Showing papers on "Extinction ratio published in 2005"
TL;DR: In this paper, a 50 nm half-pitch wire grid polarizer with high performance using nano-print lithography was reported, which is a form of aluminium gratings on a glass substrate whose size of 5.5 cm × 5. 5 cm is compatible with a microdisplay panel.
Abstract: We report the fabrication of a 50 nm half-pitch wire grid polarizer with high performance using nanoimprint lithography. The device is a form of aluminium gratings on a glass substrate whose size of 5.5 cm × 5.5 cm is compatible with a microdisplay panel. A stamp with a pitch of 100 nm was fabricated on a silicon substrate using laser interference lithography and sidewall patterning. The imprint and the aluminium etching processes are optimized to realize uniform aluminium gratings with aspect ratio of 4. The polarization extinction ratio of the fabricated device is over 2000, with transmission of 85% at a wavelength of 450 nm, which is the highest value ever reported. This work demonstrates that nanoimprint lithography is a unique cost-effective solution for nanopatterning requirements in consumer electronics components.
361 citations
TL;DR: In this paper, a temperature-insensitive 10 Gb s−1 laser diodes on a GaAs substrate at 1.3 µm were used for optical telecommunication.
Abstract: This paper presents recent progress in the field of semiconductor lasers and optical amplifiers with InAs-based self-assembled quantum dots in the active region for optical telecommunication. Based on our design in terms of the maximum bandwidth for high-speed modulation and p-type doping in quantum dots for high temperature stability, we realized temperature-insensitive 10 Gb s−1 laser diodes on a GaAs substrate at 1.3 µm. The output waveform at 10 Gb s−1 maintained a clear eye opening, average output power and extinction ratio without current adjustments from 20°C to 70°C. We developed ultrawide-band high-power amplifiers in the 1.5 µm wavelength region on an InP substrate. The amplifier showed ultrafast gain response under gain saturation, and enabled signal regeneration at 40 Gb s−1 by suppressing the '1'-level noise due to the beating between the signal and amplified spontaneous emission. We present our amplifier module with polarization diversity to enable a stable polarization-insensitive performance, and also, discuss prospects for polarization-insensitive quantum dots by the close stacking technique.
233 citations
TL;DR: In this article, an optical microfiber loop resonator was constructed in free space by creating a loop from the subwavelength-diameter waist of a short biconical optical fiber taper.
Abstract: We experimentally demonstrate an optical microfiber loop resonator. The resonator was formed in free space by creating a loop from the subwavelength-diameter waist of a short biconical optical fiber taper. The loop length was chosen so that the free spectrum range of the resonator was ∼100GHz at the optical communication wavelengths near 1.5μm. In order to change and optimize the spectral characteristics such as the effect of birefringence, the shape of resonances, and the free spectrum range, we manually varied the microfiber self-coupling by alignment of the input and output ends of the loop, which were attached to each other by Van der Waals and electrostatic forces. In particular, we tuned the microfiber loop resonator to exhibit resonances with a Q-factor exceeding 15 000 (finesse ≈10) and, also, to the regime of critical coupling with the extinction ratio of transmission oscillations exceeding 34dB. This paper was in press when we achieved the values of 95 000 and 630 000 for the loaded and intrinsi...
190 citations
TL;DR: In this paper, a near-ideal in-fiber polarizer implemented by use of 45° tilted fiber Bragg grating structures that are UV inscribed in hydrogenated Ge-doped fiber was reported.
Abstract: We report a near-ideal in-fiber polarizer implemented by use of 45° tilted fiber Bragg grating structures that are UV inscribed in hydrogenated Ge-doped fiber. We demonstrate a polarization-extinction ratio of 33?dB over a 100-nm operation range near 1550?nm. We further show an achievement of 99.5% degree of polarization for unpolarized light with these gratings. We also theoretically investigate tilted grating structures based on the Green's function calculation, therein revealing the unique polarization characteristics, which are in excellent agreement with experimental data.
154 citations
TL;DR: In this paper, a transverse-electric/transverse-magnetic (TE/TM) polarization beam splitter based on the dependence of birefringence on rib width in silicon-on-insulator waveguides is proposed.
Abstract: We design, fabricate, and test a novel transverse-electric/transverse-magnetic (TE/TM) polarization beam splitter which is based on the dependence of birefringence on rib width in silicon-on-insulator waveguides. The polarization beam splitter has high TE to TM extinction ratio, low excess loss and wide operation bandwidth. The simple fabrication method involves only single etch step.
149 citations
TL;DR: Using silicon photonic wire waveguides, compact 1 x 1, 1 x 2, and 1 x 4 Mach-Zehnder interferometer type optical switches on a silicon-on-insulator substrate are constructed and switching operations through the thermo-optic effect are demonstrated.
Abstract: Using silicon photonic wire waveguides, we constructed compact 1 × 1, 1 × 2, and 1 × 4 Mach-Zehnder interferometer type optical switches on a silicon-on-insulator substrate and demonstrated their switching operations through the thermo-optic effect These switches were smaller than 140 × 65, 85 × 30, and 190 × 75 μm, respectively At a 1550-nm wavelength, we obtained an extinction ratio larger than 30 dB, a switching power as low as 90 mW, and a switching response time of less than 100 μs Furthermore, switching operations were successfully demonstrated for the 1 × 4 switch
140 citations
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TL;DR: A light source device has a continous wave (CW) light source for emitting first direct current (DC) light, a level converter for converting optical electric power of the first DC light into second DC light, and a mixer for mixing an optical main signal having a constant extinction ratio with the secondDC light as discussed by the authors.
Abstract: A light source device has a continous wave (CW) light source for emitting first direct current (DC) light, a level converter for converting optical electric power of the first DC light into second DC light and outputting the second DC light, and a mixer for mixing an optical main signal having a constant extinction ratio with the second DC light.
138 citations
TL;DR: The effects of atmospheric turbulence, background light, source extinction ratio, amplified spontaneous emission, and receiver thermal noise are studied in the context of a semiclassical photon-counting approach and results are presented using a conditional Gaussian approximation method.
Abstract: Atmospheric optical communication systems that use optical preamplifiers and diversity reception are addressed. The particular diversity techniques that are investigated include aperture averaging, linear combining, and adaptive optics. On-off keying and binary pulse position modulation are considered. The effects of atmospheric turbulence, background light, source extinction ratio, amplified spontaneous emission, and receiver thermal noise are studied in the context of a semiclassical photon-counting approach. Numerical results are presented using a conditional Gaussian approximation method. By this method, we can measure the power penalty incurred under various operating conditions as well as the link margin improvement due to optical preamplification and diversity reception.
118 citations
TL;DR: This work proposes a simple and flexible multiwavelength Raman-fiber-laser-based long-distance remote-sensing scheme for simultaneous measurement of strain and temperature by use of fiber Bragg gratings and readily achieves simultaneous two-channel sensing probes with a high extinction ratio.
Abstract: We propose a simple and flexible multiwavelength Raman-fiber-laser-based long-distance remote-sensing scheme for simultaneous measurement of strain and temperature by use of fiber Bragg gratings. By combining two uniform fiber Bragg gratings with a tunable chirped fiber grating, we readily achieve simultaneous two-channel sensing probes with a high extinction ratio of more than ?50?dB over a 50-km distance. When strain and temperature are applied, lasing wavelength separation and shift occur, respectively, since the two uniform fiber Bragg gratings have identical material composition and different cladding diameters. This allows simultaneous measurement of strain and temperature for long-distance sensing applications of more than 50 km.
118 citations
TL;DR: In this paper, an all-optical NAND gate at 10 Gbit/s was demonstrated using gain nonlinearity characteristics of a semiconductor optical amplifier, which operates in a single cross-gain modulation mechanism.
Abstract: By using gain nonlinearity characteristics of a semiconductor optical amplifier, an all-optical NAND gate at 10 Gbit/s is demonstrated. The all-optical NAND gate operates in single mechanism, which is cross-gain modulation. In the NAND gate (AB+Ā), Boolean AB is obtained by using signal A as a probe beam and signal B as a pump beam in SOA-1. Also, Boolean Ā is obtained by using the clock signal as a probe beam and signal A as a pump beam in SOA-2. By adding the two outputs from SOA-1 and SOA-2, Boolean Ā+AB (logic NAND) can be acquired. The extinction ratio is about 6.1 dB.
111 citations
TL;DR: A new type of wire-grid polarizer that has achieved excellent optical performance and reliability and has potential for use in many integrated optical applications is developed.
Abstract: We developed a new type of wire-grid polarizer that has achieved excellent optical performance and reliability The nanowire-grid polarizer is based on a fully optimized innovative design structure that consists of not only the core nanowire grid but also the surrounding multilayer thin-film structures The surrounding structures are designed for antireflectivity to provide the best possible efficiency as well as for device reliability to provide the best possible handling robustness and environmental durability The core nanowire grid utilizes nanosized high-aspect-ratio dielectric walls as a support for forming a high-aspect-ratio metal nanowire grid that significantly reduces energy loss as a result of metal absorption for the transmitted beam while providing a high extinction ratio of the blocked beam The developed high-quality nanowire-grid polarizer has potential for use in many integrated optical applications
TL;DR: In this paper, the authors investigated the feasibility of tunable LiNbO3 photonic crystals and showed that the optimal lattice parameters can provide a Δλ=7nm shift in the photonic band gap for a Δn=0.01 variation of the refractive index with an extinction ratio of −22.5dB.
Abstract: In this letter, we investigate the feasibility of tunable lithium niobate (LiNbO3) photonic crystals. The optical response through a LiNbO3 photonic structure is theoretically determined in order to obtain a photonic band gap with optimal tunability. We show by means of a finite difference time domain simulation that the optimal lattice parameters can provide a Δλ=7nm shift in the photonic band gap for a Δn=0.01 variation of the refractive index with an extinction ratio of −22.5dB. The fabrication process and the optical characterization of these novel photonic crystal structures are also reported. The extinction ratio of the measured photonic band gap is lower than −12dB.
TL;DR: In this paper, a terahertz radiation detector that measures both the amplitude and polarization of the electric field as a function of time was developed, with an extinction ratio better than 100:1.
Abstract: We have developed a terahertz radiation detector that measures both the amplitude and polarization of the electric field as a function of time. The device is a three-contact photoconductive receiver designed so that two orthogonal electric-field components of an arbitrary polarized electromagnetic wave may be detected simultaneously. The detector was fabricated on Fe+ ion-implanted InP. Polarization-sensitive detection is demonstrated with an extinction ratio better than 100:1. This type of device will have immediate application in studies of birefringent and optically active materials in the far-infrared region of the spectrum.
TL;DR: In this article, a novel tunable microdisk resonator with microelectromechanical-system (MEMS)-actuated deformable waveguides is demonstrated for the first time.
Abstract: A novel tunable microdisk resonator with microelectromechanical-system (MEMS)-actuated deformable waveguides is demonstrated for the first time. The deformable waveguide enables us to continuously vary the power coupling ratio of the microdisks. A laterally coupled device with a quality factor of 7700 is fabricated on silicon-on-insulator substrate. An optical notch filter with variable attenuation at the resonant wavelength is successfully demonstrated, with an extinction ratio of 9 dB. The MEMS-actuated tunable microdisk is a basic building block for many dynamic wavelength-division-multiplexing circuits.
TL;DR: In this article, the design, fabrication, and characterization of monolithically integrated widely tunable all-optical wavelength converters in InP is reported, and error-free wavelength conversion at 2.5 Gbps was demonstrated over 50 nm input and 22 nm output wavelength range.
Abstract: Design, fabrication, and characterization of monolithically integrated widely tunable all-optical wavelength converters in InP is reported. The devices are based on the SGDBR laser integrated with different MZI-SOA wavelength converters. Error-free wavelength conversion at 2.5 Gbps was demonstrated over 50 nm input and 22 nm output wavelength range. Static operation, extinction ratio enhancement, signal reamplification, dynamic range, and chirp properties were characterized as well.
TL;DR: In this article, a phase shift-keying (PSK) self-homodyne detection scheme using a polarization-multiplexed pilot-carrier with an inverse return-to-zero (RZ) intensity modulation signal for 2-bit/symbol transmission at 20 Gb/s was demonstrated.
Abstract: Phase-shift-keying (PSK) self-homodyne modulation and demodulation using a polarization-multiplexed pilot-carrier with an inverse-return-to-zero (RZ) intensity modulation signal for 2-bit/symbol transmission at 20 Gb/s was demonstrated. The pilot-carrier was generated by polarization-modulation in an orthogonal polarization state with respect to a PSK signal in the transmitter, while its polarization state was rotated by 90/spl deg/ in a LiNbO/sub 3/-based hybrid module for homodyne detection in the receiver. We confirm that the proposed self-homodyne detection scheme is insensitive to cross-modulation degradation by an inverse-RZ signal with high extinction ratio, thanks to an intensity-noise reduction capability of more than 15 dB in the homodyne-balanced receiver. The proposed scheme offers robust PSK homodyne detection for multibit per symbol formats without using a complex optical phase-locked loop.
TL;DR: By the improvement of the propagation property, sub-picosecond all-optical gate with an extinction ratio of more than 10 dB was accomplished with an input pulse energy of 150 pJ and the insertion loss with the switch on was improved.
Abstract: All-optical gate-switch operation utilizing GaN intersubband-transition has been achieved by reducing edge dislocation density in the epitaxial layers. The diminution of dislocation was accomplished by MBE regrowth on an MOCVD-grown layer. Excess propagation loss for transverse magnetic polarization decreased due to the reduction of the dislocation. By the improvement of the propagation property, sub-picosecond all-optical gate with an extinction ratio of more than 10 dB was accomplished with an input pulse energy of 150 pJ. Moreover, the insertion loss with the switch on was improved.
TL;DR: In this article, a multi-wavelength fiber laser source is demonstrated with a semiconductor optical amplifier as the gain medium, and a delayed interferometer is incorporated in the ring cavity serving as a comb-like multichannel filter.
Abstract: A multiwavelength fiber laser source is demonstrated with a semiconductor optical amplifier as the gain medium. A delayed interferometer is incorporated in the ring cavity serving as a comb-like multichannel filter. A stable 75-wavelength simultaneous operation spaced at 40 GHz with the extinction ratio of 40 dB is achieved. By tuning the cavity loss, the center wavelength of the generated lasing waveband could be varied by as much as 20 nm.
TL;DR: In this article, a 10-Gb/s all-optical XOR gate based on polarization rotation induced by Kerr effect in a single highly nonlinear fiber (HNLF) was demonstrated.
Abstract: We demonstrate a 10-Gb/s all-optical XOR gate based on polarization rotation induced by Kerr effect in a single highly nonlinear fiber (HNLF). Using 2 km of HNLF with a nonlinear coefficient of 9.1 W/sup -1//spl middot/km/sup -1/, we obtain a 25-dB extinction ratio at the XOR output.
TL;DR: Almost complete polarization conversion is observed for a device less than 2 microm long, with a 14 dB extinction ratio, in a polarization converter using one-dimensional grating principles.
Abstract: We present a polarization converter using one-dimensional grating principles. The device is based on slanted slots etched deeply into an InP/InGaAsP heterostructure. Almost complete polarization conversion, with a 14 dB extinction ratio, is observed for a device less than 2 microm long.
TL;DR: Using a simple multiwavelength Raman laser configuration with a single phase-shifted FBG and a tunable chirped FBG, this work readily achieved simultaneous two-channel sensing probes with a high extinction ratio over a 50-km distance.
Abstract: We propose a simple and flexible multiwavelength Raman fiber laser based on phase-shifted fiber Bragg gratings (FBGs) and a tunable chirped FBG Using a simple multiwavelength Raman laser configuration with a single phase-shifted FBG and a tunable chirped FBG, we readily achieved simultaneous two-channel sensing probes with a high extinction ratio of more than 50 dB over a 50-km distance The multiwavelength output was stable and the peak fluctuation was less than 05 dB The temperature and strain sensitivities are estimated to be 101 pm/degrees C and 75 pm/microstrain, respectively
TL;DR: A novel integrated TM-pass waveguide polarizer with a subwavelength-wide slot is introduced and theoretically analyzed and can be used as a single polarization waveguide to guide only TM polarization modes of the light signal.
Abstract: A novel integrated TM-pass waveguide polarizer with a subwavelength-wide slot is introduced and theoretically analyzed. With a proper design of the slot, the waveguide can be used as a single polarization waveguide to guide only TM polarization modes of the light signal. With 26 microm length of this TM-pass polarizer, our computer simulations predict the insertion loss of 0.54 dB for the TM polarization mode with the extinction ratio of 20.3 dB at the wavelength of 1.55 microm.
TL;DR: In this article, a fiber Bragg grating (FBG) sensor system based on a semiconductor optical amplifier connected in a ring cavity configuration is proposed, which produces high power signal with good extinction ratio for FBGs with /spl sim/1% reflectivity.
Abstract: A fiber Bragg grating (FBG) sensor system based on a semiconductor optical amplifier connected in a ring cavity configuration is proposed. The proposed configuration produces high power signal with good extinction ratio for FBGs with /spl sim/1% reflectivity. A sensor system consists of four group of three FBGs of different wavelengths was constructed to demonstrate time- and wavelength-division multiplexing of FBG sensors.
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23 Dec 2005TL;DR: In this article, a polarization independent interferometer (PI-DPSK) is proposed for optical CDMA, secure communications, optical coherence tomography (OCT), and temporal gratings with ultra-precise timing.
Abstract: A polarization independent (PI) interferometer design that can be built from standard optical components is described. Based upon a Michelson interferometer, the PI interferometer uses a 50/50 splitter and Faraday Rotator Mirrors (FM's). The interferometer achieves good optical characteristics, such as high extinction ratio (ER) and low insertion loss (IL). Lack of polarization sensitivity reduces interferometer construction tolerances and cost, enhances performance and utility, and expands the scope of interferometric based devices. Such characteristics can be used to construct flexible, high performance, polarization insensitive, multi-rate, self-calibrating, optical DPSK receivers, power combiners, optical filters and interleavers, all-optical switches, and cascaded interferometers. Since polarization is not maintained in standard fiber optic networks, a PI-DPSK receiver allows for use of more sensitive DPSK communications over fiber, without need for costly polarization control hardware. Other applications of PI interferometers include optical CDMA, secure communications, optical coherence tomography (OCT), and temporal gratings with ultra-precise timing.
TL;DR: A cladding-pumped single-mode plane-polarized ytterbium-doped fiber laser generating 633 W of continuous-wave output power at 1.1 microm with 67% slope efficiency and a polarization extinction ratio better than 16 dB is demonstrated.
Abstract: We demonstrate a cladding-pumped single-mode plane-polarized ytterbium-doped fiber laser generating 633 W of continuous-wave output power at 1.1 µm with 67% slope efficiency and a polarization extinction ratio better than 16 dB. The laser is end-pumped through both fiber ends and shows no evidence of roll-over even at the highest output power, which is limited only by available pump power.
TL;DR: In this paper, an active mode-locking of a fiber laser with an all-fiber electrooptic modulator was demonstrated, where a 1.4-V driving signal was used, creating subnanosecond single pulses at the fundamental frequency of the cavity (12 MHz).
Abstract: Active mode-locking of a fiber laser with an all-fiber electrooptic modulator is demonstrated. A 1.4-V driving signal was used, creating subnanosecond single pulses at the fundamental frequency of the cavity (12 MHz). The modulator was a packaged Mach-Zehnder interferometer incorporating a poled twin-hole fiber in one of the arms. The switching voltage was 230 V at 1550 nm, with extinction ratio /spl sim/20 dB. The interferometer could be electrooptically tuned by 3.5 nm.
TL;DR: In this article, a new type of wire-grid polarizer, the so-called nanowire grid polarizer has been developed, which has achieved commercial quality optical performance and reliability.
Abstract: We developed a new type of wire-grid polarizer, the so-called nanowire-grid polarizer, which has achieved commercial quality optical performance and reliability. The nanowire-grid polarizer has cores composed of silicon dioxide nanowalls with metal coating on one side. These cores are surrounded by multilayer thin films for antireflection. The core nanowire grid utilizes nano-sized high-aspect ratio dielectric walls as a support for forming a high aspect ratio metal nanowire grid, which significantly reduces energy loss due to metal absorption for the transmitted beam while achieving high extinction ratio for the blocked beam. For all design simulations, we utilized a rigorous coupled-wave analysis and modal method. The nanowire-grid structure was fabricated by a wafer-based nanoreplication lithography and pattern-transfer techniques, which are capable of producing a large-area high aspect ratio nanostructure with high throughput and low cost. The optical performance of the nanowire-grid polarizer was characterized thoroughly. Furthermore, the nanowire-grid polarizer has been integrated monolithically with a Faraday magnetooptic garnet, which results in an integrated semi-isolator. Full free-space isolators based on the integrated semi-isolators have been also developed, which achieved excellent performance, good enough for commercial applications.
TL;DR: In this article, the authors show that high extinction ratio (>20 dB) modal interference in a two-mode dispersion compensating fiber can be used to build a compact, easy-to-fabricate tunable all-fiber optical comb filter.
TL;DR: In this paper, a thermooptic switch with a symmetric Mach-Zehnder interferometer structure was demonstrated with silicon photonic-crystal-slab line-defect waveguides.
Abstract: A thermooptic switch with a symmetric Mach-Zehnder interferometer structure was demonstrated with silicon photonic-crystal-slab line-defect waveguides. The device size was as small as 160/spl times/65 /spl mu/m. The optic switch operated at a wavelength of 1550 nm, and an extinction ratio greater than 30 dB was obtained by 120-mW heating (switching) power over the wavelength range of 15 nm. The switching on-off response times were about 120 /spl mu/s.
TL;DR: In this paper, a vertically coupled polymer thermo-optic switch with two waveguides laid in different but parallel layers with one waveguide crossing over the other, and an electrode heater on top was designed and fabricated.