Multi-Band Laser Source for Atom Interferometry
AREA(S): Air Platform, Battlespace, Electronics
PROGRAM: None or N/A NAE Chief Technology Office
Develop a low space, weight, and power (SWaP) system fitting into a single rack
unit for generating multiple laser frequencies to drive Rubidium85 (Rb85)
transitions relevant to atom manipulation.
The Navy is pursuing quantum sensing, both the development of new sensor
technologies and the advancement of existing technologies. One of the challenges
in this pursuit is simplifying and condensing complicated laboratory setups
into a configuration that is able to be placed on a Navy platform. One such
subset of quantum technologies is sensors based on Atom Interferometry. These
sensors require simultaneous access to multiple atomic transitions for any
given atom, which can result in complex electronic and optical setups. In
particular, Rb85-based sensors require five separate, stabilized laser
frequencies locked near the Rb85 D2 line [Ref 1-3] in order to drive the
necessary atomic transitions. The characteristics of each of these laser
outputs are listed in the specifications.
The currently employed method of accessing all necessary frequencies uses
multiple independent lasers - each with separate saturated absorption locks.
This method is demanding in terms of space and laser control electronics, and
adds the complication of requiring multiple, independent locking mechanisms to
stabilize each laser frequency and intensity. While adequate for laboratory
demonstrations, this option is unrealistic for mobile sensor development.
Integration onto a moving platform will require significant reduction in the
number of optical components requiring active stabilization and lock down in
order to maintain un-interrupted operation. Options that minimize the number of
internal laser sources required to achieve the necessary output frequencies
would have benefits in terms of complexity, ruggedness, and commonality of
The optical and electronic packaging [Ref 4] should each be consolidated into a
single 19”W x 19”D x 3.5”H rack with the optical rack having 5 polarization
maintaining, FC/APC fiber coupled outputs. Consider the ability to actively
stabilize frequency to within 10 kHz of the respective atomic transitions and
intensity fluctuations below 0.1% of the output intensity; however, the
saturated absorption reference does not necessarily need to be integrated into
the completed package. All lasers must maintain polarization stability to within
0.01 degrees, which must be set to the fiber-coupled outputs. System must
withstand the shock, vibration, pressure, temperature, humidity, electrical
power conditions, etc. encountered in a system built for airborne use [Ref 4].
Locked laser bandwidth: threshold: <200 kHz, goal <100 kHz.
Laser band and power specifications are as follows:
TRANSITION 1 (F=3 to F’=4): LASER 1 – red detuned by 6-10 MHz, coherent output,
threshold: 200mW CW, goal: 300mW CW; LASER 2 – On resonance, coherent output,
threshold: 6 mW, goal: 10 mW CW; LASER 3 – On resonance, coherent output,
threshold: 60mW CW, goal: 80mW CW.
TRANSITION 2 (F=2 to F’=3): LASER 4: red detuned by 10-15 MHz, coherent output,
threshold: 40mW CW, goal: 80mW CW.
TRANSITION 3 (F=2 to F’=3): LASER 5: red detuned by 1.5 GHz, coherent output,
threshold: 40mW CW, goal: 60Mw CW.
The final system should be capable of operating under the conditions specified
in [Ref 4]. Additionally, weight threshold: <30 lbs, goal: <10 lbs and
power threshold: <200W, goal: <50W.
I: Develop the system design, including modeling, to determine the expected
power output and phase stability, and demonstrate feasibility of the proposed
solution. The Phase I effort will include prototype plans to be developed under
II: Acquire necessary optical components, including lasers, Acousto-Optic
Modulators (AOMs), lenses, and any other optical and electrical components
required to accomplish the design developed during Phase I. Develop,
demonstrate, validate and deliver prototype based on Phase I work.
III DUAL USE APPLICATIONS: Demonstrate operation of Phase II prototype in a
magneto optical trap. Ruggedize the prototype to meet MIL-STD-810G [Ref 4]
operational conditions. Commercial and academic use of laser cooled Rubidium
will benefit from a simpler process for generating the necessary optical
frequencies leading to less expensive and more reliable systems that utilize
cooled rubidium. This could benefit existing industrial uses for cooled
rubidium in atomic clocks, gravitational sensors, and any other application
that requires laser cooling of rubidium.
Phillips, W. "Laser Cooling and Trapping of Neutral Atoms." Reviews
of Modern Physics, Vol. 70, No. 3, 1998; https://journals.aps.org/rmp/pdf/10.1103/RevModPhys.70.721
Kasevich, M. and Chu, S. “Atomic Interferometry Using Stimulated Raman
Transitions.” Phys. Rev. Lett. 67, 2, pp. 181-184, 8 July 1991. https://link.aps.org/doi/10.1103/PhysRevLett.67.181
Steck, D. “Rubidium 85 D Line Data.” (revision 2.1.6, 20 September 2013) https://steck.us/alkalidata/rubidium85numbers.pdf
MIL-STD-810G, DEPARTMENT OF DEFENSE TEST METHOD STANDARD: ENVIRONMENTAL
ENGINEERING CONSIDERATIONS AND LABORATORY TESTS (31 OCT 2008) (Section
514.6C-1, 514.-C7 pages C-19, C-20). http://everyspec.com/MIL-STD/MIL-STD-0800-0899/MIL-STD-810G_12306/
Laser; Atomic; Quantum; Rubidium; Multi-Band; Magneto Optic Trap; MOT
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