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We have fabricated low-stress polyimide membranes for use as high-resolution variable optical attenuator (VOA). Polyimide membranes are assembled with fiber collimators to perform 3-D beam spoiling that varies the optical power with 0.01-dB resolution. The measured residual stress and Young's modulus of the polyimide membrane are 3.2 MPa and 15 GPa, respectively. The 41-mum deformation of the membrane is demonstrated by the electrostatic force with 170 volts. The 0.46-dB insertion loss and >15-dB dynamic range are achieved at 1550-nm wavelength [ABSTRACT FROM PUBLISHER]

A single-mode waveguide and a 1 × 3 multimode interference (MMI) power splitter are fabricated in hybrid zirconium (Zr)-doped sol-gel material by a microreplication technology with a polydimethylsiloxane (PDMS) replica. The power splitter, as optimized using a finite-difference beam-propagation method (FD-BPM) simulation with self-imaging effects, represents one of the first experimental demonstrations of a high-tolerance manufactured device using replication methods. The fabrication of the microreplicated power splitter demonstrates high-quality optical and geometrical properties. The local uniformity in thickness of the multimode waveguide is less than 1.0%, and the average surface roughness is about 5.35 nm. The measured splitting loss is less than 0.6 dB for both transverse polarizations at the 1550-nm wavelength. Experimental achievements indicate that the soft lithography technology allows for the performance of applications in integrated optical devices in Zr-doped sol-gel materials with high standards. [ABSTRACT FROM PUBLISHER]

Optical rib waveguides with various widths and heights were fabricated on silicon-on-insulator (SOI) substrates. Silicon etching was based on dry etching with inductively coupled plasma (ICP)-type reactive ion etcher. The etching process was developed to ensure low optical losses. Propagation loss of 0.13±0.02 dB/cm was measured for the fundamental mode at the wavelength of 1550 nm in a curved 114-cm-long waveguide. The reflection losses were suppressed by applying atomic layer deposition (ALD) in the growth of antireflection coatings (ARCs). [ABSTRACT FROM PUBLISHER]

The design and fabrication of an electrostatic MEMS variable optical attenuator (VOA) is described. The VOA is a reflection type with a folded micromirror actuated by a comb-drive actuator. The VOA is fabricated by a simple single-mask process. One photolithography and subsequent deep silicon reactive ion etching define all the microstructures of the VOA. The folded micromirror structure can reduce the overall size of the device by enabling the parallel alignment of an input fiber and an output fiber. Lensed fibers are used to maximize the coupling efficiency and the ease of assembly. The electrooptic characteristics and dynamic characteristics of fabricated VOA are measured. The initial insertion loss is 0.5 dB at 1550 nm and the maximum attenuation is 45 dB, respectively. The polarization dependent loss is measured to be 0.2 dB at 20-dB attenuation. The response time for maximum attenuation is less than 5 ms. [ABSTRACT FROM PUBLISHER]

This paper presents the design, fabrication, and measurement results of a 2×2 microelectromechanical systems optical switch. The switch comprises an electromagnet and lensed fibers assembled with a micromachined movable vertical micromirror. The optical switch utilizes the out-of-plane motion of the vertical micromirror actuated by electromagnetic force compared to the comb-driven linear actuation achieved by the electrostatic force. At a wavelength of 1550 nm, the insertion loss of 0.2-0.8 dB and the polarization-dependent loss of 0.02-0.2 dB are measured. The switching time is 1 ms. A novel method of realizing a latchable optical switch using an electromagnetic actuator is also provided and verified. The latch mechanism is based on the latchability of the electropermanent magnet instead of the mechanical one using conventional arch-shaped leaf springs. [ABSTRACT FROM PUBLISHER]

A family of thin film interference filters is described that incorporates amorphous silicon layers for wide thermo-optic tunability and the potential for multiple cavity designs. Plasma enhanced chemical vapor deposition (PECVD) of hydrogenated amorphous silicon (a-Si:H) onto fused silica or crystalline silicon wafer substrates produces films with high index (n=3.71), low loss at 1500 nm (k<4×10-6), and thermo-optic index coefficients approximately ten times larger than those of the dielectric materials typically used in wavelength division multiplexing (WDM) filters. Pairing amorphous silicon with low index (n=1.77, k=1×10-6) silicon nitride companion layers followed by post-process annealing leads to multilayer film stacks which may be cycled up to 400 C without delamination or failure, resulting in thermal index modulations as large as 4% and enabling a wide variety of dynamic thin film device designs. In this paper we survey the range of device applications and show experimental demonstrations for two quite different classes of functionality. One class of filters is tunable in wavelength in the conventional sense. Single and dual-cavity narrowband filters are described with temperature coefficients of center wavelength 85-172 pm/°C in the 1550 nm WDM band and tuning ranges as large as 60 nm, an order of magnitude larger thermal tunability than for conventional thin film narrowband filters. A second class of filters is fixed in wavelength but switchable in transmission, based on hybrid structures which combine tunable semiconductor films and cavities with static dielectric films and cavities in an integrated coating design. To demonstrate the principle of a switchable add/drop filter, we fabricated a five-cavity, 117 layer, 200 GHz filter by combining a single cavity of a-Si:H/a-SixNy films deposited by PECVD with four cavities of dielectrics Ta2O5/SiO2 deposited by ion assisted e-beam evaporation. By varying the temperature, this device can be switched thermo-optically between transmission and reflection states at a fixed channel 1548.3 nm with a contrast ratio 18.4 dB. Stable devices can be obtained even with large internal temperature changes in microscopic volumes provided that layer- -to-layer and layer-to-substrate adhesion is robust, film stresses are well controlled through coefficients of thermal expansion matching, and devices are annealed at or above maximum operational temperatures. "Hitless" filters can be obtained by structuring thermo-optic filters in two independently heated portions. Thermo-optically actuated thin film semiconductor devices are manufacturable and testable on a wafer scale and may be packaged by methods adapted from those for conventional thin film filters. [ABSTRACT FROM PUBLISHER]

Single-mode perfluoropolymer waveguide structures exhibiting a polarization-independent ultra low loss of <0.05 dB/cm at 1310 nm and <0.07 dB/cm at 1550 nm with a Δn of 1.6% have been fabricated for the first time. These new low-loss structures indicate relatively high-power-handling reliability at 1310 and 1550 nm. Based on this, a highly efficient arrayed-waveguide grating multi-demultiplexer with a crosstalk of 30±2 dB and an insertion loss of 2.8±0.3 dB is realized. [ABSTRACT FROM PUBLISHER]

A polymer containing fine droplets of liquid crystal (LC) is investigated for obtaining an optical phase-shifting attenuator at 1550-nm wavelength. Two mixtures of liquid crystals and monomers are compared for a cell thickness of 15 μm. The first method uses nanosized LC droplets to achieve 2.29-rad phase shifting for an applied voltage of 230 Vrms. The second method uses microsized LC droplets to achieve 2.35-rad phase shifting for an applied voltage of 15 Vrms. Theoretical analysis of the phase shifting is developed. This optical property is used to achieve a variable optical attenuator (VOA) between two single-mode fibers. An optical architecture using graded index rod lenses and a pattern of photoresist polymer is presented. Typical characteristics of such VOA are: 12-dB range of attenuation, a maximum polarization dependence loss of 0.5 dB, 1.1-dB insertion loss, and a saturation voltage of 20 Vrms. [ABSTRACT FROM PUBLISHER]

An intensity modulation using a hybrid electrooptic (EO) polymer/sol-gel straight channel waveguide, useful in the 1550-nm wavelength regime is demonstrated without using Mach-Zehnder interferometric waveguide. The sol-gel waveguide is selectively buried so that a vertical transition into and out of an EO polymer coated on the sol-gel waveguide is arranged. The throughput ratio for transverse electric (TE) and transverse magnetic (TM) modes of the light coupled out of the hybrid waveguide is improved up to 0.9 dB with the help of reduced birefringence of the EO polymer after corona poling. We show that the fabrication process of such hybrid-type waveguides enables production of a phase modulator operating at 1550-nm wavelength. The fabricated straight channel waveguide modulator exhibits stable- and high-intensity modulation efficiency (82%) using a simple cross-polarization setup after the polarization dependence is reduced. We demonstrate an all wet-etching process to fabricate polymeric EO modulators. [ABSTRACT FROM PUBLISHER]

Micro-ring wavelength filters and resonant modulators using polymer materials at 1300 nm and 1550 nm are analyzed, designed, and demonstrated. The rings are integrated with vertically coupled input and output waveguides. The devices are fabricated using optical lithography. Filters with a finesse of 141 and free spectral range of 5 nm at 1300 nm and finesse of 117 with a free spectral range (FSR) of 8 nm at 1550 nm are demonstrated. Ring resonators with a Q as high as 1.3 × 105 at 1300 nm are demonstrated. The filters can be temperature tuned at the rate of 14 GHz/°C. Resonant ring modulators, which use an electrooptic polymer, are demonstrated. The resonance wavelength voltage tunes at the rate of 0.82 GHz/V. The modulators have a bandwidth larger than 2 GHz. Using the resonant modulator, and open eye diagram at 1 Gb/s is demonstrated. [ABSTRACT FROM PUBLISHER]

We report on a commercially reproducible silicon wafer with a high-reflectance buried distributed Bragg reflector (DBR). The substrate consists of a two-period DBR fabricated using a double silicon-on-insulator (SOI) process. The buried DBR provides a 90% reflecting surface. We have fabricated resonant cavity-enhanced Si photodetectors with 40% quantum efficiency at 860 nm and a full-width at half-maximum of 29 ps suitable for 10 Gbps data communications. We have also implemented double-SOI substrates with 90% reflectivity covering 1300 and 1550 nm for use in Si-based optoelectronics. [ABSTRACT FROM PUBLISHER]

A mode-adapted semiconductor optical amplifier (SOA) has been fabricated and packaged. At the gain peak, 1500 nm, the fiber to fiber gain was measured to be 32.5 dB. Statistics for eight packaged devices indicate that a fiber-to-fiber gain of 26.3 dB ± 1.3 dB and a saturation output power of 12.4 dBm ± 0.4 dBm are typical at a bias of 500 mA for λ = 1550 nm. Polarization sensitivity at 1550 nm was measured to be 1.1 dB ± 0.4 dB and the transverse electric (TE) polarization state noise figure (NF) was determined to be 7.0 dB ± 0.5 dB. The coupling loss was 1.3 dB ± 0.1 dB per facet. This SOA, with a 1.3-nm filter, was used as an optical preamplifier in a 10-Gb/s return-to-zero (RZ) system testbed with a pseudorandom binary sequence (PRBS) of 231 -1. A 14.5-dB improvement in receiver sensitivity was observed at a bit error rate (BER) of 10-11 [ABSTRACT FROM PUBLISHER]

We report on the integration of the Bragg filters with 1×8 multimode interference (MMI) power splitters on silicon substrate, and the demonstration of 1×8 external cavity distributed Bragg reflector (DBR) lasers. Hybrid organic-inorganic material is developed based on the sol-gel synthesis of an organically modified silicon alkoxide. The sol-gel material is spin coated on grating SiO2-Si wafers, and the designed components (splitters and filters) are UV imprinted and developed using solvent assisted photolithography. The Bragg reflectors show filtering up to 98% with a bandwidth of about 0.8 nm consistent with their theoretical prediction. Integrated reflectors and MMI splitters are then used as feedback resonators for DBR lasers. Single-mode lasing with sidemode suppressions of up to 40 dB and a linewidth of about 400 kHz is observed. At 1550- nm wavelength, the loss and power uniformity in the MMI splitters, designed on the basis of lowest loss, are, respectively, 0.13 dB and 0.03 dB poorer than their theoretical calculations [ABSTRACT FROM PUBLISHER]

A low insertion loss waveguide is fabricated in z-cut lithium niobate using femtosecond laser waveguide inscription. To fabricate a waveguide exhibiting both low propagation and coupling losses, we used the multiscan fabrication technique to control the size of the waveguide cross section. A minimum insertion loss of only 3.5 dB at 1550 nm was measured for the 18-mm-long waveguide when directly coupled to Corning SMF-28 fibers. Of this 3.5dB, we attribute 2.1 dB to coupling losses, 1.1 dB to propagation losses, and 0.3 dB to Fresnel reflections [ABSTRACT FROM PUBLISHER]

A single shallow ridge electroabsorption modulator monolithically integrated with a buried-ridge-stripe dual-core spot-size converter at the input and output port was fabricated by combining quantum-well intermixing and dual-core integration techniques simultaneously, using only a two-step low-pressure metal-organic vapor phase epitaxial process, conventional photolithography, and a chemical wet etching process. The optical insertion loss of the modulator in the on-state and the dc extinction ratio between 0 and -3 V at 1550 nm was -7.5 and 16 dB, respectively. The 3-dB modulation bandwidth was more than 10.0GHz in electrical-optical response [ABSTRACT FROM PUBLISHER]

We have presented a new configuration of a planar lightwave circuit (PLC) module coated directly with a filter which divides 1310/1550-nm wavelength bands for a wavelength-division-multiplexing passive optical network module in order to improve the conventional insertion process of thin film filter into the narrow trench located at the Y-junction of a PLC platform. The broadly tapered output facet width of a V-shaped waveguide was designed to be 12 mum to minimize the reflected loss. The receiver module integrated with a PIN-photodiode on a silicon optical bench was fabricated. Data transmission of 2.5-Gb/s was demonstrated with clear eye diagrams [ABSTRACT FROM PUBLISHER]

An opto/electrical prototype for on-board optical-to-electrical signal broadcasting operating at 10 Gb/s per channel over an interconnect distance of 10 cm is demonstrated. An improved 1times4 multimode interference (MMI) splitter at 1550 nm with linearly tapered output facet is heterogeneously integrated with four p-i-n photodetectors (PDs) on a silicon (Si) bench. The Si bench itself is hybrid integrated onto an FR-4 printed-circuit board with four receiver channels. A novel fabrication/integration approach demonstrates the simultaneous alignment between the four waveguides and the four PDs during the MMI fabrication process. The entire system is fully functional at 10 Gb/s [ABSTRACT FROM PUBLISHER]

A variable optical attenuator (VOA) based on a metal-defined polymeric optical waveguide has been demonstrated for the first time. The metal film stressor deposited on top of the upper cladding layer not only produces the refractive index change within the core layer, but also acts as a thin-film heater allowing thermal tuning of the optical power within a metal-defined optical waveguide. Fabricated devices exhibit greater than 25 dB of optical attenuation with an applied electrical current of ∼40 mA at 1550-nm wavelength. The switching speed of the VOA exhibits 800 μs of rising and 720 μs of falling time. [ABSTRACT FROM PUBLISHER]

A polymeric microring resonator has been proposed and fabricated using the nanoimprint technique based on a stamp incorporating a smoothing buffer layer. It played a pivotal role in improving the sidewall roughness of the waveguide pattern engraved on the stamp and thus reducing its scattering loss. Eventually, the quality factor of the resonator could be enhanced. It also helped narrow down the gap between the ring and the bus effectively to strengthen the coupling between them. For the fabricated device, the quality factor of ∼103 800 and the extinction ratio of ∼11 dB were achieved at 1550 nm, while the estimated scattering loss was reduced from 38 to 0.0005 dB/mm with the help of the smoothing layer. [ABSTRACT FROM PUBLISHER]

We have developed multichannel wavelength filters consisting of three-dimensional photonic crystals, which have multiple filter regions with different transmission wavelengths according to differences in the in-plane lattice constants of the crystals. In this study, we improved the design of the photonic crystal (PC) filters by making use of the photonic-bandgap edge and fabricated PC filters with a Ta2O5-SiO2 material system. This improvement enabled us to obtain a transmission wavelength shift of +36 nm at 1550 nm, which agrees well with the results of finite-difference time-domain simulations. By connecting the multichannel wavelength filters to a 100-GHz-spaced 40-channel arrayed waveguide grating (AWG), we suppressed the crosstalk in the AWG from -40 dB to less than -60 dB. [ABSTRACT FROM PUBLISHER]

Single-mode Rb+-K+ ion-exchanged channel waveguides operating at 1550-nm wavelength have been demonstrated in BK7 glasses. The ion-exchange process was carried out using RbNO3 molten bath; the melt temperature ranged from 420°C to 480°C, and the exchange time from 30 to 120 h. The waveguide properties were characterized optically, and the stress-induced index change and waveguide birefringence were also studied. The propagation losses of annealed channel waveguides were measured to be ∼0.4 dB/cm, and the diffusion constant and the activation energy of Rb+ in BK7 glasses are calculated to be 3.65 × 10-17 m2/s and 4.23 kJ/mol, respectively. [ABSTRACT FROM PUBLISHER]

We report on the fabrication of optical channel waveguide on a high-energy-beam sensitive glass using a maskless nonphotolithographic processing technique. Laser direct writing and one-step chemical etching result in high quality channel waveguide with a propagation loss of about -0.27 dB/cm at 1550-nm wavelength. [ABSTRACT FROM PUBLISHER]

A monolithic 1550-nm single-mode AlInGaAs-InP multiple quantum-well distributed feedback laser and amplifier is presented. For the 400-μm-long grating section κ=112+ 30i cm-1, while the output is taken from the 200-μm-long amplifier section. The slope efficiency of the chip was 0.21 W/A, while the kink free power from the fiber was 34 mW. Narrow linewidths of <50 kHz were measured, and the dispersion penalty remained less than 2.0 dB for a data rate of 2.5 Gb/s over 300 km of SMF-28 [ABSTRACT FROM PUBLISHER]

We demonstrate the wavelength-division multiplexing (WDM) and wavelength-encoding capability of input waveguide grating couplers. The couplers are designed to have a predetermined wavelength response in addition to their conventional function of coupling an incident beam from, e.g., an optical fiber into a planar waveguide. The first example shows the WDM function: separating each of four input wavelengths into a different focus position in the waveguide. The second example shows wavelength encoding: translating a certain wavelength into a desired configuration of focus positions that is different for four different input wavelengths. The couplers were fabricated in an InP waveguide for ~1550-nm wavelength and the separation between the wavelengths was 10 nm. A WDM coupler with a narrower channel separation of 2 nm was also fabricated and successfully demonstrated [ABSTRACT FROM PUBLISHER]

Wide-band wavelength-division multiplexers (WDMs) have been developed for applications in short-haul and satellite communications. Device designs based on Mach-Zehnder interferometers (MZIs) and arrayed waveguide gratings (AWGs) have been fabricated using AlliedSignal Inc. low-loss acrylate polymer materials. Low channel-counts and channel separations of 5-30 nm result in compact devices with relaxed processing tolerances, thus minimizing the cost and increasing the yields of the devices. Operating at around 1550 nm, the multiplexers offer crosstalk of 20-25 dB, on-chip loss of <10 dB, thermal stability within several degrees and low polarization sensitivity [ABSTRACT FROM PUBLISHER]

We have proposed and demonstrated a low-power consumption thermooptic variable optical attenuator incorporating a membrane-type asymmetric branch waveguide in polymers. The membrane structure has been introduced by partially removing the silicon substrate with a bulk micromachining technique of backside etching. As a result, the heat flow in the polymer layers has been appropriately adjusted to increase the temperature gradient between the two arms of the branch and thus to enhance the attenuation efficiency. The measured electrical power consumption of the proposed attenuator was as small as 25 mW at 1550 nm, which was reduced by about 50% compared to that of the conventional device. Further improvement is achieved by a more optimized design of the area to be etched away [ABSTRACT FROM PUBLISHER]

We report the design and fabrication of micromechanically tunable filters with a 10-nm bandwidth for the 1550-nm wavelength range. The electrostatic actuation provides a tuning range of 30 nm and a low actuation power. The filters consist of a monolithic, vertical Fabry-Perot resonant cavity based on an epitaxial InGaAsP-InP Bragg reflector. An actuable InP micromechanical structure suspended over a 1×-thick air-gap provides for the tuning of the cavity. Our design aims primarily for a device that is simple, robust and that can be integrated with an InP-based photodetector or emitter in a low-cost component for optical data interconnects [ABSTRACT FROM PUBLISHER]