bluuebunny/crossref_metadata_2025 huggingface dataset:
High-power optical transmitter for optical communication
Authors: Goldberg L. , Howerton M. M. , Greenblatt A. S. , Burns W. K.
Published: February 2023

Many optical communication systems, such as those based on free-space propagation, require significantly higher diffraction-limited transmitter power than is available from single-stripe laser diodes. An attractive solution is to use a high-power coupled stripe laser-diode array or broad stripe laser that is externally injection locked to achieve a diffraction-limited far-field emission.1 To encode the transmitted information, we could use direct array current modulation, but this requires large drive currents and is limited by relatively low modulation bandwidth of the array. One alternative is to frequency modulate the master laser for FSK transmission.2 Recent advances in optical damage-resistant waveguides3 permit the use of another approach, described here and shown in Fig. 1, where the information is first encoded as phase modulation on the master laser signal by using a LiTaO3 proton-exchanged waveguide phase modulator. Modulated output is then used to injection lock a coupled stripe array. When the phase-modulation spectral sidebands in the injected signal are within the locking bandwidth, the phase-modulated signal is amplified and transmitted by the injection-locked laser without suppression of the modulation index.4
Raman microprobe analysis of stress distribution in Si3N4 stripe GaAIAs channel optical waveguides
Authors: Radens C. J. , Boyd J. T. , Jackson H. E. , Burnham R. D.
Published: February 2023

Raman spectroscopy is a sensitive technique for the nondestructive probing of local material structural and crystalline conditions including strain in semiconductors.1 We have used the Raman microprobe to investigate strain induced by patterned Si3N4 films on GaAIAs waveguide structures.2 We previously observed a double-lobed optical mode field intensity distribution in Si3N4 stripe GaAIAs structures that was consistent with photoelastic waveguiding and confirmed the presence of a compressive stress in the GaAIAs material under the Si3N4 stripe by using the Raman microprobe.2
Spatial switching, instabilities, and chaos in a three-waveguide nonlinear directional coupler
Authors: Finlayson N. , Stegeman G. I.
Published: February 2023

In recent years it has been recognized that the existence of amplitude or power instabilities has possible utility in the area of all-optical switching.1 Jensen’s proposal2 for spatial switching in a two-waveguide directional coupler represents the seminal contribution in the field. As pointed out by Christodoulides et al.3 however, Jensen’s two-waveguide coupler may be considered only a special case of more general class of n-oscillator systems. We consider in this paper the obvious extension from two to three elements. In the linear regime the behavior of the three-guide coupler is similar to that of the conventional two-guide coupler, except for an intermediate transfer of power in to the center wave guide. For devices that are one coupling length and one beat length long the transmission characteristics of the three-waveguide coupler are markedly sharper than in the two-waveguide case and approach the characteristics of an ideal switch. At long range the field trajectories of the three-guide coupler become chaotic in the vicinity of two critical power levels.
Femtosecond measurements of the optical switching properties of semiconductor bulk and quantum-well waveguides
Authors: Anderson K. K. , LaGasse M. J. , Fujimoto J. G. , Haus H. A.
Published: February 2023

Studies of the optical nonlinearities near the band edge in semiconductors are important to determine the potential for all-optical switching in these materials. Measurements of these nonlinearities are complicated by the various processes that contribute to the optical response. These include bound and free electrons and thermal effects. In addition, the nonlinear-optical response is a sensitive function of wavelength near the band edge,1 so that measurements at different wavelengths are needed to assess the potential for optical switching properly.
25-GHz electrical correlation sampler using coded electro-optic modulators
Authors: Dolfi David W. , Nazarathy Moshe
Published: February 2023

Recent theoretical1 and experimental2 research has established that the use of pseudorandom coded phase-reversed electrode structures can provide substantial improvement in the frequency response of LiNbO3 traveling-wave integrated-optic modulators. Although the magnitude of the frequency response of these devices is greatly extended, their phase response exhibits considerable nonlinearity, which prevents the device impulse response from attaining its transform-limited extent (the reciprocal of the extended bandwidth). Recently3 we proposed electro-optic sampling and fast optical pulse generation techniques directly in the time domain to overcome these limitations and to allow time domain performance of these devices to be consistent with their performance in the frequency domain. Here we present, to our knowledge for the first time, experimental results for an electrical sampler as proposed in Ref. 3. Its sampling aperture is determined not by the device impulse response but by its autocorrelation function. The autocorrelation function is much shorter in duration for a device with spread spectrum coded electrodes.
Multifunctional semiconductor laser amplifiers: optical amplifier, detector, gate switch, and transmitter
Authors: Gustavsson Mats , Thylén Lars
Published: February 2023

Semiconductor laser amplifiers (SCLAs) are expected to play an important role in future transmission and switching systems for various applications, such as optical preamplifiers and repeaters and in local area network applications as loss compensators and as gate switches for modulation and (using the feature of simultaneous amplification and detection) for intelligent switching and routing functions.1-5 However, it would be of great interest if also a laser type transmitter could be based on the optical amplifier. Such a possibility would substantially increase the utility of near-traveling-wave (NTW) SCLAs in optical communications systems. The number of different structures for implementing amplifiers, detectors, gate switches, and transmitters would be reduced, thus simplifying the fabrication of various complex integrated photonics components.
Novel integrated acousto-optic and electro-optic heterodyning devices in a LiNbO3 waveguide
Authors: Xu G. D. , Tsai Chen S.
Published: February 2023

The conventional acousto-optic (AO) Bragg cell rf receiver is known to suffer from two limitations: limited dynamic range and incapability for phase measurement. To increase the dynamic range and to facilitate the phase measurement, we must use optical heterodyning detection. Most related works have been carried out using bulk AO Bragg cells1 in which a number of beam splitters, mirrors, and wedges were configured into a Mach-Zehnder interferometer to facilitate the required functions of beam splitting, directing, combination, and filtering for the signal and reference beams. To overcome the problems of vibrations and thermal fluctuations and subwavelength alignment tolerances required, a so-called modified Mach-Zehnder interferometer was explored recently. This expoloration was accomplished by using integrated-optic (IO) architecture2 in which a pair of proton-exchanged gratings were used as the beam splitting, directing, and combining elements. A relatively low dynamic range of 30 dB was measured owing to excessive optical losses from the gratings and the propagation in the waveguide. In this paper we present a simple IO architecture that utilizes wideband cascaded AO and electrooptic (EO) Bragg diffractions in Y-cut LiNbO3 planar waveguide to perform efficient and wideband heterodyning detection. The results obtained thus far suggest a new architecture for the realization of wideband IO interferometric rf spectrum analyzers.
Polarization converter and splitter for a coherent receiver optical network on InP
Authors: Albrecht P. , Hamacher M. , Heidrich H. , Hoffman D. , Nolting H.-P. , Schlak M. , Weinert C. M.
Published: February 2023

The TE/TM mode splitter (MS) and TE/TM mode converter (MC) are key components of the passive polarization diversity circuit. The aim of this research, which is part of the European RACE 1010 project, is to design MC, MS, and 3-dB couplers for integration on InP by using a common waveguide.
Integration of waveguide gratings for parallel data pickup
Authors: Ura Shogo , Furukawa Yukio , Suhara Toshiaki , Nishihara Hiroshi
Published: February 2023

Parallel read/write systems are attractive in optical memory applications, and integrated-optic implementation of pickup devices would result in compact/light heads with high producibility and application flexibility. By modifying an integrated-optic disc pickup device (IODPU),1 we propose and demonstrate a combination of a linearly focusing grating coupler (LFGC)2,3 and a coplanar Bragg grating lens4 (beam splitting/imaging grating; BSIG) for integrated-optic parallel pickup. Figure 1 illustrates a schematic view of the integrated-optic device. A guided wave diverging from a butt-coupled laser diode (LD) is diffracted by the LFGC to be a focusing beam of cylindrical wave front in the air. The linearly focused beam is reflected by a recorded medium, so the wave front is no longer cylindrical but modulated by the multiple digital data on the focus line. The reflected wave is back-coupled by the same LFGC into the waveguide and imaged by the BSIG onto a photodiode array.
23-dB gain upconversion pumped doped fiber amplifier operating at 850 nm
Authors: Whitley T. J. , Millar C. A. , Brierly M. C. , Carter S. F.
Published: February 2023

To date rare-earth-doped fiber amplifier research has largely been aimed at producing efficient amplifiers for operation within either the third telecommunications window between 1.44 μm and 1.6 μm, or the second telecommunications window between 1.28 μm-1.34μm[1]. However, the relatively inexpensive nature of AlGaAs transmitters and Si detectors operating near 800 nm make operation within the first tele communication window, around 0.85 μm, an attractive possibility for short distance distribution, LAN or interconnection applications. A crucial component for such systems would be a practical and efficient amplifier operating in this window. In this work we report the demonstration of a 23 dB small signal gain at a wavelength of 850 nm in an erbium doped fluorozirconate fiber.
High-performance erbium-doped fiber amplifier pumped at 811 and 980 nm
Authors: Becker P. C. , Lidgard A. , DiGiovanni D. J.
Published: February 2023

Most work on erbium-doped fiber amplifiers (EDFA) over the past few years has focussed on amplifiers pumped at 980 nm and at 1480 nm.1-3 Recently, however, there has been renewed interest for file 800-nm pump band.4 In this paper we present a comparative study of an EDFA pumped by a Ti:sapphire laser tuned to both 800 and 980 nm in order to illustrate the effects of excited-state absorption.5 The erbium-doped fiber used in the experiment has a 4-μm-diameter SiO2-Al2O3-GeO2 core with a relative index difference of 0.035 and a cutoff wavelength of ~815 nm. The erbium concentration is 200 ppm. Gain and saturation measurements were per formed on different lengths of fiber, pumped at 980 nm and at some arbitrary wavelength in the 810-nm region, the optimum wavelength having been found to increase with length. Figure 1 is a plot of normalized gain for λs = 1533 nm as a function of pump wavelength. The 3-dB bandwidth is 14 nm. The peak gain for this 12-m piece is obtained for λ
p
= 811 nm and was 25 dB for λ
s
= 1533 nm and 20 dB for λ
s
= 1553 nm. The maximum absorption, however, was found to be at 797 nm.
Simple theory of optical fiber amplifiers having nonuniform distributions of gain and spontaneous emission factor
Authors: Yamashita Shinji , Okoshi Takanori
Published: February 2023

The conventional noise theory of an optical amplifier is based on the semiclassical master equation which is known as Shimoda, Takahashi and Towns' (STT) theory. However, this theory deals only with lumped amplifiers. The present paper shows first that the noise formulas for distributed nonuniform amplifiers can be derived in a simple way by using the STT theory.
Electronically tuned erbium-doped fiber ring lasers
Authors: Smith D. A. , Maeda M. W. , Patel J. S. , Johnson J. J. , Saifi M. A. , Lin Chinion
Published: February 2023

We have made electronically-tuned erbium-doped fiber ring lasers using two very different means of wavelength selection: a liquid-crystal-filled Fabry-Perot etalon filter1 and a frequency-shift-free two-stage integrated acousto-optic filter.2 Both lasers exhibited a broad tuning range (50 nm), continuous tunability, linewidths of only a few kHz, 70% internal quantum efficiency and a switching speed of over 100 kHz (for the acoustically-tuned laser). The laser tuned by the liquid crystal filter has a switching speed of at most a few milliseconds.
Super-fluorescent sources and dye lasers based on tapered single-mode optical fibers
Authors: Mackenzie H. S. , Payne F. P.
Published: February 2023

In a series of previous experiments,1-3 we have established the tapered single-mode optical fiber, surrounded by a circulating dye solution, as a practical and versatile nonlinear device. At the first integrated photonics meeting in 1990,1 we presented results that demonstrated both efficient optical amplification and saturable absorption at optical power levels of only tens to hundreds of milliwatts. Conventional dye laser amplifiers and saturable absorbers more commonly require power levels of tens to hundreds of watts. Our ability to fabricate tapers with submicrometer waist diamters results in high optical power intensities at the taper waist for modest pump powers. For example, a taper waist of 0.5 μm (typical of our packaged devices) produces a power intensity of approximately 1 MW/cm2 at the waist for an input power of only 10 mW. From these results, we have established that low pump power, all-fiber, dye laser and superfluorescent sources are feasible. As a preliminary, we have conducted a series of experiments on the superfluorescent or amplified spontaneous emission from a tapered fiber surrounded by a circulating solution of DOTCI. The choice of this particular dye was dictated by the convenience of being able to use a visible 650-nm pump source. Peak pump powers of approximately 1 W with a 10-ns pulse width were used to excite a tapered fiber with a waist diameter of approximately 1 μm. Amplified spontaneous emission, centered on the fluroescent peak at about 720 nm, was measured with a spectral width of 40 nm (Fig. 1).
Piezoelectric polymer coated fiber-optic phase modulator
Authors: Imai M. , Yano T. , Ohtsuka Y.
Published: February 2023

All-fiber components associated with passive and active optical functions have recently received considerable attention in the field of lightwave technology, including optical fiber communication and optical fiber sensing. Among various components, a fiber-optic phase modulator acts on the phase of optical fields which propagate within the core of fiber. We have proposed coating single-mode fibers with a copolymer of vinylidene fluoride (73 mol%) and trifluoroethylene (27 mol%)1. The fiber consisted of an 80 μm cladding diamter and a gold-nickel thin-film coating was overcoated with a 80 μm thickness of VDF/TrFE copolymer radially poled. A thin metallic layer of aluminum was then vacuum-evaporated over the outside of the copolymer, and the fiber equipped with inner and outer electrodes was set on a glass-epoxy substrate to test as an all-fiber phase modulator.
GexSi1-x optical directional coupler
Authors: Campbell Joe C. , Mayer Robert A. , Jung Kim H. , Kwong Dim-Lee
Published: February 2023

Historically, GaAs- and InP-based compounds have been the dominant materials for optoelectronic devices, whereas Si has been the material of choice in the commercial electronics industry because of its ease of handling, ease of processing, and low manufacturing costs. For this reason, hybrid techniques have frequently been used to combine optoelectronic devices and electronic circuits. Since this can be costly, there has been a concentrated effort to develop III-V compound optoelectronic integrated circuits.1 A promising alternative involves the use of Ge
x
Si1-
x
layers, grown on Si substrates, to develop a wide range of Si-based optoelectronic devices and circuits. An initial step in this direction is the fabrication of waveguide structures in Ge
x
Si1-
x
layers, grown on Si substrates, to develop a wide range of Si-based optoelectronic devices and circuits. An initial step in this direction is the fabrication of waveguide structures in Ge
x
Si1-
x
.2-4 In this paper, we report, for the first time, the fabrication and characterization of Ge
x
Si1-
x
directional couplers.
Predictable control of optical coupling between intersecting waveguides by fractional doping
Authors: McCaughan Leon , Gill Douglas M. , Agrawal Niraj
Published: February 2023

For conditions in which the radiation losses can be neglected, multiple scattering analysis1,2 predicts that the fraction of coupled optical power between intersecting waveguides is where K
ev
corresponds to the single-Δn geometry (i.e., the guiding index is constant throughout the intersecting waveguide geometry) and K
fd
, the contribution from the additional doping (see Fig. 1) of the intersection region, is given by Here β, 2a, α, and γ are the propagation constant, guide film thickness, and the magnitudes of the transverse components of the wave vectors in the film and substrate [determined from the dispersion relation, γ = αtan(αa)], respectively. The change in permittivity in the intersection region, Δεfd, above that in a waveguide, εf, is related to the fractional doping thickness of Ti, Δτ/τo by Δεfd ≅ (εf-εs Δτ/εo.
Asymmetric intersecting waveguides: analysis and design for passive optical crossovers
Authors: McCaughan L. , Songwatana K.
Published: February 2023

We calculate to first order the coupling coefficient between a pair of nonidentical (unequal widths and/or refractive indices) intersecting waveguides (see Fig. 1). This approach is similar to the method used in Refs. 1 and 2. From this first-order coupling coefficient, a simple graphical representation together with a set of parametric curves are derived. These tools allow us to design zero-cross-talk optical crossovers for both the case of a single wavelength and two wavelengths.
Solution of the Helmholtz equation for semiconductor rib waveguide devices by the Lanczos recursion technique
Authors: Ratowsky R. P , Fleck J. A. , Feit M. D. , Hawkins R. J.
Published: February 2023

The solution of the paraxial wave equation by means of the split-operator fast-Fourier transform method, also known as the beam-propagation method (BPM), is now a firmly established approach for solving a variety of integrated-optics problems. One shortcoming of the paraxial equation is, however, that it is restricted to slowly varying index profiles. This means that application of the method to rib waveguide devices, which are characterized by large refractive-index discontinuities, will in general not be accurate. We need instead to apply the full Helmholtz equation, which after extraction of a carrier wave can be expressed as To generate the solution to this equation by marching requires application of a square root operator at each propagation step.1
A beam-propagation-method-type algorithm solving the vector-wave equation
Authors: Thorweihe Norbert , Schulz Dirk
Published: February 2023

Simulation and modeling methods are used to predict performance of optical devices. The frequently used beam-propagation method (BPM) rests on the scalar wave equation although this is only valid for TE modes in planar waveguides. To solve the generally accepted three-dimensional vector-wave equation, we developed a BPM-like algorithm that includes anisotropic media.
Vectorial method of lines for the analysis of waveguide structures with arbitrarily varying index profile
Authors: Rogge U.
Published: February 2023

The method of lines (MoL) has proved to be suitable for the analysis of strip-loaded optical waveguides.1 This paper describes the analysis of a variety of structures with more complicated index profile, e.g., Fig. 1.
A 1-to-30 fanout optical interconnect for planar integration applications
Authors: Wang M. R. , Sonek G. J. , Lu H. T. , Chen R. T. , Jannson T.
Published: February 2023

The use of planar integration for large fanout optical interconnection applications, based upon the concepts of diffractive and reflective optics, has recently been reported.1-3 Herein, we report on the use of multiplexed holographic diffraction gratings, and substrate wave propagation in a soda-lime glass substrate,4 to achieve a 1-to-30 channel fanout with high overall diffraction efficiency.
Simple method for estimating useable bend radii of deeply etched optical rib waveguides
Authors: Pennings E. C. M. , Deri R. J.
Published: February 2023

The successful application of OEIC's requires monomode waveguides, compact low-loss bends, and efficient fiber coupling. The deeply etched rib waveguide shown in Fig. 1 can meet these requirements.1,2 A numerical analysis of the bending loss requires involved calculations such as the three-dimensional BPM3 or the VCM.4 Here, a simple model based on the effective index method (EIM) is introduced that estimates the minimum useable bend radius. Our method does not provide the same degree of accuracy nor a value of the bending loss but does provide an extremely rapid and simple estimate of the minimum useable radius which is all that is required for most design purposes.
Heterojunction bipolar transistor waveguides on InP
Authors: Young Terry , Croston Ian
Published: February 2023

A powerful step in integrating photonics and electronics is to incorporate electronic gain into waveguides, something already reported on GaAs1 and proposed on Si.2 Here we present a design for HBTWs in InGaAsP/InP.
Effective index approximation limitations study for waveguide integrated devices on InP/InGaAsP
Authors: Mustieles F. J. , Hernandez-Gil F. , Fernandez E. , Ballesteros E.
Published: February 2023

The effective index approximation1 has been extensively used to calculate the modes in waveguides to design a wide variety of devices as: DBR and DFB lasers, directional couplers, filters, polarization control devices, etc. Its use in conjunction with the beam propagation method2 to analyze integrated optical devices is also very common. The effective index approximation is easy to implement and provides dramatic reductions in the required computational efforts, but its precision depends on the geometry and composition of the structures to be analyzed.
Theoretical investigations of optical waveguide tapers on InGaAsP/lnP
Authors: Nolting Hans-Peter
Published: February 2023

There is a need for mode transforming devices connecting dielectric waveguides with different field distributions (especially with different core materials). Taking the coupling of a glass fiber to a semiconductor passive waveguide as an example, taper geometries are investigated which have low loss, short length, and are compatible with present semiconductor fabrication technologies (precise material homogenity and thickness control, etch-stop layers, "dynamic etch mask" technology1).
Efficient vertical coupling of photodiodes to InGaAsP rib waveguides
Authors: Doldissen W. , Deri R. J. , Hawkins R. J. , Bhat R. , Soole J. B. D. , Schiavone L. M. , Seto M. , Andreadakis N. , Silberberg Y. , Koza M. A.
Published: February 2023

Monolithic optoelectronics requires optical linkage between waveguides and photodiodes. Vertical coupling offers the advantages of single-step epi-growth and ease of junction placement.1,2 Its drawback is weak coupling, resulting in long detector lengths L and high capacitance. thinner guides can reduce L,1,2 but increase input coupling difficulty. We recently demonstrated than an optical "matching layer' introduced between a thick n-/n^+ InP waveguide and an InGaAs absorber significantly enhances vertical coupling.3 Here we show that this approach provides efficient coupling between InGaAs detectors and InGaAsP waveguides of the type currently employed in photonic integration.
Small-signal analysis of the bandwidth of traveling-wave directional couplers
Authors: Chung Haeyang , Chang William S. C.
Published: February 2023

Electro-optic traveling-wave modulators may be operated at high frequency with extremely large band widths. Important factors which limit the high frequency performance are the velocity mismatch (between the optical wave and the modulating microwave) and microwave loss. An analysis of the conventional directional coupler frequency response has already derived from the time-domain impulse response for the case of zero microwave loss, and a numerical analysis for the large signal frequency-domain response has also been given.1 However, because the behavior of the directional couplers are nonlinear, the Fourier transformation of the time-domain impulse response is not generally a true frequency response. For analog operations there is a need for a small signal analysis in the frequency-domain to calculate the bandwidth. Further, general analysis of frequency response for other types of directional couplers such as 1 × 2 directional couplers2 is also not available in the literature.
Polarization rotation in asymmetric periodic loaded rib waveguides
Authors: Shani Yosi , Alferness Rod , Koch Tom , Koren Uzi , Oron Moshe , Miller Barry I. , Young Martin G.
Published: February 2023

Polarization rotation is an important effect in integrated optics. It is required in balanced polarization diversity heterodyne receivers and in polarization controllers. Polarization rotation has been demonstrated in LiNbO3and in III-V waveguides using the electro-optic effect1−3and LiNbO3using the photo-elastic effect.4
Monolithic InP-based wavelength multiplexer/demultiplexer for multichannel WDM at 1.5 μm
Authors: Soole J. B. D. , Scherer A. , LeBlanc H. P. , Andreadakis N. C. , Bhat R. , Koza M. A.
Published: February 2023

Wavelength-division multiplexed (WDM) systems are under investigation for applications ranging from high capacity inter-exchange links, through local area networks, to processor interconnects in computers.1 Compact hybrid demultiplexers have been reported.2 However, integration offers advantages in terms of size, field-worthyness, and cost. Integration in InP-based material additionally allows the possibility of combining a passive muitiplexer/demultiplexer monolithically with a laser source or a photodector for the fabrication of a multi-wavelength transmitter and receiver. Recently, there have been a couple of reports of wavelength demultiplexers implemented in InP waveguide material,3,4 on demonstrating 20 channel demultiplexing at a 4nm channel spacing.4 In this paper, we present a monolithic single grating demultiplexer which resolves 78 channels separated by 1 nm, centered on 1.51 pm in the low loss fiber band. In contrast to previous devices, this demultiplexer is essentially insensitive to the polarization of the incident light.
Generation of dark solitons by nonlinear fiber propagation
Authors: Rothenberg Joshua E.
Published: February 2023

Dark solitons1 are characterized by an intensity dip on a continuous background, which propagates unaltered. Although a true continuous background wave may be impractical, it has been shown that dark pulses on a background pulse of finite width can propagate adiabatically as solitons.2 Dark solitons have been observed in optical fibers by a few different experimental techniques3; however, the generation of the dark soliton trains from the interference and nonlinear copropagation of two delayed visible pulses in an optical fiber is numerically investigated.
Chirp mechanisms in soliton dragging logic gates
Authors: Islam M. N. , Menyuk C. R. , Chen C. J. , Soccolich C. E.
Published: February 2023

We theoretically and experimentally study the chirping mechanism responsible for the time shifts in soliton dragging logic gates.1 Crossphase modulation2 during the first one or two walk-off lengths in a birefringent optical fiber causes most of the frequency shift that translates into a time shift after propagation in a soliton dispersive delay line.
Classical theory of optical squeezing in a nonlinear fiber interferometer
Authors: Marhic M. E.
Published: February 2023

A nonlinear Mach-Zehnder fiber-optic interferometer as shown in Fig. 1 can be used for light squeezing1 and amplification.2 The mechanism can be viewed either as the Kerr effect,1 or degenerate four-wave mixing (DFWM).2 Using the classical DFWM approach, one finds that if fields of the same frequency with phasors E
s
and E
p
(′signal′ and ′pump′) are fed into the inputs, then one output phasor is given by where the nonlinear phase shift is given by δφnl= QL |E
S
E
p
| cosδ, Q is the fiber nonlinear coefficient, L is the fiber length, and δ is the phase difference between the inputs.
New finite difference schemes for the analysis of planar optical waveguides
Authors: Artiglia M. , Coppa G. , Di Vita P. , Lapenta G. , Potenza M. , Ravetto P.
Published: February 2023

The importance of the numerical simulation of integrated optics devices for optical telecommunication systems is constantly growing and much attention is being devoted to the development of new powerful and effective numerical codes for solving the paraxial wave equation for planar structures. However, the numerical techniques so far presented are not completely satisfactory because they are time consuming, and their accuracy have not been well assessed; moreover they make use of approximated boundary conditions and do not seem to be able to treat conveniently longitudinally variant geometries.
Monolithically integrated ln0.53Ga0.47As receiver with voltage-tunable transimpedance
Authors: Lo D. C. W. , Chung Y. K. , Forrest S. R.
Published: February 2023

Monolithically integrated InP-based optical receivers are attractive for long-wavelength high-density optical communications. Here we reported an In0.53Ga0.47As receiver which consists of an In0.53Ga0.47As PIN photodiode and an In0.53Ga0.47As JFET transimpedance amplifier. The In0.53Ga0.47As JFETs have previously demonstrated high stability and suitable for large-scale InP-based OEICs.1 A narrow-gate In0.53Ga0.47As JFET (5μm wide and 30μm long) is used as an active feedback resistor for the transimpedance amplifier. The output resistance of the narrow-gate transistor operated in its linear region can be dynamically tuned over a wide range. In addition to the active resistors, the transimpedance amplifier has a common source inverter, a level-shifter and an output buffer. Figure 1 shows the circuit diagram and photomicrograph of the monolithic receiver.
Optically powered monolithically integrated logic circuits
Authors: Brown J. J. , Gardner J. T. , Forrest S. R.
Published: February 2023

Optical powering of optoelectron integrated circuits (OEICs) significantly improves their performance in high density photonic systems as compared to conventional designs employing electrical powering of circuits.1 Here optical powering replaces the dc bias lines with integrated photovoltaic (PV) cells in each pixel. The PV cell is illuminated with an external light source (e.g. laser) and converts this optical power beam into electrical power which subsequently drives the circuitry within that pixel. The total absence of the parasitic capacitances and inductances in the optical beam reduces inter-pixel cross-talk as compared with conventional dc bias lines. This leads to significantly increased bandwidths in the optically powered case. In addition, optical powering reduces interconnection complexity associated with routing bias lines to each pixel in a high-density, two dimensional array. An optically powered interconnection system has already been demonstrated in hybrid form.2,3 In this present work, we discuss an integrated optoelectronic logic circuit in which the power and control are both provided using optical sources.
Spectral shape of absorption tail in high-purity GaAs
Authors: Kamath K. K. , Vaya P. R.
Published: February 2023

Recently, there has been a renewed interest in the study of absorption spectrum, particularly in the absorption tail region due to the possibility of using the semiconductor etalons for optical bistability. It has been shown that both the dispersive and absorptive optical bistability are possible in semiconductors. However, it is very difficult to obtain absorption saturation in the tail region.1 Therefore, it is very important to study the mechanism of formation, and the density of states distribution in the absorption tail region.
Scattering losses simulation in semiconductor ridge waveguides
Authors: Baquero P. , Ballesteros E. , Hernandez-Gil F.
Published: February 2023

Low-loss semiconductor waveguides are essential to realize complex photonic integrated circuits. The optimization of the material characteristics can reduce the absorption losses to levels well under the scattering losses. It has been experimentally proved that the scattering losses are strongly dependent on the waveguide structure.1 The availability of a simulation tool can be very useful to optimize waveguides design for minimum losses.
An inverse scattering approach to designing optical bistable devices
Authors: Tamil Lakshman S.
Published: February 2023

We present here a method for designing an optical bistable device using an inverse scatting method. An inhomogeneous nonlinear optical thin film is proposed for implementing the bistable optical device. The nonlinear wave equation1 governing the propagating in a nonlinear waveguide, when solved using the method of separation of variables, leads to a nonlinear differential equation in the longitudinal direction and a scalar Helmholtz equation in the transverse direction. As the longitudinal length of the device is very short and our concern here is on the presence or absence of the fundamental TE mode, our discussion of interest is on the scalar Helmholtz equation.
Monolithicaliy integrated balanced receiver OEIC with semi-insulating waveguides on InP
Authors: Kaiser R. , Feiste U. , Hochheim S. , Passenberg W. , Reier F. , Schramm C. , Trommer D. , Umbach A. , Unterbörsch G.
Published: February 2023

The worldwide installation of broadband optical communication networks calls for high-performance opto-electronic integrated circuits (OEICs). In particular, balanced coherent heterodyne receiver OEICs are currently of great interest due to increased device functionality.1,2 The main advantage of such receivers compared to single-detector circuits is their near quantum noise limited performance in the presence of weak signals and intensity noise from the local oscillator.1 In this paper the successful fabrication of a monolithicaliy integrated receiver in the InGaAsP/InP material system, incorporating two semi-insulating ribwaveguides, balanced twin-photodiodes, a junction field effect transistor (JFET), and a resistor, is reported for the first time (Fig. 1). Such components may serve as important building blocks in the OEICs described above. The major advantages of our structure are as follows: 1) Ease of epitaxy: Possibility to grow all layers in one epitaxy on planar substrates. 2) Ease of electrical isolation between the two photodiodes as well as the JFET using semi-insulating InGaAsP for the waveguide layer,3 avoiding additional isolation techniques (e.g. etching, implantation, diffusion) or two-side wafer processing (as proposed in /4/).
Progress report on the results of the COST-216 problem set
Authors: Lagasse P. , Franssens G. , Kaczmarski P. , Nolting H. , Weinert C. , Maken N. , Bastiaansen H. , van der Tol J. , Pennings E. , Krijnen G. , Hoekstra H. , Popma Th. , Tervonen A. , Leminger O. , Zesch G. , Gu J. , Taylor R. , Robbins D. , Buus J. , Croston I. , Catzula D. , Galtarossa A. , Someda C. , Di Vita P. , Potenza M. , Lapenta G. , Gerdes J. , Pregla R. , Clauberg R.
Published: February 2023

Within the working group, Device Modeling, of the European COST-216 project, various numerical techniques for modeling integrated optic S bends and directional couplers have been compared.1-3 The problem set was chosen on the basis of the availability of reliable experimental results. The directional couplers fabricated by the Heinrich Hertz Institute are based on InGaAsP waveguide grown on an InP substrate. The S bend containing offsets was made by the Dr. Neher Laboratory of the Dutch PTT and by the Technical University of Delft by using ion-beam milled waveguides with a sputtered Al2O3 core and a SiO2 cladding on a silicon wafer.
Coupling between two circular fibers with vectorial beam propagation method
Authors: Gomelsky L. , Liu J.M.
Published: February 2023

The existing beam propagation method is based on the scalar Helmholtz equation and therefore ignores the field polarization properties.1−4 The negligence of polarization properties in the existing scalar beam propagation method (SPBM) remains as a major shortcoming of this powerful technique. One simple example is that the propagation of a simple TE01 eigenmode in a circular fiber cannot be described with the current beam propagation method, let alone the coupling between two circular fibers. To overcome this limitation, a vectorial beam propagation method (VBPM) based on the vectorial wave equation has been developed. In this paper, we demonstrate the use of the VBPM to describe the propagation of a TE01 eigenmode field from a circular fiber of 4 μm core radius into a fiber of 8 μm radius.
Waveguiding properties of the wavelength-tunable YCCI3 laser structure
Authors: Baums D. , Idler W. , Schilling M. , Laube G. , Wünstel K.
Published: February 2023

Recently a novel wavelength-tunable laser based on an interferometric principle was shown to be capable of a tuning range as wide as 23nm together with a sidemode suppression ratio of >210 dB.1 This Y coupled cavity integrated interferometric injection (YCCI3) laser (fig. 1) can be employed in coherent and wavelength division multiplexing systems. High speed wavelength switching between different channels, AM and FM in the GHz range was achieved with this structure.2 It can thus be employed as a multifunctional basic element in photonic integrated circuits. In this contribution, we report on experimental waveguide studies for ultimate reduction of curvature radii without loosing the excellent device properties.
Ka-Band integrated optic modulators with periodic intermittent interaction electrodes
Authors: Schaffner James H. , Hayes Robert R.
Published: February 2023

The high-frequency performance of traveling wave optical modulators is ultimately limited by the difference in the propagation velocities between the RF and optical signals.1 This velocity mismatch leads to a phase asynchronization at higher frequencies that allows the latter part of the traveling wave structure to cancel the modulation produced by the forward part. One approach that overcomes this limitation, and that leads to efficient bandpass operation at millimeter wave frequencies, is to use a periodic intermittent interaction electrode2 (Fig. 1). The periodic electrode "resets" tire phase relationship between the RF and optical signal at predetermined points along the traveling wave structure, so that each section of the traveling-wave structure makes a positive contribution to the overall modulation. This paper presents experimental results for an X-cut LiNbO3 Mach-Zehnder interferometric modulator with a periodic electrode structure designed for optimum operation at 35 GHz.
Optical properties of serpentine superlattices
Authors: Yi Jong Chang , Dagli Nadir , Coldren Larry
Published: February 2023

Recent developments on ultrafine submonolayer epitaxy on vicinal substrates1 by molecular beam epitaxy (MBE)2 or metalorganic chemical vapor deposition (MQCVD)3,4 made it possible to fabricate arrays of quantum wires named tilted superlattices (TSL) and serpentine superlattices (SSL).2,5 Figure 1 (a) and (b) show the cross sectional profile of a TSL and a SSL. A TSL or a SSL is directly grown on an off axis or vicinal GaAs substrate by alternating deposition of two materials of different compositions by either MBE or MOCVD. The end result is an array of quantum well wires (QWW) shown in figure 1 with a period T, which is determined by the tilt angle, α of the substrate. Such QWW are considered to be superior to bulk and quantum well structures in laser applications due to a larger temperature coefficient, larger relaxation frequency, and smaller threshold current. Furthermore, these structures have several significant advantages in comparison with the arrays of QWW fabricated with the fine line lithography techniques. The lateral dimensions are in the low nanometer range which is suitable for obtaining sufficient quantum size effect, they are obtained processing free, hence is free from processing damage. There is one practical difficulty in the fabrication of a TSL, however. To keep the growth interface vertical one has to know the exact growth rates and keep them constant throughout the growth. Any deviation from the correct value would tilt the growth interface. This difficulty can be circumvented if one deliberately varies the growth rate from less than the correct value to greater than the correct value.5 Then one grows a superlattice with a curved growth interface and somewhere within the grown layer one obtains a vertical interface, hence two dimensional confinement as shown in figure 1 (b). In this paper a study of the optical properties of the SSL for quantum wire laser applications is undertaken. The most important criteria for this application is a large subband spacing, larger than the thermal energy and broadening of the energy levels due to unavoidable imperfections, and narrow subband widths to create well localized and sharp gain peaks.
Effect of dimensionality on the spatial coherence of phase-locked vertical-cavity semiconductor laser arrays
Authors: Orenstein M. , Kapon E. , Florez L. T. , Harbison J. P. , Stoffel N. G.
Published: February 2023

Phase-locked arrays of vertical-cavity surface emitting lasers (VCSELs) offer a wide range of applications, including optical computing, optical interconnects, printing, free-space communications and laser radar. The unique cavity geometry of VCSELs allows the construction of large arrays with both one- and two-dimensional (2D) configurations. For a given number of array elements, closely-packed 2D arrays should exhibit better spatial coherence since (a) their smaller diameter reduces adverse effects of wafer nonuniformities; and (b) the larger number of nearest neighbors and higher degree of connectivity in 2D arrays should yield more effective coupling. Here, we show that 2D arrays indeed exhibit improved coherence compared to their 1D counterparts because of their higher dimensionality, and demonstrate efficient phase locking of large (up to 25×25) arrays of VCSELs.
Implementation of dual parallel modulation in lithium niobate
Authors: Brooks J. L. , Maurer G. S. , Cornish P. W. , Becker R. A.
Published: February 2023

For broadband video transmission over fiber, high power linear signal transmission is desirable. Externally modulated diodepumped solid state lasers can provide high power, but linearization is required. We have implemented an approach recently analyzed by Korotky et al.1 A system performance evaluation of this dual parallel modulator approach has been submitted elsewhere.2 In this paper we focus our attention on nonideal device effects including electrical crosstalk, acoustic effects, and optical multipath interference.
Photorefractive effects in proton-exchanged LiTaO3 waveguides
Authors: Howerton M. M. , Burns W. K.
Published: February 2023

The proton exchange (PE) technique has been used to form high-quality waveguides in LiNbO3 and LiTaO3.1 LiTaO3 offers an advantage over LiNbO3 owing to its lower susceptibility to photorefractive effects (optical damage),2 making it suitable for high-power applications. Previous reports on photorefractive effects in PE LiTaO3 have primarily addressed power transmission through channel waveguides.3 At present, the mechanisms responsible for the improved photorefractive behavior of PE LiTaO3 are not well understood. Here we present quantitative results in active PE LiTaO3 devices and examine both photovoltaic and photoconductive contributions to the photorefractive effect.
Cutoff conditions and guiding characteristics of complex slab waveguides
Authors: Baruch E. , Salzman J.
Published: February 2023

With the early development of integrated-optic devices in lossy media and semiconductor lasers, the need to understand guiding conditions in complex-index waveguides became clear. Cutoff conditions in complex-index, slab waveguides were first studied by Burke1 and by Schlosser.2 The experimental implementation of gain-guided lasers, antiguide structures, guided-wave absorption sensors, and other devices motivated further theoretical investigations of guiding characteristics and modal parameters in complex slab waveguides.3,4
Optimization of tilted waveguide optical amplifiers with tolerant antireflecting coating
Authors: Salzman J. , Dembo R. , Einziger P.
Published: February 2023

Traveling-wave laser amplifiers (TWA) with angled facets were demonstrated as a feasible approach to the fabrication of devices with extremely lowmodal effectivereflectivity.1,2 Further improvement of these devices requires simple design rules to correlate the waveguide parameters, tilt angle, and optimal coating conditions in order to achieve lowest reflectivity values for TE and TM modes with maximum tolerance in the fabrication.
Bistability and unidirectional oscillation in semiconductor orbiter lasers
Authors: Oku S. , Kato H. , Okayasu M. , Ikeda M.
Published: February 2023

Semiconductor ring-type lasers that do not use cleaved-facet mirrors1,2 are promising for integrated photonic logic devices. Realization of a square-shaped laser when using straight waveguides and total reflection mirrors (hereafter an orbiter laser) would be advantageous, not only for their low-threshold operation potential but also for their novel functional capabilities exploiting clockwise and counterclockwise traveling wave oscillation. In this paper we demonstrate unidirectional oscillation of square orbiter lasers in semiconductor ring lasers for the first time. The orbiter lasers are also found to exhibit a unique optical bistability.
Coherent soliton switching in optical waveguides
Authors: Romagnoli M. , Wabnitz S. , Zoccolotti L.
Published: February 2023

The particlelike behavior of optical solitons makes them attractive for all-optical signal processing applications.1 Research in this field has involved switching elements based on optical fibers, where the nonlinearity is fast but weak. Waveguides with resonantly enhanced nonlinearities appear superior in terms of integration with the optical circuit and switching power requirements and may operate with ultrashort pulses that propagate in the coherent regime.2-3
Symmetric nonblocking integrated acousto-optic space-division switch modulo on LiNbO3
Authors: Kar-Roy A. , Tsai C. S.
Published: February 2023

Integrated-optic (IO) space-division switching architectures1 utilizing electro-optic (EO) switch arrays2,3 have been rigorously explored in recent years. In this paper we report on a symmetric nonblocking integrated acousto-optic (AO) space-division switch module that consists of a TI channel-planar-channel composite waveguide structure, a beam expanding/collimating and a focusing Ti-indiffused proton-exchanged (TIPE) waveguide lenses,4 as well as multiple tilted SAW interdigital transducers (IDTs) in a y-cut LiNbO3 substrate. Potentially, with increasing switch array size, this guided-wave AO space switch module will incur considerably lower increments in waveguide substrate size and performance parameters, such as cross talk, number of electronic drivers, insertion loss, etc., than the guided-wave EO switch modules.2 This AO switch module is capable of performing strictly nonblocking point-to-point multicast as well as multipoint-to-point switching.