N112-104 TITLE: Compact Narrow-band Laser Sources for Atom-based Sensors

TECHNOLOGY AREAS: Sensors

ACQUISITION PROGRAM: PMA-290, Maritime Patrol & Reconnaissance Aircraft

OBJECTIVE: Develop a compact high power tunable laser source with output wavelength 780 nm, 795 nm or 852 nm (Rubidium D2, Rubidium D1 and Cesium D2 transitions respectively).

DESCRIPTION: Current semiconductor laser technology can provide for very small, compact lasers. However, for applications requiring narrow line widths, external cavities are often required, increasing the size and weight of the laser. Additionally, these external cavity lasers are of lower power (tens of milliwatts (mw)). Higher power diode lasers typically cannot be stabilized to very narrow line widths. Applications requiring higher laser power therefore require an amplifier, which often produces beams of poor mode quality, poor coupling efficiency into fiber optic cables and which increases the complexity of the final system [1, 2]. Atomic sensors ranging from atomic magnetometers [3, 4] to atom interferometer gyroscopes [5] and clocks [6] rely on these lasers to interrogate the atoms being used as sensors. For certain low power applications, existing lasers are adequate. For higher power applications, typically master-oscillator combinations need to be used.

Compact laser sources are sought that satisfy the following criteria. Note that all specifications must be met simultaneously. 1) Output power greater than 500 milliwatts threshold, 2 watts objective. 2) Continuous mode-hop free scanning operation 20 GHz threshold and 100 GHz objective. 3) Line width when not scanning less than 100 kHz threshold and less than 10 kHz objective. 4) Beam quality of M squared value 1.2 threshold and better than 1.1 objective. 5) Single polarization mode with unwanted mode suppression of 20 dB threshold and 30 dB objective. 6) The laser and associated electronics must fit into a 20 cm x 20 cm x 9 cm threshold and 5 cm x 5 cm x 5 cm objective volume. Although it is not required for this topic, it is anticipated that the combination of these criteria will lead to emission of 250 mw threshold and 1.25 watts objective laser light stabilized to an atomic line appropriate for atom interferometry from a single mode polarization maintaining fiber. Lasing on the rubidium D2 line (780.24 nm) is preferred, but other atomic lines of alkali species, i.e. sodium D2 (589 nm) or D1 (590 nm), rubidium D1 (795 nm) or cesium (852 nm), will be considered.

PHASE I: Determine feasibility of proposed laser source to achieve all parameters simultaneously. Define plan for the development and demonstration of the proposed laser system.

PHASE II: Develop, demonstrate and validate prototype laser system.

PHASE III: Complete final validation of the production laser system and transition system to appropriate platforms.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Atom interferometer sensors can be used to measure gravity and gravity gradients, and would be beneficial in the oil exploration and mine and tunnel detection fields. In addition, they could be used for rotation sensing, GPS-free navigation and precision time keeping. Successful technology developed would be useful for secure communication and high bandwidth communication.

REFERENCES:
1. Abram, R.H., Gardner K.S., Riis, E. & Ferguson, A.I. (2004). Narrow line width operation of a tunable optically pumped semiconductor laser. Optics Express 12, 5435. doi:10.1364/OPEX.12.005434

2. Hunziker, L.E., Ihli, C. & Steingrube, D.S. (2007). Miniaturization and power scaling of fundamental mode optically pumped semiconductor lasers. IEEE J. Quantum Electronics, 13, 1007.
doi: 10.1109/JSTQE.2007.896631

3. Kominis, I.K., Kornack, T.W., Allredm, J.C., & Romalis, M.V. (2003) A sub femtotesla multichannel atomic magnetometer, Nature, 422, 596. doi:10.1038/nature01484

4. Acosta, V., Ledbetter, M.P., Rochester, S.M., Budker, D., Jackson-Kimball, D.F., Hovde, D.C., Gawlik, W., Pustelny, S., Zachrowski, J. & Yashchuk, V.V. (2006). Nonlinear magneto-optical rotation with frequency modulated light in the geophysical field range. Phys. Rev. A, 73, 05304 .
doi: 10.1103/PhysRevA.73.053404

5. Gustavson, T.L., Bouyer, P. & Kasevich, M.A. (1997). Precision Rotation Measurements with an Atom Interferometer Gyroscope. PRL, 78 2046. http://pm1.bu.edu/~tt/qcl/pdf/gustavst19977e600601.pdf

6. Bize, S., Laurant, P., Abgrall, M., Marion, H., Maksimovic, I., Cacciapuoti, I., Grunert, J., Vinn, C., Pereira dos Santos, F., Rosenbusch, P., Lemonde, P., Santarelli, G., Wolf, P., Clarion, A., Luiten, A., Tobar, M. & Salomon, C. (2005). Cold atom clocks and applications. J. Phsy B, 38, S449. doi: 10.1088/0953-4075/38/9/002

KEYWORDS: compact lasers; atom interferometers; atom gyroscopes; atomic magnetometers; atomic clocks, alkali vapor sensors

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between April 26 and May 25, 2011, you may talk directly with the Topic Authors to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting May 26, 2011, when DoD begins accepting proposals for this solicitation.

However, proposers may still submit written questions about solicitation topics through the DoD's SBIR/STTR Interactive Topic Information System (SITIS), in which the questioner and respondent remain anonymous and all questions and answers are posted electronically for general viewing until the solicitation closes. All proposers are advised to monitor SITIS (11.2 Q&A) during the solicitation period for questions and answers, and other significant information, relevant to the SBIR 11.2 topic under which they are proposing.

If you have general questions about DoD SBIR program, please contact the DoD SBIR Help Desk at (866) 724-7457 or email weblink.