N241-D03 TITLE: DIRECT TO PHASE II: Extended Lifetime Near-Infrared Lasers for Quantum Sensing

OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Nuclear;Quantum Science; Space Technology

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws.

OBJECTIVE: Enhance the reliability and operational lifetime of near-infrared (NIR) lasers to support the development of quantum sensors and atomic clocks.

DESCRIPTION: Atom-based instruments such as microwave and optical atomic clocks, atom interferometers, and atomic magnetometers, may be used to address a variety positioning, navigation and timing (PNT) challenges by providing ultra-precise timing, inertial sensing, and other auxiliary field measurements [Ref 1, 2]. Alkali atoms, particularly rubidium and cesium, are advantageous for low-size, -weight and power (SWaP) quantum sensors and clocks due to their high atomic vapor pressure, convenient microwave frequency ground state energy splittings, and strong optical transitions for state preparation and readout [Ref 1]. Unfortunately, the optical spectral lines of greatest interest for these atoms (particularly the D2 lines at 780 nm and 852.5 nm) fall at wavelengths near the low end of the NIR, so devices requiring these laser wavelengths do not benefit from the technical maturity and reliability of lasers developed for telecommunications (telecom) applications. The need for low-SWaP lasers operating at these alkali transition frequencies is currently well-served by distributed Bragg reflector (DBR) and distributed feedback (DFB) devices based on a Gallium arsenide (GaAs)/Aluminum gallium arsenide (AlGaAs) platform. Lasers of this type are currently limited to operational lifetimes in the range of 10,000 hours. Many applications for quantum sensors would benefit from extended operational lifetimes, enabling extended deployments on the order of 10 years or more without requiring costly servicing operations or replacement of components.

The Navy has a need for narrow linewidth, tunable NIR laser diodes in the range of 770-852.5 nm with extended operational lifetime. The increased aluminum content of the underlying epilayer material of diodes operating natively at these short wavelengths may lead to defects which reduce laser efficiency and reliability, ultimately shortening laser lifetime. Possible approaches to improving the performance of GaAs/AlGaAs devices include designs that reduce the aluminum content in active gain regions [Ref 3]. Alternative approaches to improving laser reliability include frequency-doubling a more mature, long-lifetime diode operating at a telecom wavelength [Ref 4], but this architecture requires development and miniaturization to remain SWaP-competitive with native frequency diodes.

PHASE I: For a Direct to Phase II topic, the Government expects that the small business would have accomplished the following in a Phase I-type effort and developed a concept for a workable prototype or design to address, at a minimum, the basic requirements of the stated objective above. The below actions would be required in order to satisfy the requirements of Phase I:

• Innovative approaches to the design of miniature packaged diode based lasers

• Operational lifetime exceeding 100,000 hours.

• Candidate laser technologies must be capable of single frequency operation (linewidth under 1 MHz),

• Must have the ability to be frequency-tuned to cover at least one atomic transition in the range of 770-852.5 nm (such as the Rb D2 line at 780.2 nm),

• Must produce high output power (> 100 mW) in a single transverse spatial mode.

SWaP efficiency of proposed approaches should be similar to that of existing commercial DFB/DBR devices.

PHASE II: Design, fabricate, package, and characterize a production run of high-reliability diode-based lasers meeting the linewidth, power, and tunability performance goals stated above. Lasers should be designed for nominally room temperature operation (20-30 °C). Any innovations relating to laser design and manufacture, from epitaxy through packaging may be considered in order to meet a threshold mean time to failure (MTTF) of 100,000 hours at nominal operating temperature (with a goal MTTF of 200,000 hours). An accelerated aging study shall be performed to assess the predicted lifetime of prototype devices, and a report summarizing results and methodology should be provided. A suitable laser package shall be identified for prototype laser delivery. By the end of Phase II, five (5) packaged lasers shall be delivered for testing. Each delivered device should pass initial burn-in tests, and should be characterized in terms of power and efficiency (light-current-voltage curve). Each delivered device must also be characterized in terms of its ability to be tuned over one alkali spectral line in the range 770 nm to 852.5 nm. The prototypes should be delivered by the end of Phase II.

PHASE III DUAL USE APPLICATIONS: The laser designs and fabrication processes developed in Phase II will enhance the reliability of quantum sensing and timekeeping systems. Support the Navy in transitioning the technology to Navy use. The prototypes will be evaluated through optical characterization and testing with relevant quantum sensing or timing systems. The end product technology could be leveraged to support both military/strategic applications as well as commercial applications. Military applications include optical atomic clocks and GPS denied navigation aids for long-duration missions such as quantum gravimeters and magnetometers. Additional commercial applications for these systems include resource exploration, geosensing, mapping, timing, time transfer for telecommunications, and deep space navigation.

REFERENCES:

Kitching, John. "Chip-scale atomic devices." Applied Physics Reviews, 2018, 5, 031302. https://doi.org/10.1063/1.5026238

McGilligan, J. P.; Gallacher, K.; Griffin, P. F.; Paul, D. J.; Arnold, A. S. and Riis, E. "Micro-fabricated components for cold atom sensors." Review of Scientific Instruments, 2022, 93, 091101. https://doi.org/10.1063/5.0101628

Gaetano, E. D.; Watson, S.; McBrearty, E.; Sorel, M. and Paul, D. J. "Sub-megahertz linewidth 780.24??nm distributed feedback laser for 87Rb applications." Opt. Lett., Optica Publishing Group, 2020, 45, 3529-3532. https://doi.org/10.1364/OL.394185

Caldani, R.; Merlet, S.; Pereira Dos Santos, F.; Stern, G.; Martin, A.-S.; Desruelle, B. and Ménoret, V. "A prototype industrial laser system for cold atom inertial sensing in space." The European Physical Journal D, 2019, 73, 248. https://doi.org/10.1140/epjd/e2019-100360-2

KEYWORDS: Laser reliability; Laser lifetime; Near-infrared laser; Quantum sensing; Atomic clock; Atom interferometry

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