bluuebunny/crossref_metadata_2025 huggingface dataset:
Simultaneous fabrication of grating couplers and an optical waveguide by photopolymerization
Authors: Hosokawa Hayami , Horie Noriyoshi , Yamashita Tsukasa
Published: February 2023

A grating coupler1is an attractive component in integrated optics for laser-beam application systems, such as laser-beam deflectors2and optical pick-up heads,3because of its waveguide-air interface operation. However, mass production of grating couplers, which is necessary for practical use, has not yet been achieved because of the minute patterns having submicrometer-order periods. This paper reports a simultaneous fabrication of grating couplers and an optical waveguide by photopolymerization. This method is suitable for mass production.
Numerical analysis of a Ti:LiNbO3 polarization splitter: comparison of FEM and BPM results
Authors: Strake E. , Bersiner L. , Hempelmann U.
Published: February 2023

We compare results obtained from two numerical methods: (i) a local normal mode (LNM) description using modes computed by the finite-element method (FEM), and (ii) a three-dimensional beam-propagation method (BPM) for the analysis of a passive integrated-optical polarization splitter, which is, e.g., an essential element of a tunable integrated-optical wavelength multiplexer.1By indiffusion of Ti into LiNbO3, directional couplers with large polarization sensitivity can be realized owing to the strong anisotropy of the diffusant-induced index variations.2
Polarization-independent switches on LiNbO3
Authors: Pohlmann T. , Neyer A. , Voges E.
Published: February 2023

The basic structure of the noninterferometric switch (Fig. 1) is built in three sections: two passive polarization splitters and a mode-converter section.1If no voltage is applied to the mode converter electrodes, arbitrarily polarized light incident in one of the two input arms will exit one arm. The quality of this defined switching state at zero voltage, which means the level of residual cross talk in the other output arm, depends only on the quality of the polarization splitters. By applying an appropriate switching voltage to the mode converter electrodes, the TE and TM components are transformed into their orthogonal counterparts, so that they are leaving the complementary output arm. (The structure is similar to that shown in Ref. 2).
Generation of permanent second-order susceptibility in lead-silicate glass fibers
Authors: Li Luksun , Wells Paul J. , Taylor Elizabeth R. , Payne D. N.
Published: February 2023

The creation of a permanent second-order susceptibility [χ(2)] for second-harmonic generation (SHG) in Ge-doped silica fibers has been reported by several authors using various techniques (exposure to IR,1. seeding with IR and its second harmonic,2dc-field poling with blue light,3and de field only4). Although the microscopic mechanism governing this interesting phenomenon is still not fully understood, it has been suggested that the alignment of defect centers plays an essential role.5Defect centers, however, are known to exist or can be induced in many amorphous materials, including a variety of compound glasses that are commercially available. These commercially available compound glasses provide a wide range of options for the fiber core and cladding materials. Moreover, the effect observed to date in Ge-doped silica fibers may be present in a different and stronger form in fibers fabricated from compound glasses. It is therefore interesting to study fibers fabricated from various compound glasses. In this paper we report the first results, to our knowledge, for the dc-field poling effect in lead-silicate glass fibers.
Quasi-phasematched Frequency Doubling over Several Millimeters in Poled Polymer Waveguides
Authors: Khanarian G. , Norwood R. A.
Published: February 2023

There is great interest in developing compact coherent light sources at wavelengths less than those of available AlGaAs/GaAs lasers, primarily for optical data storage applications. Several approaches have been pursued, one of the most promising of which is frequency doubling in nonlinear optical waveguides.[1] An attractive method for achieving efficient SHG in a waveguide is quasi-phasematching, and this has been demonstrated both in lithium niobate[2],[3] and poled polymers.[4] Useful features of quasi-phasematching include the ability to use the largest nonlinear coefficient of the material, optimize optical field overlaps, and operate at any wavelength where the materials are transparent. A critical parameter is the effective length, L
eff
, over which quasi-phasematching can be achieved, since the efficiency of SHG goes as L
eff
2. L
eff
depends on the size of random thickness and index variations in the waveguide layers, and on the coherence length dependence on thickness. We report here quasi-phasematching over a distance L
eff
≈ 0.4 cm by careful choice of materials and fabrication processes.
GaAs Multiple Quantum Well Waveguide Modulators on Silicon Substrates
Authors: Treyz G.V. , May P.G. , Latulipe D. , Basu S. , Wang W.I.
Published: February 2023

For applications such as optical interconnects1 it is desirable to have the ability to integrate optical modulators, waveguides and silicon electronics. One system of interest is the class of GaAs multiple quantum well (MQW) structures where optical modulation is due to the quantum-confined Stark effect (QCSE)2 integrated with GaAs/AlGaAs waveguides on Si.3 In support of this scheme, results obtained for GaAs on Si MQW reflection modulators have indicated that, in contrast to some GaAs on Si optical devices (e.g. heterostructure lasers), QCSE modulator structures are relatively insensitive to the defects associated with epitaxial GaAs on Si growth.4,5
Experimental Observation of Spatial Soliton Interactions
Authors: Silberberg Y. , Aitchison J. S. , Weiner A. M. , Leaird D. E. , Oliver M. K. , Jackel J. L. , Smith P. W. E.
Published: February 2023

Spatial optical solitons are self-trapped optical beams which propagate without changing their spatial shape because of the competing effects of diffraction and self-focusing in a nonlinear medium1. Self-trapped beams are known to be unstable in bulk media, and to lead to catastrophic self-focusing. They are stable, however, when diffraction is limited to one spatial dimension, such as in planar optical waveguides. The spatial soliton is described by the non;linear Schroedinger equation, and it is completely analogous to the temporal soliton in optical fibers. Spatial solitons have recently been reported in multimode CS2 waveguides2 and single mode glass waveguides3. The nonlinear contribution to the refractive index, essential for the observation of these solitons, can also give rise to interaction forces between pairs of solitons. These forces have been studied theoretically4 and have been experimentally observed in the temporal domain5. Here we report the first experimental observation of interaction between spatial solitons.
Ultrashort-Soliton Interactions in Optical Fibers
Authors: Hong B. J. , Yang C. C.
Published: February 2023

It is well-known that in single-mode optical fibers two picosecond-range fundamental bright solitons with the same phase attract each other when they are close; two such solitons with π phase difference are mutually repulsive. However, the scenarios of the interaction between two femtosecond-range solitons are quite different. The behaviors of femtosecond-range solitons in a single-mode fiber differ from those of picosecond-range solitons because of the higher-order dispersion, shock effect, and the more important Raman response function [1]. These effects are included in the generalized nonlinear Schrödinger equation [2]. By numerically solving this equation, it is discovered that the energy is redistributed between the two solitons during the interaction. Also, the two solitons are separate eventually. The energy redistribution between the identical input solitons depends on the initial soliton separation and relative phase. Figures 1 and 2 show the evolution of the interaction between two identical solitons of 1.51 μm wavelength, 40 fsec width and 140 fsec initial separation. It is observed that when the initial relative phase is π as shown in Fig. 1, the leading soliton keeps pumping the trailing one. However, when the initial relative phase is 0, as shown in Fig. 2, the leading soliton first receives the energy pumped by the trailing one until certain distance where the relative phase between the two solitons becomes π. After this distance, the leading soliton keeps pumping the trailing one. Similar results can be observed in the collision of two femtosecond-range solitons with different central wavelengths. Figure 3 demonstrates the interactions of two solitons at 1.5 and 1.51 μm, respectively, with 0 and π initial relative phases. Detailed interpretations about interaction mechanism will be given. The dependences on other input parameters will also be presented.
Light absorption in waveguide-integrated photodiodes on InP
Authors: Kaiser R. , Mörl L. , Rehbein W.
Published: February 2023

Photodiodes monolithically integrated with low-loss waveguides exhibiting high quantum efficiencies at small lateral photodiode dimensions are important building blocks in optoelectronic integrated circuits (OEICs) for future optical communication systems in the 1.3-1.6-μm wavelength region.
Integrated waveguide/photodiodes with vertical impedance matching
Authors: Deri R. J. , Yasuoka N. , Makiuchi M. , Wada O. , Kuramata A. , Hamaguchi H. , Hawkins R. J.
Published: February 2023

Monolithic waveguide/photodiode integration is essential for many optoelectronic integrated circuits. Evanescently coupled structures (Fig. 1) offer advantages of single-step epi-growth, ease of diode junction placement, and low diode leakage. Conventional devices (with adjacent waveguide and absorber layers), however, exhibit high capacitance and low bandwidth because of the long diode length L required for appreciable absorption (>1 mm for 3.4-μm-thick guides).1,2 Use of thin waveguide layers can reduce2,4 L but also increases fiber-waveguide coupling difficulty. Here we present a novel vertical-impedance matching (VIM) approach that enhances diode absorption by insertion of matching layers between guide and absorber. We demonstrate 500% length reduction over conventional structures without compromising fiber coupling, capacitance, or ease of fabrication.
Uniformity of driving voltage in Ti:LiNbO3 waveguide devices
Authors: Fujiwara T. , Watanabe A. , Mori H.
Published: February 2023

One of the most important issues in integrated-optic applications of Ti:LiNbO3waveguides is the uniformity of driving voltage among device elements fabricated on a single chip. In LiNbO3-based matrix switches using directional coupler switch elements, scatter of the switching voltage has been reported.1,2We report on a novel method of measuring a spatial variation of the electro-optic effect on a number of positions on x- and z-cut LiNbO3substrates in Ti-diffused form.
Stationary states of nonlinear waveguides with arbitrary cross sections
Authors: Boardman A. D. , Twardowski T.
Published: February 2023

There is great worldwide interest in nonlinear waveguide propagation.1 To date, however, work in this area has concentrated on single interfaces2 or planar waveguides,3,4 where the wave is confined in only one lateral dimension, because a study of nonlinear waveguides with complicated cross sections requires the use of advanced computing techniques. A study is now presented for guides with two-dimensional lateral confinement with cross sections that are significant in integrated and fiber optics. Exact stationary states are calculated by using a finite-element method, yielding field component profiles and the total power flow down the guide for a range of possible material and wave parameters. Because the simplest cases to deal with conceptually are rectangular and rib waveguides, these are discussed in detail. It is shown that the finite-element method is ideally suited to the solution of waveguides with arbitrary cross sections such as, for instance, in-diffused guides of the type used in directional couplers. Structures in which the substrates, claddings, or the waveguiding medium itself are anisotropic, owing to low symmetry or magneto-optic effects, are easily incorporated into the general framework and several examples will be given. The rectangular waveguide will be used to show, in detail, how the nonlinear guided waves reduce to the now familiar TE- and TM-polarized states of a nonlinear planar waveguide, as one of the dimensions of the rectangular guide begins to dominate the other. It is shown that this benchmarking onto known results in simpler structures gives valuable insight into guiding by general cross-section guides. Finally, it is emphasized that the calculations reported here are a necessary precursor to an understanding of stability, and propagation evolution, of nonlinear waves in these general structures.
Accurate Gaussian and equivalent-step-index approximations for highly nonlinear waveguides
Authors: Sammut R. A. , Pask C.
Published: February 2023

The electromagnetic field of the fundamental mode propagating in a waveguide whose core has a large nonlinear coefficient may be significantly distorted from that of the corresponding linear mode. In the special case of a step-index, planar waveguide this field can be described in terms of elliptic functions,1 but for more general refractive-index profiles numerical solutions are required.
Theory of the Raman self-frequency shift of solitons: beyond the slowly varying envelope approximation
Authors: Afanasyev Vsevolod V. , Serkln Vladimir N.
Published: February 2023

The solitoti Raman self-frequency shift effect is considered in the time domain beyond the slowly varying envelope approximation. The influence of the oscillation nature of the mixed electron-nuclear Raman nonlinearity on the dynamics of femtosecond solitons interaction and decay is investigated.
Nd:MgO:LiNbO3 waveguide laser and amplifier
Authors: Lallier E. , Pocholle J. P. , Papuchon M. , de Micheli M. , Li M. J. , He Q. , Ostrowsky D. B. , Grezes-Besset C. , Pelletier E.
Published: February 2023

Nd:MgO: LiNbO3 is a promising material that combines the good laser gain of Nd3+with the electro-optic and nonlinear properties of LiNbO3.1-3 In a waveguide configuration, this combination offers the possibility of realizing highly efficient laser-diode-pumped lasers and amplifiers, self-frequency doubled lasers, integrated laser/modulator structures, etc. Recently, we reported the first demonstration of a channel waveguide laser with this material.4 In this paper we report on increased laser performances and the first amplifier measurements using a new, low loss, and more-confined waveguide structure.
Voltage-tunable four-channel Ti:LiNbO3 wavelength-division multiplexer
Authors: Lin Jack P. , Thaniyavarn Suwat
Published: February 2023

Wavelength-division multiplexing (WDM) offers a simple method for increasing information capacity. Integrated optical WDM devices are advantageous because of the ease of fabrication and the potential for combining several devices on the same chip. Implementing WDMs on an electro-optic LiNbO3 substrate provides the flexibility for voltage tuning the channels to match available laser sources. A dual-channel WDM based on the two-mode-interference (TMI) waveguide structure has already been demonstrated.1 A two-stage, four-channel WDM based on the TMI concept has previously been proposed and analyzed.2 In this paper we report the first demonstration of such a four-channel WDM for 1.3-µm wavelength operation. The device is illustrated in Fig. 1. It consists of three dual-channel TMI WDMs that are cascaded in two stages. The long TMI section (L3) is twice as long as the short TMI sections (L1 and L2).
Integrated-optical, acoustically tunable (de-)multiplexer of adjustable coupling strength
Authors: Herrmann H. , Ricken R. , Schiller O. , Schröter M. , Sohler W.
Published: February 2023

We report a combination of an acousto-optic TM-TE mode converter using a acoustic channel guide1 and a double-mode segment, passive TM-TE polarization splitter2 on the same X-cut LiNbO3 substrate (see Fig. 1). This new integrated-optical circuit represents a low-power, acoustically tunable, narrow bandwidth (de-)multiplexer (wavelength filter) of adjustable coupling strength (transmission) designed for a wavelength range near λ = 1.5 μm. Simultaneously, it is the basic structure for the design of a polarization-independent device (with two such structures combined) and of even more complicated integrated-optical circuits like polarization-dependent and polarization-independent wavelength switching matrices.
Analysis of channel-waveguide grating output couplers
Authors: Matsumoto Masayuki
Published: February 2023

Recently channel-waveguide grating couplers with finite waveguide width have been fabricated for use in hybrid optoelectronic integrated circuits.1 For the quantitative analysis and design of such channel-waveguide grating devices,1,2 we need to develop analysis methods for three-dimensional periodic waveguides.
Analysis of the blazing effect in second-order gratings
Authors: Matsumoto Masayuki
Published: February 2023

In this paper we analyze the blazing effect in second-order gratings with asymmetric tooth shapes and examine the applicability of the effect for improving the efficiency of grating-coupled surface-emitting (GSE) lasers. Figure 1 shows a schematic of the second-order distributed Bragg reflector (DBR) analyzed in this paper. A residual or buffer layer t
g
<
x
< t
g
+ t
b
is introduced to control the coupling between the guided waves and the grating, which has a relatively large thickness in order to obtain the effect of blazing.
Polarization properties of Bragg reflection waveguides
Authors: Lenz Gadi , Salzman Joseph
Published: February 2023

Many applications in integrated optics rely on propagation or detection of a single polarization state of an optical carrier. Thus, guided-wave components with high polarization rejection ratio are required. Conventional devices are usually based on birefringence mechanisms or elaborate schemes for cutting off the TM propagating mode.
Nonlinear holography for wave-front conversion, frequency doubling, and parametric amplification
Authors: Russell P. St. J.
Published: February 2023

When beams at frequencies ω0 and 2ω0 are mixed in a medium with third-order nonlinearity χ(3) a pattern of dc polarization fringes Pdc(3) results whose grating vector is K = kso − 2kpo, where kpo(r) and kso(r) are the wave vectors at ω0 and ω0. In germanosilicate optical fibers, Pdc(3) breaks the centrosymmetry of the amorphous core material (possibly by color-center alignment), creating a periodically modulated χ(2) = χ
m
(2)cos(K · r). This χ(2) structure automatically phase matches the fundamental light to its second harmonic (SH).1,2 Because the wave fronts of the participating beams do not have to be planar, the phenomenon may be labeled nonlinear holography.3 In a germanosilicate film waveguide, for example, a SH image beam at 2ω can be reconstructed, potentially with high efficiency, from a reference pump beam at ω ≈ ω0. Phase-matched degenerate parametric amplification of a complex signal wave front at ω is also possible, and in a ring cavity parametric oscillation would permit high-efficiency re-creation of a complex beam at ω.
Local normal-mode expansion for analysis of second-harmonic generation efficiency
Authors: Isoshima Takashi , Tada Kunio
Published: February 2023

Recently, as high efficiency phase-matching method for optical second-harmonic generation (SHG), the quasi-phase-matching method using a periodic structure is attracting a lot of attention. To estimate precisely the SHG efficiency in a periodic structure waveguide, the exact electric-field distribution in a waveguide as a function of a longitudinal coordinate is required. This is true, not only in the case of a corrugated waveguide structure, but also in the case of the periodic domain inversion structure in a LiNbO3 (LN) waveguide as the domain inversion process also causes a linear refractive-index change. To describe the electric-field distribution, we use an ideal normal-mode expansion, which uses modes for a waveguide of averaged width and refractive index. However, many modes must be considered to estimate the nonlinear polarization exactly and that requires a large amount of calculation.
Three-dimensional coupled mode method for simulation of coupler and filter structures
Authors: Weinert C. M.
Published: February 2023

Numerical simulation of coupler structures with non-constant geometry along the direction of wave propagation can be solved by propagation methods or by coupled mode theory (CMT).
High speed and low loss, bulk electroabsorption waveguide modulators at 1.3 µm
Authors: Rolland Claude , Mak Gary , Prosyk K. L. , Maritan C. M. , Puetz N.
Published: February 2023

Over the past few years, external modulators have become increasingly attractive for applications in high speed, long-haul optical transmission systems. To avoid additional complexity and cost of monolithic or hybrid integration of lasers with modulators, directly modulated lasers may be preferable however the lowest frequency chirp demonstrated so far under high speed modulation have been with external modulators. Low loss1 and high speed2 modulators have previously been reported in different structures. The combination of these two properties in one device would be highly desirable for high speed communications. In this paper, we describe a λ = 1.3 µm bulk electroabsorption waveguide modulator based on a new multi-quaternary layer design with low insertion loss, high extinction ratio, low operating voltage, and a modulation bandwidth in excess of 9 GHz.
Heterostructure collinear graded index polymer waveguide modulator
Authors: Chen Ray. T. , Sadovnik Lev , Rabinson Daniel , Jannson Tomasz , Jannson Joanna
Published: February 2023

We are reporting a novel graded index (GRIN) collinear asymmetrical polymer waveguide modulator. Disparity of the waveguide pair provides us with a much larger dynamic range of phase matching condition suitable for single-mode waveguide to multi-mode waveguide coupling. Formation of a universal polymer waveguide was made possible by tuning the guiding layer index profile from stepped index to graded index through a mass perturbation method.
Transparent boundary condition for beam propagation methods
Authors: Hadley G. Ronald
Published: February 2023

The beam propagation metnod is perhaps the most widely-used tool in the investigation of optoelectronic structures such as bent waveguides and branching structures. Unfortunately, this method has been notoriously weak in dealing with structures that allow radiation loss, since that radiation tends to reflect from the problem boundaries back into the solution region. The most common way of dealing with this problem (artificial absorbers1) has a number of well recognized drawbacks, the most serious being the large variability in absorption parameters from problem to problem. In this paper I will describe a new boundary condition algorithm that allows radiation to freely escape the problem without appreciable reflection, while prohibiting the flux of radiation back into the problem region. This boundary condition has no adjustable parameters, and does not require the use of extra mesh points or an expanded problem domain.
Very high bandwidth ln0.53Ga0.47As p-i-n detector arrays
Authors: Liu Y. , Govindarajan M. , Forrest S. R. , Tangonan G. L. , Jullens R. A. , Loo R. Y. , Pikulski J. L. , Jones V. L. , Johnson M. M.
Published: February 2023

It is well known that a key element in advanced photonic system architectures are arrays of sources and detectors. For example, such devices are useful in optoelectronic switching matrices,1 byte-wide communication, and active wavelength division multiplexing. The effective bandwidth of a system is equal to the bandwidth of a single optical channel multiplied by the total number of parallel channels. Hence, the achievement of very high frequency arrays is an important step in realizing systems which operate at terabit bandwidths and beyond.
Multimode interference couplers
Authors: Soldano L. B. , Veerman F. B. , Smit M. K. , Verbeek B. H. , Pennings E. C. M.
Published: February 2023

Experimental results are presented on a new type of planar (Multimode Interference) coupler. Two-mode interference (TMI) couplers (Fig. la) were reported already in 1977 as an alternative to weak synchronous couplers,1 they are shorter and less sensitive to variations in the fabrication process, and thus have a potential for application without trimming or tuning facility. Further, they exhibit less polarization dependence.
Integrated optical differential amplifier with large dynamic range for gigahertz bandwidth electrical signals
Authors: Gookin D. M. , Berry M. H.
Published: February 2023

Some optoelectronic differential amplifiers have been developed for gigahertz signal bandwidths.1–3 These previous optoelectronic approaches were based on a balanced heterodyne receiver design. The electrical-to-optical and optical-to-electrical conversion was used to electrically isolate the two input signals. The actual signal subtraction was done electronically. In the optoelectronic differential amplifier we present here we do the signal subtraction while still in the optical domain. We have eliminated the need for a balancing network, increased the usable bandwidth, developed a variable gain mechanism, and improved the linear and spurious free dynamic range over previous opto-electronic differential amplifiers.
Determination of refractive index of MBE grown InGaAlAs from composition
Authors: Han Sang-Kook , Srivastava Ramakant , Ramaswamy Ramu V.
Published: February 2023

Recently the InGaAlAs system has attracted considerable attention since its band-gap can be tuned over a relatively large wavelength-range (0.85-1.60μm) by varying the ratio of Ga to Al. Moreover, this material system is a promising alternative to InGaAsP for the fabrication of laser diodes emitting at 1.55μm. Inspite of the growing interest in this material system, very little work has been reported on its refractive index and material dispersion.1,2 In this paper, we develop semi-empirical relations to predict the refractive index and material dispersion of bulk In0.53Ga0.47-yAlyAs in the transparent wavelength region. Our approach is based on the modified single effective oscillator model (MSEOM)3 which has been used successfully in several other III-V compound semiconductors.4
CW optical damage threshold of Rb:KTP waveguides
Authors: Buritskii K. S. , Dianov E. M. , Maslov V. A. , Chernykh V. A. , Shcherbakov E. A.
Published: February 2023

Optical waveguides in potassium titanyl phosphate (KTP) are of particularly great significance in the field of integrated optics because of their unique properties required for designing integrated optical devices, in particular, electrooptical light modulators and nonlinear frequency converters.1The main advantage of KTP is a low susceptibility to laser induced damage. The bulk optical resistance of KTP is 2-3 orders as larger as that of lithium niobate, which is widely used in integrated optics. As regards LiNbCh waveguides, they exhibit optical damage in the visibleand near IR region at the power of about 1 mW, whatincreases loss in them.2It has been shown recently that optical damage is not observed in proton-exchanged LiTath waveguides at the power of 70 mW (at 0.82 μm).3Similar measurements of KTP waveguides have not been carried out, however, these waveguides are believed to preserve their properties at a much higher light power density.
Raman gain polarizational asymmetry in low birefringence fibers
Authors: Mirtchev T. P. , Minkovski N. I. , Tomov Iv. V.
Published: February 2023

It is well known that the stimulated Raman scattering (SRS) gain is maximal for equally (linearly or elliptically) polarized pump and stokes waves1 and is a factor of 2 lower if they are depolarized. The latter case corresponds even to polarization maintaining fibers, but with relatively high birefringence. Our investigations show that in the intermediate case of low birefringence fibers excited by high power pump pulses the polarization dependence of the dispersionless SRS gain may substantially differ from the cited above. For these conditions the third-order nonlinear polarization include the additional terms2 of the type 1/3

A
x
*

A
y
2

exp

(

−
2
βz

)

where Ax and Ay are the slowly varying amplitudes of the pump pulse components and β is the propagation constants difference. These terms are responsible for the polarization ellipse rotation effect which causes the extensively studied instability of CW waves polarized close to the fast axis of a low birefringence fiber.9 It is also possible to introduce the integral Raman gain connected with the slow mode component respectively where gr is the gain coefficient and L is the fiber length. When ellipse rotation and SRS occur simultaneously the dynamics of the Raman scattering is strongly affected because the coupling of the two orthogonal components of the pump pulse, which causes periodic power exchange between them, always increases Gx and respectively lowers Gy. The relative importance of this effect depends on the angle θ between the input pump pulse polarization and the slow axis. For θ ≈ 0 the intermodal power coupling is negligible and the overall Stokes conversion efficiency is approximately equal to that for θ = 0 or θ = π/2 (determined by G= grP L / Seff, where P is the total input pump power and Seff is the fiber core effective area). If θ ≈ π/2 the power transfer is significant, the gain is distributed along the two axis and the conversion efficiency decreases.
Low-pass demultiplexing tapered fused fiber coupler using residual core guidance: modeling and realization
Authors: Black R. J. , Archambault J. L. , Gonthier F. , Lacroix S. , Ricard D. , Bures J.
Published: February 2023

With variation of tapering profile, coupler cross-section geometry and exploitation of the multi-layer nature of finite-cladding fibers, one may obtain a large range of wavelength responses for fused tapered couplers1-5 that can be quite different from those of classical designs.
High-performance magnetostatic backward volume waves-based guided-wave magnetooptic Bragg cells with application to wide-angle light beam scanning
Authors: Pu Y. , Wang C. L. , Tsai C. S.
Published: February 2023

The magnetostatic backward volume waves (MSBVW) possess the following inherent advantages(1) over the magnetostatic forward volume waves (MSFVW) in terms of the performances of the resulting guidewave magnetooptic (MO) Bragg cells(2): (1) The MSBVW of significantly higher carrier frequency can be excited at the same dc magnetic field, (2) The first passband in which the MO Bragg cell commonly operates is located at the high frequency end for the MSBVW, but at the low frequency end for the MSFVW. For example, we have calculated and concluded that for the same dc magnetic field, the operating band of the MSBVW is located higher than that of the MSFVW by at least 4.90 GHz for the pure-YIG (saturation magnetization 4πMs=1750 Oe) and 5.04 GHz for the Bi-YIG (4πMs=1800 Oe) samples. It is therefore desirable to realize guided-wave MO Bragg cells that utilize the MSBVW. Guidedwave MO interaction with the MSBVW was first studied using a Bi Lu-YIG-GGG waveguide.3 However, to the best of our knowledge, neither study on guided-light beam scanning by the MSBVW nor construction of MSBVW-based MO Bragg cells has been reported heretofore. In this paper, we report the first realization of high-performance MSBVW-based MO Bragg cells in pure and Bismuth-doped yttrium iron garnet-gadolinium gallium garnet (YIG-GGG) waveguides, and the first demonstration of wide-angle light beam scanning using such MO Bragg cells. A detailed comparison of the measured performance figures for the MSBVW- and the MSFVW-based MO Bragg cells is also presented.
All-optical time domain chirp switches with one picojoule switching energy
Authors: Islam M. N. , Chen C.-J. , Soccolich C. E.
Published: February 2023

Soliton dragging logic gates1 are one example of a novel time domain chirp switch (TDCS) architecture that is applicable to materials other than fibers. The logic in a TDCS is based on time shift keying where a "1" corresponds to a pulse that arrives within the clock window and a "0" to either no pulse or an improperly timed pulse. Although TDCS's generally incur a latency penalty, for high bit-rate applications TDCS's lead to low switching energies. For example, we illustrate an all-fiber inverter with a 1pJ switching energy and a fan-out of 28.
A picosecond optical-Kerr-shutter switch using an organic solution in a capillary waveguide
Authors: Kobayashi Hideki , Kanbara Hirohisa , Kubodera Ken'ichi , Shuto Yoshito
Published: February 2023

Optically-controlled optical switches will be key elements in time-division multiplexing devices for future optical communication and computing systems. Glass fibers have been applied to such switches1 utilizing easy fabrication of long interaction length and small core diameter in fibers, however, their optical nonlinearities are quite small. Organic nonlinear optical materials have been applied to efficient optical switches.2,3 In this paper, an even more efficient, high-speed optical- Kerr-shutter switch is demonstrated using a recently-synthesized organic material, 4-(N,N-diethylamino)-β-nitrostyrene (DEANST),4 which has large third-order susceptibility x(3) and high solubility.
Ultralong distance transmission using solitons and erbium fiber amplifiers
Authors: Mollenauer L. F.
Published: February 2023

Long-distance transmission using a chain of optical amplifiers is potentially much cheaper and faster than with conventional electronic regenerators. Er-doped fiber amplifiers, with their low pump power requirements, complete lack of pulse chirping, complete independence of gain on polarization, built-in automatic gain control, and perfect compatibility with transmission fibers, have done much to make this all-optical approach truly practical. It can be shown, however, that the full capacity of such a system can be realized only by using solitons.
Phase tuning of LiNbO3 interferometric modulators by laser ablation
Authors: Bulmer C. H. , Burns W. K. , Greenblatt A. S.
Published: February 2023

Mach-Zehnder interferometers have previously been demonstrated for electromagneticfield sensing.1 Linear modulation is achieved passively, without use of a DC voltage bias, by means of a difference in interferometer arm lengths, corresponding to an intrinsic phase bias ϕo = 90°. In practical devices imprecise fabrication results in deviations from the desired 90° angle, because of differences in phase velocity along the two arms.2 Methods to tune optical devices by phase-velocity adjustment have been reported3,4 but are relatively slow, involving lithography of an oxide cladding layer and of limited accuracy. Tuning of an annealed proton-exchanged LiNbO3 directional coupler by using a CO2 laser beam focused to ~50 μm spot size was recently reported.5 Here we report a fast, accurate method for tuning interferometers to 90° after fabrication. Tuning was performed on a packaged modulator, with the phase bias measured in situ during tuning and correction.
Monolithically integrated quantum well amplifier and interferometric intensity modulator at 1.55 µm
Authors: Zucker J. E. , Jones K. L. , Miller B. I. , Young M. G. , Koren U. , Tell B. , Brown-Goebeler K.
Published: February 2023

High-speed Mach-Zehnder (MZ) intensity modulators are critical components in long-haul, high-bit-rate optical fiber communications systems at 1.55 µm. Here MZ modulators have a clear advantage over directly modulated injection lasers and external electroabsorption modulators since the wavelength chirp can be tuned in MZs to compensate for fiber dispersion. Although much recent progress has been made in monolithic integration of electroabsorption modulators with lasers, an electrorefractive MZ modulator with optical gain has not yet been reported.
Partial collisions of solitons in birefringent optical fibers
Authors: Menyuk C. R.
Published: February 2023

Islam et al.1 have proposed logic gates based on soliton dragging. These gates work as follows: two pulses of different polarization may initially overlap—a signal pulse and a control pulse. These pulses are not really solitons as their amplitude-to-width ratios are not correct: typically, A
c
~1.1 and A
s
~0.5, where these values refer to the amplitudes of the control and signal pulses, normalized with respect to the soliton amplitudes. However, their amplitudes are large enough for the Kerr effect to act and shift the central frequencies of the signal and control pulse if they initially overlap. After the partial collision, the control pulse hasa central frequency that is different from what it would have been had there been no collision, and its velocity is altered owing to chromatic dispersion in the fiber. Consequently, the central pulse is dragged from the time slot it would have occupied had there been no interaction. The signal pulse is discarded with a polarizing filter, and the control pulse becomes the signal pulse for the next stage.
Acoustically tunable wavelength selective switch/filter with high extinction ratio and low drive power
Authors: Pohlmann T. , Voges E.
Published: February 2023

Acoustically tunable wavelength switches/filters for new wavelength routing and switched wavelength multiplexing-demultiplexing systems have recently been demonstrated.1-3 We use a simple polarization-independent structure with two cascaded strictly passive polarization splitters formed by waveguide crossings.4 When we choose an intersection angle α of 1.3°, a polarization cross talk of-30 dB is achieved.
High density optical disk system using a new two-element lens and a thin substrate disk
Authors: Maeda Fumisada , Osato Kiyoshi , Ichimura Isao , Yamamoto Kenji , Fukumoto Atsushi , Watanabe Toshio , Naito Mitsuo , Masuhara Shin
Published: February 2023

The areal density of an optical storage disk can be increased by improving the transverse resolution of the optical head which is proportional to λ/NA. In order to improve the resolution, a lot of research has been carried out to develop shorter wavelength light sources such as green or blue SHG lasers1,2) and recently ZnSe or GaN semiconductor blue lasers3). These lasers will soon become commercially available. On the other hand, it is difficult to make a high NA objective using a single molded aspherical element. Furthermore the higher the numerical aperture, the less the tolerance for variations in disk thickness, disk tilt, and focusing which are inversely proportional to the fourth, third, and second power of the numerical aperture, respectively. Other experiments have been carried out to improve the resolution using near-field optics4) such as scanning probes which can improve the areal density drastically, however, such probes seem to be tolerated only for working distances of around 100 nm.
DVD drive compatible CD recordable media
Authors: Sasakawa T. , Umehara H. , Yanagimachi M. , Tokuhiro J. , Taniguchi Y. , Misawa T. , Takuma K. , Hirose S.
Published: February 2023

The CD recordable (CD-R) system has been widely accepted in the market, because of its full backward compatibility to the existing CD players and CD-ROM drives. In 1995, the total demand of CD-R media in the world is estimated as 17 million and the rapid increase is predicted in the future. On the other hand, the new high density optical disc system called DVD is proposed and is expected as the promising successor of CD system. To ensure the smooth changing path from the CD to the DVD system, compatibility of CD's to DVD drives is essential.
High-Reflectivity Erasable CD
Authors: Ikari Yoshihiro , Tamura Reiji , Taii Toshiaki , Nishida Norio Ohta Tetsuya , Anzai Yumiko , Miyamoto Makoto
Published: February 2023

As CD-ROM market is getting larger year by year, write-once type recordable CD1) (CD-R) is consequently expanding its market scale for authoring tool of CD-ROM. We expect a fully backward-compatible erasable CD (CD-E) adds more attractive applications on CD-ROM world. In the CD-E, two important specifications in the CD Standard has to be conformed; high reflectivity of greater than 70% and large signal modulation of greater than 60%. The feasibility of the CD-E has been demonstrated2) using Ge-Te-Se phase-change material in a five-layer MIPIM structure, in which M, I and P denote metallic mirror, interference and phase-change layer, respectively. In the past study, full backward-compatible CD-E was achieved, however it required high laser power for writing, which is approximately 60mW on the disk, and less overwrite cyclability of 10 times. Our final goal in this study is to develop a practicable CD-E which has high performances in writing sensitivity and overwrite cyclability.
Integrated-Optic Disc Pickup Devices: Hybrid To Monolithic Integration
Authors: Suhara T.
Published: February 2023

There has been continuous research interest in integrated optics (IO) approaches for implementation of disc readout heads, since we proposed and demonstrated the first prototype of an IO disc pickup device using thin film waveguide in 19851. The purpose of such R&D work is to implement compact and light-weight pickup heads with a rigid structure, to enable economical mass production by the planar fabrication technique, and to exploit novel functions and improved performances offered by the use of guided-wave optics. In this paper, I would like to review the current status of the integrated-optic technology for data storage with emphasis on the author's work, and discuss the possibilities, problems and subjects for future work.
Superresolution Elements for High-Density Optical Storage
Authors: Sales Tasso R. M. , Morris G. Michael
Published: February 2023

An important strategy to increase the density of data stored in optical disks consists of using superresolution filters (SF) to increase its resolving power. There are a number of alternative schemes to achieve superresolution in optical heads1. Usual problems associated with most design techniques are reduced efficiency and large sidelobes over a limited field of view. However, with careful considerations it is possible to obtain solutions acceptable for use in optical data storage systems.
DVD/CD Compatible Pick-up Using Liquid Crystal Shutter
Authors: Kajiyama Seiji , Kano Yasuyuki , Matsumura Yoshiyuki , Tsuchiya Yoichi , Ichiura Syuichi
Published: February 2023

Owing to progress in high density disc technology and digital video compression technology, it has become possible to playback digital videos for more than two hours with a 120 mm diameter disc. The standard for DVD (digital video disc), which had two systems in the beginning, has now been standardized to one system. The characteristics of DVD are that a red laser diode and an objective lens with a numerical aperture (NA) of 0.6 have been adopted to read high density discs, and that a 0.6 mm disc thickness has been used to secure allowance for disc tilt.
Key Technologies to Realize Magneto-Optical Storage of Over 7 Gbytes in CD Sized Disk
Authors: Torazawa K. , Sumi S. , Yonezawa S. , Suzuki N. , Tanaka Y. , Takahashi A. , Murakami Y. , Ohta N.
Published: February 2023

Recently, many kinds of technologies for high density recording have been reported in the field of magneto-optical (MO) recording. Magnetically induced super resolution (MSR) is one of the most hopeful candidates, and over ten MSR types have been proposed already. However, the MSR technology is not discussed well from a view point of the total recording technology including the recording and readout method, the pick-up technology and the signal processing technology. It seems obvious that higher density recording can be realized by a better combination of related technologies.
Interactions in Servo Loops of an Optical Disk Drive
Authors: Semba Tetsuo , Bates Allen K. , Fennema Alan A.
Published: February 2023

In an optical disk drive, three servo loops are typically used to control the focus, fine tracking, and coarse tracking actuators. Optical disk drives have interactions between these servo loops attendant to the characteristics of actuators and the error signal sensing schemes employed. Simple actuators and error signal sensing methods are desirable to reduce the manufacturing costs; however, large interactions, if present may degrade the servo performance. This can result in a degradation in the error rejection ratio, seek time, and seek reliability.
Increasing Transfer Rate and Capacity in Optical Data Storage through Pit Depth Modulation
Authors: Johnson B.V. , McDermott G.A. , O’Neill M.P. , Pietrzyk C. , Shafaat T. , Spielman S. , Wong T.L.
Published: February 2023

The use of pit depth modulation (PDM) in optical data storage historically has received little attention; the only known literature to the authors is cited below in references 1-5. However, considerable improvements to both disc capacity and transfer rate can be realized by its implementation. Unlike many methods that improve disc capacity, PDM has the advantage of increasing data transfer speed in direct proportion to obtained increases in data capacity. It is also compatible with other innovations under development, including smaller pits read by shorter wavelength lasers and higher NA lenses, faster disc spin-rates, and double-sided, dual depth or multilayer discs. Performance improvements from PDM are additional to those achieved from other innovations.
A photochromic material for non-destructive readout using one wavelength
Authors: Rayfield G.W.
Published: February 2023

Optical data storage offers significant improvement over existing storage technology for high-density and high-transfer-rate data storage. A limitation in the development of this technology is the lack of a suitable optical-recording material. A suitable material would have high resolution, permanent data­storage capabilities, non-destructive readout, good sensitivity (for both writing and erasure), high photochemical and thermal stability, and optical-erase capability. Photochromies meet many of the material needs but suffer from a key limitation: Information is lost by repeated reading unless a different wavelength is used for reading and writing. This paper describes a photochromic material, bacteriorhodopsin, in which an external electric field switches its photochromic behavior. Optical information stored in the film is nonvolatile but can be erased with blue light. Non-destructive readout uses red light with the same wavelength of as that used for writing.
Ultra high density recording with atomic force microscope probes on phase change media
Authors: Tohda Tokao , Kado Hiroyuki
Published: February 2023

An ultra high density recording with scanning probe microscopes (SPMs) has been studied extensively in recent years to overcome the limits in optical and magnetic storage devices (1-3). In the SPMs, a scanning tunneling microscope (STM) and a scanning near-field optical microscope (SNOM) are not considered suitable for high speed recording operations, because they require precise control of the distance between the probe and the storage media at a nanometer scale using a feedback control system. On the other hand, an atomic force microscope (AFM) does not require the precise control if the surface of storage media is smooth at a nanometer scale, because its probe is mounted on a flexible cantilever and touches the media with an extremely weak force. In this paper, we describe an erasable recording technique with the AFM by locally controlling the conductance of phase change media without a topographic change.
Comparison of the ability of phase change media versus MO media to support high density blue laser recording (Invited)
Authors: Mansuripur M.
Published: February 2023

Much has been said in the past about the differences between phase change (PC) and magneto-optical (MO) recording technologies. The obvious differences are listed below.