-high bandwidth of more than 40 Gbits−1. The circuit composes six microring resonators made of InGaAsP/InP material with smaller ring radii of 1.5 µm, and the total physical scale of the circuit less than 100 µm2