bluuebunny/crossref_metadata_2025 huggingface dataset:
Low threshold current GaInAsP/InP Integrated Twin Guide Lasers with Distributed Bragg Reflector emitting at 1.55µm
Authors: Koyama Fumio , Arai Shigehisa , Tanbun-Ek Tawee , Kishino Katsumi , Suematsu Yasuharu
Published: February 2023

GaInAsP/InP DH lasers have been studied intensively as the most promising light source for ultra low loss optical fiber communications [1,2]. In 1.3µm wavelength region, where material dispersion problem doesn't exist, many kinds of excellent laser diodes were realized which can be applied to practical use. However, most of conventional structure lasers can't be applied to 1.5-1.6µm wavelength optical fiber communications due to spectrum broadening under high frequency modulation which limits the transmission bandwidth of optical fiber [3,4]. Thus pure spectral property of laser diode even in high frequency modulation is essential for very long distance optical fiber communication system using 1.5-1.6µm wavelength region where transmission loss of optical fiber is almost half of that in 1.3µm wavelength region. Distributed Bragg Reflector (DBR) and Distributed Feedback (DFB) lasers are only promising devices for such a long distance communication or further efficient communication methods, i.e. wavelength division multiplexing and heterodyn detection [5,6]. For these practical use, low threshold current operation of those lasers is the most important in order to get room temperature CW operation.
The Beam Propagation Method in Integrated Optics
Authors: Lagasse P.E.
Published: February 2023

Over the past flow years Feit and Fleck [1] - [ 5] have used the Beam Propagation Method (BPM) very succesfully for computing the modal properties of multimode graded index fibers. Before discussing the application of the BPM to integrated optics, it is necessary to understand the basic principles and limitations of the method.
Temperature Sensitivity of Quaternary Lasers
Authors: Thompson G.H.B.
Published: February 2023

In contrast to semiconductor lasers emitting at a wavelength less than about 1μm, the observed threshold current density in longer wavelength lasers cannot be satisfactorily accounted for in terms only of the radiative recombination that should accompany population inversion. It is necessary to postulate an additional non-radiative process. Also a reduced incremental efficiency of lasing is observed that suggests the presence of optical absorption. The threshold current density should theoretically decrease with wavelength λ approximately as λ−2. At low temperatures, this is approximately true, but above room temperature the variation with λ completely reverses, giving a greatly enhanced temperature sensitivity at longer wavelengths.
Optical Characterization of Low Losses GaAs Waveguides Fabricated by Localized Vapour Phase Epitaxy
Authors: Erman M. , Vodjdani N.
Published: February 2023

The feasibility of very low losses GaAs waveguides has been recently demonstrated [1] using localized vapour phase epitaxy. This paper deals with the optical assessment (attenuation, polarization and electrical field mapping of the eigenmodes) of various structures grown using this process. Experimental growth conditions are discussed in details in [2]. In short, the guides are grown selectively on bare parts of a GaAs substrate otherwise covered by a dielectric film. Since the growth rate is strongly anisotropic, polygonal cross sections of various forms can be obtained. An additional feature is the possibility of modulating the doping level of the epilayer. Fig. 1 gives an example of 3 typical structures on (100) GaAs along <110> azimuth. Optical confinement is varied from one type to another by changing the doping sequence. With respect to the "classical" rib type structure, these guides have a much better lateral confinement.
Low-Loss GaAs-AlxGa1-xAs Double Heterostructure Directional Coupler
Authors: Carenco A. , Sansonetti P. , Menigaux L. , Brandon J. , Rondot M.
Published: February 2023

The interest of III-V semiconductors for optical monolithic integration is well established. A fundamental problem to solve before being able to take full advantage of the large potentiality of semiconductor monolithic circuits is to realize single-mode waveguides in these materials exhibiting very low propagation loss (≲ 1 dB/cm). For instance, the problem affects electro-optic directional couplers, which are considered as basic unit in integrated optics. In spite of obvious qualities (especially concerning expected electrical bandwidth), the relatively large optical loss exhibited by the most efficient ones has precluded their use in systems. We report here the realization of an electro-optic directional coupler using double-heterostructure GaAs-AlxGa1-xAs waveguides, which provides lower propagation loss (1dB/cm) compared to previously reported results, while maintaining good switching properties (< 15 V) both at 1.3 and 1.5μm.
Thermo-Optic Phase Modulation in Single-Mode Glass Waveguides
Authors: Findakly T. , Chen B.
Published: February 2023

Low speed active integrated - optical devices fabricated on glass substrates are investigated. Glass waveguides fabricated by ion-exchange are low loss (< 0.2 dB/cm), easy to fabricate, and immune to optical damage as encounted in LiNbO3 waveguides, which make them attractive for certain applications that do not require high speeds. Thermal effects in dielectric waveguides induce refractive index perturbations.1 This, along with the thermal expansion, can be utilized to generate phase modulation in dielectric materials, such as glass. In this paper, we report the experimental results of thermo-optical phase modulation and switching in single mode integrated-optical glass structures.
Substrate Integrated Microlenses Prepared by the PCVD-Technique for Laser-Fiber Coupling
Authors: Küppers D. , Schelhas K.H.
Published: February 2023

Microlenses for laser-fiber coupling purposes were prepared using an etching process in combination with a plasma-activated chemical vapor deposition (PCVD) process. The lenses take the form of half spheres or spheres with a diameter of~ 60 μm. They were characterised using a light source whose NA = 0.4. The coupling efficiency of the lenses, obtained when coupling the light into a graded-index fiber with a core of 50 μm diameter whose NA = 0.21, was 84%.
High-Performance Focusing Grating Coupler Fabricated by Electron-Beam Writing
Authors: Suhara T. , Nishihara H. , Koyama J.
Published: February 2023

Focusing grating couplers (FGC's)1, 2 are an attractive component for integrated optics, since they have applications as thin film waveguide to LD or fiber couplers and can also be the key component for the future integration of optical disc pickup devices. The FGC's fabricated by the holographic technique1, however, have limited application since they exhibit large aberration due to the difference in wavelength between the fabrication light and the coupling light. By the electron-beam (EB) writing, aberration-free FGC's for use at arbitrary wavelength can be fabricated2. In this paper, we present a high-efficiency diffraction-limited focusing grating coupler fabricated by the EB writing.
TrLiNbO3 Guided-Wave Devices for Long Wavelength Telecommunications
Authors: Alferness R. C. , Buhl L. L. , Korotky S. K. , Divino M. D.
Published: February 2023

The recent growth in single-mode lightwave technology for communications, sensor and signal processing has heightened the prospects for practical application of TrLiNbO3 guided-wave devices. For telecommunications applications, long wavelength (λ=1.3μm–1.6μm) devices with low fiber-coupled insertion loss will be required. Here we summarize our recent work on long wavelength Ti:LiNbO3 waveguide high-speed switch/modulators, tunable filters, polarization controllers and splitters, and short, high-peak power pulse generators.
Broadband Ti:LiNbO3 Guided-Wave Lumped-Element and Traveling-Wave Interferometric Modulators*
Authors: Becker R. A.
Published: February 2023

In this paper we report the development and characterization of wideband single-mode Mach-Zehnder interferometric lumped-element and traveling-wave modulators for applications in the 0.85-μm wavelength range. Several papers have been previously published which report the design and performance of Ti-indiffused lumped-element guided-wave electrooptic modulators.1 However, none of these provides sufficient insight for designing a practical modulator for a particular frequency response nor fully evaluates proposed circuit models by investigating a number of modulators with significantly different capacitances, resistances and inductances. Here, these issues are addressed and a simple RLC equivalent circuit is shown to accurately predict measured device performance. A lumped-element modulator with a Vπ = 4 V and a small-signal linear 3-dB bandwidth of 2.75 GHz has been demonstrated. In addition, traveling-wave modulators were fabricated and characterized. A small-signal linear 3-dB bandwidth of 13.2 GHz and a 7.6-μW/MHz figure of merit were measured representing one of the widest bandwidth and most efficient modulators reported. A traveling-wave modulator transmission line analysis predicts a >17-GHz small-signal linear bandwidth for this same device when a different terminating impedance is used.
Time-Division Multiplexing/Demultiplexing and Data Encoding Experiments Using Fast T:LiNbO3 Directional Coupler Switch/Modulators
Authors: Korotky S. K. , Buhl L. L. , Alferness R. C. , Eisenstein G. , Veselka J. J. , Harvey G. T. , Read P. H.
Published: February 2023

For multi-gigabit/sec communication systems, high-speed electro-optic guided-wave modulators and switches are attractive alternatives to circumvent spectral and optical power limitations of directly modulated semiconductor lasers. These waveguide devices may be used, for example, to externally modulate and time-division multiplex/demultiplex high peak power pulses obtained from mode-locked semiconductor laser sources. Here, we report fully-connectorized and packaged, 2X1 and 3X1 Ti:LiNbO3 waveguide switches designed for 1.3 μm wavelength and experiments carried out to assess the high-speed performance of these devices in optical time-division multiplexing/demultiplexing and data encoding applications. Using the devices as switches, we have actively multiplexed optical pulse streams with output non-return-to-zero (NRZ) center-to-center bit spacings of less than 100 ps, while incurring an average optical power penalty of only 0.5 dB. We have also operated the devices as modulators to encode a pseudo-random data stream at 2Gb/s NRZ without degradation of the eye pattern or the cw semiconductor laser source spectrum.
Coherent Raman Scattering in Thin Film Waveguides
Authors: Hetherington W.M. , VanWyck N.E. , Koenig E.W.
Published: February 2023

The field localization associated with planar integrated optics makes a thin film an ideal medium for performing nonlinear optics phenomena with moderate total powers. To date, primarily second order processes1–3 have been demonstrated. Coherent Anti-Stokes Raman Scattering, i.e. CARS (CSRS) is a third order process in which two photons at ω1 combine with one photon at ω2 (or vice-versa) to produce a photon at the frequency ω3=2ω1−ω2 (or ω3=2ω2−ω1). The resulting signal is enhanced when ω1−ω2 coincides with a vibrational Raman transition in the molecules which make up the medium and hence sweeping the difference frequency yields the Raman spectrum of the medium. This process promises sensitivities orders of magnitude larger than for spontaneous Raman scattering which has already been observed in thin film waveguides4.
Behavior of Optical Solitons Which are Periodically Amplified by Stimulated Raman Process
Authors: Hasegawa Akira
Published: February 2023

Transmission properties of optical solitons which are periodically amplified by the stimulated Raman process in a glass fiber is numerically studied for various parameters.

Optical solitons have two unique merits when used for extra high bit rate transmission systems:

1. the pulse shape does not distort in spite of the group dispersion of a glass fiber and

2. the pulse shape, whose width spreads in the presence of the fiber loss, can be reshaped only by appropriate amplifications.
Progress in Distributed Reflector Lasers
Authors: Suematsu Yasuharu
Published: February 2023

To overcome the effect of chromatic dispersion of single-mode fiber for high capacity optical fiber transmission at the lowest loss wavelength region of 1.55μm [1], semiconductor lasers with distributed reflectors operating in a fixed single-mode under rapid modulation have been developed [2]. Such DSM laser consists of tightly mode-controlled resonator, and is called as a dynamic-single-mode (DSM) laser or a single longitudinal mode laser[3].
Mass-Tranported GaInAsP/InP Buried-Heterostructure Lasers and Integrated Mirrors*
Authors: Liau Z. L. , Walpole J. N. , Tsang D. Z.
Published: February 2023

The recently developed mass-transport technique1-6 offers possibilities for novel devices in integrated optoelectronics. The first demonstration was a simple method for fabrication of GaInAsP/InP buried-heterostructure (BH) lasers, in which the transported InP filled in an undercut mesa and buried the active region.1-4 In this paper, we report continued developments. First, for a more complete characterization of the new BH lasers, theoretical and experimental studies were performed to improve 1ight-current (L-I) linearity at high output powers. Second, the mass-transport phenomenon has been used in a new procedure to improve chemically etched mirror facets.7 Vertical and smooth mirrors are obtained and the BH lasers with one such mirror have high device yield and threshold currents as low as 5 mA (lowest of quaternary lasers reported to date and an order of magnitude improvement from values previously achieved in etched-mirror lasers8-10). Finally, the mass-transport technique has been used to form next to the laser a slant mirror which has the capability of deflecting the laser output upward for surface emission.
Integrated Quantum Well Laser/MESFET Transmitter Using Selective MOCVD Epitaxy and Ion Implantation
Authors: Hong C. S. , Kasemset D. , Kim M. E. , Milano R. A.
Published: February 2023

The development of GaAlAs/GaAs integrated optoelectronic devices1 and circuits2 (IOEC) has been motivated by the potential of optical communications in high-density, high–data–rate interconnection of integrated circuits or signal processing systems. Recently, we have demonstrated a monolithic integration scheme which is compatible with the ion-implanted GaAs IC fabrication.3 Here, we report a high-performance integrated quantum well laser/MESFET transmitter using this integration scheme. The use of quantum well laser structures in the transmitter design is twofold. Low threshold can be obtained with a simple stripe geometry which facilitates integration, and second, quantum well lasers exhibit better dynamic characteristics than the conventional lasers under direct modulation.
Monolithically Integrated Dynamic-Single-Mode Coupled-Cavity Lasers
Authors: Coldren L. A. , Koch T. L.
Published: February 2023

Recent results with cleaved-coupled-cavity (C3) lasers have soundly demonstrated the viability of the coupled-cavity concept far tunable single-frequency semiconductor lasers[1,2]. Previous work with monolithic groove-coupled two-section lasers[3,4] suffered in performance because of the use of gain-guided base material, which foiled both CW operation and the realization of extremely dean longitudinal mode spectra.
Fiber Optic Recirculating Analog Delay Line
Authors: Wang C. C. , Moeller R. P. , Burns W. K. , Kaminow I. P.
Published: February 2023

Single mode fibers appear to be attractive for delay line applications as their low loss and high bandwidth should lead to a large time-bandwidth product, which determines the information storage capacity of the delay line. We are interested in analog signal storage for a noncoherent radar application1 in which the optical delay line provides a time delay equal to the radar pulse repetition frequency, and radar returns are stored until they can be subtracted from the next incoming pulse. The pulse subtraction provides an indication of a moving target. Design considerations for the delay line are dynamic range, linearity, signal-to-noise ratio (SNR) and cancellation or signal-to-distortion ratio. By recirculating a 2 ns pulse around a 20 km single mode fiber five times, we obtain the equivalent of a 100 km or 0.5 msec delay and a time-bandwidth product of > 105.
High Frequency Modulation Characteristics of GaAs-Based Semiconductor Coupled-Waveguide Optical Modulators
Authors: Tada K. , Kawanishi S. , Wang M. H. , Tsuchiya M.
Published: February 2023

The coupled waveguide optical modulator/switch (the electrically switched optical directional coupler) is one of the most important components in guided-wave and integrated optics, and several device structures for GaAs-based or InP-based semiconductors have been devised[1-11]. All of them are based on the electrooptic effect in the depletion region of the reverse-biased pn junction or Schottky contact. Among them, a double-heterostructure (DH) device with pn junction in strip-loaded channel waveguide configuration as shown in Fig.1 is expected to have the lowest modulating voltage and modulating power per bandwidth P/∆f because of the most efficient overlap of the modulating electric field with the optical field [4,12]. Similar but homostructure devices were fabricaed by Carenco and others [13,14]. Recently GaAs-Al0.04Ga0.96As DH devices with nearly full switching characteristics have been fabricated for the first time [10].
High-speed modulation of semiconductor integrated etalon interference lasers
Authors: Antreasyan Arsam , Ranganath T. R. , Wang Shyh
Published: February 2023

Recently, there is a great deal of interest in achieving longitudinal mode stabilization of semiconductor lasers by introducing interferometric resonators [1-4]. Such lasers are capable of stable single longitudinal mode operation over an extended temperature range which would be ideal for high bit rate, long distance optical communications. In Ref. 1 we have reported stable single longitudinal mode operation over a temperature range of ΔT=23°C in a GaAs-GaAlAs interferometric semiconductor laser, the integrated etalon interference (IEI) laser. The IEI laser consists of a resonator having one curved segment (L2) joined at both ends to two straight segments (L1 and L3) as shown in Fig. 1. Lateral guiding is provided by a buried heterostructure (BH) type laser cavity. Interference is caused by the internal reflection and lateral mode conversion at the junction discontinuity between straight and curved waveguides.
Z-Axis Propagation and the Avoidance of Optical Damage in Lithium Niobate Waveguides
Authors: Holman R. L. , Busch J. R. , Verber C. M. , Wood V. E. , Hartman N. F. , Cressman P. J.
Published: February 2023

Optical components based on lithium niobate waveguide circuits are being widely considered for high-speed switching, modulation, phase-shifting, computation, and signal processing tasks in optoelectronic systems. One potential performance limitation is due to the laser-induced optical degradations that occur during prolonged use. Waveguide fabrication process improvements can be applied, in conjunction with more modest laser power densities and longer laser wavelengths, to reduce or forestall such performance degradations. These methods, though important, may not be sufficient to solve the problem in many applications.
Anisotropic Polarizers for Ti: LiNbO3 Strip Waveguides
Authors: Papuchon M. , Enard M. , Thyagarajan K. , Vatoux M.
Published: February 2023

Polarizers are important devices for integrated optic applications. Several solutions have been already proposed and experimentally verified with different types of waveguides. In general they can be separated into two classes:

The polarizers based on a differential attenuation for TE and TM and the polarizers working on a principle similar to anisotropic devices in classical optics.
Fiber-Optic Gyroscope Development
Authors: Udd E. , Cahill R. F.
Published: February 2023

Fiber-optic gyros offer solid-state rotation sensing capability with the intrinsic potential advantages of high reliability, small size, and low cost. A particularly attractive aspect of this technology is its potential adaptability to strapdown inertial systems, which are anticipated to be in widespread use in the future. In order to be useful in many of these applications, wide dynamic range, accurate scale factor and cold start capabilities are required. The phase-nulling concept [1,2] allows the fiber-optic gyro to meet these goals through its ability to accurately monitor fringe position. Methods that allow scale factor correction and in-flight cold-starts using this fringe-monitoring capability are described for the first time.
Phase Modulation Approach to Closed-Loop, All-Fiber-Optic Gyroscope and Scale Factor Stabilization
Authors: Kim B. Y. , Shaw H. J.
Published: February 2023

Optical fiber gyroscopes showed high sensitivity and long term stability at zero rotation rate to make their practicability promising.1-3 It is also recognized that a closed-loop operation of fiber-optic gyroscope provides wide dynamic range of rotation sensing. Frequency shifters4 and magneto-optic effects5 have been utilized to generate a nonreciprocal phase shift that nulls out the rotation induced Sagnac phase shift for closed-loop gyroscopes. However, these types of closed-loop gyroscopes are not yet realized in an all-fiber configuration because suitable devices are not available at present in fiber form.
Optical amplifiers for communication systems
Authors: O'Mahony M. J.
Published: February 2023

Semiconductor laser amplifiers have become of considerable interest in recent years. As direct optical amplifiers they will play an important role in future optical communication systems.
Continuously wavelength-tunable bundle-integrated-guide lasers with distributed Bragg reflector in the 1.5-μm region
Authors: Tohmori Yuichi , Komori Kazuhiro , Arai Shigehisa , Suematsu Yasuharu , Oohashi Hiromi
Published: February 2023

Continuous wavelength tuning in an integrated semiconductor laser is very attractive for optoelectronic applications. The first demonstration of fine wavelength tuning in a so-called dynamic single-mode (DSM) laser1 was reported as a butt-jointed builtin (BJB) distributed Bragg reflector (DBR) type.2 Furthermore, we presented an improved integrable DSM laser with a novel bundle-integrated-guide (BIG) DBR and demonstrated low-threshold current cw operation.3,4
Compact miniaturized acoustooptic Bragg cell in GaAs-GaAIAs waveguide
Authors: Lii C. J. , Tsai C. S. , Lee C. C.
Published: February 2023

Bragg diffraction of guided-optical waves from the surface acoustic waves (SAW) and the resulting acoustooptic (AO) Bragg devices in LiNbO3-based planar optical waveguides have been extensively studied.1 In fact, utilization of the resulting wideband Bragg cells for development and realization of integrated-optic rf signal processors has become an international effort. Spherical waveguide AO Bragg cells in LiNbO3 explored most recently2 have also demonstrated a number of potential applications in rf signal processing and optical frequency shifting. Such spherical waveguide AO device modules have been shown to possess a number of unique features that enable them to be more readily interfaced with the single-mode optical fibers.
Diffusion and modal characterization of Ag+–Na+ exchanged channel waveguides
Authors: Najafi S. I. , Ramaswamy R. V.
Published: February 2023

Ion-exchanged glass waveguides are expected to form the basis for the potentially inexpensive passive integrated optical components compatible with single-mode optical fibers. Recently, an improved electrolytic release technique,1 where silver ions were introduced into a bath of molten NaNO3 containing the glass substrate with the Ag+ concentration controlled to better than ± 1 μg, was used to fabricate low-loss (≈0.1-dB/cm) optical waveguides by using Ag+–Na+ exchange at elevated temperatures.
Hybrid optical integration with high-silica channel waveguides on silicon
Authors: Kawachi Masao , Kobayashi Morio , Miyashita Tadashi
Published: February 2023

High-silica channel optical waveguides, being compatible with high-silica optical fibers, appear promising for constructing guided-wave optical de vices for practical use.1-3 A hybrid integration of light sources/detectors to high-silica waveguides on silicon substrates for the purpose of realizing an active guided-wave multi/demultiplexer is described.
A Low Crosstalk 4x4 Ti:LiNbO3 Optical Switch with Permanently Attached Polarization-Maintaining Fiber Arrays
Authors: Bogert G. A. , Murphy E. J. , Ku R. T.
Published: February 2023

We describe a single polarization, non-blocking 4x4 Ti:LiNbO3 optical switch array with very low single switch crosstalk (≤ - 35dB). The inputs to one of the several devices made have been permanently attached to four laser transmitters using polarization maintaining fiber. For this purpose, an array of four fibers was assembled using specially designed silicon grooves and externally keyed polarization maintaining fiber1. The polarization maintaining fiber was lensed and aligned to the laser in a standard package.
A Novel Δβ Phase Reversal Mach-Zehnder Interferometer
Authors: Thaniyavarn Suwat
Published: February 2023

An electro-optic Mach-Zehnder Ti-LiNbO3 waveguide interferometer is by far the most popular optical intensity modulator. In this paper, we show that the modulation depth characteristics of the device is degraded when there is optical coupling between the two interferometer arms. A novel design of M-Z interferometer having a small interarm spacing is described. High modulation depth is achieved by the use of a multi-section electrode structure with alternating applied voltage polarities.
Multiple quantum well waveguide modulators
Authors: Wood Thomas H. , Weiner Joseph S.
Published: February 2023

A number of device technologies for integrated optoelectronics have been developed, including electrooptic devices in lithium niobate and electroabsorptive III–V semiconductors.1 However, there is interest in devices that could be faster and smaller, made simply, and integrated with sources and detectors. Such devices would include highspeed optical modulators and switches for lightwave systems, low switching-energy optically bistable devices, and spatial light modulators.
Monolithic Nd:YAG fiber laser
Authors: Nightingale J. L. , Byer R. L.
Published: February 2023

We report on a monolithic resonator single-crystal Nd:YAG fiber laser. The laser resonator structure is simply formed by the fiber waveguide and the polished and coated fiber endfaces. The fiber oscillator is 6.5 mm long with a mean diameter of 47 μm. The lowest-order spatial mode for such a fiber has a beam waist of 15 μm, implying a Rayleigh length in YAG of 1.2 mm. The fiber laser is thus ~5-R lengths long and may be considered a guided-wave device.
Pulsed operation of an array of diode lasers with feedback in the Fourier plane and a chirp of less than 7.5-MHz measurement resolution
Authors: Anderson K. K. , Rediker R. H. , Van Ruyven L. J.
Published: February 2023

A spatial filter (a series of 3.1-µm slits, 10.42-µm center-to-center spacing) has been placed at the Fourier plane of five external cavity diode lasers as illustrated in Fig. 1. The five antireflection-coated diode lasers are focused onto the spatial filter and then reimaged by a second lens onto a partially reflecting plane mirror at the other end of the cavity. Since all the distances between objects and lenses correspond to the focal lengths of the respective lenses, the radiation from the diode lasers undergoes a Fourier transform four times as it makes the round trip through the cavity. An ideal spatial filter, the exact Fourier transform of the laser diode array, would specify operation at a wavelength uniquely determined by the geometrical spacings of the array and the spatial filter.
Four-watt continuous GaAIAs laser grown by metal-organic chemical vapor deposition
Authors: Harnagel G. L. , Scifres Donald R. , Kung H. H. , Welch D. F. , Worland D. P. , Cross P. S. , Burnham R. D.
Published: February 2023

Multiple-stripe lasers are promising sources of high-power monochromatic cw optical energy. Lasers with ten stripes have been reported to produce in excess of 800 mW cw,1 while the highest cw power attained to date was 2.6 W from a single facet.2 These lasers have demonstrated their usefulness in pumping Nd:YAG lasers.3,4 Higher-power laser diode arrays can be realized in principle merely by adding more stripes; however, as the width of the laser approaches and exceeds the cavity length, amplified spontaneous emission (ASE) competes for carriers and hinders lasing action.5 Evidently, lasers with more than ~0.4 mm of active width and ~0.25 mm of cavity length must incorporate structures to preclude ASE.
Coupling among parallel waveguides
Authors: Hardy Amos , Streifer William
Published: February 2023

A new coupled-mode formalism1,2 is employed to analyze wave propagation and power transfer among N-parallel waveguides. The waveguides need not be identical. In the derivation, which will not be presented, we retain a residue field that is the difference between the exact array mode and superposition of the individual waveguide modes. By requiring that the residue field be orthogonal to each individual waveguide mode, we obtain a formulation in the same form as the usual theory but with more accurate propagation constants and coupling coefficients. A comparison of array modes and their propagation constants as computed by the new theory with the exact solutions shows that the new results are considerably more accurate than those obtained from the prior theory.
Low-loss broadband Ti:LiNbO3 waveguide phase modulators for coherent systems
Authors: Buhl L. L. , Alferness Rod C. , Divino M. D. , Korotky Steven K.
Published: February 2023

Coherent lightwave detection techniques offer significant system advantages including increased receiver sensitivity and flexibility for closely spaced wavelength-division multiplexing. For phase shift keyed coherent systems which offer particular sensitivity advantages, efficient low-loss broadband phase modulators will be required. Low loss is especially important, of course, to avoid sacrificing the sensitivity gained by using coherent techniques. Here we describe the design, fabrication, and characterization of very low-loss fiber-coupled Ti:LiNbO3 waveguide phase modulators fabricated on X-cut lithium niobate. Devices operating at λ = 1.55 μm with permanently attached connectorized pigtails have been made with total insertion loss of −1.8 dB, 8.5-V π phase voltage, and modulation bandwidth of ≃5 GHz. This device has been employed in heterodyne differential phase shift keyed coherent lightwave system experiments at data rates of 0.4 and 1 Gbit/sec.1
Evolution of optoelectronic integrated circuits
Authors: Hayashi Izuo
Published: February 2023

A variety of semiconductor optical devices have been utilized in optical communications and in other optical systems. They are all discrete devices and used with their electronic circuits. In the future, monolithic integration of optical devices with associated electronic circuits, optoelectronic integrated circuits (OEIC), will become important. The monolithic integration, the OEIC, will provide superior characteristics, such as higher speeds, compared with discrete devices. For example, ultrahigh speed communication systems will require such OElCs.
High-speed and low-chirp GaInAsP/InP optical intensity modulator
Authors: Soda H. , Nakai K. , Ishikawa H. , Imai H.
Published: February 2023

High-speed and low-chirp external optical intensity modulators are important for future high-bit rate transmission systems, because in direct modulation of a laser diode the transmission bandwidth is limited by the large chirp during relaxation oscillation. A GaInAsP/InP optical intensity modulator [1], [2] is one of the candidates for such an external modulator. However it has been recently pointed out that some chirp is caused in such an electroabsorption modulator by the accompanied phase modulation [3]. Until now the dynamic spectral broadening factor αE which characterizes chirp was obtained only from a ratio of average power in optical sidebands to carrier power under sinusoidal modulation [2]. But it is necessary to evaluate, the chirp under large signal pulse modulation in order to apply to the system. Here we report high-speed and low-chirp characteristics in a newly developed GaInAsP/InP optical intensity modulator.
Buried Low-Loss Fiber-Compatible Single-Mode Ion-Exchanged Channel Waveguides
Authors: Cheng H.C. , Zhenguang H. , Miliou A. , Srivastava R. , Ramaswamy R.V.
Published: February 2023

Glass waveguides made by ion-exchange technique are potential candidates for integrated optic applications such as power dividers, star couplers and multiplexers. Although recent reports [1] have demonstrated significant progress in understanding of the basic ion-exchange process, and in the fabrication of low-loss waveguides and I-O components, the structures have not been optimized for a given application such as 1.3μm operation of single-mode fiber communication systems. Most of the work reported to date has been on surface channel waveguides which are shallow, lossy and incompatible with the fibers.
LiNbO3 - A Practical Optoelectronic Waveguide Technology?
Authors: Booth R.C. , Beaumont A.R. , Lawrence M.
Published: February 2023

LiNbO3 electro-optic waveguide technology and associated devices have now been studied for over 15 years. Initially the use of these components was limited to a few specific applications such as optical modulators and simple switches [1]. With the widespread implementation of monomode optical fibre telecommunication and sensor systems however there has been an increased demand for a wide range of optical components such as filters, polarisation controllers, frequency translators etc [2]. Many of these functions have now been implemented in the laboratory using LiNbO3 electro-optic waveguide technology and there is currently a growing commercial interest in developing this technology to produce a wide range of active optical waveguide devices.
Guided-Wave Polarization Splitter Based on Two-Mode-Interference
Authors: Neyer A. , Dang D.
Published: February 2023

Polarization diversity is considered a useful technique in coherent receiver design in order to avoid polarization controllers /1/.One of the optical key components in these systems is the TE-TM polarization splitter. Several guided wave configurations have been proposed and realized using intersecting waveguides /2,3/ or directional couplers /4/. The intersecting waveguides may be operated passivly whereas the directional coupler type polarization splitter requires a DC-tuning voltage for adjusting the TE-crossover.However, in the case of intersecting waveguides, care must be taken in the design of the intersecting region, since a simple Δn-construction /2/ leads to an increased differential loss of both exited modes and, consequently ,to a reduced splitting ratio, whereas the superposition of two titanium stripes to built up the intersection /3/ is sensitive to Δn-asymmetries whith the consequence of increased crosstalk /5/.This paper explores the capability of two-mode-interference (TMI)devices as polarization splitters. The potential of electrooptic tuning in LiNbO3-devices is discussed and experimental results on passive crossing waveguides with a specially designed intersection region in Ti:LiNbO3 are presented for λ = 1.3 µm.
Stability of Ti:LiNbO3 Waveguide Modulators in an Optical Transmission System
Authors: Giles C.R. , Korotky S. K.
Published: February 2023

Lithium niobate waveguide electrooptic devices have exhibited state-of-the-art performance in experimental lightwave systems [1]. Of paramount importance for their introduction into field system use is their operational stability and immunity to environmental changes. To date, a number of phenomena affecting the stability of Ti:LiNbO3 devices have been identified, including pyroelectric biasing [2], photorefractive damage [3], buffer layer drift [4], and humidity sensitivity[5]. Here we have quantified the stability of a class of Ti:LiNbO3 external modulators by long-term measurements of bit-error-rate (BER) performance in a 1 Gb/s optical transmission system. We found that long-term changes of the optical bias point caused no more than 0.6 dBO power penalty variation and that this penalty could be prevented through automatic feedback control.
Semiconductor Finite Elements for Integrated Optics
Authors: Young T. P. , Armstrong G. A. , Smith W.P.
Published: February 2023

The increased use of semiconductors in integrated optics has lead to a requirement for accurate device modelling and CAD tools. Among the numerical techniques available the Finite Element Method (FEM) has been used to analyse optical [1,2] and electronic [3] situations independently. In this paper we describe the first attempts to solve the electro-optical effects in semiconductor waveguides directly using finite elements. The software suite consists of two solver packages. OPTIC is a general purpose waveguide solver developed at GEC Research [4] and QUADS is an adaptive mesh semiconductor solver [3,5]. This paper summarizes the formulations for these analyses and the interfacing implemented and presents preliminary results.
GHz Bandwidth Magnetooptic Interaction in YIG-GGG Waveguide Using Magnetostatic Forward Volume Waves
Authors: Young D. , Tsai C. S.
Published: February 2023

From the dispersion relations of the magnetostatic waves (MSW) in Yttrium Iron Garnet - Gadolinium Gallium Garnet (YIG-GGG) thin film[1], it is found that while the theoretical bandwidth of the magnetostatic surface waves (MSSW) decreases considerably as the carrier frequency is increased, the theoretical bandwidth of the magnetostatic forward volume waves (MSFVW) increases substantially with the carrier frequency. We have noted previously the decrease of magnetooptic (MO) bandwidth from 487 MHz to 250 MHz in noncollinear coplanar guided-wave interaction involving the MSSW[2] as the carrier frequency was increased from 3.0 GHz to 7.0 GHz. However, in view of the dispersion characteristics of the MSFVW as mentioned above, the MO bandwidth associated with noncollinear coplanar interaction involving the MSFVW can potentially be significantly larger than that involving the MSSW as the carrier frequency goes beyond 2.0 GHz. Since it is of great interest to accomplish wideband MO interaction at high carrier frequency, the MSFVW was also used in our earlier work. For example, a MO bandwidth of 550 MHz (defined at the two -3dB points) and a TM0 to TE0 mode-conversion efficiency of 0.5% were obtained in our earlier experiment with the MSFVW centered at 3.0 GHz using a homogeneous (uniform) DC magnetic, field of 2250 Oe[3]. Recently, a technique for enhancement of MO bandwidth that employs inhomogeneous DC magnetic field[4] was reported[5]. In that particular work, an increase of MO bandwidth from 30 to 350 MHz (defined between the null points or approximately 125 MHz based on the conventional definition of -3dB points) centered at the carrier frequency of 1.45 GHz was obtained at the optical wavelength of 1.15µm by switching from a homogeneous to an inhomogeneous DC magnetic field. Specifically, an inhomogeneous field that varied from 2150 to 2350 Oe across an 8.0 mm aperture of the MSFVW transducer was used. Due to the concomitant "channelization effect" with the resulting MSFVW the measured TM0 to TE0 mode-conversion efficiency was found to decrease from 1.0 to 0.03% by switching from the homogeneous to the inhomogeneous field.
Endless polarization control system with integrated optical Ti:LiNbO3 polarization transformers
Authors: Noé Reinhold , Heidrich Helmut , Hoffmann Detlef
Published: February 2023

In coherent optical transmission systems continuous or endless matching of the states of polarizations (SOPs) can be achieved by automatic control. The first working system was based on mechanical devices1. Earlier proposals for LiNbO3 exhibited a very narrow optical bandwidth2,3, required at least two devices4, or failed to demonstrate automatic operation under worst case conditions5. We present a very robust automatic polarization control system with Ti:LiNbO3 SOP transformers. The intensity losses remain below 0.12 dB even for worst case polarizations, with substantial multi-path reflexions present, and at high tracking speed.
Bandwidth Broadening of Travelling-Wave Integrated-Optic Modulators
Authors: Zolotov E.M. , Pelekhaty V.M. , Prokhorov A.M. , Tavlykaev R.F.
Published: February 2023

High-speed electrooptic travelling-wave integrated-optic modulators (TWIOM) are considered to be the key components of the sensor and communication system /I/. The main factor limiting the speed of LiNbO3 TWIOM is a mismatch between the microwave and optical velocities. The earlier proposed /2,3/ aperiodic Barker code phase-reversal electrode patterns can increase bandwidth-to-voltage ratio BVR but no more than 4 times as compared to a conventional device, and with the frequency response with the dips up to 5 dB. The paper presents the method for determining the dependance of the local electrooptical overlap integral and for designing the electrode pattern to obtain a flat frequency response FR with significant BVR increase.
Broadly-Tunable Dynamic-Single-Mode Multiple-Quantum-Well Semi-Insulating-Blocked Distributed-Bragg-Reflector Lasers at 1.5 μm
Authors: Koch T. L. , Koren U. , Miller B. I.
Published: February 2023

Broadly tunable semiconductor lasers [1-3] are expected to play a major role in both high-speed direct detection wavelength-division-multiplexed (WDM) systems and coherent heterodyne detection systems, and also may find applications in new optical switching architectures. In this paper we describe the structure and performance of tunable single-longitudinal-mode InGaAs/InGaAsP multiple-quantum-well (MQW) distributed-Bragg-reflector (DBR) lasers operating at 1.5 μm. These lasers display low threshold, excellent differential quantum efficiency, large tuning range, with both low chirp under high-speed direct modulation and narrow linewidth under CW operation.
An InGaAs/InGaAsP Distributed Feedback Quantum Well Laser With an Intracavity Phase Modulator
Authors: Koren U. , Koch T.L. , Miller B.I. , Shahar A
Published: February 2023

Quantum well (QW) lasers and modulators have been reported extensively in the GaAs/GaAlAs material system. As optical fibers have a loss minimum at 1.55 micron wavelength, there is a strong motivation to explore quantum well devices in this wavelength range for the special requirements of lightwave communication systems. Recently we have reported a four quantum well separate confinement heterostructure InGaAs/InGaAsP laser operating at 1.54 micron wavelength with a high output power and a low internal loss [1].
Integrated-Optical 2×2 Switch with Y-Branch Mode Splitters*
Authors: Johnson L. M. , Roussell H. V.
Published: February 2023

A wide variety of integrated-optical 2×2 switch designs have been either proposed or demonstrated.1-3 Here we report the initial demonstration of a 2×2 switch4 consisting of a Mach-Zehnder interferometric modulator and asymmetric Y-branch mode splitters. This switch design contains neither directional couplers which have critical fabrication tolerances nor active mode splitters which require large drive voltages. In this initial device we have demonstrated switching at a wavelength of 1.15 μm with crosstalk of less than -15 dB.
Low Crosstalk and Polarization Independent Ti:LiNbO3 Optical Waveguide Switch for OTDR
Authors: Tanisawa Y. , Aoyama T. , Ishikawa R. , Kondo M. , Ohta Y.
Published: February 2023

High speed switching of a waveguide switch is very attractive for OTDR (Optical Time-Domain Reflectometer), because it enables to get information on optical transmission line with short dead zone (unmeasurable length). However, relatively high crosstalk and polarization dependent characteristics of conventional waveguide switches prevent from using for OTDR application. This paper presents a practical Ti:LiNbO3 waveguide switch for OTDR applications, especially in optical subscriber loop transmission systems.
Optical Two-Guide Coupler Switches In GaAs: Ideal and Nonideal Operation*
Authors: Molter Lynne A. , Haus Hermann A. , Johnson Leonard M. , Donnelly Joseph P.
Published: February 2023

The two-waveguide coupler switch has recently been studied theoretically[1-3] and ex perimentally[4] to determine the configurations in which complete extinction in the “off” state can be achieved. Different switching characteristics are predicted for the two configurations of the switch shown in Fig. 1, which have been analyzed using an exact solution to the slab-guide model of the structure[5] and various versions of improved coupled-mode theory[5]. Each coupler has a single input guide. In case 1 [Fig. 1(a)], it is the initially excited guide 1 which forms the coupler output[1-3,5]; in case 2 [Fig. 1(b)], the coupled guide 2 is used as the output guide. Ideal operation with complete extinction in the "off state is predicted in case 1, and is shown to be impossible in case 2. The reason for this is the shape of the modes of the input and output guides, and the overlaps of these with the modes of the coupled-guide region. To obtain zero crosstalk in case 1, the waveguides must be appropriately detuned from synchronism, and the device length must result in a π phase shift between the coupler modes for this value of detuning (i.e., a detuned coupling length which is shorter than the synchronous coupling length Lc). In case 2, the coupler must be Lc long to achieve good transmission in the "on" state, and no improvement in switching characteristics can be achieved by varying the length[5]. LiNbO3 two-guide switches with both output configurations of Fig. 1 have previously been characterized experimentally[5]. In that work, however, because all the devices were fabricated to have an interaction length of Lc, imperfect nulls were observed in both configurations (as predicted theoretically). The results presented here demonstrate a two-waveguide switch in which the signal can be completely extinguished in the "off state (within measurement capabilities).
Low Loss Channel Waveguides and Electrooptic Modulators in KTiOPO4
Authors: Bierlein John D. , Ferretti August
Published: February 2023

In addition to being a superior material for SHG of Nd:YAG and Nd:YLF, KTiOPO4 (KTP) has been shown to have electrooptic and dielectric properties that make it attractive for various optical waveguide devices (1). It's electrooptic waveguide modulator figure-of-merit (n3r/εeff) is nearly double that of any other candidate integrated optic substrate material. A waveguide fabrication process has been previously described which is based on ion exchange of Rb, Cs, and Tl for K using various molten nitrate salts (2). This process has given refractive index increases of up to 0.23 and the channel guides fabricated show essentially no lateral diffusion. Since this is a diffusion process waveguide refractive index and depth uniformity depend critically on the uniformity of the KTP substrate ionic properties. Early work showed that fairly large variations can exist in ionic properties of typical KTP substrates which in some cases led to relatively uniform guides in certain regions of the substrate to no guiding at all in other regions. Such large variations obviously make fabrication of useable devices difficult.