bluuebunny/crossref_metadata_2025 huggingface dataset:
Buried Heterojunction Electroabsorption Modulator
Authors: Campbell J. C. , DeWinter J. C. , Pollack M. A. , Nahory R. E.
Published: February 2023

We report the successful operation of a semiconductor buried
heterojunction electroabsorption modulator. These modulators are good
candidates for integration with other devices because: (1) they do not
require additional optical elements (e.g. polarization analyzers) and
(2) they can be fabricated from the same semiconductor materials and
require the same processing techniques as the sources and detectors.
Electroabsorption modulators, which utilize the Franz-Keldish effect
to enhance absorption of light near the semiconductor bandgap, have
previously been fabricated only as planar structures, using
AℓyGa1−yAs or GaAs as the waveguiding material
for operating wavelengths near 0.9μm.1-3 The
present devices on the other hand are buried heterojunctions
fabricated from
AℓyGa1−yAs1−ySbx/GaAs1−x′Sbx′,
which by proper adjustment of the compositions can be tuned to operate
throughout the range 0.9μm to z1.2μm.4 The
buried heterojunction was chosen over planar configurations because
its two dimensional light confinement assures suitability for fiber
optic applications, while its small p-n junction area and low
capacitance permit operation at high frequencies.
Branching Waveguide Directional Coupler in a GaAs/GaAlAs Injection Laser
Authors: Scifres D. R. , Burnham R. D. , Streifer W.
Published: February 2023

An important problem in using the GaAs/GaAlAs heterostructure system for integrated optics is that of transferring the guided wave in the active region of the laser into a wider bandgap transparent waveguide. Although several types of taper couplers1,2 and twin guide couplers3 have been demonstrated, these have generally been difficult to fabricate. In this paper we describe the fabrication and operation of a new branching directional coupler, which can be readily grown by conventional liquid phase epitaxy (LPE). Although our device is used herein to provide a multi-mirror laser cavity which, because of interference effects, improves laser longitudinal mode structure, we believe it to be suitable for other integrated optical configurations.
A Balanced Bridge Modulator Switch
Authors: Ramaswamy V. , Divino M. D.
Published: February 2023

Several switches using optical waveguide directional couplers have been demonstrated1-4. We report the first experimental realization of a Mach-Zehnder interferometer, analogous to the conventional microwave balanced bridge, in the integrated optical format. This switch demonstrates the balancing of both amplitude and phase, in an integrated optical device 38 mm long incorporating several bends that interconnect waveguides of slightly different widths.
Optical Pulse Compression and Very High-Speed Light Beam Scanning Using Guided-Wave Acoustooptic Bragg Diffraction*
Authors: Tsai C.S. , Nguyen Le T. , Lee C.C.
Published: February 2023

It has been shown that guided-wave planar acoustooptic (AO) beam deflectors of large bandwidth and high diffraction efficiency can be realized in LiNbO3 substrates, (1,2) and that such AO beam deflectors are suited for a number of applications in wideband optical communications and information processing. (3) In fact, some encouraging results have already been demonstrated in the experiments involving spectrum analysis(3,4) and convolution of wideband rf signals(5) as well as deflection/switching of a light beam at moderate-speed.(3) In this paper we report research progress on further utilization of such AO beam deflectors for optical pulse compression and very high-speed light beam scanning. In order to carry out a number of additional studies including a more detailed experiment on spectrum analysis and the two new experiments just mentioned, we have recently fabricated a very wideband deflector in a Y-cut LiNbO3 Ti-diffused waveguide. This deflector employs a three-element tilted-array transducer with the center frequencies of 275, 432 and 648 MHz, and has a measured deflector bandwidth of 500 MHz. This bandwidth represents the largest that has been achieved thus far. Using the AO Bragg diffraction of a He-Ne laser guided-light beam from the surface acoustic waves generated by a linear FM rf (chirp) waveform, we have achieved a compression ratio of 200 in the optical pulse compression experiment and a scanning rate of 125 x 106 spots/sec for 50 spots in the beam scanning experiment. The detailed results of these two experiments will be reported. We will discuss means for further utilization of this wide­band deflector to obtain a much larger compression ratio and a much higher scanning rate. We will also discuss some potential applications of the resulting devices in wideband optical communications and data processing.
Integrated Optical Logic Circuits
Authors: Taylor Henry F.
Published: February 2023

Recent advances in guided wave optical device technology have made it possible to produce electrooptic modulators and switches which operate at high speeds with low electrical power dissipation. This paper explores the possibility of using guided wave components to perform logic operations. Integrated optical logic circuits (IOLCs) consisting of a number of modulators and switches interconnected by single mode waveguides could be fabricated on an electrooptic substrate such as lithium niobate. The primary advantage sought in previous optical logic schemes, that of short gate propagation delay, would also apply to IOLCs, while the power dissipation per gate could be orders of magnitude lower than for logic based on nonlinear optical effects. Gates for performing basic logic functions (AND, OR, NOT, etc.) are described and a configuration for a serial-parallel binary adder illustrates how the individual gates can be interconnected to perform digital computation.
Injection Lasers with Curved Stripe Waveguides
Authors: Scifres D. R. , Streifer W. , Burnham R. D.
Published: February 2023

Room temperature operation of GaAs/GaAlAs heterostructure injection lasers with curved stripe waveguides is reported. Because of the curved gain-induced waveguide, a stable transverse mode pattern is achieved, and undesirable non-linearities (kinks)1-3 in the output power vs. pump current characteristic are eliminated. For example, curved stripe lasers (10 μm wide stripe) emitted up to 110 mW/facet before kinking. Moreover, these lasers are free of undesirable relaxation oscillations4,3 when operated under pulsed conditions. The curved stripe geometry also provides a simple means for fabricating a variety of new injection laser geometries such as directional couplers and 3db beam splitters for integrated optical device applications.
"Electrostatic Observations of Optical Damage in LiNbO3"
Authors: Cressman P.J. , Schein L.B.
Published: February 2023

Optical damage (laser induced changes in the index of refraction) in ferro­electric materials such as lithium niobate has severely limited their usefulness in optical devices1. The physical basis of this effect, which causes a collimated laser beam in a damaged crystal to diverge2, is not yet fully understood. In an attempt to gain further insight into this problem, we have developed a new electrostatic technique for probing the damaged areas3. This technique has allowed us: 1) to observe directly the macroscopic charge separation which is associated with the damage4, 2) to determine the charge distribution from the measured potential distribution, 3) to demonstrate that one of the proposed models5 is inconsistent with the data, 4) to propose an explanation of optical clean-up6, and 5) to discover a new source of optical damage which is associated with pyroelectricity7.
Microfabrication Techniques for Integrated Optics
Authors: Namba Susumu
Published: February 2023

Pattern delineation and fabrication techniques for integrated optics by electron beam and ion beam are reviewed and problems in these techniques are discussed.
Instability of Single-Mode Communication Systems Due to Interference and Polarization Effects
Authors: Sheem S. K. , Giallorenzi T. G.
Published: February 2023

In the single-mode optical communication systems, active/passive couplers, mixers and multiplexers constitute key components. Between those components and also between terminals and those components, we need optical transmission lines of substantial lengths. Environmental changes in temperature and mechanical stress and pressure along the transmission lines cause almost constant fluctuation in the phase of any particular mode at any particular point, especially at the input ports of those optical components. When the phase fluctuation is coupled with polarization rotation in the conventional round single-mode fibers, and with interferometric couplings to be found in couplers, mixers and multiplexers, noise and mode instability occur. In this presentation, we will report theoretical and experimental studies on these problems.
CW High-power Single-mode Lasers Using Constricted Double Heterostructures with a Large Optical Cavity (CDH-LOC)
Authors: Botez Dan
Published: February 2023

Single-mode high-power cw diode lasers are ideal sources for long-distance optical communications and signal processing applications. We have previously presented a mode-stabilized laser: the constricted double-heterojunction (CDH) laser1, which operates single-mode (spatially and in frequency) to 10-15 mW cw and with a spot size of 0.6 μm x 3.5 μm (at 1/e2 points in intensity). Here, we present the combination of the CDH geometry1 in the lateral direction with the large-optical-cavity (LOC) geometry2-4 in the transverse direction (see Fig. 1a). Recently, the LOC concept has also been used for other types of mode-stabilized lasers.5-7 Our novel device (CDH-LOC) allows single longitudinal and transverse mode operation in a relatively large spot (1.7 μm x 6.5 μm) up to 40 mW cw output power from one facet, at 2.5 times above lasing threshold.
Temperature Characteristics of InGaAsP/InP DH Lasers
Authors: Nishi H. , Yano M. , Takusagawa M.
Published: February 2023

InGaAsP/InP double heterostructure (DH) lasers1) with wavelengths of 1 μm region are considered to be the most promising devices for light sources in optical fiber communication systems. In this paper, we present the theoretical and experimental study of temperature characteristics in InGaAsP/InP DH lasers. To explain the temperature variation of oscillation characteristics, especially the strong temperature dependence of threshold current2), we notice two possiblities as follows; behaviour of interfacial recombination at or near InP-InGaAsP interfaces, and leakages of injected carriers through hetero-barriers between active and cladding layers.
A Review of Recent Progress on Guided-Wave Acoustooptics with Applications to Wideband Communications and Signal Processing*
Authors: Tsai C.S. , Lee C.C. , Kim B.
Published: February 2023

Recent research in planar guided-wave acoustooptics(1) has produced very significant progress. It is now possible to design and fabricate high-performance planar acoustooptic (AO) Bragg modulators and deflectors with a bandwidth approaching one GHz.(2) For example, the deflectors of 700 and 470 MHz have been realized most recently in Y-cut LiNbO3 waveguides using multiple tilted transducers(1-3) and a tilted-finger chirp transducer,(2-4) respectively. Together with recent progress on fabrication of miniature laser sources, waveguide geodesic lenses, and photodetector arrays, integration of all or most of these components on a common substrate is becoming a reality. Clearly, the resulting integrated AO modules or circuits should find a number of unique applications in wideband multichannel optical communications and rf signal processing. One application that has already received a great deal of attention and interest is real-time spectral analysis of wideband rf signals.(5-9) Other applications, such as correlation, convolution, pulse compression and matched filtering of rf signals,(2,10) and multiport switching of optical signals in a single-mode fiber optic communication system,(2,11) should not be far behind.
Self-Apertured Facet Coatings on GaAs Laser Diodes
Authors: Ponce F. A. , Scifres D. R. , Streifer W. , Connell G. A. N.
Published: February 2023

Conventional gain-guided semiconductor injection lasers with contact stripes typically exhibit non-linearities in the light output power (P) vs. laser current (I) characteristics [1,2]. Such abrupt changes in the output characteristics known as kinks often occur at power levels of a few milliwatts for lasers with stripe widths on the order of 8 µm or greater. This phenomenon is now understood to result from spatial hole burning in the injected carrier profile which causes an instability that disposes the laser mode to shift laterally along the plane of the p-n junction. In the absence of a built-in mode guiding mechanism the lateral shift produces the kink [3-5]. As an alternative to a "built-in" waveguide it should also be possible to stabilize the mode laterally by coating the facet such that the modal reflectivity is relatively high at the center and decreases at the edges. Thus, even if as a result of spatial hole burning, a lateral mode would otherwise become unstable the higher central reflectivity serves to increases its stability and thereby increase the power level at which the kink occurs.
Advances in Ti-Diffused Lithium Niobate Waveguide Devices
Authors: Alferness R. C.
Published: February 2023

Waveguides made by metal diffusion in ferroelectric crystals - principally titanium diffused in lithium niobate - have become the basis for a variety of interesting and useful guided-wave devices2. The combination of good electrooptic and acoustic-optic effects, low propagation loss3, commercially available substrates and fabrication ease make metal diffused waveguides highly suitable for guided-wave switches, modulators, wavelength filters, mode converters, deflectors, etc.
Absorption Loss and Photorefractive Index Changes in LiNbO3:Ti Crystals and Waveguides
Authors: Glass A. M. , Kaminow I. P. , Ballman A. A. , Olson D. H.
Published: February 2023

The use of titanium diffused optical waveguides in ferroelectric LiNbO3 crystals has led to efficient high speed electro-optical directional coupler switches and modulators as well as several other devices for optical processing.1 For many applications an optical power of 0.1 to 1mW in the waveguide is desirable which requires intensities of about 1kW/cm in single mode structures. However, visible light of this intensity changes the refractive index of the waveguides. This effect is called the photorefractive (PR) effect or optical damage. While the effect can be used to advantage for certain devices (for instance using two-photon absorption2) it is a problem for most integrated optical devices. For instance it has recently been shown to be the origin of optical crosstalk drift in Δβ reversal couplers.3 Little effort has been devoted to understanding or eliminating or even characterizing the effect in Ti in-diffused guides, despite the remarkable success in reducing the effect in out-diffused layers.4
Oxide-Confined GaAs Optical Waveguides Formed by Lateral Epitaxial Growth*
Authors: Leonberger F. J. , Bozler C. O. , McClelland R. W. , Melngailis I.
Published: February 2023

We report the successful demonstration of a new class of semiconductor optical waveguides. These waveguides should in theory have considerably lower loss and smaller allowable bend radii than previously reported semiconductor guides and could lead to a number of new active and passive guided wave structures that can be monolithically integrated with other semiconductor devices. The guides were formed in thin GaAs epitaxial layers which were grown over SiO2 films on GaAs substrates by a vapor-phase lateral overgrowth technique. This paper describes the fabrication techniques and optical characteristics of the guides, which will be referred to as oxide-confined waveguides.
Structures of InGaAs Avalanche Photodiodes
Authors: Kanbe Hiroshi , Susa Nobuhiko , Ando Hiroaki
Published: February 2023

InGaAs lattice matched to InP has a suitable energy band gap for photodiodes in the 1 - 1.6 µm wavelength region, where optical fiber loss and dispersion are very low.1,2 Many efforts to realize InGaAs avalanche photodiodes have been concentrated on liquid phase epitaxially grown InGaAs on InP substrates, which have p-n junctions formed in InGaAs by epitaxial growth,3,4 or by impurity diffusion.5 This paper describes properties of photodiodes with the conventional structure which are fabricated from layers by liquid phase epitaxy (LPE) and vapor phase epitaxy (VPE). It also proposes new structures for InGaAs avalanche photodiodes, which have InP p-n junctions.
Space-Charge Effect in LiNbO3 Waveguide Modulators
Authors: Liu Pao-Lo
Published: February 2023

Electrooptic waveguide modulators based on Ti-indiffusion into the LiNbO3 have been demonstrated to perform many important functions. However, the photorefractive effect along with other causes of drift must be eliminated or compensated to provide the long term stability needed in a communication system. The photorefractive effect is associated with the photo-excitation of the Fe2+ impurities.1 In Ti-indiffused waveguide devices the carriers drift toward the electrodes and affect the light propagation via the electrooptic effect.2 By going to the infrared the photons can no longer excite the Fe2+ ions. Therefore, the photorefractive effect is greatly reduced. However, it is never entirely eliminated, presumably, there are still some other channels to provide the charge separation.
Fabrication and Performance of a Practical Lithium Niobate Waveguide Modulator For Long-term Use at 632.8nm
Authors: Holman R. L. , Cressman P. J. , Apollonio R. P.
Published: February 2023

The use of lithium niobate waveguide devices in real laser optical systems requires that they deliver a specified optical power continuously for a time period measured in thousands of hours. The primary barrier to achieving such performance has been lithium niobate’s photorefractive sensitivity, also known as optical damage [1-4]. This sensitivity, which depends on the waveguide’s thermochemical history, decreases a waveguide’s power-handling ability at the shorter laser wavelengths and at the higher laser powers [3,4]. Only those waveguides prepared by the out-diffusion process have shown promise for adequate long-term use with HeNe lasers at power levels greater than 1mW.
High Coupling Efficiencies between Single Mode Optical Fibers and Ti Diffused LiNbO3 Waveguides
Authors: Papuchon M. , Kayoun P. , Bourbin Y.
Published: February 2023

The coupling between single mode optical fibers and integrated optical devices and particularly Ti diffused LiNbO3 waveguides has been deeply investigated. Recently very good results have been obtained leading to the possibility of building pigtailed integrated optic devices (1, 2, 3).
Single Mode Integrated Optical 1XN Star Coupler
Authors: Findakly T. , Chen B.
Published: February 2023

Signal distribution from one to several ports is necessary in various optical communication networks. To meet this requirement, a new integrated optical 1XN single mode star coupler is presented. The principle of operation is based on directional coupling of channel waveguides with linearly varying spacings1. The design objective is to minimize the need for corner bends, and avoid the use of lossy γ-junctions. As a result, a minimum insertion loss is obtained for devices having all output channels equally spaced and perpendicular to a reference edge. Based on these design principles, three slightly different structures are developed, as shown in Fig.1A, B and C respectively. Essentially, the three patterns are based on the same concept of distributed coupling achieved by linearly increasing the wave­guide spacings in sets of two or three coupled waveguides. These configurations are designed to provide adequate spacing at the output end to accommodate for coupling to a fiber array. Device length is determined by the appropriate choice of the tilt angle α and the initial spacing cj at the beginning of the various interaction regions. All three patterns are expected to satisfy the requirements, however, there are some trade-offs in certain design and fabrication situations.
Monolithic Integration of a GaAℓAs Buried-Heterostructure Laser and a Bipolar Phototransistor
Authors: Bar-Chaim N. , Harder Ch. , Katz J. , Margalit S. , Yariv A. , Ury I.
Published: February 2023

One of the key elements in the fabrication of GaAℓAs/GaAs integrated optoelectronic circuits is the semiconductor laser, which should be constructed to have a very low threshold current in order to minimize the heat dissipation of the device. A very attractive candidate with this feature is the buried-heterostructure (BH) laser [1] which has been fabricated recently on a GaAs semi-insulating substrate [2].
Long-Wavelength Detectors
Authors: Stillman G.E. , Cook L.W. , Bulman G.E. , Tabatabaie N. , Chin R. , Dapkus P.D.
Published: February 2023

The InGaAsP/InP and AlGaAsSb/GaSb lattice matched alloy systems are being widely studied in many laboratories for applications in 1.3 to 1.55 μm wavelength optical fiber systems.1 The general detector requirements of high quantum efficiency, fast response, and low noise translate into the material requirements of appropriate bandgap, high purity, low dark current and, for avalanche photodiodes, a large asymmetry in the electron and hole impact ionization coefficients.
GHz Bandwidth Optical Channel Waveguide TIR Switches and 4 × 4 Switching Networks*
Authors: Chang C. L. , Tsai C. S.
Published: February 2023

Preliminary results on a double-pole double-throw optical switch which utilizes two crossed channel waveguides in a LiNbO3 substrate and a pair of parallel electrodes to induce total internal reflection (TIR) were reported by us at the 1980 Topical Meeting on Guided-Wave and Integrated Optics.(1) The straight channel waveguide intersection (termed 2Δn intersection) employed in this TIR switch differs from the conventional one. Contrary to the conventional intersection (termed Δn intersection), the refractive index change in the crossover region is twice that in the channel waveguides. As a result, the light wave is also guided in the crossover region and it is possible to achieve both low drive voltage and low crosstalk simultaneously by using a sufficiently small intersection angle. For example, a drive voltage of 5 volts for 93% switching efficiency and a crosstalk of -15.7 db were demonstrated in a switch with an intersection angle of 1.0 degree.(1) A 3 × 3 matrix switch which consists of four of the basic switches just described was also tested with encouraging results.(1)
Characteristics of a Polarization Independent Switch Using a Gaussian Taper Function
Authors: Ramer O. G. , Mohr C. , Pikulski J.
Published: February 2023

The filter characteristics of smoothly weighting or tapering the coupling between codirectional interacting waveguides and contradirectional Bragg reflection devices have been studied and reported. Filters of both types have promise for use in integrated optical waveguide circuits for light-wave communications. Specific applications that have been identified are wavelength multiplexers or demultiplexers, polarization-independent optical switches or modulators, and Bragg mirrors. The interaction between the two modes in either device is described by a nonlinear Ricatli equation.1 In general, the local coupling between the modes is described by a coupling coefficient κ(Z). Several functional relations for κ(Z) have been studied for their filter characteristics. The ones producing the lowest sidelobe levels to date have been a set of "window" functions that have been thoroughly studied for their properties as digital filters: In this paper we consider a truncated Gaussian to describe the functional behavior of κ(z).
Non-Blocking 2x2 Optical Waveguide Matrix Switch Using Dielectric Chip Motion
Authors: Kobayashi Morio , Terui Hiroshi
Published: February 2023

Optical matrix switch is an important component in optical communication systems and optical data processing systems. To construct the matrix switch, it is necessary to make a switching angle as large as possible.
Picosecond Sampling in Optical Waveguides
Authors: Haus H.A.
Published: February 2023

Single mode optical waveguides confine optical radiation to the dimensions of the waveguide with relatively low loss over distances of tens of thousands of wavelengths. Over these distances the dispersion of the waveguide has negligible effect on signals of less than 10+13 Hz bandwidth--picosecond pulses can propagate with no distortion. On the other hand, µ-wave drives of moderate power may produce significant modulation of the optical signals. This is the basis for hybrid µ-wave-optical waveguide systems designed for high speed modulation and sampling. Using a waveguide coupler, Izutsu et al.[1] and Kubota et al.[2] have built broadband modulators, extending to 11 GHz, with a µ-wave transmission line that propagates a modulation signal synchronously with the optical waveguide. Marcatili[3] has proposed a high speed sampler in which a large amplitude µ-wave drive modulates the transfer from one guide to the other in coupled waveguides so as to sample the optical wave in the first guide with a very narrow window function, the width of the window being determined by the rate of change of the µ-wave voltage at the zero crossing.
1.55µm GaInAsP/InP Distributed Bragg Reflector Integrated Laser Directly Coupled to External Waveguide
Authors: Abe Yuji , Kishino Kastsumi , Suematsu Yasuharu , Arai Shigegisa
Published: February 2023

The high-speed and ultra-long distance optical communication system can be obtained using 1.5-1.6µm wavelength region [1] if the light source with narrow dynamic spectral width is developed [2]. The lasers with periodic structure, for example DBR-ITG lasers can be operated in single longitudinal mode even under high-speed modulation condition [3]. In order to obtain high-quality DBR laser, it is important to realize highly efficient coupling between active region and DBR region which forms in a low-loss external waveguide. Various types of integrated lasers, namely, lasers with integrated external waveguide, have been studied thus far [4]. Direct-coupling integrated lasers reported in GaAs/AlGaAs system [5][7] have the advantage that the pure un-doped external waveguide can be obtained without disturbing the injection properties of the based wafer. In GaAs direct-coupling integrated lasers, coupling efficiencies were relatively low because the external waveguide structure was not optimized. However if the external waveguide is formed uniformly even at the joint with active layer, coupling efficiency of more than 90% is theoretically possible by the optimized external waveguide structure with relaxed fabrication-tolerance. It is, therefore, interesting to develop this type of GaInAsP/InP integrated laser.
Semiconductor Interferometric Laser
Authors: Fattah Ismail H.A. , Wang Shyh
Published: February 2023

Wavelength control of semiconductor lasers is important in optical communication, where mode stability, tunability, and FM modulation are vital to high quality transmission. Numerous work had been done in optimizing stripe geometry lasers to achieve mode stability. Tunability of semiconductor lasers was also achieved by the use of external cavity, grating, or modulators. However, work on wavelength control was limited to DFB and DBR lasers using the properties of periodic waveguides. On the other hand, interferometric methods had been used widely in gas lasers for mode control [1]. In this report we investigate the principle of using the interferometric techniques in building a monolithically integrated semiconductor interferometric laser (IL).
Modal Noise, A Component Interaction Problem in Guided Wave Systems
Authors: Epworth R. E.
Published: February 2023

Modal noise1,2,3 problems arise when lasers are used in conventional optical systems. To fully understand its nature, interaction between the various system components must be considered. Present generation optical systems convey information by intensity modulation of the source and it is generally assumed that the received signal is an attenuated replica of the transmitted signal. However, the use of a coherent source with a multipath transmission medium gives rise to multipath interference. In multimode fibre, this coherent interference between modes results in speckle patterns which can be seen in both the near and far field of the fibre. Generally the number of speckles in these patterns is proportional to the number of modes in which power is propagating. Phase changes between modes make the speckles move, i.e. change the spatial distribution of the power within the optical guide.
Design Rules for Low-Loss Coherently-Coupled LiNbO3 Waveguide Bends*
Authors: Johnson L. M. , Leonberger F. J.
Published: February 2023

The design of many proposed integrated optical circuits containing elements such as branching networks and device interconnections require complicated low-loss waveguide bends. We report here new experimental results on very low-loss coherently-coupled1,2 bends in single-mode Ti-diffused LiNbO3 channel waveguides which in conjunction with further analysis of earlier measurements3 now allow us to establish a set of design rules for these structures. These bends consist of successions of straight, angled waveguide sections which approximate smoothly-curved bends and are particularly useful since they are compatible with conventional photomask pattern generators. The design rules are qualitatively similar to a set previously reported4 for bend structures consisting of straight and circular waveguide sections. Losses due to curvature reversals, straight-curved transitions, and curvature alone were considered. It is found in our work that a significant portion of the loss in complicated coherently-coupled bend structures is due to curvature reversal and that the loss of a single coupled 1° abrupt bend can be as low as ≈0.085 dB.
Characterization of LiNbO3 Waveguides Exchanged in TlNO3 Solution
Authors: Chen Y.-X. , Chang W. S. C. , Lau S. S. , Wielunski L. , Hollman R. L.
Published: February 2023

LiNbO3 waveguides are fabricated most commonly by two methods, Ti-indiffusion or Li2O-outdiffusion. The disadvantages of these two methods are: (1) Ti-indiffused waveguides have low optical damage threshold and it is not possible to obtain Ti-indiffused waveguides with a mode depth less than 2 μm; and (2) waveguides obtained by Li2O-outdiffusion at high temperatures have an even larger mode depth (~ 5 μm). The use of ion exchange to make LiNbO3 waveguides with large Δn and high optical damage threshold has been reported previously by Shah (1) and by Jackel (2). Single mode LiNbO3 waveguides with small mode depth, low attenuation high optical damage threshold and low in-plane scattering noise are very important to integrated optical signal processing applications.
Optical Waveguides in InGaAsP And InP by Metal Diffusion
Authors: Kaminow I. P. , Alferness R. C. , Stulz L. W. , Dentai A. G.
Published: February 2023

Strip waveguides have been formed on semiconductor heterostructure planar waveguides by etching ridges to provide dielectric loading[1] or by the photoelastic effect[2]. Lateral guiding has also been produced in semiconductor lasers by various buried structures that require etching and regrowth. For the most part, these strip guides do not contain bends.
High Speed InGaAs PIN Photodiode Grown on Semi-Insulating InP Substrate Suitable for Monolithic Integration
Authors: Li Kenneth , Rezek Edward A. , Law H. David
Published: February 2023

The integration of a PIN photodiode with an FET is attractive to obtain low noise, high speed photoreceivers for optical communication systems. Most of the high speed photodiode work to date has been done on conductive substrates which are not suitable for monolithic integration1-4. In this paper, we report a low operating voltage InGaAs PIN photodiode suitable for optoelectronic monolithic integration, fabricated on a semi-insulating InP substrate with the lowest reported dark current density of 2.5 x 10-6 A/cm2 at -10V bias (0.2nA for a 100μm diameter diode). At the operating voltage of -5V, an external quantum efficiency of >90% at 1.3μm and >83% at 1.55μm, a rise time of <35 ps and a FWHM of <45 ps have been measured.
Permanent Low Loss Coupling of Single Mode Fiber Arrays to Waveguides
Authors: Murphy E. J. , Rice T. C. , Harvey G. T. , Read P. H.
Published: February 2023

Over the past few years, a wide range of guided wave devices have been demonstrated in LiNbO3 and glass. The next step in the development of guided wave technology is to integrate several devices on a single substrate and to use the integrated device in a practical application. To this end, there is a clear need to further explore methods for permanently bonding large linear arrays of single mode fibers to waveguides. The principal challenge is to develop a technique that can maintain the required submicron accuracy over distances on the order of several millimeters. In reference 1, we reported on the attachment of V-grooved silicon chip arrays (with two fibers per array) to waveguides in LiNbO3. Here, we report on the extension of this technique to larger arrays. Specifically, we have permanently bonded arrays of six and twelve fibers to both ends of straight waveguides in lithium niobate. In both cases, low excess loss (average 0.3dB per interface) was measured. These are the largest arrays and the lowest excess losses reported in the literature. The six element structure (fiber-waveguide-fiber) was subjected to environmental testing with favorable results.
Very High Resolution Electron-Beam Lithography and Applications to Integrated Optics
Authors: Wilkinson C.D.W.
Published: February 2023

The past few years have seen the development of lithographic techniques so that structures can be fabricated with a resolution of 10nm(1,2). The aim of this talk is to give an introduction to this new technique and to point out some of the applications to integrated optics.
InGaAsP/InP Waveguide Grating Filters for λ=1.5μm
Authors: Alferness R. C. , Joyner C. H. , Divino M. D. , Buhl L. L.
Published: February 2023

With the achievement of single longitudinal mode semiconductor lasers, the prospect of multiplexing several closely spaced wavelength channels appears quite attractive. Waveguide reflection grating filters are potential candidates for such narrowband multiplexing/demultiplexing applications. In addition, such narrowband filters may be used for FSK detection schemes. Glass waveguide grating filters for visible,1 and recently for long wavelength operation,2 have been demonstrated. However, grating filters based on InGaAsP/InP waveguides offer several advantages including the potential for electrical tunability and monolithic integration with detectors. While gratings have been incorporated into DFB lasers, their fabrication in passive InGaAsP/InP waveguides and filter response evaluation has not been previously reported. Here we report InGaAsP/InP waveguide grating filters for λ≅1.5μm with peak reflectivity >99 percent and filter bandwidths as narrow as 6Å and as broad an 80Å.
A Six Channel Single Mode Wavelength Multiplexer With A Waveguide Concentrator
Authors: Minford W. J. , Lipson J. , Murphy E. J. , Rice T. C. , Linke R. A.
Published: February 2023

Devices based on diffraction gratings offer the only clear vehicle for progressing to many channels of wavelength multiplexing.1 This is because the loss in any channel is independent of the total number of channels. In single mode implementations the critical device is the multiplexer because, unlike the demultiplexer, the input and output fibers must have nearly identical cores. This results in pass-bands with a Gaussian shape. As the dispersion of the lens-grating combination is linear the ratio of channel width to channel separation is maximized when the cores are nearly close packed. For single mode it is impractical to accomplish this with actual fiber because the outer diameters become unacceptably small. The alternative is to obtain the required separation using strip waveguides. The waveguides may have an initial spacing appropriate for fiber pigtailing which can then be gradually reduced to the desired value. In this summary we report on the first such implementation.
High-Speed Integrated Optoelectronic Signal Processing Devices*
Authors: Leonberger F. J.
Published: February 2023

Integrated optoelectronic devices are of increasing interest for high-speed signal acquisition and processing applications. Both guided-wave and conventional optoelectronic structures have been hybridized to provide important processing capabilities not readily achievable with all-electronic devices. Here, our experimental work on two wideband devices is reviewed and several new types of integrated optical signal processing devices are discussed. In particular, the current status of electrooptic A/D converters and optoelectronic switches and sampling devices is summarized and discussions given of a new guided-wave/CCD correlator structure and of the use of guided-wave/ optoelectronic devices for optical interconnections in electronic integrated circuit systems.
Characterization of Instability in Ti-indiffused LiNbO3 Modulators Due to Photorefractive and Non-Optical Sources*
Authors: Becker R. A.
Published: February 2023

The utility of Ti-indiffused LiNbO3 modulators is limited in some applications by a slow temporal instability due to photorefractive and non-optical sources. In this paper we characterize these effects, separating instabilities which occur with or without an applied voltage due to photoconductive and photovoltaic effects respectively from those caused by non-optical sources. The characterization of optically induced instabilities includes an evaluation of devices fabricated on two different crystallographic orientations as well as a demonstration of a "fixing" technique that dramatically reduces the device susceptibility to the photorefractive effect. A simple RC circuit is used to model instabilities not optically induced that occur when a dc or quasi-dc voltage is applied.
Impact of material parameters on LiNbO3 waveguide devices
Authors: Becker R. A.
Published: February 2023

The formation of optical waveguides in LiNbO3 by indiffusion
of titanium was first demonstrated in 1973, and since then many
laboratories have actively pursued this technology. However, the
usability of Ti-indiffused LiNbO3 devices in
signal-processing and sensor applications has been compromised due to
photorefractive effects which occur in the otherwise advantageous
visible and near-IR regions of the optical spectrum. These effects
cause unacceptable instabilities in the devices. The dominant effect
in LiNbO3, when exposed to high-intensity radiation, is the
photoionization of iron impurities in the Fe2+ state to the
Fe3+ state, creating a mobile electron which drifts
preferentially in the +z(+c)
direction (photovoltaic effect). The mobile electron drifts out of the
illuminated region and is trapped, thus setting up an internal
electric field. This electric field perturbs the refractive index of
the illuminated region through the electrooptic effect and changes the
phase velocity of the propagating light.1 The results of
these two types of photorefractive effect depend on wavelength and
optical power. Degradation in device properties ranges from a slow
drift in the optical index of the waveguide to large losses because of
light being scattered out of the waveguide. We will discuss methods of
evaluating these effects2,3 and relate them to device
performance.
Single-mode operation in laterally coupled cavity semiconductor lasers
Authors: Lang Robert J. , Salzman Joseph , Yariv Amnon
Published: February 2023

Single-mode semiconductor lasers are desirable for fiber-optic communications because their narrow spectrum translates into minimal pulse spreading in a dispersive fiber. Unfortunately, simple Fabry-Perot semiconductor lasers tend to oscillate in several longitudinal modes, particularly under high-frequency modulation. To combat this problem, more complicated laser structures have been proposed, including distributed feedback lasers, distributed Bragg reflectors, and coupled cavity lasers.1 These last are of particular interest due to their relative ease of fabrication. Thus far, most work has focused on longitudinally coupled lasers. In these devices, the gap between the lasers plays a critical role in determining gain selectivity, and it must be altered mechanically. Recently, we demonstrated operation of a laterally coupled laser pair, in which the coupling between two lasers of dissimilar lengths occurs via the evanescent fields of the individual lasers.2 In this paper we solve for the threshold gains of a laterally coupled cavity (LC2) laser and present experimental verification of single-mode operation.
Broadband electrooptic frequency shifter using TE/TM electrooptic conversion
Authors: Mariller C. , Papuchon M.
Published: February 2023

Several frequency shifters using electrooptic TE/TM conversion in LiNbO3have already been described.1−3They used classical orientations of the crystal, and, as the birefringence is large (~0.1), the optical bandwidth is small (~10 Å). The frequency shifting effect is obtained using a collinear interaction with a set of finger electrodes driven by a multiphase electrical signal to generate unidirectional index wave.
Phase space expression of modal distribution in multimode optical branches
Authors: Kokubun Y. , Suzuki S. , Fuse T. , Iga K.
Published: February 2023

Multimode optical branching components are becoming essential in optical networks such as subscriber systems and local area networks.1 There is a problem, however, that the branching characteristic strongly depends on the excited modal distribution,2 and stable operation of multimode branching waveguides, therefore, has not been established.
Polished Single-Mode Fiber Directional Coupler With Strong Coupling
Authors: Mao Zhong-ming , Fang Xi-sheng , Li Bin-hong
Published: February 2023

In this paper, a single-mode fiber directional coupler with strong coupling made by the polished technique is studied. Such a coupler consists of two parallelly spliced fibers with their cores touched each other. The modes become coupled directly without any evanescent fields, so the coupled mode theory fails to expound. Since the core of the coupling zone of the coupler plays most important role in guidance of lightwave, it cannot be neglected like a fused single-mode coupler with large taper ratio and/or small 7-value/1/.
High Efficiency 4 Gb/s GaInAsSb Photodetectors for Wavelengths to 2.3 μm
Authors: Bowers J. E. , Srivastava A. K. , Burrus C. A. , DeWinter J. C. , Pollack M. A. , Zyskind J. L.
Published: February 2023

Alloys of Ga1-xInxAsySb1-y lattice-matched to GaSb (where y/x ~ 0.9) span the wavelength range from 1.7 to 4.3 μm. This range is important for future communications systems utilizing novel fibers with a projected minimum loss of <0.01 dB/km1. This paper describes a GaInAsSb p-i-n homojunction photodiode that operates with high speed and high quantum efficiency at room temperature.
High-performance InGaAsP/InP phase modulators for integrated optics
Authors: Rodgers P. M. , Robertson M. J. , Chatterjee A. K. , Wong S. Y.
Published: February 2023

The single-mode phase modulator is an important component of coherent optical communications systems which are now being developed in the 1.1-1.6-μm wavelength range.1 This paper reports an efficient InGaAsP/InP ridge waveguide phase modulator fabricated on material grown by metal-organic vapor phase epitaxy (MOVPE) and liquid phase epitaxy (LPE). The structure is designed to be compatible with the type of distributed feedback laser demonstrated at BTRL2 allowing the possibility of integration.
GaAs- and InP-based optical waveguides for the 10.6-μm wavelength
Authors: Delacourt D. , Chevrier J. , De Bouard A. , Hirtz J. P. , Poisson M. A. , Razeghi M. , Papuchon Michel
Published: February 2023

The recent progress achieved in III–V compound vapor phase epitaxy and particularly the development of the MOCVD method, give new possibilities for passive and active efficient waveguiding devices for the 10.6-μm wavelength. We present results for two different planar structures: a low-drive voltage phase modulator and a low-loss waveguide.
Polarization-selective SiO2-Si resonant-reflecting waveguide
Authors: Duguay M. A. , Kokubun Y. , Koch T. L. , Pfeiffer L.
Published: February 2023

Bragg waveguides1-3 utilize the high reflectivity of a periodic layered medium to propagate light in a surface layer whose index may be lower than that of the substrate. In the case of monolithic integration of optical waveguides on high-index substrates such as GaAs, InP, and Si, the relatively low index of deposited layers makes Bragg waveguides especially useful in reducing the radiation loss due to field penetration into the substrate.
Theory and experiment on guided-optical wave mode-conversion through noncollinear interaction with magnetostatic surface waves
Authors: Chen W. , Young D. , Tsai C. S.
Published: February 2023

We reported at the 1984 Topical Meeting on Integrated and Guided-Wave Optics experimental observations on diffraction and mode-conversion of guided-optical waves at 1.152-μm wavelength in a YIG-GGG waveguide by the magnetostatic surface waves (MSSW) in a noncollinear coplanar configuration in which the propagation directions of the incident and diffracted light waves were nearly orthogonal to that of the MSSW (Fig. 1).1Specifically, by tuning both the dc magnetic field and the carrier frequency of the MSSW a bandwidth as large as 4 GHz, namely, from 3.0 to 7.0 GHz, was measured. We present a detailed theory that has been developed most recently to verify the experimental observation referred to above. The theoretical predictions have also been found to agree with the additional results obtained with the most recent experiments at 1.302-μm wavelength. Both the theoretical treatment and results of these most recent experiments will be reported.
Integrated-optic logic gates
Authors: Findakly Talal , Dougfierty B. , Moen J.
Published: February 2023

The use of integrated optics to perform logic and computation was proposed earlier by Taylor1 based on interconnected directional coupler switches and intensity Mach-Zehnder modulators. We apply the principle of polarization conversion and discrimination in integrated optical format to perform various logic functions. The principal components of the proposed logic gates are a polarization converter (TE ↔ TM) and polarizer. An illustration of the various logic gates that can be implemented by this concept is shown in Fig. 1. The logic input to these devices is an electrical voltage, equivalent to that which rotates the polarization by 90°, and the output is an optical intensity. The optical input is a linearly polarized light, and all waveguides are single mode in the TE and TM polarizations. From Fig. 1, it can be seen that logic gates such as AND, OR, NAND, NOR, EXCLUSIVE-OR, and NOT can be realized by properly arranging and cascading the polarization converters and polarizers along the waveguide pattern. Based on this concept, we report on the fabrication and demonstration of an integrated optical EXCLUSIVE-OR logic gate in Ti:LiNbO3. As shown in Fig. 2, the device consists of a single-mode straight channel waveguide along which two polarization converters are cascaded and followed by a polarizer. The principle of operation can be understood by tracking the light polarization and transmission on the application of voltages to the two converters. Consider the case where both inputs A and B are ON. Assuming that the input light is in the TE polarization, the light is converted into TM past converter A and back to TE past converter B. If the polarizer is designed to pass the TM and attenuate the TE, the output is zero consistent with the truth table requirement of an EXCLUSIVE-OR gate. Other input–output combinations can be verified following the same reasoning.