Showing papers on "Optical modulator published in 1987"
TL;DR: In this paper, a simple waveguide modulator has been fabricated which shows electro-optic r coefficients in the waveguide region to be similar to bulk KTP, and waveguide thickness of up to 15 μm has been observed.
Abstract: Planar and channel optical waveguides have been fabricated in KTiOPO4 (KTP) using ion exchange processes. The exchange kinetics are diffusion limited and depend strongly on composition and surface orientation. Increases in surface refractive index of up to 0.23 and waveguide thicknesses of up to 15 μm have been observed. A simple waveguide modulator has been fabricated which shows electro‐optic r coefficients in the waveguide region to be similar to bulk KTP.
204 citations
TL;DR: The intermodulation distortion and compression properties of an integrated optical modulator at microwave frequencies are characterized by measuring the third-order intercept and 1-dB compression points.
Abstract: We have characterized the intermodulation distortion and compression properties of an integrated optical modulator at microwave frequencies by measuring the third-order intercept and 1-dB compression points. Values of +30.0 and +21.4 dBm, respectively, were measured and agree well with theory. When operated in the shot-noise-limited regime, these devices can have spurious free dynamic ranges in excess of 100 dB, making them attractive as potential alternatives to conventional diode mixers in special applications.
189 citations
TL;DR: In this article, a liquid-crystal electro-optic modulating device similar to the surface-stabilized ferroelectric liquid crystal device is described, but instead of using a tilted smectic phase like the C* phase, it utilizes the above-lying, nonferroelectric A phase, taking advantage of the electroclinic effect.
Abstract: A new liquid‐crystal electro‐optic modulating device similar to the surface‐stabilized ferroelectric liquid‐crystal device is described. It uses the same kind of ferroelectric chiral smectics and the same geometry as that device (thin sample in the ‘‘bookshelf ’’ layer arrangement) but instead of using a tilted smectic phase like the C* phase, it utilizes the above‐lying, nonferroelectric A phase, taking advantage of the electroclinic effect. The achievable optical intensity modulation that can be detected through the full range of the A phase is considerably lower than for the surface‐stabilized device, but the response is much faster. Furthermore, the response is strictly linear with respect to the applied electric field. The device concept is thus appropriate for modulator rather than for display applications. We describe the underlying physics and present measurements of induced tilt angle, of light modulation depth, and of rise time.
157 citations
TL;DR: In this article, a novel GaAs/AlGaAs coupled quantum well structure, consisting of two 46 A wells separated by a 11.5 A barrier, was embedded in a leaky waveguide.
Abstract: A novel GaAs/AlGaAs coupled quantum well structure, consisting of two 46 A wells separated by a 11.5 A barrier, was embedded in a leaky waveguide. Polarization anisotropy and quantum‐confined Stark effect absorption changes are observed, and a 14:1 modulator is demonstrated operating at the peak of the first light‐hole transition. Although the lowest energy transitions behave as predicted by tunneling resonance calculations, higher energy states exhibit unusual behavior due to valence‐band mixing.
143 citations
TL;DR: In this article, a quantum constrained Stark effect electroabsorption modulator consisting of quantum wells of AlGaAs and GaAs on an epitaxial multilayer dielectric mirror, all grown by molecular beam epitaxy, was demonstrated.
Abstract: We demonstrated a quantum‐confined Stark effect electroabsorption modulator consisting of quantum wells of AlGaAs and GaAs on an epitaxial multilayer dielectric mirror, all grown by molecular beam epitaxy. The resulting reflection modulator avoids problems of substrate absorption, and has relatively high contrast ratio (up to ∼8:1 with peak reflectivity of 25% at 853 nm) because the light passes twice through the quantum wells. Reflection modulators are of interest for bidirectional communication systems, in parallel arrays of optical switching and processing devices and for optical interconnects. For the latter there exists the possibility of this device grown on the same substrate alongside a GaAs integrated circuit or even on Si substrates.
121 citations
TL;DR: It is demonstrated that the LCs or LC mixtures with higher nematic-isotropic phase transition temperatures have higher optimum temperatures and greater potential for improving the figure of merit.
Abstract: This paper describes analyses and confirming experiments on the optimum temperature for fast response in nematic liquid crystal (LC) modulators. It is demonstrated that the LCs or LC mixtures with higher nematic-isotropic phase transition temperatures have higher optimum temperatures and greater potential for improving the figure of merit. Also discussed is the performance of the LC mixture exhibiting optimum temperature at around room temperature.
117 citations
TL;DR: In this paper, the authors reported the intensity modulation of an optical carrier at frequencies as high as 40 GHz using a Ti:LiNbO3 optical waveguide switch and a self-electrooptic sampling technique was used to observe the modulation.
Abstract: We report the intensity modulation of an optical carrier at frequencies as high as 40 GHz using a Ti:LiNbO3 optical waveguide switch. A self-electrooptic sampling technique is used to observe the modulation.
110 citations
TL;DR: In this paper, a 1.55-μm InGaAsP/InP distributed feedback (DFB) laser and an electroabsorption (EA) modulator were integrated by three-step vapor phase epitaxy (VPE).
Abstract: Monolithic integration of a 1.55-μm InGaAsP/InP distributed feedback (DFB) laser and an electroabsorption (EA) modulator was studied. The difference between the lasing photon energy and the bandgap energy of the modulator waveguide was designed to be 30-40 meV, taking into account the linewidth-enhancement factor and the zero-bias absorption loss. The integrated devices were grown by three-step vapor phase epitaxy (VPE). The CW threshold current at 20°C of the DFB laser part with a buried heterostructure was 30-60 mA and the breakdown voltage of the modulator part with a strip-loaded stripe geometry was 20-40 V, and these values indicated satisfactory crystal quality in the VPE epitaxial layers. The operating voltage of the modulator to give on:off ratios of 10:1 and 100:1 was 1.5- 4 V and 2.5-6.5 V, respectively, depending on the length in the range 200-500 \mu m. A 3-dB bandwidth of about 2.5 GHz and a linewidth-enhancement factor of about 1.6 were obtained for the integrated modulator.
108 citations
TL;DR: In this paper, an optical electroabsorption waveguide modulator based on the quantum constrained Stark effect in an InGaAs/InP multiple quantum well waveguide was described.
Abstract: An optical electroabsorption waveguide modulator is described based on the quantum‐confined Stark effect in an InGaAs/InP multiple quantum well waveguide. The optical modulator has a high on/off ratio (47:1) with very low insertion loss (2.9 dB) and a 3‐dB modulation bandwidth of 3.0 GHz at 0.1 mW optical input power.
91 citations
TL;DR: The quantum-confined Stark effect (QCSE) as mentioned in this paper is a well-known phenomenon in semiconductor devices that enables electrically controlled optical modulators and optically controlled self-electro-optic effect devices that can operate at high speed and low energy density.
Abstract: Quantum wells, alternate thin layers of two different semiconductor materials, show an exceptional electric field dependence of the optical absorption, called the quantum-confined Stark effect (QCSE), for electric fields perpendicular to the layers. This enables electrically controlled optical modulators and optically controlled self-electro-optic-effect devices that can operate at high speed and low energy density. Recent developments in these QCSE devices are summarized, including new device materials and novel device structures. The variety of sophisticated devices now demonstrated is promising for applications to information processing.
69 citations
TL;DR: In this article, a 13μm GaAs traveling-wave electro-optic waveguide modulator with a 3dB optical bandwidth in excess of 20 GHz was reported, which was determined by directly detecting the modulated optical signal with a high-speed InP/GaInAs photodiode.
Abstract: We report a 13‐μm GaAs traveling‐wave electro‐optic waveguide modulator with a 3‐dB optical bandwidth in excess of 20 GHz The bandwidth was determined by directly detecting the modulated optical signal with a high‐speed InP/GaInAs photodiode The modulator has a coplanar strip electrode configuration with a double heterojunction Al0032Ga0968As/GaAs/Al0032Ga0968As optical guide grown by low‐pressure organometallic vapor phase epitaxy
TL;DR: In this article, a monolithic integrated device with an improved structure consisting of an InGaAsP/InP DFB laser and an In-GaAs/InAlAs MQW optical modulator was fabricated by the LPE/MBE hybrid growth technique.
Abstract: A monolithically integrated device with an improved structure consisting of an InGaAsP/InP DFB laser and an In-GaAs/InAlAs MQW optical modulator was fabricated by the LPE (liquid phase epitaxy)/MBE (molecular beam epitaxy) hybrid growth technique. The DFB laser in this device was operated at 1.556 μm under CW condition at room temperature. A narrow coupling region between laser and modulator results in a depth of modulation as high as 55 percent at a modulator reverse bias voltage of -5 V. High-speed modulation with a response time of 300 ps was also achieved in this monolithic device.
TL;DR: In this article, a Kramers-Kronig analysis is used to calculate the refractive index change induced by changes in the shape of the fundamental absorption edge when a strong electric field is applied to a semiconductor.
Abstract: A Kramers–Kronig analysis is used to calculate the refractive index change induced by changes in the shape of the fundamental absorption edge when a strong electric field is applied to a semiconductor Calculations are made for GaAs and InGaAsP over the 09 to 155 μm wavelength range For GaAs, we find that the electrorefraction is Δn=79×10−4 at λ=106 μm when the electric field is 400 kV/cm, but decreases to Δn=13×10−4 at λ=155 μm for the same electric field strength For wavelengths far below the band gap, the refractive index change has a quadratic dependence on the applied electric field The electrorefraction effect will have important applications for optical waveguide phase modulators
TL;DR: In this article, a double heterostructure ridge waveguide with multiple quantum well InGaAs/InP core and InP cladding layers has been operated as a phase modulator at 1.52 μm wavelength.
Abstract: A double heterostructure ridge waveguide with multiple quantum well InGaAs/InP core and InP cladding layers has been operated as a phase modulator at 1.52 μm wavelength. The observed phase shift coefficient was 12°/V mm. With a 1‐mm‐long device we have achieved a half wavelength shift at 15 V bias and a maximum phase shift of 420° at 35 V. Quantum confined Stark effect has been observed in the shorter 1.49–1.52 μm wavelength region. The ability to obtain λ/2 modulation with a short device and relatively low voltage makes this device very attractive for practical applications.
TL;DR: An amorphous silicon photoconductor has been demonstrated in a reflection mode nematic field effect liquid crystal spatial light modulator and the performance characteristics as well as a theoretical model for the device are reported.
Abstract: An amorphous silicon photoconductor has been demonstrated in a reflection mode nematic field effect liquid crystal spatial light modulator. The thin-film photoconductor provided high resolution of >35 lp/mm and sensitivity better than 20 microW/cm(2). In addition the switching speed was liquid crystal limited. Reported are the performance characteristics as well as a theoretical model for the device.
Patent•
03 Aug 1987TL;DR: A liquid crystal optical modulator has a liquid crystal held between two substrates each having a light-transmissive electrode on the surface, in which at least one substrate has minute alignment-treated region having two or more kinds of liquid crystal aligning abilities different from each other formed and arranged on the same substrate as mentioned in this paper.
Abstract: A liquid crystal optical modulator having a liquid crystal held between two substrates each having a light-transmissive electrode on the surface, in which at least one substrate has minute alignment-treated region having two or more kinds of liquid crystal aligning abilities different from each other formed and arranged on the same substrate.
TL;DR: In this article, an electrooptic modulation method based on signal coding through optical delays larger than the source coherence length is described, illustrated with the simultaneous transmission of several signals by path-difference multiplexing.
Abstract: An electrooptic modulation method based on signal coding through optical delays larger than the source coherence length is described. The method is illustrated with the simultaneous transmission of several signals by path-difference multiplexing. In this method, the signals are coded as a sequence of optical delays introduced by a series of electrooptic modulators working as delay lines. Decoding is carried out by temporal correlation performed by another sequence of optical delays introduced by birefringent plates, and matched to those used at the emission process. The permissible delays are shown to be ruled by the source coherence length and by the number of laser modes.
TL;DR: In this article, a light-controlled optical fiber modulator, driven by sub-picosecond, compressed, and amplified (6000 A) dye laser pulses, controlling frequency-doubled (5320 A) yttrium aluminum garnet laser pulses was presented.
Abstract: We report the ultrafast operation of a light‐controlled optical‐fiber modulator, driven by subpicosecond, compressed, and amplified (6000 A) dye laser pulses, controlling frequency‐doubled (5320 A) yttrium aluminum garnet laser pulses The operation of the modulator is based on the optical Kerr effect, and its main component is 7 mm of single‐mode optical fiber Using this system as a light‐controlled shutter, we produced either 04 ps green light pulses or 05 ps holes on the much longer duration second harmonic pulses
TL;DR: In this paper, the authors measured the intensity modulation level and the optical spectrum of the output of a multiple quantum well modulator, and used these data to deduce the electro-optic coefficients.
Abstract: We simultaneously measure the intensity modulation level and the optical spectrum of the output of a multiple quantum well modulator, and use these data to deduce the electro‐optic coefficients. The effect is quadratic, with a measured ‖s33‖=4.6×10−13 cm2/V2 at a wavelength 12 meV below the band gap. This is approximately 800 times the coefficient measured further from the band gap. We are able to achieve a fractional change in the refractive index of 3.7%. Despite the size of this effect, when we operate the device as an intensity modulator, we observe a linewidth enhancement factor of α=1.0, which means the chirp induced in the device’s output will be small.
TL;DR: In this article, the behavior of a cylindrical singlemode optical fiber piezoceramic phase modulator was investigated in the frequency range below resonance and the integral and differential phase modulation efficiencies were reported for different geometrical dimensions of the modulator and for various piezoelectric ceramic materials.
Abstract: The behaviour of a cylindrical single-mode optical fibre piezoceramic phase modulator was investigated in the frequency range below resonance. The integral and differential phase modulation efficiencies are reported for different geometrical dimensions of the modulator and for various piezoelectric ceramic materials. p ]The results obtained show that a phase-modulation depth in excess of ≪ can be easily achieved using commercially available piezoelectric cylinders, with driving voltage amplitude as low as 5 V.
TL;DR: In this article, the first demonstration of a novel optical logic device having an inverting characteristic was presented, which displays hard-limiting and optical gain of more than 10 times.
Abstract: We report the first demonstration of a novel optical logic device having an inverting characteristic which displays hard-limiting and optical gain of more than 10.
TL;DR: In this article, the quantum confined Stark effect has been studied in InGaAsP/InP rib waveguide structures grown by gas source molecular beam epitaxy and it was shown that efficient modulation at shorter wavelength cannot be obtained in structures with thinner ternary wells.
Abstract: The quantum confined Stark effect has been studied in InGaAsP/InP rib waveguide structures grown by gas source molecular beam epitaxy. Using 100‐A‐wide wells of InGaAs, a room‐temperature exciton shift of about 250 A has been observed for a bias voltage of 6 V. At a wavelength of 1.64 μm a modulation depth of 35% has been achieved at a frequency of 500 MHz. We show that efficient modulation at shorter wavelength cannot be obtained in structures with thinner ternary wells. Instead, we propose and demonstrate InGaAsP modulators operating at a wavelength as short as 1.3 μm.
TL;DR: In this article, the first measurements of large anisotropic modulation of long-wavelength light with a large on/off ratio and low driving voltage propagating along the plane of InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE) are reported.
Abstract: The first measurements of large anisotropic modulation of long-wavelength light with a large on/off ratio and low driving voltage propagating along the plane of InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE) are reported. Photocurrent response and optical modulation of waveguide pin diodes is measured for incident light polarization parallel and perpendicular to the MQW layers emitting from a color center laser. The incident-light power and wavelength dependence of on/off ratio are also determined.
TL;DR: In this article, the authors describe the fabrication and performance evaluation of X -cut and Z -cut Ti:LiNbO 3 traveling wave waveguide phase modulators designed for coherent systems applications at 1.3 and 1.5 μm.
Abstract: This article describes the fabrication and performance evaluation of X -cut and Z -cut Ti:LiNbO 3 traveling wave waveguide phase modulators designed for coherent systems applications at 1.3 and 1.5 μm. Details of device fabrication and measurements of phase shift as a function of optical wavelength, input polarization, modulation voltage, and modulation frequency are reported. Phase modulator performance in a 40-Mbit/s self-heterodyne coherent DPSK experiment is also discussed.
Patent•
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30 Dec 1987
TL;DR: An image pickup device comprises an optical modulator element (3, 53, 103) having a function of storing an optical image information of an image which is formed thereon, an imaging lens (1, 51, 121) for making an image formation of an optical images of an object on the optical modulation element, and a device (4-12, 54-57, 73-75, 77, 124-126, 128, 131) for reading the optical image image information from the optical modulation element and for generating an image information corresponding to the optical images formed on the
Abstract: An image pickup device comprises an optical modulator element (3, 53, 103) having a function of storing an optical image information of an optical image which is formed thereon, an imaging lens (1, 51, 121) for making an image formation of an optical image of an object on the optical modulator element, and a device (4-12, 54-57, 73-75, 77, 124-126, 128, 131) for reading the optical image information from the optical modulator element and for generating an image information corresponding to the optical image of the object formed on the optical modulator element.
TL;DR: GaAs PIN traveling-wave modulators with terminating resistors of various resistances operated at 1.3 microm have been fabricated from material grown by organometallic vapor phase epitaxy on n(+) (100) GaAs substrates and it was found that modulator with positive reflection coefficients at the load exhibited initial rolloff in the frequency response.
Abstract: GaAs PIN traveling-wave modulators with terminating resistors of various resistances operated at 1.3 microm have been fabricated from material grown by organometallic vapor phase epitaxy (OMVPE) on n(+) (100) GaAs substrates. It was found that modulators with positive reflection coefficients at the load exhibted initial rolloff in the frequency response. However, modulators with negative reflection coefficients at the load exhibited some peaking behavior at low frequencies at the expense of lower detected microwave powers. Based on this observation, a compromised PIN traveling-wave modulator was designed and measured to have a 3-dB bandwidth of 9.6 GHz.
TL;DR: In this paper, the design of in-line acoustooptic modulators for single-mode fibers is discussed, which consists of a cylindrically symmetric piezoelectric transducer fabricated on the fiber surface.
Abstract: The design of in-line acoustooptic modulators for single-mode fibers is discussed. The basic configuration consists of a cylindrically symmetric piezoelectric transducer fabricated on the fiber surface, so that the fiber itself acts as a cylindrical acoustic resonator. Depending on the fiber design, the acoustic wave can induce phase, birefringence, or polarization modulation of the light in the fiber. Pairs of the polarization modulators in series can be used to shift the optical frequency. Factors affecting the performance of all of these devices are discussed.
TL;DR: In this article, the authors constructed a figure of merit for broadband electrooptic modulators which compares bandwidth with launched generator voltage standardized to a common wavelength, and showed that a lumped-element III-V semiconductor device performance may be no more than a factor of two below that of typical (i.e., LiNbO 3 ) traveling wave devices and are probably easier to implement-especially in an integrated format.
Abstract: A figure of merit is constructed for broad-band electrooptic modulators which compares bandwidth with launched generator voltage standardized to a common wavelength. Comparison of various published results in terms of this figure shows that a lumped-element III-V semiconductor device performance may be no more than a factor of two below that of typical (i.e., LiNbO 3 ) traveling wave devices and are probably easier to implement-especially in an integrated format. Accurate modeling, which incorporates all transit time and velocity match effects, is described and found to agree well with experimental results. Experimental GaAs/GaAlAs modulators have been made, using a Mach-Zehnder interferometer configuration. At a wavelength of 1.15 μm and with unterminated drive a bandwidth of 6.5 GHz was obtained with V pi of 17.3 V. A shorter (34.6-v) device was ∼ 1.25-dB down at 8.4 GHz. The corresponding figures of merit are close to the maximum expected for the configurations used.
01 Nov 1987
TL;DR: In this article, the present state of passive and active single-mode fiber components are reviewed, including polarizers, directional couplers, filters, and Faraday rotators.
Abstract: A variety of optical components have been made directly from single-mode fibers. These components can be combined to construct in-line all-fiber systems such as fiber gyroscopes, fiber Raman lasers, local area networks, or coherent lightwave systems. This paper reviews the present state of passive and active single-mode fiber components. Passive components are polarizers, directional couplers, filters, and Faraday rotators. Active components require external control or optical power and include modulators, polarization controllers, frequency shifters, and amplifiers. Polarization is usually important in fiber components and discussions of polarization-maintaining and ordinary single-mode fibers are included.
Patent•
23 Sep 1987TL;DR: In an optical operation apparatus, a light source emits a light intensity-modulated on the basis of a first electrical signal, and a photoelectric converting device converts the light modulated by the modulating device into a second electrical signal as mentioned in this paper.
Abstract: In an optical operation apparatus, a light source emits a light intensity-modulated on the basis of a first electrical signal. A modulating device receives the light from the light source and intensity-modulates the light on the basis of the first signal, and a photoelectric converting device converts the light modulated by the modulating device into a second electrical signal. These functions are carried out by any of a number of different arrangements of filter elements, and electro-optical or acoustico-optical devices can be used for intensity modulation.