R. Lytel

Poled electro-optic waveguide formation in thin-film organic media

We describe a novel technique for the fabrication of electro‐optic (EO) waveguides in integrated optic device structures employing organic EO materials. The technique combines the poling and waveguide formation steps by utilizing patterned poling electrodes and the induced birefringence associated with the poling process. Several prototype waveguide devices fabricated using this procedure are reported.

20 GHz electro‐optic polymer Mach–Zehnder modulator

An electro‐optic (EO) polymer‐based integrated optic Mach–Zehnder modulator with a measured frequency response up to 20 GHz is reported. The device was fabricated with an EO polymer supplied by Akzo Research, bv, and utilized 50 Ω microstrip drive electrodes. A half‐wave voltage of Vπ=9 V and a modulation depth of 90% were measured at 2 kHz. Modulation was observed out to 8.0 GHz using direct detection and out to 20 GHz using a frequency mixing technique, limited by the drive and receiver electronics.

Thermal stability of electro-optic response in poled polyimide systems

Using polyimide as host in a guest‐host thin film we demonstrate the first poled‐polymer electro‐optic response stable at temperatures up to 150 °C (samples poled and cured at 250 °C). A coplanar‐electrode poling geometry is used so that the molecular alignment of the guest dye between the electrodes is coincident with the free volume of the host. We hypothesize that ‘‘high’’ temperature poling during the imidization process, when the polyimide forms rings and densifies, accounts for the excellent poled response stability.

Complementary optical tap fabricated in an electro‐optic polymer waveguide

An active complementary optical tap made in an electro‐optic polymer waveguide is reported for the first time. This device is the critical component of an optical railtap, a system capable of providing many optical interconnects with a single laser source. The device was fabricated by selective photobleaching of a uniformly poled polymer layer, and complementary switching was demonstrated.

DCM‐polyimide system for triple‐stack poled polymer electro‐optic devices

We report development of the first all‐polyimide system (cladding/core/cladding) suitable for fabrication of electro‐optic waveguide devices on silicon substrates. The cladding layers are spun from a low optical loss, commercially available polyimide that is suitable for multilayer stacks. The electro‐optic material consists of this same polyimide as host to a commercially available guest chromophore and is based upon our prior work on thermoplastic polyimides [J. F. Valley, J. W. Wu, S. Ermer, M. Stiller, E. S. Binkley, J. T. Kenney, G. F. Lipscomb, and R. Lytel, Appl. Phys. Lett. 60, 160 (1992)]. We present the materials and process development methodology with the results for this polymer system and demonstrate it by fabrication of an all‐polyimide Mach–Zehnder modulator operating at 830 nm.

Thermoplasticity and parallel‐plate poling of electro‐optic polyimide host thin films

We demonstrate the first polyimide guest/host system which exhibits stable electro‐optic response after parallel‐plate poling. Such systems are based on a class of polyimides which, once cured, possess a clear glass transition in their dielectric relaxation spectra, characteristic of thermoplasticity. After doping with compatible nonlinear optical molecules the polyimide host system can first be thermally imidized (cured) and then poled with an electric field. High glass transition temperatures are achieved leading to excellent thermal stability of the poled electro‐optic response.

Developments in organic electro-optic devices at Lockheed

We report on the recent development and initial test results of two electro-optic polymer based integrated optic devices for optical interconnection applications. The first is an optical railtap for the distribution of many different optical signals from a single CW laser diode, and the second is a traveling wave Mach-Zehnder integrated optic modulator, which was modulated at frequencies up to 8 GHz. Electro-optic polymer materials supplied by Akzo Research, By, were used in both devices.

Chemical imidization for enhanced thermal stability of poled electro‐optic response in polyimide guest‐host systems

Chemical imidization at room temperature is employed as a novel curing process for dc electric field poled electro‐optic (EO) polyimide guest‐host systems. Dehydration occurring through imidization of the polyamic acid is completed chemically after poling rather than thermally during poling. After thermal aging at 155 °C (above the poling temperature) chemically imidized samples retain over 30% of their original poling induced EO signal while similarly poled samples, which have not been chemically imidized, produce a null EO response.

Electro-optic polymers for optical interconnects

Glassy nonlinear optical polymers can be processed into channel waveguides. When poled, the channels become electrooptic and can switch and modulate light. Using lithographic and machining techniques familiar to the chip industry, it should be possible to integrate large numbers of electrooptic switches into a board-level package or module, and thus provide the additional benefits of active switching and reconfiguration to passive hybrid optical interconnect modules. Some of the properties of the materials, some process methods, and potential applications in optical interconnection are described.

Organic Electro-Optic Waveguide Modulators And Switches

Organic and polymeric materials exhibit many important properties as electro-optic materials. Poled polymer films are particularly well suited for integrated optic devices, due to their large electro-optic coefficients, low dielectric constants, and flexible processability. We review our work toward the fabrication of active polymer integrated optic devices based on a newly developed channel waveguide fabrication procedure, and detail some of the properties of the devices.