TECHNOLOGY AREAS: Materials/Processes, Sensors, Electronics

ACQUISITION PROGRAM: PMW-180; Ship’s Signal Exploitation Equipment, ACAT III

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: To develop Lithium Niobate (LiNbO3) based electro-optic (EO) modulators with improved modulation efficiency and low optical loss by considering designs with novel device geometries.

DESCRIPTION: The design of external EO modulators requires consideration of many factors, including modulation efficiency, optical loss, modulation bandwidth, frequency chirp, optical power handling ability, lifetime, and cost [1]. The need for low noise figure (NF) high dynamic range (DR) RF-over-fiber links for various DoD applications has driven the development of optical modulators with increased modulation efficiency, as characterized by a decreased half wave voltage (Vpi), and decreased optical insertion loss. Currently, the lowest noise figure RF photonic link performance has been achieved with links using high power 1.55 um lasers sources and external Mach-Zehnder (MZ) modulators fabricated in LiNbO3 [2]. The design of LiNbO3 modulators typically employ waveguides fabricated on a planar substrate using x-cut or z-cut LiNbO3 [1]. In fact, impressive recent developments in improving LiNbO3 modulator performance (e.g., Vpi approaching 1 V, with optical insertion loss less than 10 dB) have been achieved by device design improvements largely in electrode structure without additional major modifications to typical device geometry. Modification to the device geometry can offer improved coupling between the electric and optical fields, as well as improved velocity matching, suggesting that devices with improved modulation efficiency and wideband performance are achievable [3] [4]. This SBIR topic focuses on development of LiNbO3 modulators designs that consider novel device geometries to achieve low Vpi, and low optical loss performance beyond the current state of the art. The application of these modulators is in RF photonic links also use a high optical power source and high power photodetectors to achieve low noise figure, and high dynamic range. The proposed approach should be practical to implement leading to a relatively low-cost, high-yield manufacture process.

PHASE I: Design study of a LiNbO3 EO intensity modulator which achieves improved performance for RF analog applications as compared to the current state-of-the-art via novel device geometries to achieve high modulation efficiency and low optical loss. The study shall address all aspects of device fabrication (e.g., substrate, waveguide design, electrodes, packaging), and justify the feasibility/practicality of the approach. A specific device design shall be proposed for fabrication in phase II of the project. DoD applications require modulation bandwidths up to Ka band, therefore the approach should consider and be compatible with a traveling wave design, though the specific device to be fabricated in phase II of the project may operate at lower frequency.

PHASE II: Develop the required processes for device fabrication. Based on the phase I design, fabricate and characterize a prototype EO intensity modulator, including measurement of Vpi and optical insertion loss. While demonstration of a traveling wave design is preferred, demonstration of a low frequency device with a path to a high frequency traveling wave design is acceptable.

PHASE III: Based on the prototype developed in phase II, continuing development shall lead to production of commercial grade, low Vpi, low optical loss phase and intensity modulators with bandwidths up to Ka band.

PRIVATE SECTOR COMMERCIAL POTENTIAL.DUAL-USE APPLICATIONS: Modulators developed under this program can be applied to commercial applications, e.g., satellite base station antenna remoting, and for developing multilevel digital communication formats, e.g., high-speed QAM.

REFERENCES: 1. G.P. Agrawal, "Lightwave Technology," chapter 6.2, John Wiley & Sons Inc., (2004).

2. E. Ackerman, et. al., "Low Noise Figure, Wide Bandwidth Analog Optical Link," International Topical Meeting on Microwave Photonics, 2005, pp 325- 328.

3. R. Cheng, W. Chen, W. Wang, "MZ modulators with Lithium niobate ridge waveguides fabricated by proton-exchange wet etch and Nickel indiffusion," IEEE Photonics Technology Letters, vol. 7, (1995).

4. P. Rabiei and W.H. Steier, "Electro-optic waveguide modulators fabricated using thin films of Lithium niobate," 2005 Quantum electronics and Laser Science Conference, pp 945-947.

KEYWORDS: RF photonics; microwave photonics; electro-optic modulator; Mach Zehnder modulator; waveguides; Lithium niobate.

TPOC: Everett Jacobs
Phone: (619)553-1614
Fax:
Email: jacobs@spawar.navy.mil
2nd TPOC: William Kordela
Phone: (619)524-7316
Fax: (619)524-7374
Email: william.kordela@navy.mil

** TOPIC AUTHOR (TPOC) **

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