Polymer composites are one of the most attractive near-term means to exploit the unique properties of carbon nanotubes and graphene. This is particularly true for composites aimed at electronics and photonics, where a number of promising applications have already been demonstrated. One such example is nanotube-based saturable absorbers. These can be used as all-optical switches, optical amplifier noise suppressors, or mode-lockers to generate ultrashort laser pulses. Here, we review various aspects of fabrication, characterization, device implementation and operation of nanotube-polymer composites to be used in photonic applications. We also summarize recent results on graphene-based saturable absorbers for ultrafast lasers.

Nanotube–Polymer Composites for Ultrafast Photonics

Polymeric electro-optic materials have recently been developed that, when fabricated into devices such as Mach-Zehnder interferometers, permit drive ( Vπ) voltages of less than 1 V to be realized at the telecommunications wavelength of 1.3 and 1.55 microns. Operation of polymeric electro-optic modulators to frequencies (bandwidths) of greater than 100 GHz has been demonstrated. The total insertion loss of polymeric electro-optic modulators has been reduced to values as low as 5 dB, which is competitive with values obtained for lithium niobate modulators and is much lower than that obtained for gallium arsenide electro-absorptive modulators. Polymeric electro-optic modulators can be operated for long periods of time at temperatures on the order of 100 °C. Techniques have been developed for seamlessly integrating polymeric electro-optic circuitry with passive low loss optical circuitry (e.g., silica long-haul transmission fiber and medium-range fluoropolymer fibers) and with very large scale integration (VLSI) semiconductor electronics. These advances have created a considerable interest in the commercialization of polymeric electrooptic materials. Polymeric electro-optic materials are now being evaluated for applications such as phased array radar, satellite and fiber telecommunications, cable television (CATV), optical gyroscopes, electronic counter measure (ECM) systems, backplane interconnects for high-speed computers, ultrafast (100 Gbit/s) analog-to-digital (A/D) converters, land mine detection, radio frequency (rf) photonics, and spatial light modulators. This review discusses the structure-function relationships that had to be defined and the synthesis and processing advances achieved before materials appropriate for commercialization could be produced. Topics discussed include the design and synthesis of chromophores that simultaneously exhibit large molecular hyperpolarizability, low optical absorption, processability (e.g., solubility in various processing media), and the prerequisite (thermal, chemical, electrochemical, and photochemical) stability to survive conditions encountered in the fabrication and operation of polymeric electro-optic devices. Chromophore-chromophore intermolecular electrostatic interactions have been shown to be the most serious problem impeding the optimization of electro-optic activity in organic materials. The quantitative theoretical treatment of such interactions by equilibrium and Monte Carlo statistical mechanical methods is discussed. Rules for designing chromophores with shapes leading to maximum obtainable electro-optic activity are discussed and the synthetic realization of such structures is reviewed. The role of electrostatic interactions in influencing the choice of processing conditions is also discussed. A number of processing steps, including spin casting, electric-field poling, lattice hardening, fabrication of buried channel waveguides (including deposition of cladding layers), electrode deposition and connection with electronic circuitry, and integration of active and passive optical circuitry, are required. Each of these steps can affect device performance (e.g., influence optical loss, electro-optic activity, and stability). The systematic optimization of each of these steps is reviewed. Finally, device design and operation are reviewed and speculation on the future of the field is expressed.

Nonlinear Optical Polymeric Materials: From Chromophore Design to Commercial Applications

A common photodetecting unit detects a plurality of beams scanned by a plurality of polyhedral reflection mirrors provided in a multiple stages with a common rotation axis, and generates a synchronization detection signal based on detected beams. The reflection mirrors make a predetermined angle θ1 in a direction of rotation of the reflection mirrors. When time between two consecutive synchronization detection signals on a time line generated by the common photodetecting unit is ti, where i is a positive integer equal to or smaller than number of split beams, at least one of ti is different from others.

Optical scanning device and image forming apparatus

This paper demonstrates a flexible optical waveguide film with integrated optoelectronic devices (vertical-cavity surface-emitting laser (VCSEL) and p-i-n photodiode arrays) for fully embedded board-level optical interconnects. The optical waveguide circuit with 45/spl deg/ micromirror couplers was fabricated on a thin flexible polymeric substrate by soft molding. The 45/spl deg/ couplers were fabricated by cutting the waveguide with a microtome blade. The waveguide core material was SU-8 photoresist, and the cladding was cycloolefin copolymer. A thin VCSEL and p-i-n photodiode array were directly integrated on the waveguide film. Measured propagation loss of a waveguide was 0.6 dB/cm at 850 nm.

Flexible optical waveguide film fabrications and optoelectronic devices integration for fully embedded board-level optical interconnects

The present invention provides a process for producing a flexible optical waveguide which comprises the steps of: immersing a substrate having an optical waveguide formed thereon in water to thereby reduce adhesion between the optical waveguide and the substrate and then peeling the optical waveguide from the substrate; temporarily bonding the peeled optical waveguide to a surface of a pressure-sensitive adhesive layer containing a foaming agent; cutting the temporarily bonded optical waveguide into a given length; allowing the foaming-agent-containing pressure-sensitive adhesive layer after the cutting step to foam by heating, thereby reducing adhesion between the foaming-agent-containing pressure-sensitive adhesive layer and the optical waveguide; and peeling the optical waveguide cut into the given length from the foamed adhesive layer.

Process for producing flexible optical waveguide

Polymeric optical waveguides for optical interconnections

An optical waveguide of an optical deflector comprising a planar optical waveguide or an optical fiber type optical waveguide is cut while perpendicularly pressing a blade having a blade tip with an angle of inclination against the optical waveguide at a desired location thereof to form an oblique end face serviceable as an oblique end face mirror.

Optical deflector, process for producing the same, and blade for use in production of optical deflector

A novel method for forming high quality 45/spl deg/ mirrors in polymeric waveguides is described. Singlemode and multimode polymeric waveguide films with 450 mirrors were fabricated by cutting the waveguide with a 90/spl deg/ V-shaped diamond blade. The mirror losses were as low as 0.1 dB for the single mode and 0.3 dB for the multimode waveguides.

Polymeric optical waveguide films with 45° mirrors formed with a 90° V-shaped diamond blade

Singlemode polymeric optical waveguides are fabricated by using newly synthesised deuterated polysiloxane with high transparency and high thermal stability. The propagation loss of the waveguides is measured and found to be less than 0.1 dB/cm at 1.31 mu m and less than 0.5 dB/cm at 1.55 mu m. The propagation loss dependence on wavelength in the infra-red region of the waveguide remains unchanged after heating at 120 degrees C for 10 h.

Low-loss polymeric optical waveguides with high thermal stability

PROBLEM TO BE SOLVED: To provide an optical path changing element having high performance being effective for high integration of an optical module such as an optical transmitter-receiver and reduction of an assembling cost by forming a V groove in an optical waveguide by means of an entrance/exit plane and a tilt end face. SOLUTION: By performing cutting operation using a diamond blade 40 having a machined point of blade of about 90 deg., a V groove 12a having tilt end faces 6, 6 is formed on a planar optical waveguide. Since a dicing saw is used, machining with the positional accuracy of a sub-micron order is performed in both horizontal and height directions. The depth of machining may be deeper than the boundary surface between a core 3 and a lower clad 5 and the machining is either stopped in the lower clad 5 or cut into a substrate 1. Since the diamond blade is equally matched to an abrasive paper used for grinding optical parts, this machining process has an effect equivalent to simultaneous execution of machining of the tilt end face and surface grinding of high optical grade and the excellently smooth machined surface is obtained.

Mitsuo Usui

Papers

Polymeric optical waveguides for optical interconnections

Optical deflector, process for producing the same, and blade for use in production of optical deflector

Polymeric optical waveguide films with 45° mirrors formed with a 90° V-shaped diamond blade

Low-loss polymeric optical waveguides with high thermal stability

Optical path changing element, manufacture thereof and blade for manufacturing the optical path changing element