On-chip optical pulse shaper for arbitrary waveform generation

Optical arbitrary waveform generation (OAWG) plays a critical role in many applications, such as generating optical ultra-wide band (UWB) signal, optical pulse radar, all-optical temporal differentiator, and test of optical communication system. Although lots of OAWG schemes were reported using mature fiber grating techniques, one of the most promising solutions is prone to be the miniaturization and integration with photonic integrated circuits, such as using indium phosphide (InP) platform, silica on silicon, silicon nitride or silicon platform. In this talk, we review our recent progress on some OAWG schemes using silicon platform and their applications in photonic computing. First, we report an OAWG and high-order photonic differentiator based on a four-tap FIR silicon integrated circuit. By thermally controlling the amplitude and phase of each tap, we obtain several typical waveforms such as triangular waveform, sawtooth waveform, square waveform and Gaussian waveform, etc. Furthermore, we demonstrate first-, second- and third-order differentiation based on the optical pulse shaper, whose spectra were tailored to the transfer functions of temporal differentiators. Especially, our scheme can switch the differentiator patterns from first- to third-order freely on a fixed photonic chip, and this is unable in our previous works such as cascaded microrings or cascaded Mach-Zehnder interferometers (MZIs). Second, we demonstrate radio-frequency arbitrary waveform generation using temporal synthesis. We compare two schemes of cascaded microring resonators and finite impulse response. There functional photnic chip has only millmeter size, low power consumption, and high frequency response. Third, we will demonstrate an OAWG scheme based on superposition of differentiated waveforms. Compared to the first two schemes, this one shows a more compact size and a more flexible operation.

We demonstrate optical arbitrary waveform generation and characterization using spectral line-by-line control with high resolution grating based pulse shapers. Such integrated capabilities are the enabling techniques for high-fidelity optical arbitrary waveform generation.

Dynamic optical arbitrary waveform generation and detection in InP photonic integrated circuits for Tb/s optical communications

This paper presents the concept of an optical transmitter based on optical arbitrary waveform generation (OAWG) capable of synthesizing Tb/s optical signals of arbitrary modulation format. Experimental and theoretical demonstrations in this paper include generation of data packet waveforms focusing on (a) achieving high spectral efficiencies in quadrature phase-shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM) modulation formats, (b) generation of complex data waveform packets used for optical-label switching (OLS) consisting of a data payload and label on a carrier and subcarrier, and (c) repeatability and accuracy of duobinary (DB) data packet waveforms with BER measurements. These initial demonstrations are based on static OAWG, or line-by-line pulse shaping, to generate repeated waveforms of arbitrary shape. In addition to experimental and theoretical demonstrations of static OAWG, simulated results show dynamic OAWG, which involves encoding continuous data streams of arbitrary symbol sequence on data packet waveforms of arbitrary length.

This paper experimentally demonstrates flexible-bandwidth networking by splitting a 500-GHz waveform generated by optical arbitrary waveform generation into its two tributary spectral slices using a liquid-crystal spatial light phase modulator as a wavelength selective switch.

This paper discusses THz bandwidth information and signal processing based on RF-photonic technologies. In particular, we will emphasize integrated circuit approaches to RF-photonics where highly stable THz bandwidth information and signal processing can take place. We will demonstrate THz signal generation by optical arbitrary waveform generation (OAWG), and will describe its inverse process, optical arbitrary waveform measurement (OAWM). Further, we will discuss an RF-photonic lattice filter useful for optical equalization and other THz signal processing replacing traditional electronic digital signal processing which cannot currently scale to THz. The paper will also cover future prospects for the THz information and signal processing by integrated RF-photonic methods.

Recently, we proposed the concept of a microring-based optical pulse train generator, which uses a series of microrings coupled to a waveguide and time-interleaves a trigger pulse propagating on this waveguide to generate an optical pulse train. When each ring is electrically modulated, this electronic-photonic integrated circuit (EPIC) can be used for optical arbitrary waveform generation (OAWG) and ultrafast electro-optic (EO) modulation. This paper presents the proof-of-concept experimental demonstration of this technique with two four-stage chip prototypes fabricated on silicon-on-insulator (SOI) substrate. Device fabrication and testing of the chip prototypes are presented. The measurement results show that from a 20-ps-wide input trigger pulse, two circuits generate four sequential pulses at the output with a constant stage delay of 55 ps and 30 ps respectively, which translate into pulse repetition rates of 18 GHz and 33 GHz.

We demonstrate optical arbitrary waveform generation using self-injection-locked Kerr micro-combs that are synchronized to an electronic clock via a closed-loop control. We show 200 GBd 32QAM transmission and FMCW LiDAR with an unprecedented resolution of 0.75 mm.

Optical pulse shaping is a widely adopted technique in which intensity and phase manipulation of optical spectral components allow synthesis of user-specified ultrashort pulse fields according to a Fourier transform relationship. Furthermore, mode-locked lasers producing combs of frequency-stabilized spectral lines have resulted in revolutionary advances in frequency metrology. However, until recently pulse shapers addressed spectral lines in groups at low spectral resolution. Line-by-line pulse shaping, in which spectral lines are resolved and manipulated individually, leads to a fundamentally new regime for optical arbitrary waveform generation (O-AWG) in which the advantages of pulse shaping and of frequency combs are exploited simultaneously. Bringing pulse shaping and frequency combs together allows O-AWG with both a controllable ultrafast time structure and long-term coherence. Intuitively, full control of individual frequency comb lines require (1) frequency-stabilized sources to generate stable spectral lines and (2) high-resolution pulse shapers to resolve and control individual spectral lines. O-AWG promises a broad impact both in optical science, allowing for example coherent control generalizations of comb-based time-frequency spectroscopies, and in technology, enabling new truly coherent multiwavelength processing concepts for spread spectrum light wave communications and lidar. This chapter is organized as follows. The significance of spectral line-by-line shaping will be first compared to conventional pulse shaping. Shaper setup will be explained. Line-by-line shaping examples using an actively mode-locked fiber laser will be presented in the second section. Impact of frequency comb frequency instabilities over line-by-line shaped waveforms are explored in the third section. In the fourth section, shaping examples using alternative comb sources are given.

We demonstrate fast optical arbitrary waveform generation by using MEMS digital micro-mirror arrays. Experimentally, we obtain ~120MHz waveforms that can be controlled by using 1024×768 mirror arrays. 1GHz waveforms reconfigurable in 1μs are also achievable.

We demonstrate fast optical arbitrary waveform generation by using the MEMS digital micromirror arrays. The desired radio-frequency waveforms are achieved by properly shaping the spectrum of the broadband optical source via using micromirror arrays as a digital spatial light modulator preceded by wavelength-to-time mapping through the dispersive medium. We obtain up to 280-MHz sawtooth and 200-MHz square waveforms that can be controlled by using 1024 × 768 mirror arrays in the preliminary experimental results. Based on currently available digital mirror technologies, we estimate that arbitrary waveforms up to 1-GHz rate and reconfigurable in ~ 30 μs are achievable by using the proposed approach.

We propose an optoelectronic arbitrary radar waveform generator. It permits to generate predefined electrical waveforms according to radar specifications by driving phase and amplitude distributions of optically carried microwave signals. The control of amplitudes and phases of each radar spectrum frequency component is optically achieved by spatial light modulators (SLM). We present and experimentally demonstrate two ways to achieve the kilohertz high resolution between the frequency components of a radar signal at 7.1 GHz central frequency.

We demonstrate a compact monolithically-integrated InP optical arbitrary waveform generator, consisting of an arrayed waveguide grating pair with 10 GHz channel spacing, 10 high-speed optical amplitude modulators, and 10 high-speed optical phase modulators.

Advances in high repetition-rate femtosecond laser technology for optical arbitrary waveform generation will be described. Combs spanning two octaves, from 500nm to 2μm, based on GHz modelocked Ti:sapphire and erbium-fiber lasers, have been carrier-envelope stabilized and frequency referenced.

A monolithically integrated InP chip for optical arbitrary waveform generation (OAWG) and/or pulse-coding/decoding is demonstrated using a 20-GHz AWG pair and 10 high-speed phase modulators. The fabrication and performance of the InP chip will be presented.