Polymeric Waveguide Film Research Articles

Surface morphology of refractive-index waveguide gratings fabricated in polymer films

The characteristic modifications are reported on the surface of polymeric waveguide film in the process of volume- grating fabrication. The light from a mode-locked 76 MHz femtosecond laser with pulse duration of 200 fs and wavelength of 800 nm is focused normal to the surface of the sample. The surface morphology modifications are ascribed to a fact that surface swelling occurs during the process. Periodic micro-structure is inscribed with increasing incident power. The laser-induced swelling threshold on the grating, which is higher than that of two-photon initiated photo-polymerization (TPIP) (8 mW), is verified to be about 20 mW. It is feasible to enhance the surface smoothness of integrated optics devices for further encapsulation. The variation of modulation depth is studied for different values of incident power and scan spacing. Ablation accompanied with surface swelling appears when the power is higher. By optimizing the laser carving parameters, highly efficient grating devices can be fabricated.

Polymeric Waveguide Optical Switch With Bascule Structure Using Novel Trench Forming Process

We develop a polymeric waveguide optical switch with a bascule structure. Our novel matrix switch diverts light from one waveguide to a crossing waveguide in a polymeric waveguide film, using total internal reflection (TIR) of the interface between a waveguide and a trench at the waveguide cross point by mechanical actuation. The key technique for achieving a low-loss property is a novel cleaving method of forming trenches at waveguide cross points. We achieved a loss of 5 dB for the longest path of an 8 times 8 matrix switch demonstrator, high speed switching operation up to 100 mus, and reliable performance over 10 million times switching.

Polymeric Waveguide Film With Embedded Mirror for Multilayer Optical Circuits

A polymeric waveguide film with embedded mirrors is presented for a multilayer optical circuit. For the polymeric waveguide fabrication, arrayed waveguide patterns were directly formed on a metallic master body using ultra-precision machining (UPM) method, and 45deg-angled mirrors as beam reflector were constructed at the master pattern ends. We have achieved excellent surface roughness of the pattern and mirror facet using UPM. The waveguide lines and 45deg-angled mirrors were simultaneously fabricated on an under-clad sheet using an imprint method with a mirror-integrated master. We manufactured polymer waveguide films with embedded beam reflectors and consequently measured the optical characteristics of waveguides.

Polymeric Waveguide Optical Switch Using Rotary Drive Mechanism

We propose a polymeric waveguide optical switch using a novel drive mechanism. The switch uses a flexible polymeric waveguide film where trenches are formed at cross-points of the waveguides. Light passes through the trench while it is closed. When the trench opens, light path changes by total internal reflection between the air gap and the polymeric waveguide. Therefore, we can control light paths by changing the trench state between closed and open one. In order to realize this, a rotating arm is inserted near the trench. As rotational force transfers to the trench through the arm and the film, the trench switches from closed to open state and vice versa. We investigated this rotary drive mechanism by three-dimensional (3D) structural analysis, designed the optical switch, and experimentally demonstrated the switching operation.

Polymer waveguide grating fabricated by two-photon initiated photopolymerization and its application as an input coupler

Two-photon polymerization, initiated by 1-[(1E)-2-(4-{[4-((1E)-2-{4-[4-N,N-di-methylamino]phenyl}vinyl)phenyl]phenylamino}phenyl)vinyl]-4-[4-N,N-di- methylamino]benzene, is employed to fabricate volume index gratings in polymer waveguide. We demonstrate the implementation of input coupling by this grating into the polymeric waveguide film at 632.8nm wavelength. A simple approach to measure the refractive index and thickness of the polymer waveguide through the grating coupler is presented. The calculated refractive index and thickness are 1.51 and 1.99μm, respectively.

The fabrication of index-modulated grating coupler in a polymeric waveguide using two-photon initiated photopolymerization

A simple process suitable for fabrication of volume phase grating coupler in planar optical waveguide by two-photon initiated polymerization is presented. The volume phase grating has been written by scanning femtosecond laser pulses directly on the polymeric thin-film through a high numerical aperture lens. The areas of the index-modulated grating without morphology are 1.5 mm × 1.5 mm. The microstructure feature of coupling grating was illustrated. The corresponding index modulation reaches 0.03. We demonstrated the implementation of input coupling by this grating into the polymeric waveguide film. The measured coupling efficiency was about 11%.

Refractive index‐modulated grating in two‐mode planar polymeric waveguide produced by two‐photon polymerization

AbstractA polymeric waveguide film was manufactured by spinning the materials on quartz substrate. Two‐photon‐initiated photopolymerization was carried out by tight‐focusing femtosecond laser pulses in the two‐mode planar waveguide. A typical index‐modulated grating of 2.5 × 2 mm areas without morphology was fabricated. The results show that peak‐to‐peak modulation depth of the surface profile of grating region was only about 7 nm. The diffraction efficiency (DE) of the grating with a spacing period 2 µm was 0.17% and the corresponding index modulation reached 5.7 × 10−3. Copyright © 2007 John Wiley & Sons, Ltd.

Fabrication of grating waveguide using photopolymerization

Two ternary materials systems, which comprise photoinitiator/two-photon initiators, oligomer and binder were prepared. Polymeric waveguide film was manufactured by spinning the materials on optical glass (refraction index=1.5), the two-photon initiated photopolymerization (TPIP) and single-photon holographic photopolymerization were carried out respectively in the polymer waveguide film. The preparation of these materials was explained and absorption spectra were tested. The experimental results including the micrographs and diffraction patterns verifying the formation of grating waveguide structures were given. The results show that grating waveguide microstructures can be holographically fabricated by single-photon photopolymerization with low-power (tens mW) continuous-wave (CW) laser at 532 nm successfully. Because the continuous-wave laser at 532 nm is handier than one at 514 nm.

Electrical and optical properties of planar waveguide using the field-induced polypelargonamide material

Abstract New polymeric waveguide films were fabricated by electric field poling procedures and the electric and optical properties of the poled films were examined with polarized infrared spectroscopy and m-line spectroscopy. The lowering of the amide band intensity in the infrared spectra shows direct evidence of the poling treatments. The optimum poling treatments could be determined by means of the I–V curves. The anisotropic refractive indices of the poled polypelargonamide slab waveguide were determined by the m-line angle spectrum. From the in situ relaxation investigation for the remaining current and the TE-mode reflected intensity of the samples, it was found that the decay curve can be expressed by a simple exponential function of time; the average relaxation time was approximately 25 min.

A fabrication of coupling grating in the polymeric waveguide by using two-photon initiated photopolymerization

A ternary materials system, which comprises two-photon initiator, oligomer and poly(methyl methacrylate), was prepared. A polymeric waveguide film was manufactured by spinning the materials on ITO, and the two-photon initiated photopolymerization (TPIP) was carried out successfully in the waveguide film. Consequently, an approach using TPIP is demonstrated for fabrication of coupling grating in a thin polymeric film possessing waveguide properties. The results show that the incident laser can be coupled into the polymeric film by this coupling grating obtained from TPIP. The microstructure feature of coupling grating is illustrated, and waveguide mode and transmission loss of the polymeric film are investigated.

High-Resolution Pattern Reproduction by Cold Ultra Violet Stamping in Optical Polymeric Films

In this paper, we present a new method of waveguide-type device fabrication using an optical polymer. This method is applied to the fabrication of a grating on top of a polymeric waveguide film where, we used a mixture of pentaerythritol triacrylate, N-methyldiethanolamin, and eosin as a polymer material. This mixture, called henceforward PNME, acts as a negative-type photoresist polymeric material. Exposure of the material to light of specific wavelength makes the material solidify. Using this particular property of PNME and the fact that before the solidification PNME material is liquid, and thus copies the volume of the vessel where it is contained, we were able to fabricate polymeric films and waveguides with a relief grating on their surfaces. It was also determined that the interface between the side walls of the vessel and the PNME material plays a vital role in the fabrication process. Moreover, the presented method of fabrication is a high-resolution, high-output, and low-cost method of optical device fabrication and thus it is particularly suitable for commercial use.

Implementation of active interposer for high-speed and low-cost chip level optical interconnects

A novel optoelectronic input/output interface module termed "active interposer" and polymeric waveguide film lamination technologies have been developed for optical interconnects between large-scale integration chips. The fabricated active interposers comprise vertical cavity surface emitting lasers, metal-semiconductor-metal photodiodes, submount, and Si circuits stacked via through-hole electrodes built inside the optoelectronic devices and submounted to achieve high-speed low-crosstalk noise and high-density interconnect performances. Also, waveguide film lamination technologies developed are capable of cost reductions. This paper describes the prototype demonstration of the active interposers assembled on the waveguide film-laminated printed circuit boards. Processing and test results of the fabricated optoelectronic devices suitable for three-dimensional stacking are also addressed.

Polymeric optical waveguide films for short-distance optical interconnects

We describe three different applications of polymeric waveguide films as short-distance optical interconnects. We fabricated the waveguide films, which were 6.5 cm long and mounted in MT-compatible (MTC) connectors by passive alignment, for MM fiber systems with a 50-/spl mu/m diameter graded index (GI) core. The average insertion loss of these devices was approximately 0.6 dB at 0.85-/spl mu/m wavelength. We also fabricated waveguide films with a 350 mirror and an MTC connector for use as 90/spl deg/ out-of-plane optical deflectors, and they exhibited an insertion loss of 1 dB. Two silica planar waveguides for single-mode (SM) fiber systems were also connected by a polymeric waveguide film. Low insertion losses were obtained in both MM and SM films designed to be employed as bending waveguides. This reveals their good potential for use as practical short-distance optical interconnects.

Packaging for a 40-channel parallel optical interconnection module with an over-25-Gbit/s throughput

NTT is currently working on developing a high-throughput interconnection module that is both compact and cost effective. The technology being developed is called parallel inter-board optical interconnection technology, or ParaBIT. The ParaBIT module that has been developed is the first step; it is a front-end module with 40 channels, a throughput of over 25 Gbit/s, and a transmission distance of over 100 m along multimode fibers. One major feature of this module is the use of vertical-cavity surface-emitting laser (VCSEL) arrays as very cost-effective light sources. These arrays enable the same packaging structure to be used for both the transmitter and receiver. To achieve super-multichannel performance, high-density multiport bare-fiber (BF) connectors were developed for the module's optical interface. Unlike conventional optical connectors, these BF connectors do not need a ferrule or spring. This ensures physical contact with an excellent insertion loss (less than 0.1 dB per channel). A polymeric optical waveguide film with a 45/spl deg/ mirror for coupling to the VCSEL and photo-diode (PD) arrays by passive optical alignment was also developed. To facilitate coupling between the VCSEL/PD array chips and the waveguide, a packaging technique was developed to align and die bond the optical array chips on a substrate. This technique is called transferred multichip bonding (TMB); it can be used to mount optical array chips on a substrate with a positioning error of only several micrometers. These packaging techniques enabled ultra-parallel interconnections to be achieved in prototype ParaBIT modules.

Polymeric optical waveguides for optical interconnections

Free-standing polymeric optical waveguide films with 45° mirrors and MT connectors (mechanically transferable spacing connectors) were fabricated by spin-coating, photolithography and reactive ion etching. The spin-coated films had sufficient thickness controllability and surface smoothness for them to be used to fabricate multimode waveguides with a low loss of less than 0.02 dB/cm at 0.83 μm using deuterated-polymethylmethacrylate for the core and UV-cured resin for the cladding. For application to optical interconnections, a 45° mirror was formed in the waveguide by using a 90° V-shaped diamond blade, and the mirror loss was 0.3–0.7 dB depending on the measurement conditions. Free-standing polymeric waveguide films were mounted in an MT-compatible connector made of Pyrex glass by using UV curable resin. The insertion loss was about 1 dB which was sufficiently low for practical use.

ポリマー光導波路フィルムの表面状態の評価

Polymeric optical waveguide films have been developed with a view to optical interconnection module applications. Three fabrication processes are employed: (1) spin coating to form thick films, (2) reactive ion etching (RIE) to form core ridges, and (3) cutting with a diamond saw to form 45° mirrors. We evaluated the surface roughness of the fabricated films, core-ridges and mirrors using an atomic force microscope (AFM) and a scanning electron microscope (SEM), and discuss them in relation to the optical characteristics. Spin coating provides a uniform film with a roughness of less than 3nm. The etched surfaces of the core ridges fabricated by RIE have a roughness of less than 0.3μm, which suggests that this roughness causes the loss of the curved waveguide. The diamond saw cutting process generated a roughness of 50nm over the whole surface with occasional projections several hundred nanometers high, suggesting that this roughness causes the mirror loss.We confirmed that it is possible to fabricate polymer optical waveguide films with sufficient levels of performance for use in optical interconnection modules.

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

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