High-Performance Optical Atomic Clocks

Use this document to detail specifications/requirements for an item and/or ancillary services. 🛈 TITLE: High-performance optical atomic clocks to contribute to official US time. 🛈 Requesting Lab/Division/Group: PML/Time and Frequency 688/Time realization and distribution 688.40 General Statement of Need 🛈 NIST seeks two high-performance, robust optical atomic clock to integrate into the timescale in Boulder, Colorado that generates UTC(NIST), NIST’s realization of Coordinated Universal Time (UTC). This high-stability clock will augment an ensemble of microwave atomic clocks and receive high relative weight in the UTC(NIST) computation algorithm, thereby reducing reliance on microwave standards. NIST requires units that can support timescale instabilities of 0.1 ns/day while providing excellent short term stability. NIST seeks robust systems that can operate with minimal input from technical staff. In particular, the clock performance should be minimally affected by environmental fluctuations, greatly reducing the demands on NIST staff to maintain highly controlled environmental conditions and increasing the resiliency of UTC(NIST) should facility environmental control be unexpectedly lost. Beyond improving holdover capabilities of UTC(NIST), the high-stability RF signals from the clock will directly benefit experiments that require excellent short-term performance such as precision atomic and molecular spectroscopy, optical clock comparison and dimensional metrology. Items and/or Ancillary Services 🛈 Item 1: Optical atomic clock system Quantity: 2 Specifications: 1.1 System accomplishes frequency discipline of an oscillator to an atomic or molecular spectroscopic transition, basic demonstrations of which are documented by at least two published research studies in technical journals or conference proceedings. 1.2 Clock outputs at any or all of the nominal frequencies: 5 MHz, 10 MHz, 100 MHz, 1 GHz 1.3 Radio frequency outputs terminate in SMA-female connectors as single-ended sinusoidal signals matched into 50 Ohm transmission lines and loads, with amplitudes no less than +5 dBm. 1.4 Optical output of stabilized continuous-wave laser, coupled in a single-mode polarization-maintaning fiber and terminated as an FC/APC fiber-optic connector. Optical wavelength is between 1000 nm and 1625 nm and optical power is greater than 0.1 mW. 1.5 Short term frequency instability of all outputs (optical- and radio-frequency), expessed as the Allan deviation (ADEV) at 1-second average intervals, should be less than 1E-13. The ADEV after 100,000s of averaging (approx. 1 day) should be below 8E-15. 1.6 Electrical power dissipation less than 150 W among all components contributing to clock stability. For example, if powered by a remote power supply, power dissipation in control or power-supply components do not count towards the 150 W limit. Requirement applies after any specified warm-up interval, and should assume an ambient temperature between 20 °C and 25 °C, relative humidity between 40% RH and 50% RH. 1.7 Total power dissipation of system must be less than 500 W and have no additional cooling requirements beyond placement in still air. 1.8 System power input accepts 110-120 V ac, 60 Hz, IEC 60320 C13 connector or equivalent. 1.9 Physical dimensions: systems must be compatible with mounting within industry standard 19-inch (482.6 mm) rack enclosures (e.g. industry standard EIA-310-D). Excluding a front panel with compatible fasteners or mounting holes, the system width must be less than 450.85 mm. The system depth must be less than 760 mm. The total system height must be less than 267 mm (“6U” in 19-inch rack spacing). 1.10 Integrated control and monitoring functions. System must include all elements necessary for maintaining continuous oscillator locking, and diagnostic monitoring of the clock health. System must include a digital command/control interface over standard serial (e.g. USB, RS232 or other UART) or network (e.g. Ethernet LAN) formats. Additionally, system must include all elements necessary for discipline and monitoring of the system responsible for optical-to-microwave translation. 1.11 Frequency accuracy and adjustability. The nominal frequencies in Specification 1.2 must be accurate to a fractional inaccuracy of 1E-11 upon delivery. This requirement is waived if the system allows digital adjustment of the output frequency with a minimum step size no larger than 1E-16. All clock outputs, optical- and radio-frequency, must remain mutually coherent with any tuning. 1.12 Optical output of stabilized femtosecond-laser frequency comb (fs-comb), terminated in FC/APC female fiber optic coupler. Output spectrum need not be octave-spanning but should represent the stabilized fs-comb oscillator. Fs-comb pulse repetition rate is subject to the ADEV requirements in Specification 1.5 above. Fs-comb pulse repetition rate does not have to represent one of the nominal frequencies named in Specification 1.2 above. 1.13 Environmental Sensitivity. A change of the ambient temperature of 1 degree Celsius should fractionally change the RF and optical frequency by less than 1E-14. …