Statement of Work.docx

NIST Requirements Document high-finesse, dual-wavelength reference cavity (HDRC) system

I. Background The Fundamental Thermodynamics Group (685.09) conducts fundamental and applied research to improve the measurement of thermodynamic quantities. Develops new measurement methods for pressure, vacuum, and temperature using atomic and molecular gases, refractometry, solid-state point defects, optomechanics, integrated photonics, advanced nanofabrication technologies, and advanced AI. Continuously improves the performance of legacy national standards, participates in national and international intercomparisons to validate these standards, and produces assessments of their respective measurement uncertainty. Provides calibration services for piston gauges, capacitance diaphragm gauges, spinning rotor gauges, ionization gauges, and gas leaks.

The group has recently been begun developing primary thermometers based on measurements of the Doppler effect in atomic gases, specifically cesium and ytterbium.

II. Scope Accurately extracting the thermodynamic temperature from the Doppler absorption spectrum of a gas requires a laser system with very low frequency noise. Sufficiently suppressing the 1/f frequency noise that dominates at low Fourier frequencies requires the laser be locked to a stable, narrow frequency reference. To achieve the desired accuracy of the Doppler thermometer, we require a high-finesse, dual-wavelength reference cavity system to serve as the frequency reference for both the cesium and ytterbium spectroscopy lasers. To allow common mode rejection of small, long-term frequency drifts, we require that the high-finesse, dual-wavelength reference cavity system that integrates high-finesse cavities for both the cesium and ytterbium spectroscopy lasers into a single cavity spacer. This procurement is essential for meeting the goals of an IMS project.

III. Minimum Requirements The system shall meet or exceed the minimum requirements identified below. All items must be new. Used or remanufactured equipment will not be considered for award. Experimental, prototype, or custom items will not be considered. The use of “gray market” components not authorized for sale in the U.S. by the Contractor is not acceptable. All line items shall be shipped in the original manufacturer’s packaging and include all original documentation and software, when applicable.

The Contractor shall provide the following high-finesse, dual-wavelength reference cavity (HDRC) system that meet the following minimum specifications:

A. High-finesse, dual-wavelength reference cavity system:

1. The system shall have:

EITHER

a. Two Fabry-Perot (FP) optical cavities in a single cylindrical cavity spacer with size no larger than 50 mm diameter x 100 mm length, material of the cavity spacer shall be Ultra-Low Expansion (ULE) glass.

i. The 1st FP cavity shall have a mirror pair with the following parameters:

I. 1st mirror shall be made from Ultra-Low Expansion (ULE) glass, 1” diameter x 0.25” thick, plano (flat)/plano (flat) mirror surfaces, with a mirror coating on the first surface (S1) and an anti-reflective coating on the second surface (S2).

II. 2nd mirror shall be made from ULE glass, 1” diameter x 0.25” thick, plano/concave (pl/cc) mirror surfaces with 50 cm radius of curvature (ROC), with a mirror coating on the concave surface (S1) and an anti-reflective coating on the second surface (S2).

III. Both mirrors shall have polished finish with surface quality of 10-5 on S1 surface and 20-10 on S2 surface.

IV. Mirror coating on S1 surface of both mirror substrates shall be sufficient to achieve a cavity finesse larger than 100,000 at 555.8 nm wavelength.

V. Anti-reflective coating on S2 surface of both substrates shall have less than 0.1 percent reflectivity at 0° angle-of-incidence (S2 AR % 0° AOI) at 555.8 nm wavelength.

ii. The 2nd FP cavity shall have a mirror pair with the following parameters:

I. 1st mirror shall be made from Ultra-Low Expansion (ULE) glass, 1” diameter x 0.25” thick, plano (flat)/plano (flat) mirror surfaces, with a mirror coating on the first surface (S1) and an anti-reflective coating on the second surface (S2).

II. 2nd mirror shall be made from ULE glass, 1” diameter x 0.25” thick, plano/concave (pl/cc) mirror surfaces with 50 cm radius of curvature (ROC), with a mirror coating on the concave surface (S1) and an anti-reflective coating on the second surface (S2).

III. Both mirrors shall have polished finish with surface quality of 10-5 on S1 surface and 20-10 on S2 surface.

IV. Mirror coating on S1 surface of both mirror substrates shall be sufficient to achieve a cavity finesse larger than 100,000 at 894.6 nm wavelength.

V. Anti-reflective coating on S2 surface of both substrates shall have less than 0.1 percent reflectivity at 0° angle-of-incidence (S2 AR % 0° AOI) at 894.6 nm wavelength.

OR

b. A dual-wavelength Fabry Perot optical cavity in a cubic cavity spacer with size no larger than 50 mm width x 50 mm length, material of the cavity spacer shall be Ultra-Low Expansion (ULE) glass.

i. The dual-wavelength FP cavity shall have a mirror pair with the following parameters:

I. 1st mirror shall be made from Ultra-Low Expansion (ULE) glass, 1” diameter x 0.25” thick, plano (flat)/plano (flat) mirror surfaces, with a mirror coating on the first surface (S1) and an anti-reflective coating on the second surface (S2).

II. 2nd mirror shall be made from ULE glass, 1” diameter x 0.25” thick, plano/concave (pl/cc) mirror surfaces with 50 cm radius of curvature (ROC), with a mirror coating on the concave surface (S1) and an anti-reflective coating on the second surface (S2).

III. Both mirrors shall have polished finish with surface quality of 10-5 on S1 surface and 20-10 on S2 surface.

IV. Mirror coating on S1 surface of both mirror substrates shall be sufficient to achieve a cavity finesse larger than 100,000 at 555.8 nm wavelength and at 894.6 nm wavelength.

V. Anti-reflective coating on S2 surface of both substrates shall have less than 0.1 percent reflectivity at 0° angle-of-incidence (S2 AR % 0° AOI) at 555.8 nm wavelength and at 894.6 nm wavelength.

2. The integrated linewidth of each FP cavity mode shall be 15 kHz or less.

3. The system shall have vacuum housing to accommodate the cavity spacer. The optical cavity spacer shall be positioned horizontally within the vacuum housing.

4. Vacuum housing of the system shall have windows with an antireflection coating with < 0.1 % reflectivity (AR at 0° AOI) at the wavelengths for the optical cavities specified in A1a or A1b above. There should be optical access to each cavity (see A1a and A1b) through housing windows on both ends of the vacuum housing.

5. Vacuum housing of the system shall have an ion pump and ion pump controller to provide 10-6 torr pressure or lower.

6. Vacuum housing of the system shall have an active temperature control system with internal temperature shields, heaters, thermistors, and an external temperature controller.

7. The optical cavity spacer’s temperature shall be stable with a temperature drift less than 1 mK/day.

8. The ambient temperature sensitivity of the housing shall be less than 4 mK/°C.

9. The thermal expansion zero-crossing temperature of the cavity spacer shall by characterized.

10. The FP cavity housing shall be tunable to the thermal expansion zero-crossing temperature of the cylindrical cavity spacer.

11. The linear drift rate of the system shall be no larger than 15 kHz/day (170 mHz/s) at both 555.8 nm and 894.6 nm after 2 years.

a. The linear drift rate of the system when delivered shall be no larger than 80 kHz/day at 555.8 nm and 50 kHz/day at 894.6 nm.

12. The system shall have two collimator assembly modules that are attached to the vacuum housing: one module for each FP cavity (see A1a) or one for each wavelength of the dual-wavelength cavity (see A1b). Each collimator module shall provide alignment, mode matching, and coupling of light at the appropriate wavelength from an optical fiber to the associated FP cavity (A1a) or associated wavelength (A1b). Each collimator assembly shall include a quarter waveplate and beamsplitter to separate light reflected from the associated FP cavity at the associated wavelength (A1a and A1b). Each collimator assembly will include a camera and detector to image and measure light transmitted through the associated FP cavity at the associated wavelength. All optical components shall be pre-aligned.

a. If the FP cavity and spacer is as specified in A1b, then dichroic mirrors to separate light from the two collimator assembly modules are also required on both ends of the vacuum housing.

13. Each collimator assembly (A12) shall include a photodetector with DC-coupled and AC-coupled outputs that can be used to generate a Pound-Drever-Hall signal using the light reflected from the associated FP cavity at the associated wavelength. The detector shall be pre-aligned to the reflected light created by the collimator assembly (A12).

14. The system shall have a minimum of 1 year warranty, lead time 14 weeks or less.

Deliverables:

IV. Site Preparation The high-finesse, dual-wavelength reference cavity system will be installed in 222/B149 or an equivalent laboratory space. NIST will prepare the site for high-finesse, dual-wavelength reference cavity system installation and testing.

V. Delivery Delivery shall be FOB Destination (or equivalent terms, such as INCOTERMS Delivered Duties Paid) are required and shall occur not later than (NLT) 14 weeks ARO.

FOB Destination means: The contractor shall pack and mark the shipment in conformance with carrier requirements, deliver the shipment in good order and condition to the point of delivery specified in the purchase order, be responsible for any loss of and/or damage to the goods occurring before receipt and acceptance of the shipment by the consignee at the delivery point specified in the purchase order; and pay all charges to the specified point of delivery. The contractor shall deliver all Line Items to:

National Institute of Standards & Technology 100 Bureau Drive, Building 222, Room B149 Gaithersburg, MD 20899

VI. Inspection and Acceptance In addition to the inspection and acceptance terms articulated in 52.212-4, the Government reserves the right to perform such performance tests and evaluations as defined below to verify specified system performance. Such tests and evaluations, if performed, shall be conducted within the environment that the system is to be operated. The Contractor has the right to be present during the tests and evaluations, if performed, at the Contractor’s expense.

Before shipping the system to NIST, the Contractor shall test the system that it meets all stated technical requirements and provide test results to NIST. Contractor shall measure and document vacuum and thermal properties of the vacuum enclosure as well as verify finesse and linewidth of each FP cavity. The contractor shall pre-align the collimator module assemblies (A12 and A13 requirements).

Upon receiving the performance of high-finesse, dual-wavelength reference cavity system, the system will be tested at the NIST site. First, the NIST team will test the performance of the vacuum enclosure for vacuum level, vacuum leak, and thermal stability, thermal drift, and thermal time constant of the enclosure. The NIST team will test the pre-aligned collimator assembly module and FP cavity at 894.6 nm using a NIST-supplied 894.6 nm laser source. In particular, the NIST team will test that light can be effectively coupled to the FP cavity at 894.6 nm and detected on both reflected and transmission sides of the FP cavity. The NIST team will measure the free spectral range (FSR), finesse, and linewidth of the FP cavity at 894.6 nm. NIST team will measure the linear frequency drift rate of the system using a wavelength meter and the NIST 894.6 nm laser source.

Similar tests of the collimator assembly and FP cavity at 555.8 nm wavelength will also be conducted by the NIST team with a NIST-supplied 555.8 nm laser source if such a laser source is available within the extended testing period.

The Government will test, inspect, and accept the equipment onsite within 30 business days of the receipt of the high-finesse, dual-wavelength reference cavity system. A visual inspection of the high-finesse, dual-wavelength reference cavity system will be performed by the NIST TPOC to identify surface defects or any form of indication that the high-finesse, dual-wavelength reference cavity system was damaged during transport to NIST. The Government shall have sole discretion to require repair or replacement of damaged and/or nonconforming supplies at no cost to the Government. The Government at any time prior to acceptance shall reject the high-finesse, dual-wavelength reference cavity system due to defects and/or nonconformance.

VII. Installation The system will be installed by the NIST personnel. The system will be tested that it meets contract specifications as in VI above.

VIII. Warranty The contractor shall warrant the entire system for a period of a minimum of 1 year after receipt of the equipment and shall be in accordance with terms in FAR 52.212-4

IX. Payment Schedule The Contractor shall be paid, in accordance with Net 30-day payment terms, upon receipt and acceptance of a proper invoice, in accordance with the following schedule:

1. 100% after installation and acceptance by the TPOC of fully installed system.

2. The Government anticipates inspection will occur upon:

a. After the testing procedures set forth in this document have been completed