Dechang An

Thermo-optically tuned cascaded polymer waveguide taps

Polymer thermo-optic-waveguide taps have a potential application as light routers for guided-wave optical interconnects involving cascaded fanouts. The taps can guide light from an optical bus bar and direct it into other devices in a switching/modulation network. Thermo-optic waveguide taps are designed and fabricated on silicon wafers using standard very large-scale integrated fabrication techniques. Coupling of light into an adjacent waveguide tap is observed to increase by 12.3% from 38.7% to 51.0% with the application of 34 mW of power.

Polymeric waveguide prism-based electro-optic beam deflector

Beam steering devices without moving parts are highly desir- able for their potential application in emerging optical technologies such as holographic optical storage systems, all optical networks, and optical switches. We demonstrate a thin-film waveguide beam deflector device that consists of an electro-optic prism array within a polymer waveguide. An electrode structure defines the prism array within the planar wave- guide. The deflection efficiency of 28 mrad/kV and the maximum deflec- tion angle of 68.4 mrad at 6300 V are obtained for this demonstration device. Further optimization of electrode-field poling and processing is likely to improve these results by at least an order of magnitude.

Polymeric electro-optic modulator based on 1×2 Y-fed directional coupler

We have demonstrated a polymeric electro-optic modulator based on a 1×2 Y-fed directional waveguide coupler. The symmetric geometry of the 1×2 Y-fed directional coupler provided the modulator unique characteristics of intrinsic 3 dB operating point and two complementary output ends. A low switching voltage of 3.6 V and a high extinction ratio of 26 dB were obtained with the modulator operating at a wavelength of 1.34 μm. The modulator was fabricated with a novel electro-optic polymer that was synthesized from polyurethane cross-linking with a chromophore.

Electroptic Polymer Linear Modulators Based on Multiple-Domain Y-Fed Directional Coupler

We developed an analytical method to optimize the design of Y-fed direction couplers at large modulation depth from 10% to 50%. Simulation results indicate that three and four-domain devices can obtain 45 dB higher distortion suppression than two-domain devices, which can potentially achieve 120 dB spurious free dynamic range. We also experimentally demonstrated that the two-domain electrooptic modulator obtained 94 dB distortion suppression at 20% modulation depth, which is 47 dB higher than a conventional Mach-Zehnder modulator.

High-performance unidirectional electrooptic modulator based on polymeric highly multi-mode waveguides

Abstract : A unidirectional electro-optic modulator based on polymeric highly multi-mode waveguides was constructed using the standard VLSI techniques. A high unidirectional coupling efficiency of 100% was achieved. A high modulation depth of 99% was also experimentally achieved at 633nm wavelength. The modulator was packaging enhanced by vertically configuring the guiding multi-mode waveguide and the dumping planar waveguide. The device packing density improved by a factor of two. Based on the same configuration, a packaging enhanced polarization-insensitive thermo-optic was also built. The switch operating at wavelengths of 632.8nm and 1.3 micrometers has been demonstrated experimentally with extinction ratios of 21dB and 22dB, respectively. Such devices have an intrinsic wide optical bandwidth due to the large dynamic range of the phase-matching condition implied by the multi-mode waveguides. These devices can be used in optoelectronic interconnects for data communications.

Ultra-low-loss polymeric waveguide circuits for optical true-time delays in wideband phased-array antennas

The optical true-time-delay line is a key building block for modern broadband phased-array antennas, which have become one of the most critical technologies for both military and civilian wireless communications. We present our research results in developing an optical polymer-based waveguide true-time-delay module for multilink phased- array antennas by incorporating wavelength-division multiplexing (WDM) technology. The demonstrated optical polymeric waveguide circuits can provide a large number of optical true-time delays with a dynamic range of 50 ns and a time resolution of 0.1 ps. Various fabrication techniques are investigated for producing ultralong low-loss (0.02 dB/cm) polymeric channel waveguides with tilted waveguide grating output couplers. Fast photodiode arrays are fabricated and rf signals with frequencies of 10 to 50 GHz are generated through the optical heterodyne technique. A detailed study of waveguide amplification to achieve loss-less polymeric waveguide is conducted. The optical amplification of 3.8 dB/cm is achieved at a wavelength of 1064 nm in a Nd3+-doped polymeric waveguide. WDM techniques are also employed for potential multilink applications. The presented methodologies enable hybrid integration with a reduced cost in optoelectronic packaging and an increased reliability and decreased payload for the next generation of phased-array antennas.

Highly efficient linear waveguide modulator based on domain-inverted electro-optic polymers

A Y-branch waveguide directional coupler modulator based on domain-inverted electro-optic polymers is demonstrated for highly ef- ficient analog modulation. A detailed theoretical analysis is given to show its working principles based on coupled-mode theory. Domain-inverted electro-optical polymers are obtained by using a high-voltage pulsed pol- ing technique. The demonstrated domain-inverted polymers represent a promising technology for creating a new class of electro-optic modula- tors with superior performance over conventional counterparts. By using domain inversion in a Y-branch waveguide directional coupler, the poly- meric electro-optic waveguide modulator provides a highly linear modu- lation transfer curve that shows a ;100% modulation efficiency with an intermodulation distortion less than 230 dB. The demonstrated modula- tor also features a switching voltage of 10 V and an extinction ratio of 228 dB at operation wavelength of 1.32 mm. A linear modulation transfer curve and a 3-dB operating point are obtained without a bias voltage or an asymmetric device structure through a single uniform electrode.

Temperature sensitivity of passive holographic wavelength-division multiplexers–demultiplexers

We derive a set of concise formulas to characterize the temperature sensitivity of holographic wavelength-division multiplexers-demultiplexers (H-MUXs-H-DMUXs). The normalized parameters such as dispersion abilities, central wavelength shift rate, and variations of insertion loss hold for general grating-based wavelength-division multiplexing-demultiplexing (WDM-WDDM) structures. The results are applicable to both wide-WDM-WDDM and dense ones working in 800-, 1300-, and 1550-nm optical wavelength windows, regardless of whether their input-output ports are single-mode or multimode fibers. Detailed analysis and experiments are carried out on a fully packaged four-channel H-MUX-H-DMUX. The experimental results at temperatures from 25 to 80 degrees C fit nicely with the theoretical prediction. We conclude that passive grating-based H-MUXs-H-DMUXs are promising for meeting the requirements on temperature sensitivity in optical data communications and telecommunications. Most of the analysis can be applied to other types of Bragg-grating-based WDM-WDDM.

Polymeric multimode waveguide based electro-optic modulator with a vertically configured dumping planar waveguide

An electro-optic modulator based on a polymeric multimode waveguide coupler was developed. A guiding multimode waveguide with a vertically configured dumping planar waveguide was employed in the design to increase the device packing density. A modulation depth of 91% at 1330 nm was experimentally achieved. This device shows that the multimode optical waveguide with the vertically configured dumping planar waveguide is promising in electro-optic modulator designs. This modulator can be used in multimode optical interconnection systems such as data communications and fiber sensor networks.

Polarization-insensitive thermo-optic switch based on multimode polymeric waveguides with an ultralarge optical bandwidth

A promising polarization-insensitive thermo-optic switch based on multimode polymeric waveguides is reported. This device has a packing density of 40 channels/cm. Simulation result shows that an extinction ratio of greater than 20 dB can be achieved with the device–electrode interaction length of 30 mm. The thermo-optic switch operating at wavelengths of 632.8 nm and 1.3 μm has been demonstrated experimentally with extinction ratios of 21 and 22 dB, respectively. Such a device has an intrinsic wide optical bandwidth due to the large dynamic range of the phase-matching condition implied by the multimode waveguides. The material employed provides us with a switching speed of 100 μs.