Multistage Polymeric Lens Structures Integrated into Silica Waveguides

Lenses are among the key components in optical signal processing and computing systems(1). Realization of such optical systems in a waveguide substrate has long been considered one of the major applications of integrated optics. Recently, the prospects for this realization are significantly advanced through progress in guided-wave microoptic components of both active and passive types. Aside from the study on integrated acoustooptic RF spectrum analyzers(2) that has become an international effort, serious attempts to utilize the integrated optic devices for optical computation of both analog and digital data are also being made at various research institutions. Accordingly, it is of great importance to develop viable techniques for fabrication of waveguide lenses with application to optical computing. A variety of planar waveguide lenses including the geodesic, chirp-grating, Fresnel, and Luneburg types have been reported in the literature. A common characteristic of these lenses is a relatively long focal length and a relatively small numerical aperture. It is to be noted that a channel waveguide lens involving multiple coupled-waveguides has also been proposed most recently(3). In this paper we report on the single-mode planar waveguide microlenses and microlens arrays in LiNbO3 that are formed using titanium indiffused-proton exchange technique(4). These waveguide lenses have demonstrated desirable properties including very short focal length, large numerical aperture, very small focal spot size for a wide range of focal length, and low optical insertion loss at the 6328 Å He-Ne laser wavelength.

High silica glass planar circuits (Planar Lightwave Circuits: PLCs) are circuits that integrate fiber-matched silica waveguides on silicon substrate to provide an efficient means of interaction for the guided-wave optical signals. These circuits include FDM filters for extracting a specific optical signal from multiple signal channels and 8 148 8 matrix switches with thermo-optic (TO) switching elements. Silica waveguides are fabricated with a combination of Flame Hydrolysis Deposition (FHD) and Reactive Ion Etching (RIE). Since a waveguide structure is well defined, device performance can be predicted quire precisely by the numerical simulation and the desired circuits are fabricated with high precision and reproducibility.

Design optimization of a novel integrated triplexer based on planar lightwave circuit (PLC) for fiber-to-the-home applications is described. The two-mode interference coupler and Mach-Zehnder interference are used to construct the filter chip. Simulation results of high isolation and low insertion loss are gotten for proposed design. Technique tolerance is improved for fabricating device.

This presentation will describe the Air Force Research Laboratory Highly Integrated Photonics Program (AF HIP) and its objective to integrate on a monolithic device, all of the optical components required to serve as a bus coupler in an all optical data communication network. This research and development program utilizes advanced technologies in silicon on insulator (SOI) and silica planar lightwave circuits (PLC) to design, develop, characterize, and demonstrate highly integrated photonic devices that can be transitioned into both current and emerging tactical platforms for the U.S. Air Force. This effort strives to overcome several existing constraints with respect to the integration and packaging aspects of the current generation of COTS optical devices. Monolithic integration (chips fabricated out of a single material system) remains the ultimate vision for integrated optics.

A transmission-type refractive index sensor, based on planar lightwave circuit (PLC) technology is proposed. In the proposed structure, we introduce a combination of coarse measurements, using the dependence of the angle of refraction and fine measurement, and the dependence of the phase on the refractive index to measure the absolute refractive index precisely, without expensive optical measurement equipment. The theoretical model of the proposed refractive index sensor is derived based on Fourier optics and transfer function to simulate its performance. The simulation results for the use of the 2.5%-Δ silica-based PLC technology indicate that the proposed structure has the potential to achieve a refractive index error of approximately 1 × 10−6 RIU or less when a monitored power deviation of ±0.05 dB is accepted.

In this paper an accurate measurement method for optics system based on the lunar imaging is presented, and this method has the following steps. Firstly, the optical imaging system observes the lunar and acquires the image on the ground or in orbit, and records the position and the time simultaneously, with which the distance to the lunar can be computed. Secondly, the initial region of the lunar in the acquired image is decided by the gray value threshold, and the Canny edge detection method with parabola fitting is used to acquire the sub-pixel image edge points. Thirdly, the extracted edge points are used to preliminary fit the lunar disc, and the lunar ring is formed based on the fitted lunar disc expanded two pixels, then the initial coarse fitting disc is acquired according to the maximum number of edge points located in the lunar ring. Fourthly, the sub-pixel lunar disk can be obtained via the least squares fitting on the base of the initial coarse fitting disc. At last, the focal length of the optical imaging system can be computed with the position relationship between the optical imaging system and the lunar. Experiments show that this method has the ability to focal length measurement with high accuracy and frequency. By the means of imaging to the lunar, taking advantage of the long distance, sub-pixel edge detection and fitting for the lunar disc diameter, etc, whether in the full lunar and the waning lunar，the focal length could be measured accurately. It has a wide application prospects both in the developing and in orbit operating stage for optical imaging system.

The increasing diffusion of WDM communication systems requires low cost and efficient optical add-drop devices to add or drop channels at predefined wavelengths with reduced insertion loss and cross-interference. Many fiber based devices have already been proposed, however their integration allows an increase in the compactness and mechanical stability. We designed an integrated OADM that is composed of an asymmetric adiabatic transition followed by an asymmetric grating that converts the supermodes of the combined structure. In this paper we focus our attention mainly on the design of the transition that, besides having low insertion losses, should also be tolerant to the variation of the fabrication parameters and in particular of the grating position. Assuming typical glass on silica waveguides, the transition geometry has been determined using the coupled mode theory. Then the result have been verified and optimized with BPM simulations.

While silica waveguide PLC products have been deployed in various systems and applications, hybrid integration of semiconductor opto-electronic devices on silica-based planar lightwave circuit (PLC) has become the mainstream platform for small form factor, low-cost and high volume integrated transceiver modules. One of the main benefits of hybrid integration is the wafer-scale process, which greatly reduces chip/module size and assembly cost. This paper reviews the development of this technology, and as an example, presents a hybrid integrated transmitter with four wavelengths on silica PLC chip for LX4 and 10GbE applications.

Silica-based planar lightwave circuit (PLC) devices are starting to be introduced into commercial optical communication systems. PLC devices such as optical splitters, wavelength-insensitive coupler (WINC) arrays, and hybrid- integrated wavelength-division-multiplexing (WDM) transceivers are used to construct cost effective optical access systems. In trunk lines, on the other hand, arrayed-waveguide gratings (AWG) are employed for dense WDM systems to increase the transmission capacity. This paper reviews the current status and recent progress on these practical PLC devices.

Optical splitters are essential for the construction of optical networks such as fiber-to-the home systems. These devices should exhibit not only good optical characteristics such as low loss and polarization insensitivity but also long-term reliability. Silica-based planar lightwave circuits (PLCs) on Si can form one of the most suitable Y-branching splitters because they have the advantages of low loss, low coupling loss to optical fibers and high reproducibility[l]. When PLC splitters are used in practice, the input and output fibers must be connected to waveguides. Therefore, it is necessary to establish a precise connection technique and confirm its long-term stability. However, neither the connection performance of splitters with up to 32 ports nor the long-term reliability of fiber-connected splitters have yet been evaluated in detail. Here, we describe the connection performance and reliability of 1×8 and 1×32 splitter modules. We have chosen strict Bellcore requirements [2] as the first step in evaluation of the PLC splitter reliability. The requirements are recognized as a standard for reliability tests on optical devices, and define the optical criteria as well as the test conditions.

Fluorinated polyimide (FPI) is an attractive material for fabricating low-loss optical waveguides at 1.55 micrometers , because of its superior optical and thermal properties. Although FPI planar lightwave circuits (PLCs) are usually fabricated on silicon substrate, such PLCs exhibit relatively high polarization dependence and high transmission loss compared with those of silica PLCs. Use of an FPI substrate overcomes these problems that mainly originate from the difference in thermal expansion coefficient between FPI and silicon. It improves the optical property of FPI waveguides, e.g., the transmission loss and polarization dependent loss for straight waveguides reduce to less than 0.3 dB/cm and 0.1 dB, respectively, in the 1.55-micrometers band. The use of FPI substrates will enable the fabrication of high-optical-quality FPI PLCs such as 1x8 splitters.

One of the key challenges in Silicon based optical interconnect system remains to be the efficient coupling of optical signals from the submicron size on-chip waveguides to standard single mode (SM) fibers with low insertion loss (IL) and relaxed alignment tolerance. Large optical alignment tolerance allows optical connectors to be attached to on-chip waveguides passively using standard semiconductor pick-and-place assembly tools that have placement accuracies of 10- 15μm. To facilitate the assembly, optical fiber coupling elements need to be modular and compact. They have to also have low profile to avoid blocking air flow or mechanical interference with other elements of the package. In this paper we report the development of a two-dimensional (2D) SM optical fiber coupling architecture that consists of Si based photonic lightwave circuit (PLC) substrate and a high-density micro-lensed fiber optic connector. The system is compact, efficient and has large optical alignment tolerance. At 1300nm an insertion loss of 2.4dB and 1.5dB was measured for the PLC module and the fiber optic connector, respectively. When the PLC module and connector was aligned together, a total insertion loss of 7.8dB was demonstrated with x,y alignment tolerance of 40μm for 1dB optical loss. The SM optical coupling architecture presented here is scalable, alignment tolerant and has the potential to be manufactured in high volume. To our knowledge, such a system has not been reported in the literature so far.

Effects of Ar and O 2 additives on photopatternable sol–gel etching in an SF 6-based plasma for planar lightwave circuit fabrication

Since the growth of fiber optic communications, extremely low cost optical modules have been expected to be realized. Particularly for the subscriber applications and local area networks (LANs), less than half of past module cost is required. In accordance with the spread of fiber optic transmission, higher volume manufacture is also needed. To attain both of low cost and high productivity, we developed passive alignment technique and optical coupling structure that is suitable for automatic assembly. We also developed automatic assemble equipment for producing several types of optical modules. To reduce optical module cost, it is important to cut down the assembly cost and expensive parts such as optical lens. The passive alignment technique brings us to realize easy assembly of modules and minimize the constructed components of optical coupling. Our mass production techniques include not only for optical coupling but also packaging of the module. We have several types of optical modules according to different fiber communication systems; there are laser modules, detector modules, optical interface modules that are integrated optical coupling and electrical circuit, and PLC (Planar Lightwave Circuit) modules that are integrated passive component. Basically all modules have same optical coupling structure and keep the design rules for automatic assembly. Accordingly, we can use the same equipment for the same assembly process. In this paper, we will introduce basic assembly process and our mass production line for optical coupling and packaging by using passive alignment technique.

We have investigated an optical signal processor using electro-optic polymer waveguides operating at a wavelength of 1.55 mum. Due to recent developments, many useful optical devices have become available such as optical filters, modulators, switches, and multiplexers. It will be useful to have a single optical device, which is reconfigurable to implement all of these functions. We call such a device an ldquooptical signal processor,rdquo which will play a similar role to digital signal processors in electrical circuits. We realize such an optical device in a planar lightwave circuit. Since the planar lightwave circuits are based on the multiple interference of coherent light and can be integrated with significant complexity, they have been implemented for various purposes of optical processing such as optical filters. However, their guiding waveguides are mostly passive, and the only viable mechanism to reconfigure their functions is thermal effects, which is slow and cannot be used for high-speed applications such as optical modulators or optical packet switches. On the other hand, electro-optic polymer has a very high electro-optic coefficient and a good velocity match between electrical and optical signals, thus, permitting the creation of high-speed optical devices with high efficiency. Therefore, we have implemented a planar lightwave circuit using the electro-optic polymer waveguides. As a result, the structure is complex enough to generate arbitrary functions and fast enough to obtain high data rates. Using the optical signal processor, we investigate interesting applications including arbitrary waveform generators.