To fully realize the potential of OPGaAs-based nonlinear optical materials, researchers must still address some significant challenges. Although 1 mm thick HVPE-grown GaAs is now possible, the material’s periodic pattern is often lost after the first few hundred microns, as the alternating regions grow together (see Figure 2). This limits the area in which nonlinear conversion can occur. A second issue with these materials is optical loss resulting from both scatter and absorption. This loss is generally higher in patterned regions than in unpatterned regions (suggesting that the boundaries between alternating domains may play a role), but the specific causes and mitigation strategies remain unclear. A loss coefficient of 0.01 cm-1 is generally considered favorable for practical devices, but this represents an order of magnitude better performance than most current samples attain. Finally, researchers must improve HVPE thick-layer growth methods to achieve a reliable, safe, production-oriented process.

Through the CARMA program and related efforts, AFRL sensors scientists are working with industry partners to address these challenges, as well as to extend the orientation patterning technique to other promising materials. Future plans include both a follow-on effort to build upon CARMA’s accomplishments and a collaboration with AFRL’s Survivability and Sensor Materials Division scientists to leverage their expertise and improve fabrication processes for a broad spectrum of candidate materials.

Dr. Rita Peterson, of the Air Force Research Laboratory’s Sensors Directorate, wrote this article. For more information, contact TECH CONNECT at (800) 203- 6451 or place a request at http://www. afrl.af.mil/techconn_index.asp. Reference document SN-H-06-02.

References

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