Polymeric 16×16 arrayed-waveguide grating router usingfluorinated polyethers operating around 1550 nm

A 16×16 arrayed waveguide grating (AWG) router with a channel spacing of 0.8 nm (100 GHz) operating around the 1550-nm wavelength has been fabricated using newly synthesized fluorinated polyethers. It has a good processibility and a high thermal stability up to 510°C. The propagation loss of the buried-channel waveguide is about 0.4 dB/cm at the 1550-nm wavelength. The on-chip insertion loss ranges from 5.5 to 11 dB and the crosstalk is less than -27 dB. The AWG router shows good cyclic rotation property of the wavelength channels with an error smaller than 0.03 nm     

Recent advances in electrooptic polymer modulators incorporatinghighly nonlinear chromophore

Based on a nonlinear optical polymer with a highly nonlinear chromophore (CLD) dispersed in an amorphous polycarbonate (APC), we have developed electrooptic (EO) polymer modulators operating at 1550-nm wavelength with low loss and good thermal stability. By incorporating polymer insulation layer, push-pull poling was successfully performed without film damages. We also demonstrated that the propagation loss of the EO polymer waveguide could be reduced as low as 1.2 dB/cm at 1550 nm when the large core waveguide structure was incorporated. The long-term reliabilities of the EO polymer modulator made of CLD/APC polymer were investigated. When the modulator was hermetically sealed in an inert gas, the V_π change of a Mach-Zehnder modulator was negligible over 30 d of operation with 20-mW exposure to the waveguide input. In the thermal stability measurement, 25% V_π increase was observed from the sample heated to 60°C over 40 d, though the sample left at room temperature showed no decay of nonlinearity     

Polarization insensitive, low-loss, low-crosstalk wavelengthmultiplexer modules

A method for compensating polarization sensitivity of arrayed waveguide gratings (AWG's) based on silica-on-Si waveguide technology using stress release grooves and its realization are described. These stress release grooves compensate fabrication-induced waveguide birefringence without performance degradation. An advanced design for low-loss, low-channel imbalance, and low-crosstalk multiplexer is given and results of the realized modules are presented. The TE/TM passband shift could be reduced from 0.7 nm to below 0.05 nm. Insertion loss of the fully packaged wavelength multiplexer modules is <5 dB and adjacent channel crosstalk is as low as <-40 dB     

Integrated optical, wavelength selective, acoustically tunable2×2 switches (add-drop multiplexers) in LiNbO3

Fully packaged, polarization independent, integrated acoustooptic 2×2 switches have been developed which can be also used as add/drop multiplexers. The devices have been fabricated in X-cut Y-propagating LiNbO₃ and can be operated at wavelengths around 1550 nm. They consist of passive polarization splitters and acoustooptic TE-TM converters with weighted coupling. A filter bandwidth of 2.0 nm and a tuning range of 130 nm have been obtained. The fiber-to-fiber insertion loss is <4.6 dB and a residual polarization dependence of 1.3 dB for bar-state and 0.1 dB for cross-state routing has been achieved     

Microring Resonators Made in Poled and Unpoled Chromophore-Containing Polymers for Optical Communication and Sensors

Poled and unpoled chromophore-containing polymers offer some unique advantages in device functionality and fabrication. UV light and electron beam (e-beam) can bleach out the color of chromophores and reduce the index of refraction of the polymer. The photobleaching and e-beam bleaching methods form optical waveguides in a single step and do not involve solvents or wet chemicals, and can be applied to polymers that are not compatible with other waveguide fabrication techniques. A variety of microring resonator devices for fiber-optic telecommunication and sensors have been realized with chromophore-containing polymers. A novel broadband fiber-optic electric field sensor is presented as an example. The sensor uses a polymer with chromophores preferentially aligned after electric poling, and the microring resonator is directly coupled to the core of optical fiber. The feasibility of vertical integration of a poled electrooptic polymer waveguide device interfaced with silicon microelectronic circuits is also demonstrated.     

Theory of design parameters for quasi-phase-matched waveguides andapplication to frequency doubling in polymer waveguides

A theory of dispersion in single-mode symmetric waveguides is presented for phase-matching second harmonic generation (SHG) of the fundamental modes, based on the approximate analytical waveguide theory of Botez. The theory is used to derive new equations for the maximum phase-matching distance allowed when there are random fluctuations in waveguide thicknesses, under critical and noncritical phase-matching conditions. The theory is also used to calculate the overlap integral as a function of the waveguide parameters V^ω and V^2ω. A new expression is derived for the efficiency of SHG in waveguides in terms of waveguide parameters that can be used to optimize SHG. Theoretical results are presented for typical LiNbO₃ and polymer waveguides. Quasi-phase-matched (QPM) waveguides are fabricated from nonlinear optical (NLO) polymers using the techniques of periodic poling and bleaching, and channel waveguides are printed by the bleaching of the NLO polymers. The NLO polymers are characterized for their refractive indexes, optical loss, NLO coefficients, and bleaching characteristics. Phase-matched SHG results are presented for the different fabrication methods over a distance of 0.5 cm, and an assessment is given of the relative strengths and weaknesses of the different fabrication approaches     

Self-Aligned Single-Mode Polymer Waveguide Interconnections for Efficient Chip-to-Chip Optical Coupling

Single-mode (SM) ultrashort optical interconnections between the fibers and waveguides using self-forming polymeric waveguides with low optical losses at 1300 and 1550 nm were demonstrated. The localized refractive index in the SM regime is estimated by measuring the surface topography induced by monomer diffusion during the waveguide formation. A loss less than$-1$dB can be obtained from self-aligning SM-to-multimode (MM) fibers and SM-to-SM fibers interconnections, respectively. A self-formed waveguide-to-fiber interconnection is fabricated and measured with loss less than 0.2 dB at 1550 nm. The polymer waveguide relaxes the positioning requirements for single-mode chip-to-chip optical interconnections, showing great potential to improve the short-term yield and long-term reliability.     

Characteristics of polymer waveguide notch filters using thermooptic long-period gratings

We demonstrate experimentally the feasibility of a polymer waveguide notch filter using a thermooptic long-period grating. This notch filter consists of a channel waveguide, a cladding surrounding the channel, and buffer layers sandwiching the cladding. Periodic heaters formed on the upper buffer layer induce a long-period grating thermooptically. Thus, they generate temporarily a resonance band of notch type in the transmission spectrum of the filter. Using thermocurable polymers, we have fabricated notch filters 1 and 2 that have different cladding thicknesses. Experimental results demonstrate two features of the notch filters. One feature is dynamical controllability of the attenuation of a resonance band. For TE mode, the maximum attenuation of notch filters 1 and 2 increases from 0 to 27 dB as the power applied to notch filters 1 and 2 increases from 0 to 851 and 1170 mW, respectively. The other feature is controllability of the direction and magnitude of the center wavelength shift occurring when the attenuation is tuned. The shift property depends on the cladding thickness. The measured characteristics of notch filters 1 and 2 are qualitatively in good agreement with our theoretical analysis. Using this feature, we may implement the notch filter whose attenuation is adjustable without center wavelength shift. This polymer waveguide notch filter may be used to implement a compact filter whose spectrum is dynamically tailored.     

Photonic Bandgap Microcavities With Flat-Top Response

In this paper, the analysis and the design of a photonic bandgap (PBG) microcavity waveguide filter with flat-top spectral characteristics are theoretically presented. The split filter analysis and the bidirectional eigenmode propagation method are applied to the investigation of this waveguide structure to obtain the design parameters of the filter with nearly unity transmittance and a squared passband. It shows that the radiation loss in the PBG mirrors diminishes the transmittance of the filter, and a mirror with anomalous dispersion region in reflection phase could be used to assemble an optical filter with the flat-top passband. A 1-D PBG monorail waveguide microcavity filter centered at 1554 nm with a maximum transmission of -0.55 dB and full-width at half-maximum (FWHM) of 13.6 nm is numerically carried out by using 3-D finite-difference time-domain method     

Compact evanescent optical switch and attenuator withelectromechanical actuation

We report the design and the realization of an out-of-plane bending structure supporting a waveguide that is used as an optical attenuator and an optical switch. Both devices are based on evanescent field interaction induced by spatial confinement either between two waveguides or between one waveguide and an absorbing medium. The attenuator exhibits typical attenuation of 65 dB/cm. Even if the bad quality of the waveguide has prevented the correct operation of the switch, we show that the attenuation figure establishes the feasibility of a compact evanescent optical coupler with mechanical drive featuring a total length below 1 mm     

Discretely Tunable Semiconductor Lasers Suitable for Photonic Integration

A sequence of partially reflective slots etched into an active ridge waveguide of a $hbox{1.5} mu$m laser structure is found to provide sufficient reflection for lasing. Mirrors based on these reflectors have strong spectral dependence. Two such active mirrors together with an active central section are combined in a Vernier configuration to demonstrate a tunable laser exhibiting 11 discrete modes over a 30 nm tuning range with mode spacing around 400 GHz and side-mode suppression ratio larger than 30 dB. The individual modes can be continuously tuned by up to 1.1 nm by carrier injection and by over 2 nm using thermal effects. These mirrors are suitable as a platform for integration of other optical functions with the laser. This is demonstrated by monolithically integrating a semiconductor optical amplifier with the laser resulting in a maximum channel power of 14.2 dBm from the discrete modes.      

Polymeric optical waveguide films for short-distance opticalinterconnects

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-μm diameter graded index (GI) core. The average insertion loss of these devices was approximately 0.6 dB at 0.85-μm wavelength. We also fabricated waveguide films with a 350 mirror and an MTC connector for use as 90° 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     

Ku波段小型化铁氧体隔离器仿真设计

介绍了一种Ku波段小尺寸波导隔离器的设计方法,通过对结式环行器原理分析,采用阻抗匹配设计,利用HFSS软件仿真计算并优化,最终研制出完全满足设计要求的波导隔离器。在工作温度-40~+85℃范围内,器件的技术指标为:电压驻波比≤1.16,正向损耗≤0.2 d B,隔离度≥30 d B,外形尺寸为12.7×33.3×38.3 mm。该隔离器的传输方向尺寸为常规隔离器的一半左右,符合微波通信器件小型化和集成化的发展要求。     

Planar waveguide optical spectrum analyzer using a UV-inducedgrating

An optical spectrum analyzer is demonstrated using a UV-induced, chirped grating on a planar waveguide and a linear detector array. The grating provides both the dispersion with respect to wavelength and the imaging function. The spectral response has a full-width at half-maximum of 0.15 nm and a bandwidth of 7.8 nm. A chirp of -1.75 nm/cm and a 12-cm focal length were used. The design parameters are discussed in terms of the chirp, focal length and resolution. The wavelength dependence of the optimal chirp limits the resolution for small focal lengths. For longer focal lengths, the spotsize is diffraction limited and high resolution can be achieved with minimal fabrication complexity     

Electrooptic planar deflector switches with thin-film PLZT active elements

First prototypes of electrooptic (EO) planar deflector switches (PDSs) are fabricated with hybrid integration on Si substrates. Planar optical modules, made in silica-on-silicon technology, consist of input and output (I/O) waveguide microlenses facing each other and slab waveguides in between. The modules interconnect the I/O fibers with laterally collimated light beams less than 400 /spl mu/m in width at distances up to 100 mm with losses lower than 3 dB. Thin lead lanthanum zirconium titanate (PLZT) films with prism-shaped electrodes grown on SrTiO/sub 3/ substrates form the deflector elements. The PLZT films are more than 10 /spl mu/m thick with EO coefficients about 40 pm/V. The deflector assembly technology provides chip vertical positioning accuracy better than 1 /spl mu/m. The deflector chips are attached to the optical substrates with thermo-compression flip-chip bonding. The optical power losses of the modules with test silica chips can be as low as 3.6 dB. However, the lowest module losses achieved with PLZT are about 10 dB. The channel-to-channel switching operations are demonstrated at about 40 V and switching times less than 500 ns.     

Electrical embedding-new polyamides

The embedding of electrical/electronic connections and components is becoming more critical as these are being used in more hostile environments. These environments include automotive uses and industrial plants. Embedding of electrical or electronic connections in automobiles is important, as more functions are computer controlled. A wide range of processes and materials are used for making these embedded connectors, but durability of the assembly is critical to long-term performance. A good embedding material needs to have very specific properties to protect the connection under a variety of conditions. The typical polymers used in these applications have been epoxies, silicones, and urethanes. Each polymer has advantages and disadvantages that determine its suitability to a specific application. There are also newer materials, such as thermoplastic and thermoset dimer-based polyamides. These newer materials can overcome some of the processing or performance limitations of the typical polymers now being used     

Design of tapered SAW waveguide for wavelength‐selective optical switches using weighted acoustooptic interaction

Optical wavelength‐selectivity in optical switches using waveguide‐type collinear acoustooptic interaction is studied from the viewpoint of sidelobe suppression. It is found that the sidelobe level can be reduced from ?9.3 dB to ?20 dB by weighting the coupling coefficient over the interaction region. A method to realize the sidelobe suppression by means of modifying the surface acoustic wave (SAW) waveguide is proposed and theoretically analyzed to design the SAW waveguide. A sidelobe suppression at ?20 dB is realized with a SAW waveguide of a dense‐flint glass strip whose width and thickness are varied accordingly in the ranges of 700 to 26 µm, and 0.4 to 1.0 µm, respectively, on a Y‐X LiNbO₃ substrate. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 154(1): 36–46, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20251     

1.55-μm InGaAsP-InP laser arrays with integrated-mode expandersfabricated using a single epitaxial growth

We report on two techniques for the realization of expanded-mode laser arrays with a single epitaxial growth step and conventional fabrication techniques. Laser arrays with integrated adiabatic-mode expanders (AME) based on a tapered active region and an underlying passive coupling waveguide are demonstrated at the 1.55-μm wavelength. These lasers butt couple to standard cleaved single-mode fibers (SMF's) with a loss of only 3.6 dB. This coupling efficiency compares with a theoretical calculation of 3.2 dB. We also propose a novel realization of a laser with an integrated-mode expander based on resonant coupling between a tapered active waveguide and an underlying coupling waveguide. Three-dimensional (3-D) beam propagation method (BPM) results are presented which show that compact, efficient mode expanders with a mode transformation loss of only 0.36 dB can be realized using this method. Butt-coupling efficiencies of 2.6 dB are possible to standard cleaved single-mode fibers     

Advanced Ti:Er:LiNbO3 waveguide lasers

This paper reviews the latest developments of diode-pumped Ti,Er:LiNbO₃ waveguide lasers emitting at wavelengths around 1.5 μm. In particular, harmonically mode-locked lasers, Q-switched lasers, distributed Bragg reflector (DBR)-lasers, and self-frequency doubling lasers are discussed in detail. Supermode stabilized mode-locked lasers have been realized using a coupled cavity concept; a side mode suppression ratio of 55 dB has been achieved at 10-GHz pulse repetition rate with almost transform limited pulses. Q-switched lasers with a high extinction ratio (>25 dB) intracavity electrooptic switch emitted pulses with a peak power level up to 2.5 kW and a pulsewidth down to 2.1 ns at 1-kHz repetition frequency. Numerical simulations for both lasers are in a good, almost quantitative agreement with experimental results. A DBR-laser of narrow linewidth (≈3 GHz) with a permanent (fixed) photorefractive grating and 5 mW output power has been realized. Self frequency doubling lasers have been fabricated with a periodic microdomain structure inside an Er-doped laser cavity; simultaneous emission at the fundamental wavelength, 1531 nm, and at the second harmonic wavelength, 765 nm, has been obtained     

Applications of Highly-Nonlinear Chalcogenide Glass Devices Tailored for High-Speed All-Optical Signal Processing

Ultrahigh nonlinear tapered fiber and planar rib Chalcogenide waveguides have been developed to enable highspeed all-optical signal processing in compact, low-loss optical devices through the use of four-wave mixing (FWM) and cross-phase modulation (XPM) via the ultra fast Kerr effect. Tapering a commercial As₂Se₃ fiber is shown to reduce its effective core area and enhance the Kerr nonlinearity thereby enabling XPM wavelength conversion of a 40 Gb/s signal in a shorter 16-cm length device that allows a broader wavelength tuning range due to its smaller net chromatic dispersion. Progress toward photonic chip-scale devices is shown by fabricating As₂S₃ planar rib waveguides exhibiting nonlinearity up to 2080 W^-1ldr km^-1 and losses as low as 0.05 dB/cm. The material's high refractive index, ensuring more robust confinement of the optical mode, permits a more compact serpentine-shaped rib waveguide of 22.5 cm length on a 7-cm- size chip, which is successfully applied to broadband wavelength conversion of 40-80 Gb/s signals by XPM. A shorter 5-cm length planar waveguide proves most effective for all-optical time-division demultiplexing of a 160 Gb/s signal by FWM and analysis shows its length is near optimum for maximizing FWM in consideration of its dispersion and loss.