George F. Lipscomb

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.

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.

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.

Narrowband electrooptic tunable notch filter

We describe the theory of a narrowband electrooptic tunable filter based on a Fabry-Perot etalon with distributed Bragg reflectors. The filter can be in either bulk or waveguide form. The input to the filter must be prefiltered to the stop-band of the Bragg mirrors. Once this is accomplished, the etalon possesses a very narrow notch in the Bragg filter stop-band. The notch width is extremely narrow when the Bragg reflectance is high. The location of the notch in the Bragg stop-band is determined by the etalon cavity length and can be tuned by application of an electric field to the electrooptic material comprising the etalon cavity. Absorption in the cavity and Bragg reflectors is included in the theoretical model of the filter. The filter can be constructed from any one of several existing electrooptic organic polymer crystals, if the gratings are made either by partial polymerization of the monomer in crossed-UV beams or by corrugating the surface of the polymer. We show a theoretical example of a notch filter operating at a center wavelength of 1 microm that is 62.75 microm thick, with a notch width of under 1 A and a transmission of 35%. This type of filter should have applications in high-speed optical modulation and Q-switches for lasers.

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

We report the background leading to the 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. The synthesis and purification of this chromophore and an analog is discussed. We also 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. CMOS-compatible switching using a device based on the new material has been demonstrated.

Poled polyimides as thermally stable electro-optic polymer

Using polyimide as host in a guest-host electro-optic thin film a thermally stable poled electro- optic response is demonstrated at temperatures at 150 degree(s)C and 300 degree(s)C. A coplanar-electrode poling geometry is used so that the guest molecular alignment between the electrodes is coincident with the free volume of the host. Electric field poling during curing process including imidization (170 - 230 degree(s)C) and densification (340 - 380 degree(s)C) accounts for the highly thermally stable electro-optic response.

Advances in Organic Electro-Optic Devices

We report initial experiments on the fabrication of active and passiveintegrated optic device structures based on poled polymer electro-optic buried channel waveguides. The process of channel waveguide definition and fabrication through electric field poling is described and experimental results are presented. The fabrication, theoretical performance modeling and experimental evaluation of several integrated optic device structures, including phase modulators, directional couplers and Y-branch interferometers, are also reported.