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Photonics Technology Letters, IEEE

Issue 5 • Date May 2002

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Displaying Results 1 - 25 of 44
  • Multiple-quantum-well GaInNAs-GaNAs ridge-waveguide laser diodes operating out to 1.4 μm

    Publication Year: 2002 , Page(s): 591 - 593
    Cited by:  Papers (41)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (198 KB)  

    Results from a ridge waveguide laser diode (LD) structure, with three GaInNAs quantum wells (QWs) and GaNAs barriers, are presented. The sample was grown by solid source molecular beam epitaxy with an RF plasma nitrogen source. These devices differ from previously reported GaInNAs QWs LDs that used GaAs as the barrier material. The introduction of nitrogen into the barriers reduces the spectral blue shift caused by post-growth annealing. Long wavelength emission out to 1.405 μm was observed. The devices exhibited threshold current densities as low as 1.5 kA/cm2, high differential efficiency of 0.67 W/A, and a maximum output power of 350 mW." View full abstract»

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  • A novel fabrication technique for multiple-wavelength photonic-integrated devices in InGaAs-InGaAsP laser heterostructures

    Publication Year: 2002 , Page(s): 594 - 596
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (184 KB)  

    We report the fabrication of multiple wavelength chips in InGaAs-InGaAsP laser structure using a novel ion implantation induced quantum-well (QW) intermixing technique. This technique first consists of using a gray mask photolithography and reactive ion etching process to create a SiO2 implant mask with variable thickness on the sample. This is followed by a single 360-keV phosphorus ion implantation at a dose of 1×10/sup 14/ cm/sup -2/ at 200/spl deg/C, which creates different amounts of point defects in the sample depending on the local thickness of the SiO2 mask. A subsequent thermal annealing step induces QW intermixing through the diffusion of the point defects across the structure. With this technique, we have successfully fabricated 10-channel multiple wavelength laser diodes, with lasing wavelength spreading over 85 nm (between 1.47 and 1.55 μm), monolithically integrated on a single chip. Only a limited increase of threshold current density of 17% (i.e., from 1.2 to 1.4 kA/cm2), has been observed between the least intermixed and the most intermixed lasers. View full abstract»

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  • High T0 long-wavelength InGaAsN quantum-well lasers grown by GSMBE using a solid arsenic source

    Publication Year: 2002 , Page(s): 597 - 599
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (202 KB)  

    We demonstrate high performance, /spl lambda/=1.3- and 1.4-μm wavelength InGaAsN-GaAs-InGaP quantum-well (QW) lasers grown lattice-matched to GaAs substrates by gas source molecular beam epitaxy (GSMBE) using a solid As source. Threshold current densities of 1.15 and 1.85 kA/cm2 at /spl lambda/=1.3 and 1.4 μm, respectively, were obtained for the lasers with a 7-μm ridge width and a 3-mm-long cavity. Internal quantum efficiencies of 82% and 52% were obtained for /spl lambda/=1.3 and 1.4 μm emission, respectively, indicating that nonradiative processes are significantly reduced in the quantum well at /spl lambda/=1.3 μm due to reduced N-H complex formation. These Fabry-Perot lasers also show high characteristic temperatures of T0=122 K and 100 K at /spl lambda/=1.3 and 1.4 μm, respectively, as well as a low emission wavelength temperature dependence of (0.39/spl plusmn/0.01) nm//spl deg/C over a temperature range of from 10/spl deg/C to 60/spl deg/C. View full abstract»

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  • Wide tunable double ring resonator coupled lasers

    Publication Year: 2002 , Page(s): 600 - 602
    Cited by:  Papers (50)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB)  

    A double ring resonator coupled laser (DR-RCL) is proposed and analyzed in this letter. Benefiting from the uniform peak transmission, narrow bandwidth and other superior characteristics of traveling wave supported high-Q resonators, DR-RCLs offers many promising advantages over the conventional tunable lasers, including ultra wide wavelength tuning range, high side mode suppression ratio, uniform threshold and efficiency, narrow linewidth, low frequency chirp, and simple fabrication. A DR-RCL with a moderate optical loss /spl sim/10 dB/cm in the ring resonators can achieve a wavelength tuning enhancement of /spl sim/50. With such a large tuning leverage, DR-RCLs could utilize the electrooptic effects to achieve ultrafast tuning speed with a wide tuning range covering the material gain bandwidth. View full abstract»

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  • Two-segment spectrally inhomogeneous traveling wave semiconductor optical amplifiers applied to spectral equalization

    Publication Year: 2002 , Page(s): 603 - 605
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    Spectral equalization devices for an optical analog-to-digital (A-to-D) converting system have been theoretically analyzed and fabricated. Selective area growth was used to define a multiple-section active region. Two-segment semiconductor optical amplifier with current adjustable gain spectrum is demonstrated. View full abstract»

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  • L-band multiwavelength fiber laser using an elliptical fiber

    Publication Year: 2002 , Page(s): 606 - 608
    Cited by:  Papers (42)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (199 KB)  

    In this letter, we propose and demonstrate a simple and novel technique to get multiwavelength operation in the L-band by using an elliptical core erbium-doped fiber. The principle of operation is based on the anisotropic gain effect in a polarization-maintaining fiber. Stable multiwavelength operation is achieved at room temperatures. The lasing lines may be controlled by a polarization controller. View full abstract»

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  • 1.55-μm Ce,Er:ZBLAN fiber laser operation under 980-nm pumping: experiment and simulation

    Publication Year: 2002 , Page(s): 609 - 611
    Cited by:  Papers (12)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (202 KB)  

    Fiber laser operating property at 1.55-μm band in a newly developed Ce,Er:ZBLAN fiber by a continuous-wave laser diode pumping at 980 nm is presented. The output characteristics of the Ce,Er:ZBLAN fiber laser system are analyzed in detail based on the rate equations model by taking into account the energy transfer between Ce/sup 3+/ and Er/sup 3+/ ions, as well as the upconversion mechanisms. The promotion role of the Ce in the erbium-doped ZBLAN for the 1.55-μm band fiber laser operation has been realized. View full abstract»

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  • Switchable multiwavelength erbium-doped fiber laser with cascaded fiber grating cavities

    Publication Year: 2002 , Page(s): 612 - 614
    Cited by:  Papers (71)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB)  

    We propose a new concept to produce switchable multiwavelength oscillations with a cascaded fiber Bragg grating overlapping cavity erbium-doped fiber laser. The laser can be designed to operate in multiwavelength or in wavelength switching modes. The different lines have different thresholds. For three-wavelength oscillation, the output powers are linear or piecewise linear functions of the input pump power. An output with a variation of only 1.5 dB has been achieved with an input pump power of 100 mW. For wavelength switching, three single-wavelength and two dual-wavelength operation regions have been obtained toy adjusting the input pump levels. View full abstract»

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  • Fully packaged polymeric four arrayed 2 x 2 digital optical switch

    Publication Year: 2002 , Page(s): 615 - 617
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    A fully packaged polymeric four arrayed 2/spl times/2 digital optical switch is fabricated. Crosslinkable fluorinated polymers with a large thermooptic coefficient and a low loss are used for a low electrical power consumption and a low insertion loss. We improve the uniformity, crosstalk, and insertion loss with introducing a rib waveguide, a channel waveguide, and a tapered waveguide in the polymeric four arrayed 2/spl times/2 digital optical switch. The deviation of crosstalks is /spl plusmn/2 dB at 250 mW. The crosstalks are less than -30 dB for all four 2/spl times/2 digital optical switch elements with each total electrical power of 250 mW. The fall and rise times are less than 5 ms. The polarization-dependent losses are in the range of 0.2-0.7 dB. The total insertion losses range from 3.5 to 4.0 dB. View full abstract»

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  • A mechanically biased electrooptic polymer modulator

    Publication Year: 2002 , Page(s): 618 - 620
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB)  

    Mechanical biasing of an electrooptic polymer modulator is proposed and demonstrated by heterogeneously integrating waveguide structures with a piezoelectric element. Biasing is achieved by changing the path-length of one arms of a Mach-Zehnder interferometer by mechanically bending the waveguide structure. Applying ac voltage to the piezoelectric element generates a pilot tone, which is used to monitor the bias point of the modulator, while applying dc tunes the modulator to quadrature. The method separates the biasing and RF modulation of the device, thus avoiding the need for external biasing components and eliminating electrical bias drift. View full abstract»

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  • Heterodyne technique for measuring the amplitude and phase transfer functions of an optical modulator

    Publication Year: 2002 , Page(s): 621 - 623
    Cited by:  Papers (14)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (186 KB)  

    We propose a technique based on heterodyne detection for accurately and simultaneously measuring the amplitude and phase transfer functions of an optical modulator. The technique is used to characterize an InGaAsP multiple quantum-well electroabsorption modulator. From the measurements we derive the small-signal /spl alpha/-parameter and the time-dependent chirp for different operation conditions. View full abstract»

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  • Improved magnetooptic modulator for ultrafast current pulses

    Publication Year: 2002 , Page(s): 624 - 626
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (179 KB)  

    A technique is proposed to improve the optical response of a magnetooptic (MO) modulator. The rate at which a MO modulator can operate is limited by the relatively slow relaxation of electron spin carrier populations within the MO material. This relaxation time can be more than an order of magnitude longer than the excitation time. Using a current pulse guided by a superconducting stripline it is possible to create a magnetic field within an MO material. This magnetic field rapidly excites electron spin carriers, resulting in the rapid polarization rotation of an optical beam. Providing a second current pulse of opposite sign to the system generates a second rapid excitation of opposite sign electron spin carriers and returns the polarization to its initial direction. This push-pull technique has the potential to create picosecond optical pulses and provides for the full utilization of the picosecond response time of MO materials. View full abstract»

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  • Analysis of PMD compensators with fixed DGD using importance sampling

    Publication Year: 2002 , Page(s): 627 - 629
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (186 KB)  

    In this letter, we use importance sampling to analyze polarization-mode dispersion compensators with a constant differential group delay (DGD) element. We optimize the value of the fixed DGD element of the compensator with respect to the outage probability. We show that the optimum value of the fixed DGD element of the compensator can reduce the outage probability by several orders of magnitude, even though it does not provide a substantial reduction of the average penalty due to polarization-mode dispersion in the cases that we studied. By contrast, choosing the fixed DGD element to maximally reduce the average penalty may lead to an outage probability that is orders of magnitude larger than the optimal choice. View full abstract»

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  • Emulator of first- and second-order polarization-mode dispersion

    Publication Year: 2002 , Page(s): 630 - 632
    Cited by:  Papers (12)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    Contrary to approaches which try to mimic a standard fiber as closely as possible, the emulator presented here gives constant (but user adjustable) values for differential group delay (DGD) and ratio of first- to second-order polarization-mode dispersion (PMD). Once it is set, the ratio is conserved while the DGD can be easily varied within a range of 0-300 ps. This allows to investigate the low-probability events of large DGD and second-order PMD important for system outage. View full abstract»

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  • Analysis of timing and amplitude jitter due to intrachannel dispersion-managed pulse interactions

    Publication Year: 2002 , Page(s): 633 - 635
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (222 KB)  

    Transmission impairments due to nonlinear intrachannel crosstalk in strongly dispersion-managed systems are investigated. Analytical expressions to estimate timing and amplitude jitter due to intrachannel pulse interactions are provided. Timing jitter is found to be a dominant limiting factor for small values of map strength, whereas amplitude jitter is responsible for system performance degradation especially for large map strength. The analysis agrees with direct numerical simulations of the full system. View full abstract»

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  • Temporal reshaping of optical pulses using quadratic spatial soliton generation and spatial filtering

    Publication Year: 2002 , Page(s): 636 - 638
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB)  

    We perform a temporal reshaping of laser pulses by means of quadratic spatial soliton excitation combined with a spatial filtering of the output beam. We demonstrate that the device presents a behavior similar to the one of a saturable absorber, and numerically investigate the parameters giving optimum temporal filtering. View full abstract»

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  • Thermally poled channel waveguides with polarization-independent electrooptic effect

    Publication Year: 2002 , Page(s): 639 - 641
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (201 KB)  

    We present a systematic investigation of the poling-induced electrooptic (EO) effect in germanium and nitrogen codoped channel waveguides. The channel waveguides show attractive properties: (1) almost polarization independent EO effect; (2) a flat frequency response with the modulation frequency up to 100 kHz; and (3) low linear loss and low polarization dependent loss, which demonstrate great technological potential. View full abstract»

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  • Out-of-plane losses of line-defect photonic crystal waveguides

    Publication Year: 2002 , Page(s): 642 - 644
    Cited by:  Papers (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (205 KB)  

    A numerical model is presented for computing the out-of-plane losses of a general class of two-dimensional photonic crystals superimposed. onto a slab confinement structure. The usefulness of this model is demonstrated by calculating the propagation loss of a single-row-defect waveguide composed of hexagonal air holes etched into two different slab structures. The results are interpreted in terms of a simple coupled-mode-theory picture in which loss is due to resonant coupling between the fundamental and certain radiative slab modes. These calculations show that low-loss photonic crystal waveguides should be possible by carefully designing the slab waveguide. View full abstract»

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  • Application of Bi-CGSTAB to waveguide discontinuity problems

    Publication Year: 2002 , Page(s): 645 - 647
    Cited by:  Papers (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    Scattering at a waveguide end facet or other waveguide discontinuities can be calculated by an iterative method together with rational approximations to the related square root operators. Previous work uses the classical Neumann series as the iteration scheme. We demonstrate that the method can be significantly improved if bi-conjugate gradient stabilized is used instead. View full abstract»

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  • A.2.5 GHz-spaced 1080-channel tandem multi/demultiplexer covering the. S-, C-, and L-bands using an arrayed-waveguide grating with Gaussian passbands as a primary filter

    Publication Year: 2002 , Page(s): 648 - 650
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (273 KB)  

    We describe a low-loss 25-GHz-spaced multi/demultiplexer with more than 1000 channels that covers the S-, C-, and L-bands of optical fiber amplifiers. It was achieved by cascading a 2.5-THz-spaced arrayed-waveguide grating (AWG) with Gaussian passbands as a primary filter and ten 25-GHz-spaced 1/spl times/200 AWGs as secondary filters in a tandem configuration. View full abstract»

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  • New design for low-loss star couplers and arrayed waveguide grating devices

    Publication Year: 2002 , Page(s): 651 - 653
    Cited by:  Papers (4)  |  Patents (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (219 KB)  

    We propose a new loss reduction method in star couplers employing UV-written tapers that replace the free propagation region in the conventional star couplers and apply them to an arrayed waveguide grating (AWG) device. The insertion loss of the new AWG device can be reduced to 0.31 dB, which is about 0.7 dB lower than that of the AWG without UV-written tapered waveguides. View full abstract»

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  • Multiwavelength optical signal processing using multistage ring resonators

    Publication Year: 2002 , Page(s): 654 - 656
    Cited by:  Papers (7)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    We show that all-pass filters based on multistage ring resonators can be used to perform optical signal processing. In particular, using numerical simulations, we demonstrate their use for performing real-time Fourier transformation and for pulse repetition rate multiplication (temporal Talbot effect) simultaneously over multiple wavelength signals. View full abstract»

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  • Step-changed long-period fiber gratings

    Publication Year: 2002 , Page(s): 657 - 659
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (195 KB)  

    The spectral characteristics of a new type of long-period grating (LPG) structure, step-changed LPG, are investigated theoretically and experimentally. It is shown that the spectral profile of such gratings can be tailored by adjusting the step parameters. A good agreement between simulated results and measured spectra is obtained. This type of LPG has potential applications in gain flattening of erbium-doped fiber amplifiers. View full abstract»

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  • Experimental demonstration of all-optical regeneration using an MMI-SOA

    Publication Year: 2002 , Page(s): 660 - 662
    Cited by:  Papers (9)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    A novel all-optical 2R regenerator based on a multimode interference coupler (MMI) semiconductor optical amplifier is presented. Static measurements of the transfer function reveal a digital transfer characteristic and a high increase in extinction ratio. The experiments are in good agreement with simulations, which have been done using a modified beam propagation method program. The device has a high tolerance to the MMI length. It has been fabricated in an all-active layout, avoiding the need for active/passive integration and is very compact. View full abstract»

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  • Nonlinearly strain-chirped fiber Bragg grating with an adjustable dispersion slope

    Publication Year: 2002 , Page(s): 663 - 665
    Cited by:  Papers (23)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (206 KB)  

    In this letter, we demonstrate an adjustable dispersion slope compensator for waveform distortion compensation based on a nonlinearly strain-chirped fiber Bragg grating. The dispersion slope of the device can be tuned up to -18.9 ps/nm/sup 2/ with a bandwidth >2.4 nm. After transmission through a 120-km-long dispersion-shifted fiber, the resulting waveform distortion for a 2.65-ps pulse is successfully compensated by using this device. View full abstract»

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Aims & Scope

This letters journal addresses all aspects of the IEEE Photonics Society Constitutional Field of Interest with emphasis on photonic/lightwave components and applications, laser physics and systems and laser/electro-optics technology.

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Meet Our Editors

Editor-in-Chief
Dr. Seb J. Savory
University College London