The maximization of the intrinsic optical nonlinearities of quantum structures for ultrafast applications requires a spectrum scaling as the square of the energy eigenstate number or faster. This is a necessary condition for an intrinsic response approaching the fundamental limits. A second condition is a design generating eigenstates whose ground and lowest excited state probability densities are spatially separated to produce large differences in dipole moments while maintaining a reasonable spatial overlap to produce large off-diagonal transition moments. A structure whose design meets both conditions will necessarily have large first or second hyperpolarizabilities. These two conditions are fundamental heuristics for the design of any nonlinear optical structure.
Spatially extended molecular structures, modeled as quantum graphs with one-dimensional electron dynamics,
exhibit optical responses that can approach the fundamental limits. We present the results of a comprehensive
study of the topological dependence of the nonlinearities of quantum graphs and show exactly how the first and
second hyperpolarizability of a graph depend upon its topological class and how the hyperpolarizability tensors
vary with graph geometry. We show how graphs with star motifs share universal scaling behavior near the
maximum nonlinear responses and articulate design rules for quantum-confined, quasi-one dimensional systems
that may be realized using molecular elements and nanowires.
We study the effect of geometry on the nonlinear response of a network of quantum wires that form loops. Exploiting
the fact that a loop’s transition moment matrix and energies are exactly solvable for each wire segment,
they can be pieced together to determine a loop’s properties. A Monte Carlo method is used to sample the
configuration space of all possible geometries to determine the shape that optimizes the intrinsic hyperpolarizability.
We suggest that a combination of wire geometry and confinement effects can lead to artificial systems
with ultra-large nonlinear response, which can be potentially made using known nanofabrication techniques.
Quantum graphs are graphical networks comprised of edges supporting Hamiltonian dynamics and vertices conserving probability flux. Lateral confinement of particle motion on every edge results in a quasi one-dimensional
quantum-confined system for which nonlinear optical effects may be calculated. Our ongoing research program
is the first to investigate the nonlinear optical properties of quantum graphs. We seek to discover configurations
with intrinsic first and second hyperpolarizabilities approaching their respective fundamental limits, to explore
the NLO variation with the geometry and topology of the graphs, and to develop scaling laws for more complex
graphs with self-similar properties. This paper describes a new methodology for calculating the hyperpolarizabilities
of a class of graphs comprised of sequentially-connected edges. Such graphs include closed-loop topologies
and their geometrically-similar but topologically-different open loop cousins, as well as other bent wire graphs
and their combinations.
Planar polymer waveguide technologies have shown the promise for applications in multi-port modulation and switching systems. We describe a key application of electro-optic polymer waveguides to modulator arrays and then illustrate the state-of-the-art performance obtained with our lxN thermo-optic switches.
Electro-optic (EO) poled polymer materials exhibit low dispersion and low dielectric constants. EO polymer materials have been modulated flat to 40 GHz and exhibit few fundamental limits for ultrafast modulation and switching. Channel waveguides and integrated optic circuits can be defined by the poling process itself, by photochemistry of the EO polymer, or by a variety of well understood micro-machining techniques. EO polymer materials have been used to fabricate high-speed Mach-Zehnder modulators, directional couplers, Fabry-Perot etalons, and even multi-tap devices. Practical issues remain to be solved before polymer photonic technology may be exploited in systems such as datacom and telecom. These include reliable, low cost fiber-attach and packaging, support circuitry and interfaces, and the scale-up to high volume production. This talk reviews requirements for practical exploitation and displays recent progress toward achieving reliable products.
Electro-optic polymer waveguide modulators may be used in parallel external modulation arrays supplied by branching structures providing fanout from a cw laser for a variety of applications, including CATV and data communications. This paper highlights some of the benefits of using EO polymer modulators in arrays for point-to-point digital data communications.
Electro-optic polymer waveguide modulators may be used in parallel modulation arrays supplied by branching structures providing fanout from a CW laser for a variety of applications, including CATV and data communications. This paper highlights some of the benefits of using EO polymer modulators in arrays for point-to-point digital data communications.
An approach to optical interconnect networks at the module level is presented that addresses the requirements imposed by electronic system manufacturing, such as thermal stability, low cost, and compatibility with standard electronic design, fabrication, and assembly processes. Research is presented on poled polyimide electro-optic materials with extended thermal stability, poled polyimide integrated optic switches acting as transmitters, and a demonstration of a CMOS-compatible optical interconnect.
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.
The exceptional electro-optic properties of poled polymer films, coupled with the power and flexibility of thin film fabrication and photolithographic processing, may make possible the hybrid integration of electronic and photonic devices, combining the processing power of VLSI with a dense, high bandwidth, photonic interconnection and switching network in a single, large format, package. In this paper, we describe the potential applications and benefits of electro-optic polymers for optical interconnection and present a review of some of the relevant progress to date in electro-optic polymer materials and devices. Development of an all-polyimide electro-optic polymer system (cladding/core/cladding) based entirely on commercially available components is described. An integrated optic Mach-Zehnder modulator was fabricated using this material system and used in a 200 Mbit/sec digital signal transmission optical interconnection demonstration. Lastly, a potential increase in electro-optic polymer integration density was illustrated by a proof of concept demonstration of three levels of waveguide structures on a single substrate.
Electro-optic (EO) polymers have emerged as a new class of materials for integrated optics and lightwave
device applications. We provide a concise engineering description of the state of EO polymer materials
development and then introduce their application to switchable, guided wave optical interconnections.
Such interconnections potentially offer higher routing density, lower noise, lower propagation delay, and
the simplification of many problems encountered in the design of high-frequency on- and off-module
connections for high-performance electronic systems.
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.
The exceptional electro-optic properties of poled polymer films, coupled with the power and flexibility of thin film fabrication and photolithographic processing, may make possible a new class of integrated optic systems: photonic large scale integration (PLSI). PLSI systems are characterized by the hybrid integration of electronic and photonic devices, combining the processing power of VLSI with a dense, high bandwidth, photonic interconnection and switching network in a single, large format, package. In this paper, we describe the potential applications and benefits of PLSI and present a review of some of the relevant progress to date in electro-optic polymer materials and devices, including the demonstration of polymer switch based 100 Mbit/sec digital signal transmission for optical interconnection and a 20 GHz electro-optic polymer modulator.
Electro-optic polymers exhibit many useful properties for distribution and routing of light on optical multilayer boards and modules. With the development of more robust materials it should soon be possible to use these materials to provide high-density interconnects at significant power savings and with reduced noise at frequencies above 100 MHz. We review the research toward creating new materials and devices for applications to packaging technology.
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.
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.
Glassy polymers, doped with nonlinear optical moieties, may be coated onto a variety of substrates and other polymers as
guiding layers for optical waveguides. A nonzero electro-optic effect is achieved in these materials by inducing a partial
alignment of the moieties. This paper describes a number of key properties of the materials and exhibits some of the features
of these materials that may lead to practical integrated optical components and modules.