TECHNOLOGY AREAS: Sensors, Electronics

OBJECTIVE: Develop a wavelength agile (tunable), high energy per pulse, high repetition rate, blue laser for airborne oceanographic LIDAR systems.

DESCRIPTION: A wavelength agile, high energy per pulse, high repetition rate blue fly-able laser for oceanographic LIDAR systems is sought. While current state of the art technologies (including Optical Parametric Oscillators (OPOs), wavelength doubling of Ti:Sapphire based lasers, doubling and tripling of other laser hosts, and blue laser diodes), meet a few of the required characteristics, there are none that meet all of the requirements to support our objectives. Our system requires all of the design thresholds in order to be effective. Additionally, currently funded SBIR projects for developing blue laser technologies can not be leveraged due to design constraints limiting those efforts to a fixed, single wavelength and lower energies than required.

The desired laser should have the following characteristics (in order of priority but all are required to be met simultaneously):
1. Wavelength agile (tunable) blue laser output (Threshold: tunable through 460-485nanometer; Objective: tunable through 450-490nanometer, both with suitable power and repetition rate in a range listed in objectives 2 and 3). Laser wavelength needs to be agile after construction: i.e. wavelength needs to be user tunable, not fixed after design implementation.
2. High energy per pulse (Threshold: at least 10 milli joule per pulse @1KHz rep rate, Objective: at least 15 milli joule per pulse@1 KHz rep rate)
3. High repetition rate (Threshold: >750 hertz, Objective 1000 hertz)
4. Short nanosecond pulse width, Threshold: 30 nanosecond pulse width (FWHM), Objective: 10 nanosecond pulse width (FWHM)
5. Beam Quality: Threshold: M2 < 1.5 symmetric, Objective: M2 < 1.1 symmetric
6. Line width of: Threshold: <0.1nanometer, Objective: <0.01nanometer
7. Divergence: Threshold: 5 milli radian, Objective: 1 milli radian

PHASE I: Determine feasibility of producing a laser with the characteristics listed above. The final product must meet ALL of the above requirements. However, emphasis during Phase I should be placed on meeting characteristics 1, 2 and 3 with a clear path to implementing a design that meets all of the above specs during Phase II.

PHASE II: Build a bread board, laboratory laser based on the method from Phase I which exhibits all characteristics listed above. Test and fully characterize the system operation in the laboratory.

PHASE III: Build a ruggedized brass board system for operation by NAVAIR employees proficient in laser systems operation in aircraft environments and obtain certification for flight on a NAVAIR aircraft to be determined. Provide support to NAVAIR during test and evaluation flights.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: High energy per pulse lasers have applications in manufacturing and lithography. Oceanographic bathymetry systems for survey and exploration work would benefit greatly from this laser. Higher repetition rate versions of this laser could have applications to underwater communications systems.

REFERENCES:
1. Y. Chen, H. Peng, W. Hou, Q. Peng, A. Geng, L. Guo, D. Cui and Z. Xu, "3.8 W of cw blue light generated by intracavity frequency doubling of a 946-nm Nd:YAG laser with LBO" Applied Physics B, 83, 241, (2006).

2. Y. Kong, X. Lin, R. Li, Z. Xu and X. Han, "A novel blue light generation by frequency doubling of a diode-pumped Nd:YAG thin disk laser," Optics Communications, 43, 405, (2004).

3. M.O. Ramírez, J.J. Romero, P. Molina and L.E. Bausá , "Near infrared and visible tunability from a diode pumped Nd3+ activated strontium barium niobate laser crystal," Applied Physics B, 81, 827, (2005).

4. H. Peng, W. Hou, Y. Chen, D. Cui, Z. Xu, C. Chen, F. Fan, and Y. Zhu, "Generation of 7.6-W blue laser by frequency-tripling of a Nd:YAG laser in LBO crystals," Optics Express, 14, 6543, (2006).

5. O. Kimmelma, M. Kaivola, I. Tittonen and S. Buchter, "Short pulse, high peak power, diode pumped, passively Q-switched 946 nm Nd:YAG laser," Optics Communications, 273, 496, (2007).

6. Fundamentals of Photonics; B.E.A. Saleh; Wiley Interscience; 2007.

7. A. Kaminskii, et.al, "High efficiency nanosecond Raman lasers based on tetragonal PbWO4 crystals," Opt. Comm. 183, Pg. 279 (2000).

KEYWORDS: Wavelength Agile; Tunable; Blue Laser; High Power; High Energy Per Pulse; High Repetition Rate; Oceanographic Lidar