Lattice-form CWDM interleave filter using silica-based planar lightwave circuit

We demonstrate an eight-channel coarse wavelength-division-multiplexing interleave filter that employs a silica-based lattice-form filter. The filter incorporates phase-generating couplers to convert a conventional frequency interleave filter into a wavelength interleave filter with a constant channel spacing with respect to wavelength. We fabricated the designed interleave filter on a 1.5%-/spl Delta/ silica-based waveguide and realized a constant channel spacing of 20 nm with a wavelength displacement of within /spl plusmn/0.5 nm and an insertion loss of less than 1.7 dB over eight channels.     

Integrated thin film heater and sensor with planar lightwave circuits

This paper describes the use of integrated heaters and closed-loop applications for temperature control of planar waveguide circuits. The history of arrayed waveguide gratings (AWG) temperature control is discussed along with the difficulties in applying this control. Modeling and measurement results for external and integrated heaters will be presented. Fundamental considerations as well as modeling and measurement of the thermal characteristics of various physical constructions are discussed, and the rationale for applying these disciplines to a given problem is highlighted. In this work, we will present the evolution of these unique integrated thin film heaters and review thermal-optical modeling to experimental demonstration of the AWG. The goal of the work is to provide a solution path for integration of multiple optical devices on a single substrate from a thermomechanical as well as optical discipline point of view.     

III-nitride-based planar lightwave circuits for long wavelength optical communications

Planar lightwave circuits based on III-nitride wide-bandgap semiconductors are proposed and the feasibility of developing III-nitride-based novel photonic integrated circuits for applications in fiber-optical communications is discussed. III-nitrides have low attenuation in the near-infrared wavelength region because of their wide bandgaps, while as semiconductors their refractive indexes can be modulated by carrier injection. III-nitrides are also well known for their ability to operate at high temperatures, high power levels and in harsh environments. These characteristics make III-nitrides ideal candidates for tunable optical phased-array (PHASAR) devices for optical communications. We have characterized the optical properties of Al/sub x/Ga/sub 1-x/N epilayers in the 1550-nm wavelength region, including the refractive indexes and the impact of Al concentrations. Single-mode ridged optical waveguide devices using GaN-AlGaN heterostructures have been designed, fabricated and characterized for operation in the 1550-nm wavelength window. The birefringence of wurtzite GaN grown on sapphire substrate has been observed. Refractive indexes were found to be different for signal optical field perpendicular and parallel to the crystal c axis (n/sub /spl perp// /spl ne/ n/sub ///). More importantly, we found an approximately 10% change in the index difference /spl Delta/n=n/sub ///-n/sub /spl perp// with varying the waveguide orientation within the c plane, and a 60/spl deg/ periodicity was clearly observed. This is attributed to the hexagonal structure of the nitride materials. Various functional waveguide devices have been realized, including 2/spl times/2 directional couplers and eight-wavelength array-waveguide gratings. Theoretical predictions of temperature sensitivity and the efficiency of carrier-induced refractive change are provided.     

Polarization mode converter with polyimide half waveplate insilica-based planar lightwave circuits

A TE/TM polarization mode converter, with an excess loss of 0.26 dB, is constructed by inserting a polyimide half waveplate into a groove formed in a silica-based single mode waveguide. The polarization dependence of an arrayed-waveguide grating multiplexer is completely eliminated with this mode converter     

New structure of silica-based planar lightwave circuits forlow-power thermooptic switch and its application to 8 × 8 opticalmatrix switch

We propose a novel structure that reduces the switching power of a silica-based thermooptic switch (TOSW). The structure consists of silicon trenches and heat insulating grooves, which are formed beneath and beside the arms of a Mach-Zehnder interferometer, respectively. We optimize the structure using the differential-element method (DEM) and fabricate a 2 × 2 TOSW with a switching power of only 90 mW, namely, 75% less than that of a conventional TOSW. We also obtain an insertion loss of about 1 dB and an extinction ratio of over 30 dB with a response time from 0% to 90% of 4.9 ms. We then use the structure to fabricate an 8 × 8 matrix switch and confirm a total power consumption of 1.4 W with an average insertion loss of 7.4 dB and an extinction ratio of 50.4 dB for 64 possible optical paths     

High frequency electrical circuits on a planar lightwave circuitplatform

We investigated the propagation losses and the characteristic impedances Z_L of coplanar waveguides (CPWs) and microstrip lines (MSLs) on a planar lightwave circuit (PLC)-platform formed on a silica/silicon substrate. The loss of the CPWs was 2.7 dB/cm at 10 GHz on the PLC-platform with 30 μm thick silica layer. Thus, a cm-order circuit of this CPW is difficult to fabricate in the 10 Gb/s module. This is because the silicon substrate has a large loss tangent (tan δ). On the other hand, the loss of the MSLs, where a ground plane shielded the high loss silicon substrate, could be improved to 0.9 dB/cm at 10 GHz with 30 μm thick polyimide. These lower loss MSLs on a PLC-platform can be applied to module operation at 10 Gb/s. Furthermore they have the advantage that they are suitable for application to array device circuits or circuits in a module where several devices are integrated because unlike CPWs the ground planes are not divided by signal lines or DC bias lines. The structure of CPWs and MSLs on a PLC-platform with a Z_L of 50 Ω was also studied in detail     

Birefringence compensated silica-based waveguide with undercladdingridge

A novel waveguide structure with an undercladding ridge designed to compensate for the birefringence of silica-based waveguides is proposed. The proposed structure was applied to a 16-channel arrayed-waveguide grating, and successfully demonstrated low polarisation dependence (<0.01 nm) without any degradation in waveguide characteristics     

High-density integrated planar lightwave circuits using SiO2-GeO2 waveguides with a high refractive indexdifference

GeO₂-doped silica waveguides with a high refractive index difference of 1.5% are successfully fabricated on Si substrates. Their propagation loss, measured in 200-cm-long test circuits with a minimum curvature radius of 2 mm, is 0.073 dB/cm. The waveguides are used as high-density integrated planar lightwave circuits in 1×4 Mach-Zehnder (MZ) type multi/demultiplexers for optical frequency division multiplexing (FDM) transmission systems and in modified MZ type multi/demultiplexers with a ring resonator, which have a compact device size of 15×50 mm² and a frequency spacing of 10 GHz     

Trimming phase and birefringence errors in planar lightwave circuits with deep ultraviolet femtosecond laser

A deep ultraviolet femtosecond laser was employed to trim phase and birefringence errors in silica planar lightwave circuits. A permanent refractive index change of /spl sim/3.8/spl times/10/sup -4/ and a birefringence change of 1.0/spl times/10/sup -4/ were induced in hydrogen-free Mach-Zehnder planar waveguide circuits. The ultrafast laser enhances the ultraviolet photosensitivity response in silica waveguides by two orders of magnitude greater than that of a nanosecond 248 nm KrF excimer laser.     

Bringing telecom networks up to speed [planar lightwave circuits]

Planar lightwave circuits (PLCs) provide various important devices for WDM systems, TDM systems, and subscriber networks. This article reviews the recent progress and future prospects of PLC technologies including arrayed-waveguide grating (AWG) wavelength filters, optical add/drop multiplexers (ADMs), programmable dispersion equalizers, and hybrid optoelectronics integration technologies. Continuous improvements in waveguide fabrication, circuit design, and device packaging will further bring these technologies to a higher level of integration of optics and electronics, aiming at the next generation of telecommunication systems     

Polarization sensitivity of a silica waveguide thermooptic phaseshifter for planar lightwave circuits

A thermooptic (TO) phase shifter, which consists of a thin-film heater loaded on a silica-based single-mode waveguide on a Si substrate, was found to exhibit a sli1h,t polarization dependence of about 3.1% between the TE and TM modes. This dependence, which is caused by anisotropic stress concentration due to local heating, was successfully reduced by forming stress-releasing grooves on either side of the heater     

Low-loss athermal silica-based lattice-form interleave filter with silicone-filled grooves

We describe a low-loss athermal silica-based interleave filter with a lattice-form structure. We athermalize the filter by using a silicone-filled groove formed in each delay line and we employ a low-loss design to reduce the accumulated groove excess loss in the multiple delay lines. By using these designs, we obtained a very low groove excess loss of 0.4 dB and achieved satisfactory temperature insensitivity and optical characteristics with this filter.     

Improved 8×8 integrated optical matrix switch usingsilica-based planar lightwave circuits

An improved 8×8 optical matrix switch was fabricated using silica-based planar lightwave circuits (PLCs) on a silicon substrate. Three improvements were made. First, the waveguide material was changed from titanium-doped silica (SiO₂₂-TiO₂) to germanium-doped silica (SiO₂₂-GeO₂) to reduce propagation loss. Second, offset driving powers were supplied to every switch unit to realize high extinction ratios. Third, the dummy switch units were modified to suppress the crosstalk through these units. The average insertion loss of the fabricated device was 3.81 db in the TE mode and 3.82 dB in the TM mode. The average extinction ratio of the switch units was 25.3 dB in the TE mode and 22.3 dB in the TM mode. The accumulated crosstalk was estimated to be less than -14 dB in the TE mode and -11 dB in the TM mode. The average driving power of the phase shifter in the on-state was 0.54 W in the TE mode and 0.52 W in the TM mode. The switching response time was 1.3 ms. The packaged 8×8 matrix switch with additional fiber-waveguide coupling loss of 2.7 dB was successfully employed in photonic multimedia switching and photonic inter-module connector system experiments     

Photosensitivity and application with 157-nm F/sub 2/ laser radiation in planar lightwave circuits

Photosensitivity studies of germanosilica planar waveguides were carried out with short-wavelength 157-nm light from an F/sub 2/ laser. More than a 5/spl times/10/sup -3/ refractive-index change was induced in a nonuniform index profile concentrated near the cladding-core interface and confirmed by an atomic force microscopy in 157-nm radiated fiber. This profile geometry narrows with the laser exposure to offer practical application in trimming phase errors and controlling birefringence in frequency domain modulators where a 1.7/spl times/10/sup -3/ effective index change and a 5/spl times/10/sup -4/ birefringence change were induced, respectively. The 157-nm photosensitivity response is more than 15 times stronger than that by a 248-nm KrF laser and more than twofold stronger than that by a 193-nm ArF laser.     

Large-scale and high-density planar lightwave circuits with high- Delta GeO/sub 2/-doped silica waveguides

GeO/sub 2/-doped silica waveguides with a high refractive index difference ( Delta ) of 2% and a propagation loss of 0.1 dB/cm are fabricated on Si substrates. 200 cm-long test circuits and ring resonators are demonstrated, both with a minimum curvature of 2 mm.<>     

Ion implanted integrated optics (I3O) technology for planar lightwave circuits fabrication

The Ion Implanted Integrated Optics (I3O) technology, using titanium ion implantation in bulk silica to fabricate passive compact planar lightwave circuits (PLCs), is presented in this paper. Its advantages are described and compared with other waveguide fabrication technologies. It is demonstrated that the guided electromagnetic field can be tailored by adjusting the titanium ion dose either to fit the guided mode of standard single-mode fibers or to allow a sharp radius of curvature of bent waveguides.     

Large reduction of singlemode-fibre coupling loss in 1.5% Δplanar lightwave circuits using spot-size converters

Reduction of singlemode fibre coupling loss in 1.5% Δ planar lightwave circuits from 1.8 to 0.2 dB/point is achieved using simple vertically and laterally tapered spot-size converters. These spot-size converters were used to realise an arrayed-waveguide grating with a very low insertion loss of 0.7 dB     

Low switching power silica-based super high delta thermo-opticswitch with heat insulating grooves

A silica-based 2×2 thermo-optic switch with super high delta planar lightwave circuits has been fabricated and used with a low switching power configuration. This switch has two features that aid switching power reduction, namely heat insulating grooves and a thick undercladding. Dependence of the switching characteristics on these features has been examined both theoretically and experimentally. A very low switching power of 45 mW has been achieved     

离子交换单模玻璃平面波导折射率分布的确定

用Ag-Na离子交换技术制备了玻璃平面波导.求解扩散方程得到Ag离子在玻璃内部浓度分布.使用一次多项式模拟的方法求解折射率变化与Ag离子浓度变化之间的关系,从而得到了单模平面波导的折射率分布,并验证其与同等实验条件(离子交换时间除外)的多模波导获得的折射率分布函数基本一致.