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Photonics Technology Letters, IEEE

Issue 4 • Date Feb.15, 2013

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Displaying Results 1 - 25 of 29
  • [Front cover]

    Publication Year: 2013 , Page(s): C1
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    Freely Available from IEEE
  • IEEE Photonics Technology Letters publication information

    Publication Year: 2013 , Page(s): C2
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    Freely Available from IEEE
  • Table of contents

    Publication Year: 2013 , Page(s): 321 - 322
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    Freely Available from IEEE
  • Widely Tunable Single Longitudinal Mode Fiber Laser With Cascaded Fiber-Ring Secondary Cavity

    Publication Year: 2013 , Page(s): 323 - 326
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (493 KB) |  | HTML iconHTML  

    A widely tunable single longitudinal mode (SLM) fiber laser with cascaded Type I and Type II fiber ring secondary cavities, which uses a tunable fiber Bragg grating (FBG) as the mode-restricting and wavelength-tuning element, is proposed and demonstrated. Since the cascaded fiber rings can effectively expand the pass-band spacing to make the mode selection with the FBG easier, the stability of SLM oscillation can be improved by suitably optimizing the coupling ratio of optical couplers in Type II fiber ring to ensure that at least one and only one longitudinal mode dominates in the selected pass-band. When the fiber ring lengths are designed to make their expanded pass-band spacing be a value from 0.5 to 1 times of the 3-dB bandwidth of the FBG, the mode competitions between both neighboring pass-bands and main cavity modes, may be effectively eliminated, making the laser maintain mode-hop-free SLM oscillations while it is widely tuned. View full abstract»

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  • An All-Optical Modulation Format Conversion for 8QAM Based on FWM in HNLF

    Publication Year: 2013 , Page(s): 327 - 330
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2807 KB) |  | HTML iconHTML  

    In this letter, we propose and experimentally demonstrate an all-optical modulation format conversion scheme from amplitude shift keying (ASK) and quadrature phase shift keying (QPSK) to 8-ary quadrature amplitude modulation (8QAM), using four-wave mixing (FWM) effect in highly nonlinear fiber. In the FWM process, a 20-Gbits/s return-to-zero QPSK (RZ-QPSK) signal and a 10-Gbit/s ASK signal are utilized as probe light and pump light, respectively. A 30-Gbits/s RZ-8QAM signal, which is the idler light, is successfully obtained with optical signal-to-noise ratio larger than 30 dB and bit-error rate lower than 10-5. View full abstract»

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  • Elliptical Hollow Fiber With Inner Silver Coating for Linearly Polarized Terahertz Transmission

    Publication Year: 2013 , Page(s): 331 - 334
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (421 KB) |  | HTML iconHTML  

    Silver-coated elliptical hollow polycarbonate fibers for transmission of linearly polarized terahertz (THz) radiation are fabricated and characterized. A polarization ratio of 90% and a transmission loss of 0.79 dB/m at 0.65 THz are obtained for a 290-mm long fiber with major and minor inner radii of 2.42 and 1.18 mm. Modal birefringence in the order of 10-3-10-2 is predicted in the frequency region of 0.3-1.5 THz. We also investigate the transmission characteristics of deformed fibers and found that the fiber with a semicircle cross section could rotate the direction of a linear polarization. View full abstract»

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  • Widely-Tunable and Background-Free Ultra-Wideband Signals Generation Utilizing Polarization Modulation-Based Optical Switch

    Publication Year: 2013 , Page(s): 335 - 337
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (707 KB) |  | HTML iconHTML  

    A simple widely-tunable and background-free ultra-wideband (UWB) pulse shaper by utilizing the polarization modulation-based optical switch is proposed and demonstrated. By virtue of the excellent switch isolation and the complementarity between two inverted baseband signals output from the optical switch, the local oscillator leakage signal and the low frequency components of the obtained UWB signals are suppressed very well. The UWB pulse with center frequency up to 28 GHz is generated. View full abstract»

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  • Fluidic Optical Switch by Pneumatic Actuation

    Publication Year: 2013 , Page(s): 338 - 340
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (378 KB) |  | HTML iconHTML  

    We proposed a fluidic optical switch based on pneumatic actuation. A small amount of liquid is suspended in a cylinder in vertical position and separates the hollow cylinder into two chambers. A clear pillar with a ball head is fixed in the top chamber. An air channel is used to connect the bottom chamber and a syringe. By controlling the air pressure of the bottom chamber, the liquid can be moved up and down easily. When the liquid is lifted up, the pillar head can enter the liquid and a channel is opened. When the liquid moves down, the liquid can get rid of the pillar and the channel is closed. Our results show that the device can obtain a high optical attenuation (~1178:1) within a reasonable response time (~97 ms). The aperture of the channel is highly circular. The diameter of the channel can be tuned from ~0 to ~4.5 mm. Such an optical switch has potential applications in light shutters, variable optical attenuators, and adaptive irises. View full abstract»

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  • 40-Gb/s Colorless Reflective Amplified Modulator

    Publication Year: 2013 , Page(s): 341 - 343
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (516 KB) |  | HTML iconHTML  

    In this letter, we demonstrate a colorless reflective amplified modulator operating within the C- and L-band spectral ranges with the modulation data rate up to 40 Gb/s. We obtain a stable, open eye performance of the device at the temperature until 85°C. The presented device is fabricated using an indium phosphide (InP) monolithic integration platform, which relies on an AlGaInAs quantum well active material, gap engineering by selective area growth, and low-parasitic RC semi-insulating buried heterostructures. View full abstract»

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  • Refractive Index Sensor Based on S-Tapered Photonic Crystal Fiber

    Publication Year: 2013 , Page(s): 344 - 347
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (652 KB) |  | HTML iconHTML  

    The S-tapered PCF interferometer for refractive index sensing was demonstrated in this letter. The whole fabrication process was carried out using a standard splicing machine. It has a compact and stable structure since the S-shape assumes the same function with elongating taper. The sensor exhibits highly SRI sensitivity, which is found to be 8.0 10-5 RIU in 1.38-1.44 and the temperature dependence is only 4.2 pm/°C low 100°C. View full abstract»

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  • High Detectivity Mechanism of ZnO-Based Nanorod Ultraviolet Photodetectors

    Publication Year: 2013 , Page(s): 348 - 351
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    ZnO nanorod arrays are grown on Mg-doped GaN layer using the vapor cooling condensation system. To suppress the surface states and the dangling bonds residing on the sidewall surface of the ZnO nanorods, photoelectrochemical (PEC) surface passivation is carried out on the ZnO nanorods. The peak photoresponsivity of the unpassivated and the passivated ZnO nanorod photodetectors operating at -5 V was 3.0 × 103 A/W and 4.6 × 102 A/W, respectively. The PEC treatment dramatically reduces the noise equivalent power level and increased the specific detectivity up to a value of 1.43 × 1015 cmHz1/2W-1 Moreover, the noise power density spectra of the ZnO nanorod array photodetectors changed from the dependence of 1/f2 to 1/f. These results demonstrate that the generation-recombination centers are successfully passivated by the PEC oxidation method. View full abstract»

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  • InP-Based Photonic Multiwavelength Transmitter With DBR Laser Array

    Publication Year: 2013 , Page(s): 352 - 354
    Cited by:  Papers (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (848 KB) |  | HTML iconHTML  

    We demonstrate an InP-based photonic multiwavelength transmitter realized by integrating an array of distributed Bragg reflector lasers with modulators in Mach-Zehnder configuration. An arrayed waveguide grating is used to multiplex the generated signals into a common optical output. The device is designed according to a generic integration concept, using standardized building blocks, and is fabricated in a multiproject wafer run. The device delivers up to 4 dBm of optical power into the fiber with a modulation data rate of 12.5 Gbps per transmission channel. The obtained performance makes it very promising for application in the next generation optical access networks as a key source in the central office part of the telecommunication systems. View full abstract»

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  • Efficient Quasi-Three-Level Laser Operation of Nd:Gd:LuAG Crystal and Blue Light Generation

    Publication Year: 2013 , Page(s): 355 - 358
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (476 KB) |  | HTML iconHTML  

    The quasi-three-level laser operation of Nd:Gd:LuAG crystal is reported for the first time. The maximum continuous-wave (CW) output power of over more than 3 W was obtained with an optical conversion efficiency of 40.0% and a slope efficiency of 55.5%. With Cr:YAG as the saturable absorber, the passively Q-switched laser was achieved with the maximum average output power, shortest pulse width and pulse energy of 820 mW, 21.3 ns, and 124 μJ, respectively. By using a type-II cut LBO crystal as the intracavity frequency doubler, the maximum output power of 802 mW for CW operation and 331 mW for passively Q-switched operation were achieved at the wavelength of 474 nm. View full abstract»

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  • Compact 1625-nm Noncritically Phase-Matched {\rm KTiOPO}_{4} Optical Parametric Oscillator Intracavity Driven by the {\rm KTiOAsO}_{4} Raman Laser

    Publication Year: 2013 , Page(s): 359 - 361
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (291 KB) |  | HTML iconHTML  

    Raman lasers offer great potential for efficiently pumping optical parametric oscillation (OPO) and achieving parametric radiations with high beam quality. Compact noncritically phase-matched 1625-nm KTiOPO4 (KTP) OPO intracavity driven by the 1091-nm KTiOAsO4 (KTA) Raman laser is demonstrated. The maximum average output power at the signal wavelength of 1625 nm is 180 mW obtained under the LD pump power of 8 W. Corresponding pulse repetition rate and pulse width are, respectively, measured to be 8 kHz and 2.1 ns, with the single pulse energy and peak power calculated to be 22.5 μJ and 10.7 kW, respectively. The M2 factor of the signal wave is measured to be 1.3 by knife-edge technique. The cascaded Raman conversion in KTA and OPO in KTP may provide a new method for obtaining 1625-nm laser with high beam quality, a potential light source for optical time-domain reflectometer. View full abstract»

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  • Polarization-Insensitive Phase-Preserving Regenerator Based on a Fiber Optical Parametric Amplifier With Dual Orthogonal Pumps

    Publication Year: 2013 , Page(s): 362 - 364
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (480 KB) |  | HTML iconHTML  

    We investigate the gain-saturation characteristics of a dual-orthogonal-pump fiber optical parametric amplifier. Nearly uniform power transfer functions have been obtained for various input signal polarizations by adjusting the total pump power. Based on this physical behavior, we demonstrate polarization-insensitive phase-preserving amplitude regeneration of 40-Gb/s nonreturn-to-zero differential phase-shift keying signals. The receiver sensitivity has been improved by a maximum value of 4.7 dB. View full abstract»

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  • 1060-nm Tunable Monolithic High Index Contrast Subwavelength Grating VCSEL

    Publication Year: 2013 , Page(s): 365 - 367
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (513 KB) |  | HTML iconHTML  

    We present the first tunable vertical-cavity surface-emitting laser (VCSEL) where the top distributed Bragg reflector has been completely substituted by an air-cladded high-index-contrast subwavelength grating (HCG) mirror. In this way, an extended cavity design can be realized by reducing the reflection at the semiconductor-air interface using an anti-reflective coating (ARC). We demonstrate how the ARC can be integrated in a monolithic structure by oxidizing AlGaAs with high Al-content. The HCG VCSEL has the potential to achieve polarization stable single-mode output with high tuning efficiency. The HCG VCSEL shows a total tuning range of 16 nm around an emission wavelength of 1060 nm with 1-mW output power. View full abstract»

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  • Generation of Picosecond Pulses Over a 40-nm Wavelength Range Using an Array of Distributed Bragg Grating Mode-Locked Lasers

    Publication Year: 2013 , Page(s): 368 - 370
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (951 KB) |  | HTML iconHTML  

    A set of distributed Bragg Reflector mode-locked semiconductor lasers are presented that generate picosecond pulses over a spectral range of 40 nm on a single chip. The same technology is used to realize an integrated laser with two separate Bragg gratings coupled into a common gain and saturable absorption section. This laser is shown to lock together the two spectral slices from each grating in a single pulse train. View full abstract»

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  • Using {\rm BCl}_{3} -Based Plasma to Modify Wet-Etching Pattern Sapphire Substrate for Improving the Growth of GaN-Based LEDs

    Publication Year: 2013 , Page(s): 371 - 373
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB) |  | HTML iconHTML  

    Wet-etching pattern sapphire substrates (PSS) have been used to grow GaN-based light-emitting diodes (LEDs). However, after wet etching, several sidewall facets are exposed on the patterns of PSS. These sidewall facets would grow zincblende GaN and form irregular voids. In this letter, BCl3-based plasma is used to solve this problem and improve the performance of GaN-based LEDs. View full abstract»

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  • Optical and Thermal Analyses of Thin-Film Hexagonal Micro-Mesh Light-Emitting Diodes

    Publication Year: 2013 , Page(s): 374 - 377
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (645 KB) |  | HTML iconHTML  

    Vertical thin-film light-emitting diodes (LEDs) with integrated micro-mesh arrays are reported. By removing the sapphire substrate through laser lift-off, vertical current conduction becomes possible, improving current spreading capability and thus electrical properties. Compared with the as-grown device, the thin-film micro-mesh LEDs emits 61% more optical power, attributed to enhanced light extraction through the micro-mesh, evidence of which is provided by confocal imaging. At 100 mA, the enhancement factor rises to >;100% attributed to low junction temperatures due to efficient heat conduction as verified by infrared thermometric imaging. View full abstract»

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  • Interleaved Multiplexing Optical Fast OFDM Without the Interference Between Subchannels

    Publication Year: 2013 , Page(s): 378 - 381
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (358 KB) |  | HTML iconHTML  

    This letter studies the interference between the even and the odd subchannels in the interleaved multiplexing optical fast orthogonal frequency-division multiplexing system, which is caused by the non-orthogonal demultiplexing transform at the receiver. To eliminate this interference, frequency and timing offsets are introduced deliberately at the receiver to form orthogonal bases, which coincide with the discrete cosine and sine transforms of type-IV. Thus, the symbols can be demultiplexed at the receiver without any interference between subchannels, and the proposed receiver design can be implemented efficiently. Finally, analysis and simulation are provided to verify its feasibility and the ability to eliminate such interference. View full abstract»

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  • Frequency Locked Single-Mode Optoelectronic Oscillator by Using Low Frequency RF Signal Injection

    Publication Year: 2013 , Page(s): 382 - 384
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (560 KB) |  | HTML iconHTML  

    We propose a new injection-locked optoelectronic oscillator (OEO) which is locked by a low frequency RF signal and without adding high speed devices. From a low frequency modulated optical carrier, the injection-locking effect in a Fabry-Pérot laser diode is able to generate and selectively amplify one high order harmonic component, which is subsequently injected into a single-loop OEO to lock one of the oscillation modes. This process can improve the injected signal quality and simultaneously implement a single-mode OEO with precise oscillation frequency. In the experiment demonstration, a 20-GHz single-mode OEO locked by a 1-GHz RF signal is obtained. The measured side-mode suppression ratio is 65 dB and the phase noise at 1-kHz frequency offset is -94.7 dBc/Hz. View full abstract»

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  • Multiwavelength Single-Longitudinal-Mode Ytterbium-Doped Fiber Laser

    Publication Year: 2013 , Page(s): 385 - 388
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (622 KB) |  | HTML iconHTML  

    We demonstrate a multiwavelength single-longitudinal-mode (SLM) ytterbium-doped fiber laser. Two Sagnac loop mirrors are inserted into the cavity to ensure multiwavelength and SLM operation, respectively. Three wavelengths with a wavelength spacing of 1.8 nm are generated under stable operation, and the linewidth of each wavelength is measured to be narrower than 100 kHz. A side-mode suppression ratio of greater than 56 dB is achieved for each wavelength. The maximum power fluctuation was less than 0.8 dB for each wavelength. This scheme has the potential to be employed as a useful source in optical communications, fiber optical sensing, and high resolution spectroscopy in the 1-μm wavelength band. View full abstract»

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  • Random Population Model for Self Pulsation in Single-Section Quantum-Dot Lasers

    Publication Year: 2013 , Page(s): 389 - 392
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB) |  | HTML iconHTML  

    A new mechanism of self-pulsation in single section Fabry-Pérot (F-P) quantum-dot (QD) lasers is studied in this letter. Since Fermi-Daric statistics are not readily applicable to QD lasers for picosecond pulse generation, we use a random population model to simulate single-section QD F-P lasers. It is demonstrated that some QDs contribute as gain media, while others can still be absorptive, even though the overall device is biased above lasing threshold. This can lead to pulse generation without the typical nonlinear effects, such as four-wave mixing, Kerr nonlinearity, and spatially inhomogeneous current distribution, previously reported in single section self-pulsating semiconductor lasers. View full abstract»

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  • Passive Photonics in an Unmodified CMOS Technology With No Post-Processing Required

    Publication Year: 2013 , Page(s): 393 - 396
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (658 KB) |  | HTML iconHTML  

    Passive photonic components consisting of sub-micrometer waveguides, grating couplers, and ring resonators are demonstrated in an unmodified commercial complementary metal-oxide-semiconductor (CMOS) process. Waveguides demonstrate propagation losses of approximately 1 dB/mm at 1.3-μm wavelengths. Grating couplers achieve better than -5.8-dB coupling efficiencies. Ring resonators exhibit Qs greater than 5000 with extinction ratios of more than 20 dB. Furthermore, due to the utilization of front-end-of-the-line design layers for creating the waveguide cores coupled with a relatively thick buried-oxide layer standard within the process, no post-processing is required at the chip or wafer level to achieve the reported device performance. Hence, for the first time, designers without processing capabilities may design custom CMOS photonic circuits for a broad range of applications. One such application which may appropriately leverage the low-cost platform could be disposable bio-photonic sensor arrays. View full abstract»

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  • MAMSK-OFDM Signal for RoF Access With Increased Tolerance Toward Frequency Offset

    Publication Year: 2013 , Page(s): 397 - 400
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    A novel multi-amplitude minimum shift keying (MAMSK) orthogonal frequency division multiplexing (OFDM) signal is proposed for 60-GHz radio-over-fiber (RoF) access system. It can increase the tolerance toward frequency offset of an OFDM signal due to the faster roll-off side-lobe. In the experiment, a 3.21-Gb/s 2AMSK-OFDM signal is transmitted over 22 km single mode fiber (SMF) and 5 m air link successfully. Compared with a conventional 8QAM-OFDM signal, the signal-to-interference ratio (SIR) of 2AMSK-OFDM is improved by 11.5 dB at a frequency offset of 0.15. The performance is improved by 1.7 dB under a normalized frequency offset (FO) of 0.2. 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.

Full Aims & Scope

Meet Our Editors

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