bluuebunny/crossref_metadata_2025 huggingface dataset:
Guided Wave Devices in Ferroelectrics
Authors: Schmidt R. V.
Published: February 2023

The field of research called integrated optics has come to encompass all optical devices which utilize guided optical waves and planar processing technology. Work has been directed towards both new and improved devices, and the integration of several devices on a single substrate to perform complex signal processing functions. Three material systems have received considerable attention: glasses, semiconductors such as GaAs and its relatives, and ferro-electrics, in particular LiNbO3 and LiTaO3. Each material system has unique properties which makes it most suitable for a particular application. Glass systems have demonstrated the lowest loss optical waveguides but are only suitable for passive device applications. Active devices can be fabricated in both semiconductors and ferroelectrics. The ferroelectrics LiTaO3 and LiNbO3 and the III-V semi-conductors have good electrooptic and acoustooptic properties. Semiconductors can also be used for sources and detectors. However, ferroelectrics, which are dielectrics, have lower propagation losses than semiconductors, about 1 dB/cm in strip waveguides compared to greater than 1 cm−1 or 4.3 dB/cm for semiconductors.
Tunable Optical Waveguide Directional Coupler Filter
Authors: Alferness R. C. , Schmidt R. V.
Published: February 2023

In future optical fiber communication systems it is likely that several optical carriers of different wavelength will be multiplexed onto a single fiber to increase its information carrying capacity. Recently wavelength multiplexors have been demonstrated which are compatible with multimode fibers. These multiplexors use graded index lenses and bulk frequency selective elements such as dielectric mirrors,1 prisms,2 and diffraction gratings.3 In this paper we demonstrate a monolithic integrated optical wavelength multiplexing filter using coupled optical waveguides.
Integrated Electrooptic Nonlinear Fabry-Perot Devices
Authors: Smith P. W. , Kaminow I. P. , Maloney P. J. , Stulz L. W.
Published: February 2023

Recently, a Fabry-Perot resonator containing an electrooptic element driven by the transmitted light has been shown to exhibit hysteresis and bistability1. Such a device is capable of functioning as an optical switch, pulse shaper, and optical limiter. In this paper we demonstrate that such a device can be built in an integrated optics format to produce a compact, low energy optical switching element.
Single Transverse and Longitudinal Mode Operation of Semiconductor Lasers
Authors: Nakamura M. , Kuroda T. , Umeda J. , Aiki K. , Ito R.
Published: February 2023

Single transverse and longitudinal mode operation of semiconductor lasers is an ultimate objective of laser device designing. It has recently been demonstrated that the transverse mode instability encountered in conventional stripe-geometry (AlGa)As lasers can be prevented by introducing a passive waveguide structure: a channeled-substrate-planar (CSP) structure.1) The CSP semiconductor laser operates stably in the fundamental transverse mode at current levels higher than twice threshold. In this paper, the details of the CSP laser, in particular its transverse and longitudinal mode control, are discussed.
High-Power Fundamental-Transverse-Mode Strip Buried Heterostructure Lasers with Linear Light-Current Characteristics
Authors: Tsang W. T. , Logan R. A.
Published: February 2023

A new laser structure, the strip buried heterostructure (SBH) laser (Fig. 1(a)), is described and tested. In this structure, the thin active p-GaAs layer (~0.2 μm) is present in the form of a narrow strip with widths of ~2.5 μm - ~10 μm grown on top of an N-Al0.3Ga0.9As planar layer of thickness ~1 μm - ~1.5 μm. This combination constitutes’a strip optical waveguide which is contained between the usual P-Al0.3Ga0.7As and N-Al0.3Ga0.7As cladding layers. Lateral current injection confinement is accomplished by a single top built-in reverse-biased n-p junction1,2,3 Low current threshold is achievable in this laser because the active p-GaAs is kept thin (<0.2 μm) and because carrier diffusion out of the active strip is limited by the surrounding N-Al0.1Ga0.9As and P-Al0.3Ga0.7As layers. There is still appreciable current spreading. However, it should be possible to reduce current spreading with more effective lateral current injection confinement schemes.3
Further Applications of Tapered Velocity Couplers
Authors: Teh G. A. , So V. , Stegeman G. I.
Published: February 2023

Tapered velocity couplers have been applied to a number of problems in integrated optics since their introduction in 1974.1 This technique has pro­ven useful for transferring optical energy between waveguide modes whenever the β’s, i.e. the wavevector components parallel to the surface, cross. The fraction of energy transferred depends on the optical wavelength, the coupling between the guides and the length of the interaction region. Furthermore, tapered couplers are quite insensitive to tolerance errors, as long as a velocity crossing occurs. This technique has been used to transfer light between waveguide modes on the same substrate,2 from thin films to rectangular fibres,3 from in-diffused guides to thin films4 and to fabricate a 3 db coupler.5 In this paper we describe three additional applications, namely efficient transfer between waveguides on two separate substrates, from a thin film to a cylindrical fibre and as a frequency filter.
Long-Wavelength Single-Mode Fiber Transmission Systems
Authors: Kimura Tatsuya , Kanbe Hiroshi
Published: February 2023

Introduction Single mode fiber transmission systems in the 1.0 - 1.7 μm wavelength region have many advantages favorable for public telecommunication network as well as information transmission means in industries.1-3 (1) Loss is extremely low in low OH content fibers owing to reduced Rayleigh scattering.4 (2) Dispersion in silica material vanishes at 1.27 μm5 and the total dispersion, including waveguide dispersion, can be reduced in the 1.3 - 1.6 μm wavelength range.1 (3) Large core size for single mode fibers at 1.3 μm, typically about 10 μm, is favorable for low splicing and connection loss, as compared to values for 0.85 μm wavelength. Splice and connector losses are now comparable with those for multimode fibers. (4) Optical sources fabricated by InGaAsP/InP double hetero-structures can be used in the 1.0 - 1.55 μm wavelength range. Preliminary reliability evaluation showed that InGaAsP lasers will have longer ultimate lifetime than AlGaAs lasers.6 (5) Germanium avalanche photodiodes can be used as detectors in the 1.0 - 1.6 μm wavelength range with sufficient quantum efficiency and pulse response.7 Ternary and quaternary III-V compound devices are now under extensive study to obtain dark current and multiplication noise performance superior to germanium. (6) Yttrium iron garnet, which has large Verdet constant, can be used.as compact non-reciprocal devices in its transparent wavelength region beyond 1.1 μm.8 Isolators can be used to secure stable oscillator operation independent of possible reflection from fiber lines.
High Efficiency Single-Mode Fiber/Channel Waveguide Flip-Chip Coupling
Authors: Sheem S. K. , Bulmer C. H. , Moeller R. P. , Burns W. K.
Published: February 2023

The application of integrated optical devices in many communication or signal processing systems will require efficient coupling between single­mode optical fibers and channel waveguides. Although high coupling efficiencies have been predicted, their realization in a practical configuration has remained elusive, primarily due to the extremely stringent alignment tolerances involved. In this presentation, we will report an improved version of the Si V-groove/flip-chip coupler,1 in which tapered alignment fibers2 are used to achieve precise vertical positioning of the coupling fibers. We have found this approach to routinely provide near theoretical (> 70%) coupling efficiencies between single-mode fibers and Ti diffused LiNbO3 channel waveguides. The coupler is compact, can be made rigid, and allows for simultaneous multiple coupling on a single chip. Finally by choosing propagation directions along the LiNbO3 major axes, we avoid anisotropic effects3 and achieve coupling efficiences and propagation losses essentially independent of input optical polarization.
Optical Bistability and Modulation in Semiconductor Etalons
Authors: Gibbs H. M. , McCall S. L. , Venkatesan T. N. C. , Passner A. , Gossard A. C. , Wiegmann W.
Published: February 2023

Optical signal processing using all-optical circuitry is an increasingly attractive goal with the recent progress in long- lived light sources, high quantum efficiency detectors, and low- loss high-bandwidth optical fibers. Devices which permit one light beam to control another or which provide an optical memory afford a capability essential to the success of all-optical logic systems. Much progress has been made toward practical bistable1 devices since the first observation2 of optical bistability in sodium vapor. (By optical bistability we refer to devices containing no inverted medium, so that bistable lasers3 are explicitly excluded.) The most practical device so far, a semiconductor etalon consisting of 4 μm of GaAs between 0.2 μm of Al0.42Ga0.53As with R = 0.9 coatings, is described herein.
Stabilized 1.3μm Laser Diode-Isolator Module for a Hybrid Optical Integrated Circuit
Authors: Kobayashi K. , Matsushita S. , Seki M. , Odagiri Y. , Mito I. , Sugimoto M.
Published: February 2023

Integrated optics is coming to a stage of small scale integration where a few optical components are integrated to make a durable and reliable optical devices. Integration of a laser diode (LD) with other optical components seems to be effective in making an optical source, with new functions and/or with high quality, for fiber-optic communications, optical data processing and other applications. We report here the significance in the optical integrated circuit design consideration of the external optical feedback effects on LD properties with experimental results indicating its seriousness. We also report, as a practical solution for this problem, a small and low- loss LD-isolator module developed by integrating, in a hybrid fashion, a 1.3μm InGaAsP/InP double heterostructure (DH) LD, a high efficiency coupling circuit, a micro-optic isolator and a single mode fiber.
Single-Mode CW Ridge-Waveguide Laser Emitting at 1.55μm
Authors: Kaminow I. P. , Nahory R. E. , Pollack M. A. , Stulz L. W. , DeWinter J. C.
Published: February 2023

Single-mode semiconductor lasers operating near 1.55μm are of considerable interest for long-distance communications. The lowest reported fiber losses1 occur here, making this wavelength attractive for either single- or multi-mode operation. In addition, for single-mode fibers, the waveguide-mode-compensated material dispersion can be made to vanish2 in this region, so that it is especially desirable for wideband optical communications.
Broadband Modified Chirp Transducers*
Authors: Joseph T. R. , Chen B. U.
Published: February 2023

An integrated optics spectrum analyzer, IOSA, utilizes the Bragg diffraction of a guided optical wave by a surface acoustic wave, SAW. The details of IOSA operation have been discussed elsewhere [1]. The design of the SAW transducer determines the bandwidth and the operating frequency of the IOSA as well as impac ting the deflection efficiency value. In this paper we will discuss the current re sults of an on-going study of a new and unique transducer design which can achieve low insertion loss and large (octave) acoustic and acousto-optic bandwidths.
Progress on The Development of Integrated Optic Spectrum Analyzer
Authors: Chen B. , Ranganath T.R. , Joseph T.R. , Lee J.Y.
Published: February 2023

A concept for implementing an RF spectrum analyzer using integrated optics has been recently proposed. According to this scheme, a surface acoustic wave (SAW) fed by an RF signal of undetermined spectral composition interacts with an optical beam propagating in a surface waveguide. The light beam generated in this interaction is deflected from the original beam path by an amount proportional to the frequency of the acoustic beam. This concept has been utilized in bulk optical spectrum analyzers, but only recent developments in single mode planar waveguides, diffraction limited geodesic lenses, wide band surface acoustic wave transducers, single mode lasers, laser to waveguide coupling and electronically scanned detector arrays, made the integrated optics spectrum analyzer (IOSA) a viable approach. The system promises not only to be small, rugged, and reliable, but will also provide real time spectral decompositions with a finesse of several MHz, and a bandwidth greater than 400 MHz.
Diamond-Turned Aspheric Geodesic Waveguide Lenses in Lithium Niobate*
Authors: Mergerian D. , Bradley J.C. , Pautienus R.P. , Hutcheson L.D. , Kellner A.L. , Malarkey E.C. , Marx G.E.
Published: February 2023

Single point diamond turning has been increasingly exploited in recent years to produce optical components of exceptional optical quality for high power lasers and other optical systems. We report here on the successful application of this machining process to the fabrication of aspherically-corrected geodesic lenses in lithium niobate substrates for integrated optics. Not only are these lenses capable of producing near-diffraction-limited images at moderate f-numbers, but the images are also precisely located in predetermined focal planes. This greatly enhances the economic promise of IO because it eliminates the costly and time consuming optical characterization and subsequent design correction which are necessary adjuncts of other lens fabrication methods. High yields and excellent reproducibility have been demonstrated in every machining run.
Evaluation of a Photosensor for Integrated Optics Spectrum Analyzers
Authors: Marx G.E. , Borsuk G.M.
Published: February 2023

A photosensor specifically designed for use in an integrated-optical intercept receiver has been designed, fabricated and tested. Integrated optical devices, such as the hybrid integrated optics spectrum analyzer, exhibit unique physical properties and geometry that require new photosensor array designs. The most important physical requirements of the array include minimal pixel pitch, low crosstalk, large signal dynamic range detectability, and adaptability to a hybrid IO structure. In addition, the access time per pixel for the entire array must be of the order of 2 μsec to be capable of signal identification in many proposed system applications and exploiting to the fullest the acousto-optic interaction. The optical response characterization of the silicon-based photosensor array is reported below.
Monolithically Integrated Lasers and Amplifiers Using A Cleaved Substrate Tecnnique
Authors: Chang M. B. , Garmire E.
Published: February 2023

Monolithically integrated optical circuits require use of a laser which is fabricated by a technique which is compatible with the planar technology. Typically it has been suggested that this will be a DFB or DBR laser structure. Other monolithic lasers have utilized etch steps fabricated chemically or by ion beam milling, or facets fabricated by crystal growth. Each of these techniques is limited by fabrication difficulties. We suggest here a simple and rapid fabrication method which has given excellent results reproducibly, and may have application in several devices. We demonstrate the usefulness of this technique in a study of integrated optics laser amplifiers and report measurements of gain.
Low Frequency Noise in Fiber Coupled Diode Lasers
Authors: Miles R. O. , Burns W. K. , Giallorenzi T. G.
Published: February 2023

The development of fiber optic interferometric sensor systems has created new demands for single mode semiconductor diode lasers with low output noise power. Recently, several single longitudinal and transverse mode GaAlAs laser diodes have become available. Several experimenters have reported the deleterious effects of optical feedback resulting from fiber optic coupling on the laser's mode structure and high frequency noise spectrum.1-3 Our interest for interferometric sensors is in the low frequency noise, up to a few kilohertz. We report here the first such low frequency noise measurements in fiber coupled and uncoupled single mode diode lasers. Additionally, we also show that the use of index matching fluid can be used to greatly reduce optical feedback and its associated low frequency noise, upon coupling into an optical fiber.
High Speed Directional Coupler Switch/Modulators Measured with a Novel Picosecond Optical Pulse Sampling Technique
Authors: Economou N. P. , Alferness R. C. , Buhl L. L.
Published: February 2023

Efficient high speed optical switches and amplitude modulators will be important components for utilizing the large available bandwidth of single-mode lightwave systems. In addition to amplitude modulation for digital coding, fast optical switches may prove very useful for high speed time division multiplexing. Presently several guided-wave optical switch/modulators have been reported with demonstrated modulation bandwidth of approximately 1 GHz.1,2 For high speed operation, accurate switching speed measurements under electrical pulse operation are hampered by the finite speed of the pulsing circuit and the photodetector. Generally it is necessary to estimate the actual device switching time by deconvolving the response time of the pulser and detector from the measured output optical pulse.1 We have developed a novel measurement technique utilizing picosecond optical pulses to overcome some of these limitations. In a parallel effort we have designed and fabricated very short length (L = 750 μm) switched directional couplers using Ti-diffused lithium niobate waveguides which can be modulated with 6 volts. Using our novel measurement technique, preliminary results indicate a switching rate of at least 5 GHz with this device.
Fabrication of Strip Waveguides in LinbO3 by Combined Metal Diffusion and ION Implantation
Authors: Heibei J. , Voges E.
Published: February 2023

Optical waveguides in LiNbO3 are commonly fabricated by the in-diffusion of thin Ti layers /1/, and suppression of the accompaning out-diffusion of Li2O by additional means /2/. This technique yields low-loss optical waveguides, and embedded strip waveguides are easily produced by a suitable patterning of the metal layer.
Optical Waveguide Channel Branches in Ti-diffused LiNbO3
Authors: Burns W. K. , Moeller R. P. , Bulmer C. H. , Yajima H.
Published: February 2023

Optical branching waveguides were first investigated experimentally by Yajima,1 who observed mode splitting behavior in planar glass waveguide branches. Yajima2 and Burns and Milton3 introduced a normal mode analysis of a step transition model to analyze branch behavior. The latter authors pointed out the power dividing limit of steep, symmetric branches, and showed that power transfer in near-symmetric branches was a function of a single parameter. This theoretical approach has recently been further improved and extended to multimode branches,4 which support more than two local normal modes. The importance of branching waveguides has been demonstrated by their utilization in various integrated optical modulators and switches. These have included passive branches in interferometers and directional couplers as well as active branches where the splitting ratio is electrically controlled. We report here experimental measurements of splitting ratios in various Ti:LiNbO3 channel waveguide branches as a function of branch angle and asymmetry. To characterize the diffused channel mode dispersion we utilize a dispersion model based on the effective index method.5 We then compare our experimental results with computer calculations for similar, but simpler, planar, homogeneous LiNbO3 branches. Our results are shown to be generally consistent with theoretical predictions and will provide a guide for future branch design.
Microfabrication for Guided-Wave Optical Devices*
Authors: Smith Henry I.
Published: February 2023

Guided-wave optical devices generally consist of complex planar structures with extremely small dimensions. Typically, the components of these structures must be placed relative to one another with a precision even finer than minimum lateral dimensions. Components frequently include periodic and quasi-periodic gratings, and several layers. Also, high demands are placed on the quality of the materials used. For these reasons, guided-wave optical devices present formidable challenges for microstructure fabrication technology.
Low Loss Optical Waveguides Fabricated by Solid State Electro-thermal Diffusion of Metals Into Glass
Authors: Findakly T. , Garmire E.
Published: February 2023

Numerous references have reported the formation of optical guiding layers in glass by ion exchange from molten salts of high electronic polarizability ions.(1-3) This talk will describe the fabrication of diffused optical waveguides in glass by an easily controllable dry process; i.e., from an evaporated metallic layer. In addition, it will be shown that the application of an electric field during the diffusion process increases the solubility of the metal and makes possible single mode guides of small dimensions, as well as highly multimode thicker guides. Finally, with this technique it is possible to bury the guide below the surface, thus reducing the loss due to surface scatter.
Monolithic Integration of a GaAlAs Injection Laser with a Schottky-gate FET
Authors: Fukuzawa T. , Nakamura M. , Hirao M. , Kuroda T. , Umeda J.
Published: February 2023

Semiconductor lasers are small-sized, high-efficiency light sources which can be modulated up to a few GHz by current injection. They have been finding practical uses in various fields as the result of recent major improvements in reliability and mode stabilization. In order to take maximum advantage of direct highspeed modulation capabilities, GaAs Schottky-gate FETs have been successfully used as driver-transistors.1) The high cut-off frequency of GaAS FETs, typically 20-30 GHz for 1 µm gate lengths, makes it easy to realize few-Gb/s light sources usable for high-speed optical fiber communications.
A High Speed Photoconductive Integrated Optical Receiver
Authors: Gammel J.C. , Ballantyne J.M.
Published: February 2023

A GaAs MESFET (Metal on Semiconductor Field Effect Transistor) is a promising photoconductive detector for sensitive, high speed optical detection.1,2,3,4 We previously named this device an OPFET1 (Optical Field Effect Transistor). Response times of 50 to 100 psec with photoconductive gains of 2 to 5 were realized. The OPFET gain, speed, low noise, and low voltage form a unique set of characteristics which make it unrivaled for many applications in optical communications.
External cavity operation with complete removal of sub-cavity effects for mode-locking injection lasers
Authors: Holbrook M.B. , Kirkby P.A. , Bradley D.J.
Published: February 2023

To date attempts to mode-lock semiconductor injection lasers have not produced clean transform-limited pulses. It was formerly thought (1) that dispersion was the principal problem preventing good mode-locking, but as pointed out by Ho(2) this effect does not become important in external cavity operated systems for pulse durations greater than 1ps. Within an external cavity operated injection laser system the effect of the sub-cavity formed by the laser facets shows up as deep Fabry-Perot modulation of the lasing spectrum similar to that seen in the amplified spontaneous emission (A.S.E.) spectrum of the isolated diode. While anti-reflection coating does not completely remove this effect polishing the facet at an angle to the lasing direction does. However, modern stripe geometry double heterostructure GaAlAs lasers have cleaved, not polished facets. Angle-polishing by chemical means of the multi-component structure is not possible and mechanical polishing introduces the risk of damage.
Graded Heterostructure Light Sources and Receivers for Wavelength Multiplexing
Authors: Portnoy E. L. , Miserov M. N. , Alferov Zh. I.
Published: February 2023

Summary not available.
Study of Second Harmonic Generation in a Channel Ti:LiNbO3 Optical Waveguide
Authors: Buritsky K.S. , Zolotov E.M. , Prokhorov A.M. , Chernykh V.A.
Published: February 2023

Optical waveguides formed in nonlinear crystals provide the effective nonlinear interactions at comparatively low power light sources. This paper is concerned with the theoretical and experimental investigation of second harmonic generation (SHG) in a channel Ti:LiNbO3 waveguide using He-Ne laser (λ = 1.15 µm) as a fundamental light source.
Spectral Characteristics of Laser Diodes with Optical Feedback
Authors: Goldberg L. , Dandridge A. , Taylor H. F. , Miles R. O. , Weller J. F.
Published: February 2023

The spectral characteristics of semiconductor lasers are important for optical transmitters and fiber optic sensor systems. Both line narrowing and line broadening of laser diodes due to optical feedback into the laser cavity have been investigated recently.1-4 Here we report the dependency of the linewidth and wavelength stability on the amount of radiation fed back into the laser cavity.
Optoelectronic Pulse-Forming Networks with Novel Input and Output Junctions**
Authors: Li K. K. , Whinnery J. R. , Dienes A.
Published: February 2023

We have shown that electrical pulses narrower than the optical pulses can be generated by discharging a pulse-forming line with optical pulses in the nanosecond regime. The present work uses picosecond optical pulses to switch the pulse-forming network, with several interesting variations of the charging and switching junctions of the line.
GaInAsP/InP Double Heterostructure Laser with Monolithically Integrated Passive Waveguide
Authors: Liau Z. L. , Walpole J. N.
Published: February 2023

Monolithic integration of passive waveguides with double heterostructure (DH) lasers has the potential for a number of interesting device applications, including lasers with distributed Bragg reflectors or integrated external cavities, intensity or frequency modulators, and mode-locked DH lasers. Previous attempts to achieve this structure with GaAs/GaAlAs or GaInAsP/InP systems resulted in relatively high threshold current densities.(1-6) We have developed in this work a liquid-phase epitaxial (LPE) technique to grow

Ga

x
2

In

1
−

x
2

As

y
2

P

1
−

y
2

/
InP

DH Passive waveguides integrated with and precisely aligned to previously grown

Ga

x
1

 In 

1
−

x
1

As

y
1

P

1
−

y
1

/
InP

DH laser structures. Uniform waveguide layers and good surface morphology have been achieved in the LPE regrowth. Relatively low threshold current densities (2.4 - 3.1 kA/cm2) were obtained for broad area lasers with one integrated passive waveguide section.
The All fiber Gyroscope: A Practical Alternative for Rotation Sensing
Authors: Bergh R. A. , Cutler C. C. , Lefevre H. C. , Newton S. A. , Pavlath G. A. , Shaw H. J.
Published: February 2023

Optical fibers are of great potential importance for sensor systems, because they are environmentally sensitive and because they can be used in interferometers for measurement of very small phase shifts. Fiber gyroscopes, like their predecessors the ring laser gyros, are based on the Sagnac effect,1,2 whereby light traveling around a closed path experiences a phase shift proportional to the rotation rate in inertial space. The detected phase shift represents an optical path difference that may be less than one thousandth of an angstrom in length.
Fabrication of Integrated Optical Components by Ion Implantation*
Authors: Kurmer J. P. , Tang C. L.
Published: February 2023

Existing techniques for fabricating grating-couplers for thin-film optical waveguides apply mostly to surface gratings. By comparison, optical grating-couplers implanted inside waveguides by ion bombardment will lead to much smaller perturbations on the surfaces and interfaces of the optical waveguide. This will have device implications. It is, therefore, important to evaluate this technique for fabricating grating couplers as well as other optical components. In this talk, we report on the successful fabrication of optical grating-couplers (for a schematic, see Fig.1) and one- and two-dimensional waveguide structures (Figure 2) in glass waveguides by ion implantation.
Fiber-Coupling Loss and Drive Voltage Simultaneous Reductions by Tapered Titanium-Thickness Diffusion in LiNbO3 Waveguide Switches
Authors: Kondo M. , Komatsu K. , Ohta Y.
Published: February 2023

Titanium-diffused LiNbO3 waveguide switches and modulators are foreseen as elements in optical switching networks1) or external modulators2) in high bit-rate optical communication systems, because of their broadband and low loss capability. In practical applications, both low insertion loss, when coupled to optical fibers, and low operating voltage for high speed driving are required in these devices. Recently, low Ti:LiNbO3 waveguide to single-mode fiber coupling loss has been reported.3) The relation between drive voltage and waveguide structure has also been discussed.4) However, a low loss and low drive voltage switch or modulator has not been realized, because the conditions for achieving the above two purposes are different. That is, mode size matching between waveguide and fiber is required for low loss coupling. On the other hand, small mode size is preferable for low drive voltage.
Planar Guided-Wave Magnetooptic Diffraction By Magnetostatic Surface Waves In Yig/Ggg Waveguides*
Authors: Tsai C.S. , Young D. , Adkins L. , Lee C.C. , Glass H.
Published: February 2023

Modulation and switching of light waves in Yttrium iron garnet (YIG)–Gadolinium gallium garnet (GGG) waveguides using Farady rotation(1), and light propagation and mode-conversion in a thin-film dielectric waveguide using magnetooptic YIG substrate(2,3) had been studied in detail. More recently, propagation and mode-conversion in a YIG/GGG waveguide with an isotropic top layer using Faraday rotation was also analyzed.(4) In this paper we report on wideband modulation at multigigahertz (2 to 7 GHz) center frequency that results from planar magnetooptic diffraction by magnetostatic surface waves in the YIG/GGG waveguide.
Integrated Optical Signal Processing Devices Employing Magnetostatic Waves
Authors: Fisher A. D. , Lee John N.
Published: February 2023

Optical techniques are being increasingly called upon to meet the ever-growing data rate requirements of communications and signal processing applications. A new class of magneto-optical devices1,2 based on Bragg diffraction of light by magnetostatic waves (MSWs) offers the potential of extending optical processing capabilities from the present acousto-optical Limitation of a few GHz to large time-bandwidth signal processing at 20 GHz and beyond. These devices take a thin-film integrated optical form in order to avoid shape-factor demagnetization effects.1,3 The interacting MSW and guided-optical waves thus propagate in a common ferrite film, as illustrated in Fig. 1.
Channeled-Substrate GaAs/AlGaAs Multiple Quantum-Well Lasers Grown by Molecular Beam Epitaxy
Authors: Wu Yao-Hwa , Werner Michael , Wang Shyh
Published: February 2023

Single and multiple quantum-well (MQW) lasers have been extensively investigated1,2. Besides their low threshold current density, these quantum-well heterostructure lasers exibit good linearity in light-output versus current characteristics, a high external differential quantum efficiency, and a high value of To which is a measure of lesser temperature sensitivity. To date, however, there have been few studies3,4 concerning the index-guiding of these quantum-well lasers which is of great interest for practical applications. For fiber-optical communications at high data rates, the control and stability of the lasing modes have become of great concern. Although it is commonly believed that crystal growth using molecular beam epitaxy (MBE) reproduces substrate features with uniform thickness, we have found that growth is sufficiently inhomogeneous to produce thickness variation in the epilayer over the channels. From our laboratory, we have reported the achievement of a single-longitudinal-mode operation of AlxGa1−xAs/GaAs simple double-heterostructure (DH) lasers made by MBE over the channels along [110] direction which provides for lateral modes stabilization. In this paper, we are going to present the fabrication processes and the characteristics of channeled-substrate AlxGa1−xAs/GaAs MQW lasers grown by MBE.
InGaAsP Semiconductor Lasers With Integrated Semiconductor Amplifier-Modulators at 1.3 μm Wavelength by
Authors: Eisenstein G. , Lee T. P. , Tucker R. S. , Burrus C. A. , Sessa W. B. , Besomi P.
Published: February 2023

We describe experimental investigations of two types of semiconductor light sources comprising lasers integrated with amplifier - modulators. The integrated amplifier-modulators were obtained by antireflection (AR) coating the output facet of one section of a cleaved-coupled-cavity (C3) laser. In the first configuration, the modulator operates in conjunction with a CW single-frequency laser while in the second, it is used to gate a train of narrow pulses from a laser which is mode-locked in a fiber resonator. In both cases, the modulated signal has a high on/off ratio (20 dB) and the output spectrum is not affected by the modulator.
An Analysis of Cleaved Coupled Cavity Lasers
Authors: Streifer William , Yevick David , Burnham Robert D. , Paoli Thomas L.
Published: February 2023

We present results of a cleaved coupled cavity (C3) laser [1-3] analysis which in contrast to previous studies incorporsates all the following: (1) a model of the gain variation with pumping current and photon energy [4]; (2) the refractive index dependence of the active region injection current [5]; (3) traveling wave equations for each laser segment; and (4) spontaneous emission as the laser excitation [6]. Based on our realistic formulation, we have developed a numerical algorithm to solve for the precise current required by one segment to attain threshold when the current in the other segment is specified. The calculation determines the minimum threshold current, whereas in analyzing this complex device it is possible to compute false higher thresholds. Simultaneously, the calculation finds the spectrum as a single lasing mode. Thus we obtain the spectral behavior as either segment current is varied and we are able to illustrate the progression of longitudinal mode hops through the spectral line. In addition, we calculate quantitatively previously unreported jumps from one extreme of the gain spectrum to the opposite extreme in particular current ranges. We study both configurations in which the two cavities are of similar lengths (called long-long) and of quite dissimilar lengths (long-short). The results illustrate that device behavior is very' sensitive to the gap spacing between the two segments.
Extended Precision in Video-Bandwidth Analog-to-Digital Converters Using Optical Techniques
Authors: Taylor Henry F.
Published: February 2023

Analog-to-digital converters (ADCs) are widely used to translate sensor measurements into the digital language of computing, information processing, and control systems. There is presently considerable interest in high-precision (8-10 bit) conversion at rates of 10-20 Msamples/sec for use in digital transmission and recording of television signals.1 However, for some applications (e.g., in radar signal processing) even higher precision at video sampling rates is desired for enhanced dynamic range. It has proven very difficult to achieve precision beyond 10 bits at these rates using conventional silicon integrated circuit technology.
High Speed Modulation of Semiconductor Injection Lasers at f > 10GHz
Authors: Lau K.Y. , Bar-Chaim N. , Ury I. , Yariv A.
Published: February 2023

A fundamental relation between the direct modulation bandwidth of an injection laser and the various laser parameters is as follows: where P0 is the optical power density at the active region, A is the differential gain constant and τ
p
is the photon lifetime. It is obvious that the bandwidth can be increased by increasing P
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Ti:LiNbO3 Linear Interferometric Modulators and Photorefractive Effects
Authors: Bulmer C. H. , Burns W. K. , Hiser S. C.
Published: February 2023

Linear operation of a Ti:LiNbO3 channel waveguide interferometric modulator with asymmetric arms was previously demonstrated at 633 nm.1 Such a device, when driven by a dipole antenna and coupled with single mode fibers,2 would form an integrated optic electromagnetic field sensor. Much improved dynamic range has now been achieved at 830 nm using a single-polarization interferometer. We have also observed the effects of photorefractive induced index change (optical damage) on device performance.
Tunable Integrated Optical Ringresonator
Authors: Tietgen K.-H.
Published: February 2023

Optical fibre systems, especially coherent optical fibre communications systems require wavelength stabilization. This is usually being done by using stabilization circuits with Fabry-Perot-resonators /1/. However, application of Fabry-Perot-resonators for this purpose has two drawbacks: first strong wavelength dependent reflections occur and second it is not an integrated optic solution. The first drawback can be handled by using ringresonators. A fibre optic solution was recently described by Bachus et al. /2/. An integrated optical ringresonator was also realized recently using silver ion exchange in glass /3/. The disadvantage of both devices is that alignment and tuning are almost impossible. It follows from this considerations that an integrated optical ringresonator is required which is adjustable and tunable.
Three-dimensional representation of phase-mismatch switching in coupled two-state systems
Authors: Korotky Steven K.
Published: February 2023

Coupled single-mode optical waveguides with adjustable phase-mismatch are a key component in many electrooptic devices. Here we introduce and present key results for a three-space representation of the transfer characteristics of optical circuits employing coupling and phase-mismatch between waveguides. This approach permits an intuitive understanding of the operation of devices, such as the directional coupler and Mach-Zehnder switches, the Δβ-reversal coupler, optical combiners, and polarization transformers. As such, the method is conducive to innovative device design. A novel class of switch has been identified using this formalism and has been demonstrated experimentally.
Ti:LiNbO3 guided-wave electrooptic modulator arrays
Authors: Ashley Paul R. , Chang William S. C.
Published: February 2023

Optical signal processing requires spatial as well as temporal dimensionality. Large guided-wave modulator arrays can provide this capability with total control of both parameters and with very high speed. These devices may be used for such operations as correlations, complex transformations, and matrix-vector computations. Reported here is the demonstration of a ten-channel modulator array. Parabolic horn couplers are used on each input channel for increased gain. Compact and efficient mode extinction modulators provide linear response. Fabrication considerations including the use of isolation channels to reduce crosstalk are also reported.
InGaAsP/InP Monolithic Integrated Circuits for Laser Switching and Optical Amplification
Authors: Katsuyama T. , Nakamura H. , Sakano S. , Inoue H. , Morosawa K. , Matsumura H.
Published: February 2023

Monolithic optical integrated circuits are key components for future optical communications as well as optical signal processing systems.1 Up to the present, various structures have been proposed for the integration of optical devices. However, crystal growth and process technology for fabrication is so complicated that only a few reports on the fabrication have been published. Furthermore, key devices for integration, such as small-sized optical switches, have not yet been developed.
Efficient H+:LiNbO3 Travelling-Wave Modulator
Authors: Parsons N.J. , Wong K.K. , O’Donnell A.C.
Published: February 2023

A significant problem which limits the practical application of Ti:LiNbO3 devices at shorter wavelengths (λ ≤ 1 μm) is that of index instabilities caused by the photorefractive effect, which have been observed at guided power levels as low as 30 μW at λ = 830 nm [1]. A possible solution to this is to use waveguides formed by proton-exchange, which have been reported to handle power densities at least four orders of magnitude greater [2]. However, some undesirable effects have been observed in these waveguides, including long-term index instability, and reduced electro-optic efficiency [3]. We recently reported [4] that by using a dilute-melt (DMPX) process, these effects can be overcome, and we obtained Vπ's between 1.7 and 2.7 V for an 8 mm-long push-pull interferometer at 830 nm wavelength, comparable with titanium-indiffused devices. Here, we report that travelling-wave modulators formed by DMPX behave as expected, and show no measurable degradation in microwave characteristics as a result of the increased photoconductivity of the waveguides.
Ultra High Gain Ga0.47 In0.53 As Photoconductive Detectors Grown by Chemical Beam Epitaxy
Authors: Antreasyan A. , Tsang W. T.
Published: February 2023

We report the fabrication and performance of planar, interdigitated Ga0.47In0.53As photoconductive detectors in the wavelength range 1.1-1.6μm. The devices have been fabricated on top of a 1.5μm thick undoped GalnAs layer which is grown on a semi-insulating InP substrate by chemical beam epitaxy (CBE) [1]. The ternary layer grown by this novel technique had a background doping level of N ~ 5x1015 cm-3 and Hall mobilities of 10500 and 45000 cm2v-1s-1 at 300°K and 77°K, respectively.
High-extinction AlGaAs/GaAs waveguide modulator
Authors: Gee C. M. , Thurmond G. D. , Yen H. W. , Blauvelt H.
Published: February 2023

External modulators based in GaAs are potentially useful for fiber-optic systems and high-speed signal processing. In contrast to LiNbO3 devices, a negligible photorefractive effect is observed for wavelengths near 0.8 μm, and GaAs modulators can be monolithically integrated with semiconductor lasers. Over the past few years, a number of GaAs modulators which incorporate AlGaAs/GaAs multiquantum well (MQW) structures have been demonstrated. Wood and co-workers1 recently reported a MQW modulator with a 131-ps impulse response and on/off ratio of 1.7:1 when light was propagated perpendicular to the MQW layers. To achieve better extinction, they also developed a waveguide modulator in which the light propagated parallel to the MQW layers.2 Extinction of 10:1 was achieved when the modulator (150 μm long) was driven from 7 to 11 V.
Linearization technique for a guided-wave electrooptic Bragg modulator
Authors: Ashley Paul R. , Chang William S. C.
Published: February 2023

Many types of optical intensity modulator have a transfer curve which approximates a sinusoidal function. These include Bragg modulators of both the acoustooptical and electrooptical varieties.1 Also included are the Mach-Zehnder and directional coupler electrooptical modulators.2 For most analog applications a linear transfer curve is desired. Using a Fourier analysis, it is possible to generate any given transfer curve shape with combinations of properly chosen sinusoidal components. Therefore, by combining harmonically related modulator elements, a triangular transfer curve shape can be created. Demonstrated here is use of the third harmonic to extend the linear range of a Bragg-type electrooptic modulator in the planar waveguide. It is possible to extend this technique to the other types of modulator mentioned as well. Based on a straight line curve fit, a deviation of the output intensity of less than ±1 % from the linear voltage intensity relationship has been observed over a 97% modulation range. This was accomplished while maintaining a high efficiency with 7.2 V for complete modulation.
Thermal index changes by optical absorption In group III–V semiconductor waveguides
Authors: Gabriel M. C. , Haus H. A. , Ippen E. P.
Published: February 2023

Large fast-relaxing intensity-dependent refractive-index changes would be of use for all-optical waveguide signal processing devices. In III–V compounds, many different physical processes compete to produce light-induced index changes with different strengths and response times in different wavelength ranges. In this work, waveguide Fabry-Perot interferometer structures of un-doped and lightly doped material were used to measure small index changes produced by laser excitation below the absorption edge.
Tunnel superlattice optoelectronic devices and high-speed 1.3–1.6-μm quantum well avalanche photodiodes
Authors: Capasso Federico
Published: February 2023

Recent results of a new class of tunnel superlattice optoelectronic device and on novel long-wavelength high-speed avalanche photodiodes are discussed.
Electrical crosstalk in PIN arrays
Authors: Kaplan Daniel R. , Forrest Stephen R. , Johnson Julia G.
Published: February 2023

Recently we reported a monolithic 1 × 12 array of long-wavelength (0.95–1.65-μm) PIN photodiodes with convenient electrical and optical interconnects.1 One aspect of arrays which makes them different from discrete devices is the possibility of undesirable coupling between channels leading to sensitivity penalties when used in receiver applications. In this work we analyze both theoretically and experimentally the effects of electrical crosstalk on receiver performance.
Epitaxial silicon guided-wave optical components for ̩λ = 1.3 µm
Authors: Soref Richard A. , Lorenzo J. P.
Published: February 2023

Single-crystal silicon is a promising new material for integrated-optical components, both active and passive, that operate at λ = 1.3 and 1.6 µm. According to the data of Fan et al.1 and Swimm,2 high-purity monocrystal silicon is highly transparent at the 1.3- and 1.55- µm fiber-optical communications wavelengths. (The absorption spectrum is shown in Fig. 1.) The absorption coefficient can be as low as 10−3 cm−1 when ρ = 104 Ω cm. Thus, in theory, silicon is suitable for low-loss waveguiding at these wavelengths. Experimentally, we have examined the conditions of epitaxy, ion implantation, diffusion, annealing, and doping that are appropriate for making guiding layers. It is important to control the morphology and crystallinity of the guiding layer because optical scattering and absorption will increase if grain boundaries and lattice defects are present. Thus polycrystalline-Si and amorphous-Si are less desirable for guiding than crystalline-Si. In recent years, epitaxial growth techniques for single-crystal Si have been perfected for VLSI and discrete electronic device applications.
Phase Modulation in Impurity-Induced-Disordered AlGaAs/GaAs Quantum-Well and Double-Heterostructure Waveguides
Authors: Hausken T. R. , Huang T. C. , Lee K. W. , Simes R. J. , Dagli N. , Coldren L. A.
Published: February 2023

Recently, there has been considerable interest in the use of quantum-well disordering techniques to form waveguides and devices in AlGaAs/GaAs wafers without the need for precise etching or complex crystal reqrowth techniques [1-4]. Such a technology should be particularly useful in the development of optoelectronic integrated circuits for optical signal processing and communication applications.