WOMBAT 2015 Tutorial

Transcription

1 WOMBAT 2015 Tutorial

2 Stimulated Brillouin scattering Eggleton et al,. Adv. Opt. Photon 5 (2013) Applications: Fiber sensing Narrow linewidth laser Slow light/ delay line RF and optical filtering Microwave oscillator Microwave signal processing Microwave photonic applications of Brillouin Cavity optomechanics scattering Applications: Quantum optical measurement Displacement sensing Tunable optical filter Slow light/ delay line Optomechanical oscillator Bao et al,. Sensors 11 (2011) Metcalfe, App. Phys. Rev 1 (2014) Aspelmeyer et al., Rev. Mod Phys. 86 (2014)

3 Fundamentals of Microwave Photonics Stimulated Brillouin Scattering Applications: Bandpass and bandstop filters Tunable delay lines and phase shifters Low noise microwave oscillators Future of SBS microwave photonics

4 Microwave photonics

5 Microwave photonics (MWP): manipulation of RF signals using photonic techniques/components Capmany and Novak, Nat. Photon 1 (2007) Seeds and Williams, J. Lightwave Technol.24 (2006) Yao, J. Lightwave Technol. 27 (2009) Marpaung et al., Laser Photon. Rev. 7 (2013) vs. Heavy (copper, 567 kg/km) High loss(190 6 GHz) Rigid and large cross section Lightweight Low loss(0.25 db/km) Very flexible

6 Radio over fiber Antenna remoting Filtering Phase shifter, tunable delay Ultra-wideband (UWB) Low phase noise synthesizer Spectrum analyzer IFM receiver

7 E/O conversion O/E conversion f = 0 f =p f = 0 Optical frequency Intensity modulation (IM) Optical frequency Phase modulation (PM) LS Optical frequency Single sideband (SSB) modulation f = 0 f =Df Challenges Optical frequency Complex modulation E/O and O/E conversion losses Laser phase and intensity noise (RIN) Nonlinear distortion Photodetector shot and thermal noise

8 E/O conversion O/E conversion Figures of merit Link gain RF to RF loss (typical:-30 db, good: ~ 0 db ) Noise figure SNR in/snr out (typical: 30 db, good: <10 db) Dynamic range margin of noise and distortion (typical: db, good >110 db)

9 Functionalities filtering delay frequency conversion Application Spectrally crowded environments Wireless communications (5G) Radar and EW

10 Power Functionalities filtering delay frequency conversion Application Spectrally crowded environments Wireless communications (5G) Radar and EW Solution Interference mitigation and filtering Interferer Frequency agile Tunable MWP interferer filter Signal Radio frequency

11 Functionalities filtering delay frequency conversion Application Satellite communications On-board wifi and live television Solution Tunable true time delay Phased array antenna

12 AWG (Purdue) Silicon modulator, WGs Optical beamformer (U.Twente & LioniX) Si 3 N 4 Passive WGs, thermal tuners Discriminator filters (UPV) InP WGs, thermal tune, BPD OEO (OEWaves) LiNbO 3 WGMR, electronics Marpaung et al, Laser Photonics Rev. 7, No. 4, (2013)

13 Stimulated Brillouin Scattering

14 Stimulated Brillouin Scattering (SBS) One of the strongest nonlinear optical effects Results from a coherent interaction between vibrations and electromagnetic waves The fundamental physical effects of the interaction are: Electrostriction: The photo-elastic effect: Electric field causes material compression Compressive strain causes change in refractive index [Light influences sound] [Sound influences light] Robert W. Boyd, Nonlinear Optics, San Diego, CA: Academic press

15 Stimulated Brillouin Scattering (SBS) The main effect of SBS is to resonantly excite an acoustic grating, which back-reflects the pump at exactly the acoustic frequency W. Intensity compresses material (electrostriction) waveguide Pump 1 w 1 Doppler effect: Pump reflected, down-shifted to w 2 Compression Excites creates acoustic index wave grating (photoelasticity) frequency W Pump 2 w 2 w= 2 =w w 11 - W Robert W. Boyd, Nonlinear Optics, San Diego, CA: Academic press Eggleton et al,. Adv. Opt. Photon 5 (2013) 11/12/12 15

16 W W G B Gain (Stokes) Slow light w p Loss (anti-stokes) Fast light w SBS leads to a narrow Stokes peak in the counter-propagating direction The Brillouin shift W is determined by the acoustic wave frequency The linewidth is determined by the acoustic lifetime (~ 9 ns for silica) W ~ 7-11 GHz Typical values (Silica) G B ~ MHz Kramers-Kroenig relation: gain resonance refractive index change sharp amplitude and phase (delay) responses 11/12/12 16

17 First theoretical predictions 1,2 First demonstration of SBS 3 SBS in liquids 4 SBS in gases 5 On-chip SBS 10 SBS in silicon 12 Invention of the laser Year of discovery 1. Brillouin, Annals of Physics 17, 88, (1922) 2. Mandelstahm, Rus. J. Phys. Chem (1926) 3. Chiao et al. Phys. Rev. Letters 12, 592 (1964). 4. Brewer et al. Phys. Rev. Letters 13, 334 (1964). 5. Hagenlocker et al. Appl. Phys. Letters 7, 236 (1965) 6. Ippen et al. Appl. Phys. Lett. 21, 539 (1972) 7. Hill et al., App. Phys. Lett, 28 (1976) 8. Dainese et al. Nature Physics 2, 388 (2006) 9. Grudinin et al. Phys. Rev. Lett. 102, (2009) 10. Pant et al. Opt. Exp. 19, 8285 (2011) 11. Lee et al. Nat. Photon. 6, 369 (2012) 12. Shin et al. Nature Comm. 4, (2013). SBS in optical fibres 6 SBS on chip-scale devices First Brillouin laser 7 SBS in PCF 8 SBS in WGM resonators 9 SBS in wedge resonators 11 High-Q resonators Waveguides with large Brillouin gain Eggleton et al,. Adv. Opt. Photon 5 (2013)

18 On-chip SBS is challenging because the waveguides are very short. The gain is g 0 = Brillouin gain coefficient P p = Pump power L eff = Waveguide length A eff = optical mode area How to get enough gain in a chip scale device? 1) Material with high refractive index 2) Small mode area cladding 3) Low loss optical waveguides 4) Good opto-acoustic overlap Guiding/confinement of acoustic mode Determined by acoustic velocity in materials x y z Core Pant et al., Opt. Express 19 (2011) Poulton et al. JOSA B 30 (2013)

19 7 cm Chalcogenide waveguide: High index material As 2 S 3 (n~2.45, g 0 ~n 8 ) Small mode area (A eff ~ 2.3 µm 2 ) Low propagation loss (~0.2 db/cm) Large overlap of acoustic and optical modes Eggleton et al., Nature Photonics, (2011) v IPG ~ 1500 m/s v chalc ~ 2600 m/s v silica ~ 6000 m/s Key parameters: g 0 ~0.74*10-9 m/w (~100 x silica) W ~ 7.7 GHz G B ~ 34 MHz 16 db gain for 300 mw pump Pant et al., Opt. Express 19 (2011)

20 Silicon has high refractive index But no acoustic confinement in Si core Phonon lifetime is very short for small waveguides Poulton et al. JOSA B 30 (2013) Si 3 N 4 membrane for acoustic confinement Forward SBS Low gain ( <1 db) (n =3.48) (n =1.45) SOI waveguide Si (v a ~ 8000 m/s) (v a ~ 6000 m/s) SiO 2 Phonon leakage Shin et al, Nature Communications. 4 (2013) Breakthrough in SBS on chip Under etched silicon Forward SBS with ~4 db of gain

21 Application: filtering

22 Power Gain Loss RF out On chip SBS bandpass filter RF Frequency Phase modulator RF in Probe SBS medium Pump 2-12 GHz tuning 20 db extinction SBS gain MHz tunable bandwidth Df = ±p f = 0 Byrnes et al., Opt. Express Optical 20, frequency (2012) > 50 db extinction 6 MHz 3-dB width 11/12/12 Pagani and Shania., (unpublished) Zhang et al., IEEE Photon. Tech. Lett. 23 (2011) 22

23 Broad reconfigurable bandwidth (tens of MHz-to GHz) Flat passband Sharp and high extinction Stern et al., Photon. Res. 2 (2014) Polarization pulling to enhance filter suppression Pump sweeping for broad SBS Result : 44 db selectivity, 250 MHz -1 GHz tunable bandwidth 3 db passband flatness 11/12/12 23

24 Electrical comb for SBS pump Digital feedback for shape control Non-uniform pump spacing to mitigate FWM improve flatness Dual fiber stage to limit SRS and FWM improve selectivity 50 MHz to 4 GHz tunable bandwidth > 40 db suppression up to 2 GHz width ~ 1 db passband flatness Improve SNR Wei et al., Opt. Express 22 (2014) Wei 11/12/12 et al., IEEE Photon. Tech. Lett.. 27 (2015) 24

25 Power Gain Loss RF out Notch SSB modulator Probe SBS medium Pump SBS loss (anti-stokes) RF Frequency RF in Optical frequency 2-8 GHz tuning 20 db extinction 120 MHz 3-dB width (FWHM) High pump power (350 mw) 11/12/12 Morrison et al., Opt. Comm. 313 (2014) 25

26 Notch attenuation 3-dB Bandwidth Desired properties High peak attenuation (>50 db) High resolution (FWHM ~ 10 MHz) Large frequency tuning (tens GHz) Bandwidth reconfigurability State-of-the-art RF filter RF Frequency M. Rasras, J. Lightwave Technol. (2009) IMWP filter SOI ring Rejection 30 db FWHM 910 MHz Tuning 12 GHz Attenuation >50 db Bandwidth ~ 10 MHz Tuning: 3-4 GHz B. Kim, IEEE Trans. Elect. Dev. (2013)

27 Power Power Input RF signal Novel MWP filter Output RF signal Notch RF frequency Laser EO modulator SBS gain filter Photodetector RF Frequency f = 0 f =Df Df = ±p f = 0 LS US LS US Amplitude matching Optical frequency Phase cancellation Optical frequency Filter response Phase and amplitude control Phase and amplitude filter

28 Conventional SSB G = 1 db Rejection: 1 db Conventional SSB G = 20 db Rejection: 20 db Pump = 350 mw Novel filter G = 0.8 db Rejection: 55 db Pump = 8 mw D. Marpaung et al, Postdeadline paper Frontiers in Optics 2013 FW6B

29 2900% fractional tuning Q= 375 at 30 GHz D. Marpaung et al., Optica, 2, (2015)

30 Conventional filter Cancellation filter D. Marpaung et al., Optica, 2, (2015)

31

32 Application: delay and phase shift

33 Extreme broadening: 25 GHz bandwidth slow light Ultra-long delay: High gain SBS 10.9 ps delay Song et al., Opt. Lett. 32 (2007) On chip SBS slow light Song et al., Opt. Lett. 30 (2005) Analog applications 230 ps delay 1 GHz bandwidth Pant et al., Opt. Lett. 37 (2012) Zadok et al., IEEE Photon. Tech Lett. 19 (2007)

34 Problem: Applications require tunable large delays (~ns), large bandwidths (~GHz), high carrier frequency (microwave, mm-wave) But it is difficult to achieve a (1) tunable, (2) large slope (3) wide band linear phase response (w) Real phase response True-time-delay bandwidth Ideal phase response Actual phase Desired phase w c w c w c ww w c c c w RF w RF w RF w Burla et al., Opt. Express 19(22) (2011)

35 100 MHz delay bandwidth 0.03 ns to 9.9 ns tunable delay 300 o carrier phase tuning Chin et al., Opt. Express 18 (2010)

36 Phase Magnitude Sideband Carrier Optical signal spectrum: ω c ω RF ω c ω RF frequency response SBS pump spectrum: ω p2 Ω B Ω B RF frequency Amplitudes Full tuning cancel range (360 o ) 3 db ωamplitude p1 fluctuations Bandwidth limited to 2W B SBS phase shift: Loayssa & Lahoz, IEEE Photon. Tech Lett. 18 (2006) Phases add up ω RF frequency

37 Two degrees of freedom: amplitude and phase Ultra-wideband operation: 1 31 GHz Record-low amplitude fluctuations (< 0.5 db) Pagani, et al., Opt. Lett., 39 (2014)

38 Application: signal generation

39 Silica on silicon wedge resonator Q = 875 million FSR matched to SBS shift Narrow linewdith SBS laser H. Lee, et al., Nat. Photon, 6 (2012) 1 st and 3 rd Stokes beating to generate microwave frequency (~ 21 GHz) Electronic frequency division to achieve lower frequencies Low phase noise, comparable to commercial RF synthesizers J. Li, et al., Nat. Commun. (2013)

40 Future direction

41 Computer-controlled smart RF filter with high performance

42 1-30 GHz continuous frequency tuning Tunable notch extinction Tunable filter resolution Tunable bandpass

43 Marpaung et al., Nonlinear integrated microwave photonics, Journal of Lightwave Technol. 32 (invited, 2014)

44 AOM operating at 10 GHz Reconfigurable filtering (?) Link and interaction with SBS Potential for wider comb (?) Miniaturizing high quality light and RF source

45 Microwave photonics Manipulation of RF signals using photonic techniques Promise: reduced footprint and weight, wide bandwidth Challenge: conversion losses, noise, distortion SBS applications in MWP Tunable filtering with performance unmatched by any technology RF phase shifter with record-low amplitude fluctuation RF synthesizer with low phase noise What the future holds: High SBS gain in CMOS compatible chip Functional SBS circuit (modulator, detectors, SBS engine) Chip scale optical and RF sources

46 Alvaro Casas-Bedoya, Amol Choudhary, Irina Kabakova, David Marpaung, Birgit Stiller, and Benjamin J. Eggleton University of Sydney Duk-Yong Choi, Steve J. Madden, Barry Luther-Davies Australian National University Christopher G. Poulton, Christian Wolff University of Technology Sydney (UTS) Main contributors Mattia Pagani Blair Morrison Shayan Shania Hengyun Jiang Iman Aryanfar

47 Thank you