Batio3 Thin Film Waveguides and Related Modulator Devices (24060)

A low-voltage, wide bandwidth, strip-loaded BaTiO3 thin film electrooptic amplitude modulator for use in high-speed optical communication networks has been created by Northwestern researchers. Broadband modulation out to 40 GHz has been demonstrated, offering the potential for low power electrooptic waveguide modulators with high EO coefficient.

ADVANTAGES: The new modulator construct indicates 3-dB operational bandwidth in excess of 40 GHz is achievable through optimized design.

SUMMARY: Electrooptic waveguide modulators are essential for high speed and wide bandwidth optical communication systems. Lithium Niobate (LiNbO3) has been widely used for low loss, low drive voltage, high-speed modulators because of its large electrooptic coefficient and excellent optical transparency. However, Barium Titanate (BaTiO3) with a 1300 pm/V bulk electrooptic coefficient (forty times greater than Lithium Niobate) promises improved performance while employing smaller devices. Nevertheless, the large bulk dielectric constant of BaTiO3 limits its high modulation bandwidth operation. Use of a BaTiO3 / MgO composite affords a lower effective microwave index and improves velocity matching between the microwave and optical waves. Furthermore, BaTiO3 can be integrated with silicon substrates using a thin film MgO buffer layer, allowing integration on a single multicomponent chip with reduced packaging costs.

This invention presents a modulator composed of low refractive index Si3N4 strips deposited on a BaTiO3 / MgO substrate (Figure 1). A modulator with 5.0 mm long electrodes exhibits a 1.0 V low half-wave voltage. A 360pm/V effective electrooptic coefficient at 1561 nm was determined. The strip-loaded geometry exhibits extremely low propagation (0.9 dB/cm) and polarization dependent (0.1 dB/cm) losses.–3 dB bandwidth of 15 GHz was demonstrated and modulation up to 40 GHz was observed. (Figure 2)

STATUS: Sample materials have been produced and characterized. Northwestern University seeks a partner to commercialize this invention. 7,224,878

Patents:
US 7,224,878

Inventor(s): Pingsheng Tang, David Towner, Anthony Meier and Bruce Wessels

Type of Offer: Licensing



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