1.05 SOW_Menlo_FreqComb.pdf

Statement of Work

Frequency Comb Transferring Stabilization at 1315 nm to Blue Wavelengths and RF

Clock Development Division, Precise Time Department

U.S. Naval Observatory

BACKGROUND

The United States Naval Observatory (USNO) is the authoritative source of time for the

Department of Defense. For this purpose the USNO’s Precise Time Department maintains an ensemble of high-performing atomic clocks that is used to generate precise time. Because of the lack of commercial vendors for the highest performing clocks, stocking the clock ensemble with systems based on cutting-edge technology requires that these systems be designed and built in-house.

Within the Precise Time Department, the Clock Development Division is investigating atomic clock technology using optical spectroscopy on an atomic beam of calcium. The calcium clock transition corresponds to a wavelength of 657 nanometers (nm), atomic ground state detection utilizes a transition at 423 nm, and excited state detection utilizes a 431-nm transition. We have procured a laser to generate 657 nm spectroscopic light by frequency doubling a cavity-stabilized

1315 nm laser, since 1315 nm laser technology is further developed than that at 657 nm.

Similarly, we are procuring laser systems at 826 nm and 862 nm to generate the detection laser light via frequency doubling.

We require a frequency-comb system that will lock to our narrow 1315 nm laser and transfer the stability to the detection laser systems at 826 nm and 862 nm, as well as transferring the stability to radio-frequency (RF) signals of 100 mega-Hertz (MHz) and 10 MHz.

REQUIREMENTS

The USNO seeks to procure a frequency-comb system with the following specifications:

Turn-key, robust, fiber frequency comb centered at 1560 nm that automatically mode-locks and remains mode locked for >6 months in a well regulated environment.

Repetition rate of 125 MHz. Supports fractional frequency stability below 10-15 at 1 second (s). Rack-mounted, taking up 3RU (rack units) or less space.

Input, beat-detection unit (BDU) and all locking electronics to stabilize frequency comb repetition rate to external, user-supplied narrow (approximately 1 Hz linewidth) 1315 nm laser. Faithful transfer of frequency stability of 1315 nm laser to frequency comb and divided down RF outputs. Back-reflection port (reflecting 10% of input light) enabling fiber-noise cancellation on 1315 nm input fiber.

Microwave/RF generation, providing signal outputs of 1 pulse-per-second (pps), 10 MHz and 100 MHz. The frequency stability of the 100 MHz output must be better than 10-14 at

1 s and the stability of the 10 MHz output must be better than 210-14 at 1 s, and the power levels >7 dBm. The phase noise at 1 Hz offset from carrier must be below -140 dBc/Hz at 10 MHz and below -125 dBc/Hz at 100 MHz.

The system must include frequency-comb extensions at 846 nm and 862 nm, with inputs for external user-supplied lasers at these wavelengths and high-SNR balanced BDUs for generating locking signals with less than 100 microWatts (W) of external laser power.

The system must support long-term frequency stability and linewidth narrowing to below

100 Hz for these external lasers.

System must be mounted into USNO-specified Mid-Atlantic 19” width and 26” depth equipment rack, allowing room for cabling within the enclosure. Fluid chiller shall be included and integrated to provide temperature stabilization of the laser baseplates. All cable management, fluid lines, sliding shelves, etc. must be incorporated in a fashion that enables end user access to all necessary components for adjustment or remediation.

All control electronics and all components necessary to make the lasers operational as

“turn-key” systems must be included.

Installation and training must be provided on site in Washington, DC.

FACILITIES, EQUIPMENT, AND TRAVEL:

Planning and support for the completion of these tasks will be coordinated with the technical

POCs listed below for the USNO. No travel is anticipated for this order.

PERIOD OF PERFORMANCE:

The period of performance is nine (9) months or sooner for the delivery of components from award date.