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Photonics Technology Letters, IEEE

Issue 8 • Date Aug. 1989

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Displaying Results 1 - 21 of 21
  • On the design of synchronously pumped mode-locked dye lasers with improved noise characteristics

    Publication Year: 1989 , Page(s): 189 - 192
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    An analysis of a synchronously pumped mode-locked (SPML) dye laser that is less susceptible to external noise sources is presented. Approximate, analytic formulas for the pulsewidth and peak intensity of an SPML dye laser are derived in the limit of a short pump pulse and a short coherence time. Using these expressions the sensitivity of the pulsewidth, the peak intensity, and a pulse energy on the cavity length mismatch and the pump level are explored. It is found that the detrimental effects of pump laser jitter (level and timing) can be decreased if a higher pumping level is achieved. Long-term pulse-to-pulse fluctuations in energy can be reduced by increasing the cavity losses.<> View full abstract»

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  • High-pressure infrared xenon laser with X-ray preionization

    Publication Year: 1989 , Page(s): 193 - 195
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (267 KB)  

    The first experimental results are presented of an X-ray preionized argon-buffered xenon laser. The X-rays are generated by a simple electron-beam device located below the 23-cm inner diameter laser chamber. The advantages of X-ray preionization for high-pressure discharge-pumped lasers include the long X-ray penetration depth, high preionization density, and spatial uniformity. The combination of X-ray preionization and techniques to eliminate surface flashover allows energetic operation in 4 atm of argon buffer for the first time in a photopreionized discharge laser. The argon-xenon mixtures lased primarily at 1.73 mu m and 2.63 mu m with a peak energy of 340 mJ at 4 atm, and a specific energy output of 0.85 J/liter.<> View full abstract»

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  • Analysis of transient gain saturation and recovery in erbium-doped fiber amplifiers

    Publication Year: 1989 , Page(s): 196 - 199
    Cited by:  Papers (34)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (274 KB)  

    An analysis of transient gain dynamics in erbium-doped fiber amplifiers is presented to provide a qualitative explanation of its time constants. The theory yields analytical solutions at the fiber amplifier input end, making it convenient to study the time dependence of gain saturation and recovery under changing input signal conditions. It is shown that, independently of the pump wavelength, gain saturation and recovery effects have long characteristic times (0.2-10.0 ms) which advantageously reduce saturation-induced crosstalk in the amplifier. The effect of saturation-induced gain modulation is found to vanish at signal frequencies above F=1 kHz, which is in good agreement with observed experimental results.<> View full abstract»

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  • Corrugation-pitch-modulated phase-shifted DFB laser

    Publication Year: 1989 , Page(s): 200 - 201
    Cited by:  Papers (17)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (135 KB)  

    A corrugation-pitch-modulated phase-shifted distributed feedback (DFB) laser is proposed to reduce the spatial-hole-burning effect along the laser cavity. The structure of the proposed corrugation-pitch-modulated phase-shifted DFB laser is illustrated. A reduction in this effect is confirmed from its spectral behavior as a function of driving current. Consequently, stable single-longitudinal-mode operation up to high-output powers is obtained.<> View full abstract»

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  • Two-dimensional surface emitting distributed feedback laser arrays

    Publication Year: 1989 , Page(s): 202 - 204
    Cited by:  Papers (11)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB)  

    The demonstration of two-dimensional arrays of surface-emitting distributed feedback lasers is reported. A 30-element array is shown to produce up to 6.8 W of pulsed output power. A 27-element array bonded on a silicon microchannel water-cooled heat sink is shown to produce as much as 3 W of continuous-wave output power. The high continuous wave power is possible due to the low thermal resistance in the p-side down design of the surface-emitting distributed feedback lasers and effective heat extraction by a silicon microchannel heat sink.<> View full abstract»

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  • Low-threshold-current-density vertical-cavity surface-emitting AlGaAs/GaAs diode lasers

    Publication Year: 1989 , Page(s): 205 - 208
    Cited by:  Papers (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (258 KB)  

    The optimization of electrically pumped vertical-cavity surface emitters (VCSEs) with conductive semiconductor-stack rear reflectors and mirror-reflectivity products of 0.93 for minimum threshold current density, J/sub th/, is presented. Devices of two different active layer thicknesses are fabricated: 3 mu m, as for conventional devices, and 0.6 mu m, which, according to theoretical calculations, provides J/sub th/ for lasers with a mirror reflectivity product in the 0.90-0.95 range. For structures of 0.16- mu m thick active layers, J/sub th/ values as low as 10 kA/cm/sup 2/ are obtained, in good agreement with theory. Analysis shows that for active layer thicknesses > View full abstract»

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  • Picosecond optical properties of a grating surface emitting two-dimensional coherent laser array

    Publication Year: 1989 , Page(s): 209 - 211
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (242 KB)  

    The picosecond dynamical properties of a two-dimensional grating surface emitting (GSE) laser array are investigated by recording with a streak camera the optical emission under low duty cycle, 200-ns pulsed operation. The elements of the two-dimensional GSE arrays are index-guided ridge lasers. The array (a 10*2 array) consists of two groups of ten laterally coupled laser elements which are coupled longitudinally by an intervening grating, and gratings on either end of the two groups which provide the necessary feedback for the laser cavities. A variety of nonlinear dynamic behavior regimes, ranging from quiescent through periodic, to erratic is observed during the course of a single-drive current pulse. The transition from one regime to another may be due to transient heating during the pulse.<> View full abstract»

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  • Intensity dependence of the linewidth enhancement factor and its implications for semiconductor lasers

    Publication Year: 1989 , Page(s): 212 - 214
    Cited by:  Papers (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (189 KB)  

    The linewidth enhancement factor is shown to become intensity dependent when the intraband relaxation effects responsible for nonlinear gain and index changes are incorporated in the theory of semiconductor lasers. The intensity dependence of the linewidth enhancement factor influences many laser characteristics such as the frequency chirp, the modulation response, the injection-locking range, and the phase noise. In particular, it leads to a power-independent contribution to the laser linewidth. Furthermore, for semiconductor lasers detuned to operate away from the gain peak, the nonlinear index changes can even lead to a rebroadening of the laser linewidth at high-output powers.<> View full abstract»

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  • Dynamic and CW linewidth measurements of buried heterostructure distributed feedback lasers

    Publication Year: 1989 , Page(s): 215 - 217
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (191 KB)  

    Measurements of frequency chirp as a function of modulation current, data rate, and bias level for the etched-mesa buried heterostructure distributed feedback (EMBH-DFB) laser are presented. The results show that the chirp increases with increasing modulation current and is significantly larger if the laser off-state is below threshold than if it is above-threshold. The 20-dB down chirp widths are in the range of 4 to 6 AA for 40 mA of modulation current at 5 Gb//s under above threshold bias. Using the EMBH-DFB laser, a system experiment over 22-km fiber at 16 Gb/s has been carried out which shows less than 0.5 dB dispersion power penalty. The continuous-wave (CW) linewidths of the asymmetric facet-coated DFB lasers are in the range of 10 to 40 MHz at 6 mW of output power. This wide range arises principally from a variation of the phase of the grating at the high-reflectivity coated facet.<> View full abstract»

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  • 5 Gbit/s direct optical DPSK modulation of a 1530-nm DFB laser

    Publication Year: 1989 , Page(s): 218 - 220
    Cited by:  Papers (16)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    5 Gb/s direct optical differential-phase-shift-keying (DPSK) modulation of a 1530-nm distributed feedback (DFB) laser is demonstrated using injection current modulation with a bipolar signal format. Delay demodulation is performed using an interferometer with a delay time T equal to the duration of one bit. The input and differentially encoded nonreturn to zero (NRZ) signals are shown. The bipolar modulation current signal is basically the time derivative of the NRZ signal. There was no degradation of the optical DPSK signal due to thermal frequency modulation of the laser. The direct DPSK modulation technique avoids the insertion loss and systems complexity of external DPSK modulators.<> View full abstract»

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  • A DFB-LD module integrated with 60 dB optical isolator for coherent lightwave transmission systems

    Publication Year: 1989 , Page(s): 221 - 223
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (201 KB)  

    The coupling efficiency between the distributed feedback-laser diode (DFB-LD) chip is presented and the single-mode fiber is as high as -5.7 dB (27%) including the insertion loss of the isolator. The spectral linewidth measurement using the self-delayed heterodyne method shows 26 MHz under the condition of IF=I/sub th/+50 mA. No changes in the DFB-LD chip properties are observed after packaging. The comparison to another DFB-LD module with a 30-dB isolator confirms the immunity of the spectrum against -14-dB Fresnel reflection. The results show that the DFB-LD module is sufficiently stable to be applied to the coherent lightwave transmission systems.<> View full abstract»

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  • 20 channel coherent FSK system using subcarrier multiplexing

    Publication Year: 1989 , Page(s): 224 - 226
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (215 KB)  

    A 20-channel multioctave coherent frequency shift keying (FSK) system using subcarrier multiplexing techniques is described. The microwave subcarriers range from 2.1 to 5.9 GHz with a 200-MHz channel spacing. The receiver consists of a p-i-n photodiode, electrical isolator, low-noise amplifier, and bandpass filter to provide channel selection. The channels are modulated at 100 Mb/s, corresponding to one digitized video channel. Results for the optimal phase modulation index and degradation due to second- and third-order intermodulation distortion are discussed. For the worst-case channel, a receiver sensitivity of -27 dBm was achieved.<> View full abstract»

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  • Low-switching-voltage InGaAsP/InP waveguide interferometric modulator for integrated optics

    Publication Year: 1989 , Page(s): 227 - 229
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    An InGaAsP/InP electrooptic Mach-Zehnder modulator consisting of two 3-dB Y-branch couplers and phase modulation arms is fabricated by the metal-organic vapor-phase epitaxy growth method. A schematic illustration and cross section of the interferometric modulator as well as the current-voltage characteristics of the arms are shown. The modulator is formed by a waveguide having almost the same cross-sectional configuration as a double-heterostructure laser diode. The switching voltage of 4.5 V applied to one arm of the modulator results in an excitation of about 7 dB.<> View full abstract»

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  • A new type of Ti-LiNbO/sub 3/ integrated optical Y branch

    Publication Year: 1989 , Page(s): 230 - 231
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    A report on the experimental verification of the basic operation of the proposed type of integrated optical Y branch using Ti-diffused lithium niobate is presented. The advantages of this Y branch include low-branching loss, compact size, no need for extra bending or curved elements when used as a 3-dB coupler in M-Z type switches, and freedom from critical fabrication requirements. A branching loss of 0.5 dB is achieved. The necessary three-dimensional analysis of the Ti-diffused Y-branch structure is described.<> View full abstract»

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  • New polarization-insensitive antiresonant reflecting optical waveguide (ARROW-B)

    Publication Year: 1989 , Page(s): 232 - 234
    Cited by:  Papers (10)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (199 KB)  

    A type of antiresonant reflecting optical waveguide (ARROW-B) is proposed to reduce the polarization dependence of propagation loss in ARROW. A low-loss propagation (<1 dB/cm) for both transverse electric (TE) and transverse magnetic (TM) modes is demonstrated. The features of the conventional waveguide, ARROW, and ARROW-B are summarized. The conventional ARROW is advantageous in constructing some functional devices such as a waveguide-type polarizer or wavelength demultiplexer. On the other hand, the ARROW-B seems to be suitable for applications requiring a primarily polarization-insensitive function, such as optical interconnection.<> View full abstract»

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  • An etch tunable antireflection coating for the controlled elimination of Fabry-Perot oscillations in the optical spectra of transverse modulator structures

    Publication Year: 1989 , Page(s): 235 - 237
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (270 KB)  

    A technique is described whereby an Si/sub x/N/sub y/ coating of a noncritical thickness in excess of 1/4 ( lambda /n/sub c/) is deposited and, using a process of repeated wet etching and measurement of the optical transmission spectrum, the thickness of the film is precisely adjusted to obtain an optimized antireflection coating. Although this technique was developed for transverse modulators, it should prove beneficial for optically characterizing any structure susceptible to unwanted Fabry-Perot effects. Peak-to-peak oscillations as large as 20% of the maximum transmitted signal are reduced to zero over a 35-nm range. This effective range can be progressively shifted through the spectra so that spectra completely free of Fabry-Perot oscillations can be obtained.<> View full abstract»

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  • Efficiency of a periodic array with nearly ideal element pattern

    Publication Year: 1989 , Page(s): 238 - 240
    Cited by:  Papers (11)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (193 KB)  

    The array is composed of a planar arrangement of coupled dielectric waveguides radiating into free space. Most of the power supplied to any of the array elements is radiated uniformly in the Brillouin zone of order zero by means of an array of coupled waveguides. This result is shown for a planar geometry satisfying the scalar wave equation.<> View full abstract»

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  • Efficient multichannel integrated optics star coupler on silicon

    Publication Year: 1989 , Page(s): 241 - 243
    Cited by:  Papers (50)  |  Patents (17)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (302 KB)  

    The design and fabrication of a 19*19 star coupler suitable for lightwave distribution in high-capacity local area networks with a measured efficiency of 55% at a wavelength of 1.3 mu m is reported. The coupler consists of two arrays of channel waveguides separated by a slab waveguide fabricated on a silicon substrate using SiO/sub 2//Si technology. The integrated optics design is well suited to manufacture. It is argued that the coupler performance does not depend critically on the fabrication accuracy. In fact, the efficiency is primarily determined by the radiating element pattern, whose effective angular aperture is essentially determined by the width Omega of the first Brillouin zone, and, therefore, it is not greatly influenced by the fabrication process.<> View full abstract»

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  • Characteristics of dispersion-flattened depressed-cladding single-mode fluoride fibers from 1.55 to 3.1 mu m

    Publication Year: 1989 , Page(s): 244 - 247
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB)  

    An analysis of chromatic dispersion in single-mode fluoride fibers is presented. It is shown that it is possible, with a simple depressed-cladding profile, to obtain the necessary flexibility to achieve simultaneously dispersion-flattening and minimum extrinsic losses. Hence, optimum performance is obtained over a broad wavelength region. Dispersion sensitivity to small variations in the design parameters is also reported. Some preliminary comparison is made to present-day silica fibers.<> View full abstract»

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  • Ionization-induced nonequivalent absorption in a birefringent silica fiber

    Publication Year: 1989 , Page(s): 248 - 249
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (203 KB)  

    The response of a single-mode highly birefringent fiber, operating at a wavelength of 1.3 mu m and irradiated by a source of 200 MeV pulsed protons, is presented. The fiber fast and slow axes of birefringence were optically excited and observed to exhibit transient absorption at different rates which scaled linearly over the pulsed exposure range of 2.6-17.4 krad (Si). Mechanisms possibly affecting the fiber birefringence are discussed including the introduction of transient electric and magnetic fields arising from the ionizing radiation.<> View full abstract»

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  • High-speed performance of OMCVD grown InAlAs/InGaAs MSM photodetectors at 1.5 mu m and 1.3 mu m wavelengths

    Publication Year: 1989 , Page(s): 250 - 252
    Cited by:  Papers (27)  |  Patents (15)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (277 KB)  

    A report is presented on the fabrication of high-speed In/sub 0.53/Ga/sub 0.47/As metal-semiconductor-metal (MSM) photodetectors incorporating a high-quality lattice-matched InAlAs barrier enhancement layer, grown by organometallic chemical vapor deposition (OMCVD). Fast responses of approximately 55 ps full-width half-maximum at 1.5 mu m and approximately 48 ps at 1.3 mu m wavelengths are observed, corresponding to intrinsic device bandwidths of approximately 8 GHz and approximately 11 GHz, respectively. The absence of any tail to the pulse response, and of any low-bias DC gain, indicates a low-trap density at the InAlAs/InGaAs heterointerface. Bias independent dark currents of 10-20 mu A are observed below breakdown, which occurred at >30 V in devices with a 500-A-thick InAlAs layer.<> 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