S A Diddams

Publications (145)391.89 Total impact

• Article: Sub-femtosecond absolute timing precision with a 10 GHz hybrid photonic-microwave oscillator

  T. M. Fortier, C. W. Nelson, A. Hati, F. Quinlan, J. Taylor, H. Jiang, C. W. Chou, T. Rosenband, N. Lemke, A. Ludlow, D. Howe, C. W. Oates, S. A. Diddams
  [show abstract] [hide abstract]
  ABSTRACT: We present an optical-electronic approach to generating microwave signals with high spectral purity. By circumventing shot noise and operating near fundamental thermal limits, we demonstrate 10 GHz signals with an absolute timing jitter for a single hybrid oscillator of 420 attoseconds (1Hz - 5 GHz).
  05/2012;
• Source

  Available from: tf.nist.gov

  Article: Diode-pumped Yb:KYW femtosecond laser frequency comb with stabilized carrier-envelope offset frequency

  S. A. Meyer, J. A. Squier, S. A. Diddams
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  ABSTRACT: We describe the detection and stabilization of the carrier envelope offset (CEO) frequency of a diode-pumped Yb:KYW (ytterbium-doped potassium yttrium tungstate) femtosecond oscillator that is spectrally centered at 1033nm. The system consists of a diode-pumped, passively mode-locked femtosecond laser that produces 290fs pulses at a repetition rate of 160MHz. These pulses are first amplified, spectrally broadened and temporally compressed to 80fs, and then launched into microstructured fiber to produce an octave-spanning spectrum. An f-2f nonlinear interferometer is employed with the broadened spectrum to detect and stabilize the CEO frequency through feedback to the pump laser current. These results demonstrate that such a Yb-doped tungstate laser can provide an efficient, compact, high-repetition-rate optical frequency comb with coverage from 650–1450nm.
  The European Physical Journal D 04/2012; 48(1):19-26. · 1.48 Impact Factor
• Source

  Available from: arxiv.org

  Article: Noise Floor Reduction of an Er:Fiber Laser-Based Photonic Microwave Generator

  Haifeng Jiang, J. Taylor, F. Quinlan, T. Fortier, S.A. Diddams
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  ABSTRACT: The generation of microwaves from optical signals suffers from thermal and shot noise inherent in the photodetection process. This problem is more acute at lower pulse repetition rates where photodiode saturation limits the achievable signal-to-noise ratio. In this paper, we demonstrate a 10-15-dB reduction in the 10-GHz phase noise floor by multiplication of the pulse repetition rate. Starting with a 250-MHz fundamentally mode-locked erbium (Er):fiber laser, we compare the following two different approaches to repetition rate multiplication: 1) Fabry-Perot cavity filtering and 2) a cascaded, unbalanced Mach-Zehnder (MZ) fiber-based interferometer. These techniques reduce the phase noise floor on the 10-GHz photodetected harmonic to -158 and -162 dBc/Hz, respectively, for Fourier frequencies higher than 100 kHz.
  IEEE Photonics Journal 01/2012; · 2.32 Impact Factor
• Source

  Available from: Chris Oates

  Conference Proceeding: Optical frequency combs for low phase noise microwave generation

  F. Quinlan, T.M. Fortier, M.S. Kirchner, J.A. Taylor, J.C. Bergquist, T. Rosenband, N. Lemke, A. Ludlow, Y. Jiang, C.W. Oates, S.A. Diddams
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  ABSTRACT: An optical frequency comb locked to a stable optical reference can serve as a source for microwave signals having very low close-to-carrier phase noise. This has recently been confirmed by comparing two independent systems, yielding an absolute phase noise of -104 dBc/Hz at 1 Hz offset from a 10 GHz carrier. The corresponding timing jitter is 760 attoseconds, integrated from 1 Hz to 1 MHz. Here we describe the system architecture, as well as technical and fundamental noise limitations.
  General Assembly and Scientific Symposium, 2011 XXXth URSI; 09/2011
• Conference Proceeding: Noise limitations in microwave generation from optical references

  F. Quinlan, T.M. Fortier, M.S. Kirchner, J.A. Taylor, J.C. Bergquist, T. Rosenband, N. Lemke, A. Ludlow, Y. Jiang, C.W. Oates, S.A. Diddams
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  ABSTRACT: Combining a femtosecond laser optical frequency comb (OFC) with the high quality factor (Q) available in optical cavities allows for the realization of microwave signals with phase noise properties surpassing state-of the-art microwave oscillators. Optical Fabry-Perot (FP) resonators can have Q values exceeding 10¹¹, greater than room temperature microwave dielectric resonator oscillators (DRO) at ~10⁵ , and even exceeding that of cryogenic DROs at ~10⁹ . When an optical frequency comb is phase locked to an optical reference, the comb can be thought of as a high fidelity frequency divider, transferring the stability of the optical reference to the microwave domain. With this division in frequency comes a division in phase noise, thus an optical reference with a fractional frequency stability of ~4-10^-16 (and assuming flicker FM) can ideally generate a 10 GHz signal with phase noise of ~110 f³ dBc/Hz. At 1 Hz offset from the carrier, this represents a 40 dB improvement over the best room temperature 10 GHz microwave oscillators, and is below what has been demonstrated with cryogenic 10 GHz oscillators. Work with Er:fiber-based frequency combs has shown a residual phase noise in optical-to-microwave conversion ~118 dBc/Hz at 1 Hz offset from a 11.55 GHz carrier. In recent works, the authors demonstrated absolute phase noise below -104 dBc/Hz at 1 Hz offset from a 10 GHz carrier by comparing two independent systems that employ 1 GHz mode-locked Ti:sapphire laser combs. The results were presented in this paper and this to the authors knowledge represents the lowest close-to-carrier phase noise yet reported on a 10 GHz source.
  Lasers and Electro-Optics Europe (CLEO EUROPE/EQEC), 2011 Conference on and 12th European Quantum Electronics Conference; 06/2011
• Conference Proceeding: Towards an optical frequency comb with mm-scale microresonators for distributing atomic standards

  S.B. Papp, S.A. Diddams
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  ABSTRACT: We will discuss progress on the fabrication of optical microresonators for generation of a frequency comb via nonlinear parametric oscillation. With disk-like resonators of quartz we have achieved Q = 10⁹.
  Lasers and Electro-Optics (CLEO), 2011 Conference on; 06/2011
• Conference Proceeding: Low-noise remote transfer of a phase-encoded frequency comb through a 320m phase-stabilized fiber

  M.S. Kirchner, S.A. Diddams
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  ABSTRACT: 640 frequency-stabilized comb modes are controlled in a line-by-line pulse shaper and transmitted through a noise-cancelled 320m fiber. This allows for transmission of phase-stable, high-fidelity shaped waveforms to a remote location.
  Lasers and Electro-Optics (CLEO), 2011 Conference on; 06/2011
• Conference Proceeding: Characterization of a difference-frequency based mid-infrared comb source

  T.W. Neely, T.A. Johnson, S.A. Diddams
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  ABSTRACT: We characterize a broad bandwidth mid-IR comb source generated through difference frequency mixing of a Yb femtosecond fiber laser. The relationship between amplitude noise, timing jitter, and output power is explored.
  Lasers and Electro-Optics (CLEO), 2011 Conference on; 06/2011
• Source

  Available from: arxiv.org

  Article: Ultralow phase noise microwave generation with an Er:fiber-based optical frequency divider

  F. Quinlan, T M Fortier, M S Kirchner, J. A. Taylor, M. J. Thorpe, N. Lemke, A. D. Ludlow, Y. Jiang, C. W. Oates, S A Diddams
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  ABSTRACT: We present an optical frequency divider based on a 200 MHz repetition rate Er:fiber mode-locked laser that, when locked to a stable optical frequency reference, generates microwave signals with absolute phase noise that is equal to or better than cryogenic microwave oscillators. At 1 Hz offset from a 10 GHz carrier, the phase noise is below -100 dBc/Hz, limited by the optical reference. For offset frequencies > 10 kHz, the phase noise is shot noise limited at -145 dBc/Hz. An analysis of the contribution of the residual noise from the Er:fiber optical frequency divider is also presented.
  05/2011;
• Source

  Available from: nist.gov

  Article: Generation of Ultrastable Microwaves via Optical Frequency Division

  T. M. Fortier, M. S. Kirchner, F. Quinlan, J. Taylor, J. C. Bergquist, T. Rosenband, N. Lemke, A. Ludlow, Y. Jiang, C. W. Oates, S. A. Diddams
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  ABSTRACT: There has been increased interest in the use and manipulation of optical fields to address challenging problems that have traditionally been approached with microwave electronics. Some examples that benefit from the low transmission loss, agile modulation and large bandwidths accessible with coherent optical systems include signal distribution, arbitrary waveform generation, and novel imaging. We extend these advantages to demonstrate a microwave generator based on a high-Q optical resonator and a frequency comb functioning as an optical-to-microwave divider. This provides a 10 GHz electrical signal with fractional frequency instability <8e-16 at 1 s, a value comparable to that produced by the best microwave oscillators, but without the need for cryogenic temperatures. Such a low-noise source can benefit radar systems, improve the bandwidth and resolution of communications and digital sampling systems, and be valuable for large baseline interferometry, precision spectroscopy and the realization of atomic time.
  01/2011;
• Source

  Available from: nist.gov

  Article: Grism-based pulse shaper for line-by-line control of more than 600 optical frequency comb lines.

  M S Kirchner, S A Diddams
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  ABSTRACT: We construct a line-by-line pulse shaper using a grism (grating plus prism) dispersive element, which provides constant angular dispersion over 13.4 THz centered at ~311 THz (965 nm). When combined with a dual-mask liquid crystal modulator, this grism-based shaper is capable of line-by-line amplitude and phase control of over 600 modes of a 21 GHz stabilized optical frequency comb.
  Optics Letters 10/2010; 35(19):3264-6. · 3.40 Impact Factor
• Source

  Available from: nist.gov

  Conference Proceeding: Phase noise in the photodetection of ultrashort optical pulses

  J.A. Taylor, F. Quinlan, A. Hati, C. Nelson, S.A. Diddams, S. Datta, A. Joshi
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  ABSTRACT: Femtosecond laser frequency combs provide an effective and efficient way to take an ultra-stable optical frequency reference and divide the signal down into the microwave region. In order to convert optical pulses into a usable RF signal, one must use high-speed photodetection; unfortunately, excess phase noise from both technical and fundamental sources can arise in the photodetection process. In order to ultimately minimize the noise effects of the photodetector, we must first characterize some of the known sources for noise arising in these devices. In this paper, we will study two sources of excess noise in high-speed photodiodes - power-to-phase conversion and shot noise. The noise performance of each device will give us clues as to the nature of the sources, their effect on the output signal, and what design features of the photodiode minimize these noise effects.
  Frequency Control Symposium (FCS), 2010 IEEE International; 07/2010
• Source

  Available from: arxiv.org

  Article: A 12.5 GHz-spaced optical frequency comb spanning >400 nm for near-infrared astronomical spectrograph calibration.

  F Quinlan, G Ycas, S Osterman, S A Diddams
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  ABSTRACT: A 12.5 GHz-spaced optical frequency comb locked to a global positioning system disciplined oscillator for near-infrared (IR) spectrograph calibration is presented. The comb is generated via filtering a 250 MHz-spaced comb. Subsequent nonlinear broadening of the 12.5 GHz comb extends the wavelength range to cover 1380-1820 nm, providing complete coverage over the H-band transmission window of earth's atmosphere. Finite suppression of spurious sidemodes, optical linewidth, and instability of the comb has been examined to estimate potential wavelength biases in spectrograph calibration. Sidemode suppression varies between 20 and 45 dB, and the optical linewidth is approximately 350 kHz at 1550 nm. The comb frequency uncertainty is bounded by +/-30 kHz (corresponding to a radial velocity of +/-5 cm/s), limited by the global positioning system disciplined oscillator reference. These results indicate that this comb can readily support radial velocity measurements below 1 m/s in the near IR.
  The Review of scientific instruments 06/2010; 81(6):063105. · 1.52 Impact Factor
• Conference Proceeding: Photodiode limitations in the generation of low-noise microwave signals from stable frequency combs

  J.A. Taylor, S.A. Diddams, S. Datta, A. Joshi
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  ABSTRACT: An optically-stabilized femtosecond laser frequency comb can generate low phase noise microwave signals; however, excess noise arises in the photodetection process. We study the impact of photodetector shot noise, saturation, and power-top phase conversion on 1-10 GHz signal generation.
  Microwave Photonics, 2009. MWP '09. International Topical Meeting on; 11/2009
• Article: Optical frequency stabilization of a 10 GHz Ti: sapphire frequency comb by saturated absorption spectroscopy in^{87} rubidium

  D. C. Heinecke, A. Bartels, T. M. Fortier, D. A. Braje, L. Hollberg, S. A. Diddams
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  ABSTRACT: The high power per mode of a recently developed 10 GHz femtosecond Ti:sapphire frequency comb permits nonlinear Doppler-free saturation spectroscopy in 87Rb with a single mode of the comb. We use this access to the natural linewidth of the rubidium D2 line to effectively stabilize the optical frequencies of the comb with an instability of 7×10−12 in 1 s of averaging. The repetition rate is stabilized to a microwave reference leading to a stabilized and atomically referenced comb. The frequency stability of the 10 GHz comb is characterized using optical heterodyne with an independent self-referenced 1 GHz comb. In addition, we present alternative stabilization approaches for high repetition rate frequency combs and evaluate their expected stabilities.
  Phys. Rev. A. 11/2009; 80(5).
• Source

  Available from: arxiv.org

  Article: Spin-1/2 optical lattice clock.

  N D Lemke, A D Ludlow, Z W Barber, T M Fortier, S A Diddams, Y Jiang, S R Jefferts, T P Heavner, T E Parker, C W Oates
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  ABSTRACT: We experimentally investigate an optical clock based on ;{171}Yb (I = 1/2) atoms confined in an optical lattice. We have evaluated all known frequency shifts to the clock transition, including a density-dependent collision shift, with a fractional uncertainty of 3.4 x 10;{-16}, limited principally by uncertainty in the blackbody radiation Stark shift. We measured the absolute clock transition frequency relative to the NIST-F1 Cs fountain clock and find the frequency to be 518 295 836 590 865.2(0.7) Hz.
  Physical Review Letters 08/2009; 103(6):063001. · 7.37 Impact Factor
• Conference Proceeding: Low-noise microwave synthesis up to 80 GHz with line-by-line processing of an optical frequency comb

  Shijun Xiao, L. Hollberg, S.A. Diddams
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  ABSTRACT: 10 GHz optical pulses are generated by line-by-line phase compensation on an optical frequency comb. Residual pulse timing jitter les 10 fs and high power signals at harmonics up to 80 GHz are measured.
  Lasers and Electro-Optics, 2009 and 2009 Conference on Quantum electronics and Laser Science Conference. CLEO/QELS 2009. Conference on; 07/2009
• Source

  Available from: nist.gov

  Article: A deep-UV optical frequency comb at 205 nm.

  E Peters, S A Diddams, P Fendel, S Reinhardt, T W Hänsch, Th Udem
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  ABSTRACT: By frequency quadrupling a picosecond pulse train from a Ti:sapphire laser at 820 nm we generate a frequency comb at 205 nm with nearly bandwidth-limited pulses. The nonlinear frequency conversion is accomplished by two successive frequency doubling stages that take place in resonant cavities that are matched to the pulse repetition rate of 82 MHz. This allows for an overall efficiency of 4.5 % and produces an output power of up to 70 mW for a few minutes and 25 mW with continuous operation for hours. Such a deep UV frequency comb may be employed for direct frequency comb spectroscopy in cases where it is less efficient to convert to these short wavelengths with continuous wave lasers.
  Optics Express 06/2009; 17(11):9183-90. · 3.59 Impact Factor
• Source

  Available from: nist.gov

  Article: Generation of 20 GHz, sub-40 fs pulses at 960 nm via repetition-rate multiplication.

  M S Kirchner, D A Braje, T M Fortier, A M Weiner, L Hollberg, S A Diddams
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  ABSTRACT: Optical filtering of a stabilized 1 GHz optical frequency comb produces a 20 GHz comb with approximately 40 nm bandwidth (FWHM) at 960 nm. Use of a low-finesse Fabry-Pérot cavity in a double-pass configuration provides a broad cavity coupling bandwidth (Deltalambda/lambda approximately 10%) and large suppression (50 dB) of unwanted modes. Pulse durations shorter than 40 fs with less than 2% residual amplitude modulation are achieved.
  Optics Letters 05/2009; 34(7):872-4. · 3.40 Impact Factor
• Source

  Available from: arxiv.org

  Article: Probing interactions between ultracold fermions.

  G K Campbell, M M Boyd, J W Thomsen, M J Martin, S Blatt, M D Swallows, T L Nicholson, T Fortier, C W Oates, S A Diddams, N D Lemke, P Naidon, P Julienne, Jun Ye, A D Ludlow
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  ABSTRACT: At ultracold temperatures, the Pauli exclusion principle suppresses collisions between identical fermions. This has motivated the development of atomic clocks with fermionic isotopes. However, by probing an optical clock transition with thousands of lattice-confined, ultracold fermionic strontium atoms, we observed density-dependent collisional frequency shifts. These collision effects were measured systematically and are supported by a theoretical description attributing them to inhomogeneities in the probe excitation process that render the atoms distinguishable. This work also yields insights for zeroing the clock density shift.
  Science 05/2009; 324(5925):360-3. · 31.20 Impact Factor