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Optical Frequency Combs for Stable Radiation in the Microwave, Terahertz and Optical Domains

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Optical Frequency Combs for Stable Radiation in the Microwave, Terahertz and Optical Domains Optical frequency combs for stable radiation in the microwave, terahertz and optical domains Qudsia Quraishi Department of Physics, University of Colorado Time and Frequency Division, National Institute of Standards and Technology Boulder, CO 1 overview stabilized frequency combs from mode-locked femtosecond lasers provide new opportunities for…. § optical frequency metrology § optical clocks § measuring distance § time & frequency transfer § laboratory tests of fundamental physics § carrier-envelope phase control (key technology for attosecond science) § femtosecond pulse synthesis & arbitrary optical waveform generation § generation of ultralow noise microwaves § new spectroscopic techniques § harmonic generation § coherent control § spread-spectrum secure communications § part of a Nobel Prize! 2 overview stabilized frequency combs from mode-locked femtosecond lasers provide new opportunities for…. § optical frequency metrology § optical clocks § measuring distance § time & frequency transfer § laboratory tests of fundamental physics § carrier-envelope phase control (key technology for attosecond science) § femtosecond pulse synthesis & arbitrary optical waveform generation Jan Hall § generation of ultralow noise microwaves § new spectroscopic techniques § harmonic generation § coherent control Ted Hänsch § spread-spectrum secure communications § part of a Nobel Prize! 2 microwave frequency synthesizers power RF signal carrier frequenc y specifications 250 kHz – 20 GHz + low phase noise 10, 007, 482, 279 GHz Agilent E8257D frequency synthesizer 3 microwave frequency synthesizers user defined: power (a) frequency RF signal (b) amplitude (c) noise (to some extent) carrier frequenc y uses: specifications (i) references (ii) comparisons 250 kHz – 20 GHz + (iii) microwave electronics low phase noise 10, 007, 482, 279 GHz Agilent E8257D frequency synthesizer 3 microwave frequency synthesizers user defined: power (a) frequency RF signal (b) amplitude (c) noise (to some extent) carrier frequenc y uses: specifications (i) references (ii) comparisons 250 kHz – 20 GHz + (iii) microwave electronics low phase noise 10, 007, 482, 279 GHz pretty good… 1 part in 1010 Agilent E8257D frequency synthesizer 3 commercial optical frequency synthesizer idea: optical frequency synthesizer FREQUENCY: 352, 567, 323, 826, 841 Hz POWER: 2 nW NOISE: -100 dBc/Hz at 1 Hz port 1 port 2 4 commercial optical frequency synthesizer idea: optical frequency synthesizer FREQUENCY: 352, 567, 323, 826, 841 Hz POWER: 2 nW NOISE: -100 dBc/Hz at 1 Hz port 1 port 2 850 nm (352 THz) 4 commercial optical frequency synthesizer idea: optical frequency synthesizer FREQUENCY: 352, 567, 323, 826, 841 Hz POWER: 2 nW really good… NOISE: -100 dBc/Hz at 1 Hz 1 part in 1015 ! port 1 port 2 850 nm (352 THz) 4 commercial optical frequency synthesizer microwave or optical reference atoms stable or molecules cavity your are only as good as your reference idea: optical frequency synthesizer FREQUENCY: 352, 567, 323, 826, 841 Hz POWER: 2 nW really good… NOISE: -100 dBc/Hz at 1 Hz 1 part in 1015 ! port 1 port 2 850 nm (352 THz) 4 microwave pulse generators Picosecond Pulse Labs 2600C specifications rise time 250 ps dynamic range 70 dB pulse duration 1 ns to 100 nsec repetition rate 1 Hz – 100 kHz 5 optical pulse generators? pulse duration: 20 fs repetition rate: 1 GHz phase profile: 20 fs2 port 1 port 2 each cycle: 2.5 fs (800 nm) stabilized combs have subfs timing jitter from pulse-to-pulse 6 optical pulse generators? pulse duration: 20 fs SUB FEMTOSECOND repetition rate: 1 GHz phase stability ! phase profile: 20 fs2 port 1 port 2 each cycle: 2.5 fs (800 nm) stabilized combs have subfs timing jitter from pulse-to-pulse 6 frequency combs are extending our ideas about user-defined frequency sources, from the microwave to the optical 7 optical spectrum is discrete, appearing every frep 10 cm kerr lens modelocked OC frequency comb pump TiS xstal 600 mW modelocked power 1 GHz repetition rate pulses E(t) 15 fs 8.5 W pump beam at 532 nm time hundreds of nm 600 700 800 900 1000 wavelength (nm) 8 optical spectrum is discrete, appearing every frep 10 cm kerr lens modelocked OC frequency comb pump TiS xstal 600 mW modelocked power 1 GHz repetition rate pulses E(t) 15 fs 8.5 W pump beam at 532 nm S(ν) time frep hundreds of nm ν 600 700 800 900 1000 wavelength (nm) measured cavity modes 8 optical spectrum is discrete, appearing every frep 10 cm kerr lens modelocked OC frequency comb pump TiS xstal 600 mW modelocked power 1 GHz repetition rate pulses E(t) 15 fs 8.5 W pump beam at 532 nm S(ν) time frep f0 hundreds of nm ν 600 700 800 900 1000 wavelength (nm) dispersionless measured cavity modes cavity modes 8 optical spectrum is discrete, appearing every frep 10 cm kerr lens modelocked OC frequency comb pump TiS xstal 600 mW modelocked power 1 GHz repetition rate pulses E(t) 15 fs vn = n frep + f0 8.5 W pump beam at 532 nm S(ν) time frep f0 hundreds of nm ν 600 700 800 900 1000 wavelength (nm) dispersionless measured cavity modes cavity modes 8 stabilization of optical frequency comb • offset controlled by modulating pump • rep. rate or beatnote (with CW laser) controlled with cavity mirror OC pump laser TiS xstal AOM or EOM frep or fbeat f0 100 MHz RF spectrum f:2f interferometer 9 stabilization of optical frequency comb • offset controlled by modulating pump • rep. rate or beatnote (with CW laser) controlled with cavity mirror OC pump laser TiS xstal AOM or EOM ofset frequency lock frep or fbeat f0 100 MHz RF spectrum f:2f interferometer 9 stabilization of optical frequency comb • offset controlled by modulating pump • rep. rate or beatnote (with CW laser) controlled with cavity mirror OC pump laser TiS xstal AOM or EOM ofset frequency lock f or repetition rate or rep heterodyne beat lock fbeat f0 100 MHz RF spectrum f:2f interferometer 9 comb equation predicts optical frequencies v = n f + f S(ν) n rep 0 ν 10 comb equation predicts optical frequencies v = n f + f S(ν) n rep 0 frep f 0 ν 10 comb equation predicts optical frequencies v = n f + f S(ν) n rep 0 frep f 0 ν meaning that if I measure: f0 = 120 MHz frep = 1000 MHz 10 comb equation predicts optical frequencies v = n f + f S(ν) n rep 0 frep f 0 ν meaning that if I measure: then I know *all* the optical frequencies: the n=500,000 mode has a freq. of: f0 = 120 MHz v = n f + f = 5e5(1GHz) + 120 MHz f = 1000 MHz n rep 0 rep = 500,000,120,000,000 Hz 10 comb equation predicts optical frequencies v = n f + f S(ν) n rep 0 limit to optical freq. accuracy: reference for rep. and offset frep f 0 ν meaning that if I measure: then I know *all* the optical frequencies: the n=500,000 mode has a freq. of: f0 = 120 MHz v = n f + f = 5e5(1GHz) + 120 MHz f = 1000 MHz n rep 0 rep = 500,000,120,000,000 Hz 10 …on the other hand… …we can extract microwave signals from stabilized combs. 11 comb equation predicts optical frequencies f = (v + f )/ rep nlock 0 S(ν) n ν 12 comb equation predicts optical frequencies f = (v + f )/ rep nlock 0 S(ν) n f 0 ν 12 comb equation predicts optical frequencies f = (v + f )/ rep nlock 0 S(ν) n vref 657 nm (457 THz) fbeat f 0 ν 12 comb equation predicts optical frequencies f = (v + f )/ rep nlock 0 S(ν) v – f n ref beat vref 657 nm (457 THz) fbeat f 0 ν 12 comb equation predicts optical frequencies f = (v + f )/ rep nlock 0 S(ν) v – f n ref beat vref 657 nm (457 THz) fbeat f 0 ν meaning that if I measure: f0 = 120 MHz fbeat = 300 MHz 12 comb equation predicts optical frequencies f = (v + f )/ rep nlock 0 S(ν) v – f n ref beat vref 657 nm (457 THz) fbeat f 0 ν meaning that if I measure: then I know *all* the microwave frequencies: the n=500,000 divided mode is: f0 = 120 MHz frep = (457e12 – 300 MHz – 120 MHz)/n fbeat = 300 MHz = 914 MHz (this moves with CW reference say, 1 Hz per second) 12 comb equation predicts optical frequencies f = (v + f )/ rep nlock 0 S(ν) v – f n ref beat limit to microwave v 657 nm (457 THz) ref freq. accuracy: CW optical reference fbeat f 0 ν meaning that if I measure: then I know *all* the microwave frequencies: the n=500,000 divided mode is: f0 = 120 MHz frep = (457e12 – 300 MHz – 120 MHz)/n fbeat = 300 MHz = 914 MHz (this moves with CW reference say, 1 Hz per second) 12 comb equation predicts optical frequencies v combs stability δ 0 v0 S(ν) Ca at 657 nm Hg ref. at 1064 nm ν locke measured d 13 comb equation predicts optical frequencies δ v0 δvCa combs stability ~ optical reference stability v0 vCa S(ν) Ca at 657 nm Hg ref. at 1064 nm fractional stability same along *entire* comb ν locke measured d 13 comb equation predicts optical frequencies δ v0 δvCa combs stability ~ optical reference stability v0 vCa S(ν) Ca at 657 nm Hg ref. at 1064 nm fractional stability same along *entire* comb ν locke measured …thus, can compare d two standards 13 frequency measurements: simplified with combs 14 frequency measurements: simplified with combs stabilized frequency comb frequency measurements of laser-based frequency standards 1.E-05 1.E-06 Less than 100 THz 1.E-07 Greater than 100 THz 1.E-08 1.E-09 1.E-10 1.E-11 1.E-12 1.E-13 Cs Primary Freq.
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