bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub-picosecond Raman Spectroscopy of Electron - LO Phonon Dynamics in GaAs
Authors: Kash J.A. , Tsang J.C. , Hvam J.
Published: February 2023

Highly excited ("hot") conduction band electrons in GaAs lose their energy primarily by the emission of zone center LO phonons1. The quantitative study of this emission process requires the ability to measure the vibrational spectrum of GaAs on a sub-picosecond time scale. We have combined a sync-pumped dye laser with a filtered fiber optic pulse compressor to obtain spectrally clean 600 femtosecond pulses for wavelengths between 580 nm and 610 nm. A pump pulse generates excited carriers and a weaker, delayed probe pulse measures the Raman scattering from the phonons created by these carriers. Because the average probe beam power is of the order of 1 milliwatt and has a spectral full width at half maximum of about 30 cm-1, the weak Raman scattered spectrum is detected by a cooled, microchannel plate photomultiplier with a position sensitive resistive anode. Changes of less than 10% from the equilibrium room temperature phonon population can be observed using this system. Spectral shifts of the order of 10 cm-1 can be resolved.
Semiconductor Lasers for Ultra High Speed Applications
Authors: Yariv Amnon
Published: February 2023

There exist two important modes of modulation of semiconductor lasers: (1) direct current sinusoidal or pulse modulation, and (2) mode locking.
Suppression of Timing and Energy Fluctuations in a Modelocked Semiconductor Laser by CW-Injection
Authors: Mengel Finn , Lin Chinion , Gade Niels
Published: February 2023

Active modelocking of semiconductor diode lasers in an external cavity by synchronous electrical pumping is a simple and attractive method for generation of short optical pulses in the wavelength region of interest for optical communication [1]. Up to now, most attention has been paid to the time-averaged behaviour of pulse width, optical spectrum and time-bandwidth product, but pulse intensity fluctuations are of major importance in communications and logic applications. In this paper we investigate this type of noise and demonstrate a partial suppression by cw injection locking. Similar results have previously been demonstrated in a CO2 laser [2].
Femtosecond nonlinearities of standard transparent optical glasses
Authors: Etchepare J. , Thomazeau I. , Grillon G. , Migus A. , Antonetti A.
Published: February 2023

Several standard silicate glasses have been shown to present large third order susceptibilities (χ(3)≃10−14 esu)1. We report here kinetics of induced anisotropies resolved on a femtosecond time scale. For all the studied glasses, we find responses always limited by the pulsewidth which implies that the processes involved are of electronic origin. A correlation is verified between the nonlinearities and the linear indices of refraction and spectral dispersion.
Quantum-Confined Stark Effect in InGaAs/InP Quantum Wells Grown by Metal-Organic Chemical Vapor Deposition
Authors: Bar-Joseph I. , Klingshirn C. , Miller D. A. B. , Chemla D. S. , Koren U. , Miller B. I.
Published: February 2023

Multiple quantum well (MQW), composed of alternate very thin layers of two different semiconductors, show unusual optical properties at room temperature. One effect of particular recent interest is the quantum-confined Stark effect (QCSE)1. In the QCSE, electric fields applied perpendicular to the MQW layers can shift the optical absorption edge to lower photon energies with the exciton absorption peaks remaining clearly resolved. This electroabsorptive effect has been applied to make small, high-speed optical modulators2 and optical switching and signal-processing devices3 in GaAs/GaAlAs MQW.
Characteristics and Applications of Wideband Guided-Wave Devices
Authors: Gee C.M. , Thurmond G.D. , Yen H.W.
Published: February 2023

High-speed guided-wave devices are important for fiber-optic systems and high-speed signal processing applications. These devices are considerably more compact and require lower drive power than bulk electro-optic devices. Over the past several years, a number of high-speed guided-wave modulators and switches have been demonstrated.1-10 Table 1 lists a few of these devices which operate at multi-gigahertz frequencies. The widest bandwidth modulator is 17 GHz3 and the lowest switching voltage is 2V.4 In this paper, we will review design considerations and trade-offs for fabricating high-speed modulators.
Electrical Pulse Compression by Traveling-Wave Photoconductivity
Authors: Auston D. H. , Nuss M. C. , Smith P. R.
Published: February 2023

A substantial amount of work has been devoted to the development of nonlinear optical techniques for compressing ultrashort optical pulses to even shorter durations. To our knowledge, the possibility of developing analogous techniques for compressing picosecond and subpicosecond electrical pulses has not yet been considered. Although loaded nonlinear transmission lines have been used to propagate electrical soliton and shock-type waves, these techniques have not yet been adapted to the picosecond time range.
Picosecond Optoelectronic Study of a Thin Film Transmission Line Structure
Authors: Arjavalingam G. , Halbout J-M. , Kopcsay G.V. , Ketchen M.B.
Published: February 2023

In several laboratories high-speed logic circuits which are capable of generating electrical pulses with risetimes in the order of ten picosecond have been demonstrated [1]. Consequently it is now important to be able to transmit these pulses without significant distortion and to be able to characterize the transmission line structures used for this purpose with picosecond time resolution. In addition to the delay and distortion of the pulses as they propagate between generating and receiving points, knowledge of the noise coupled onto adjacent lines is of critical importance to the workings of computers and communication systems. Here we present measurements of high-speed pulse propagation and coupling on an experimental thin film transmission line structure. Photoconductive switches are used for generating and sampling the ultrashort electrical pulses used in this study [2].
MESFET Compatible IMSM Detectors
Authors: Rogers D. L.
Published: February 2023

One of the challenges in using high speed fiber optic links in computer communications is the recovery of the low level, high speed, electrical signals generated in the photodiode. Not only is high frequency, low noise amplification needed but a very small coupling loop between the detector and amplifier is required to reduce the noise coupled inductively from nearby circuits. Indeed, as the data rate goes up this noise increases as the square of the frequency.
Molecular Beam Epitaxy (MBE) for High Speed Devices
Authors: Cho A. Y.
Published: February 2023

Recent development in molecular beam epitaxy (MBE)(1) is to broaden the scope of the technology to cover a wider range of materials from semiconductors to metals and insulators. For III-V compounds, gas source molecular beam epitaxy (GS MBE, MO MBE or CBE) is used to grow compounds containing phosphorous(2-6). Precisely controlled electron-gun evaporation is used for Si-MBE(7) and metal-MBE(8). Fast loading of Hg source is used for II-VI compounds(9). The impact of MBE does not only contribute to new discoveries in quantum physics(10,11) but also to technology for generating a whole new generation of microwave(12) and optical(13) devices. The capability of MBE to engineer the band structure by superlattices and spatially varying the composition of semiconductors to create a specific gradient at the conduction and valence band edge or to accurately and abruptly control the layer growth to atomic dimensions pushes the frontier of devices to the ultimate imagination of device physicists and engineers.
An Optically Strobed Sample and Hold Circuit*
Authors: McConaghy Chuck
Published: February 2023

Radiation damaged photoconductors have been shown to be useful devices for sampling repetitve electrical signals with time resolution to less than a PicoSecond1,2. However, the sampling of low repetition rate or single shot events with these photoconductors has not been possible due to the need for lock in detection methods to observe the sampled signal. In this paper, a radiation damaged photoconductor serves as the sampling element in a sample and hold circuit. It has been possible to sample single shot electrical signals with about a 10 picosecond aperture time. Once sampled the signal can be held for about 1 microsecond by an on-chip holding amplifier.
Photoconductive Generation of Sub-Picosecond Electrical Pulses and their Measurement Applications*
Authors: Grischkowsky D. , Chi C-C. , Duling I.N. , Gallagher W.J. , Halas N.J. , Halbout J-M. , Ketchen M.B.
Published: February 2023

The generation of short electrical pulses via optical methods has for some time been performed by driving Auston switches (photoconductive gaps) with short laser pulses.(1) The shape of the electrical pulse depends on the laser pulseshape, the material properties of the semiconductor, the nature of the charge source, and the characteristics of the associated electrical transmission line. The same techniques can also measure the generated electrical pulses by sampling methods. An alternative measurement approach has been to use the electro-optic effect in a nonlinear crystal.(2) In this case, the field of the electrical pulse is sampled through the rotation of the polarization of the optical sampling pulse. Because it has demonstrated 460 fsec time resolution,(3) the electro-optic method is presently considered to be the fastest sampling technique. However, recent work utilizing photo-conductive switches has generated and measured subpicosecond electrical pulses.(4) This order of magnitude reduction in the generated pulsewidth demonstrates the ultrafast capability of the Auston switches and calls into question the conventional wisdom that electro-optic methods must be used to obtain ultrafast time resolution.
"Fast GaAs photoconductive detectors with high sensitivity integrated in coplanar sytems onto GaAs substrates"
Authors: Schumacher H. , Salz U. , Beneking H.
Published: February 2023

Hitherto optically activated switches consist of a gap between two metallic contact pads on a semiconductor substrate (fig. 1a). To gain a low "On"-resistance a focused laser beam of relatively high intensity has to be applied.
Comparison of Sampling Oscilloscopes with < 35 PS Transition Durations
Authors: Andrews James R.
Published: February 2023

The purpose of this paper is to compare transient responses of all of the various ultrafast sampling oscilloscopes. This study was limited to the fastest samplers with transition durations (10-90% risetimes) of <35 ps and corresponding bandwidths of >10 GHz. It is very important for users of these instruments to realize that none of them will give the correct answer when measuring picosecond domain signals. The same pulse signal measured with different samplers will result in different pulse waveforms as displayed on the CRT's.
A Technique for Wing Suppressed IR Sampling
Authors: Nees John , Williamson Steve
Published: February 2023

Short pulses in infrared are useful as in situ probes for devices fabricated on electro-optic semiconductors like GaAs.1 Sources of such pulses are under development with wavelengths extending to 1.6 μm.2 The most prominent technique currently used to achieve picosecond pulses in the IR is compression of Nd:YAG 1.064 μm in a fiber grating pair.3,4 It has been shown that propagation of short (100 ps) pulses through long (2 km) lengths of monomode fiber can lead to picosecond pulses with very low energy outside the central intensity spike. This method of compression makes use of the positive dispersion available in glass fibers at 1.064 μm. In an effort to extend in situ electro-optic sampling far below the bandgap of GaAs or to the sample in InP wavelengths longer than 1.35 μm are necessary, but the dispersion in glass fibers also begins to change sign. At color-center wavelengths from 1.4 to 2.3 μm there is no existing technique for such wing suppression.
Electro-Optic Sampling Analysis of Timing Patterns at Critical Internal Nodes in Gigabit GaAs Multiplexers/Demultiplexers
Authors: Zhang X.-C. , Jain R.K. , Hickling R.M.
Published: February 2023

Picosecond electro-optic sampling (EOS) has already been demonstrated by several researchers1-4to represent a unique capability for direct non-invasive probing of GaAs integrated circuits with high temporal resolution. In this presentation, we describe the use of this capability for a detailed analysis of on-chip waveforms at critical internal nodes in gigabit sequential logic circuits. Besides providing vital timing information between such internal nodes (and thereby providing the first clear measurements of timing parameters such as set-up and hold-times in flip-flops, and gate propagation delays is normally-loaded and normally-exercised gates), such EOS measurements report the first observation of effects such as clock feedthrough at internal nodes, as well as provide indispensable information on the accuracy of the modelling/simulations (typ. SPICE) that are usually done for the analysis of quirks in the internal behavior of such circuits.
16 Gbit/s Direct Modulation of an InGaAsP Laser
Authors: Gnauck A. H. , Bowers J. E.
Published: February 2023

The fastest transmission systems demonstrated to date are at a bit rate of 8 Gbit/s [1,2]. Laser modulation experiments at 10 Gbit/s NRZ and 8 Gbit/s RZ were recently reported [3,4] as well as simulations using the highest frequency components of a 16 Gbit/s NRZ code [5,6]. Recent improvements in the cut-off frequency of FETs and increases in laser modulation bandwidth now allow the investigation of optical systems at higher speeds by electronically multiplexing pseudorandom 2 Gbit/s signals of length 215-1 into a 16 Gbit/s NRZ bit stream.
Graphite as a Picosecond Laser Activated Opening Switch
Authors: Chauchard E.A. , Lee Chi H. , Huang C.Y. , Malvezzi A.M.
Published: February 2023

In a recent experiment, Malvezzi et al. have observed a large decrease in the reflectivity of a semimetallic sample of highly oriented pyrolytic graphite (HOPG) as it is illuminated by an intense picosecond laser pulse when the fluence is above the melting threshold. They have found that the imaginary part of the refactive index reaches lower than =0.5 at 566 nm [1]. This unexpected result indicates that a phase transformation occurs and that the high temperature phase, which they believe to be liquid, is non-metallic. This experimental observation is consistent with the result of the recent pseudo-potential calculation that there is an energy gap in "isotropic" carbon [2]. The time resolved experiments [1] also show that the phase transformation is completed in time scales as short as ~10 ps.
A Proposed Quantum Well Injection Transit Time Device (QWITT)
Authors: Kesan Vijay P. , Neikirk Dean P. , Streetman Ben G.
Published: February 2023

Oscillators using resonant tunneling through a quantum well have been the focus of much research recently [1-4]. Although they are potentially capable of very high frequency operation with low noise, the output power is in the order of tens of microwatts. Transit time devices like the IMPATT (impact ionization avalanche transit time) are capable of operating at 94 GHz and 140 GHz with 0.5 and 0.12 W power output respectively [5,6]. But collision effects in transit time devices seriously degrade the power and efficiency beyond 90 GHz and result in poor noise characteristics. Tunneling in the TUNNETT (tunnel injection and transit time) was proposed as a low noise alternative to the IMPATT, but poor injection phase delay lowers the efficiency of operation [7,8].
Nonequilibrium Phonons and Disorder in AlxGa1-xAs
Authors: Kash J.A. , Tsang J.C. , Jha S.S.
Published: February 2023

Despite alloy disorder, picosecond Raman measurements show significant nonequilibrium phonon effects in AlxGa1-xAs. The virtual crystal approximation is demonstrated to apply. Implications for heterojunction devices are considered.
Investigation of Photoconductive Picosecond Microstripline Switches on Self-Implanted Silicon on Sapphire (SOS)
Authors: Polak-Dingels P. , Burdge G. , Lee Chi H. , Seabaugh A.C. , Brundage R.T. , Bell M.I. , Albers J.
Published: February 2023

Optoelectronic switches, fabricated on amorphous- and implantation-damaged semiconductor thin films, have proven to be among the fastest of the picosecond photoconductors, with switching times less than 50 ps [1]. Ion implantation offers a systematic way to vary the disorder of materials from partially damaged to amorphous. With such materials, the relationship between implantation damage and carrier transport can be explored. Smith and Auston measured the dose dependence of the picosecond photoresponse for oxygen implanted into SOS, reporting an excess carrier lifetime of less than 10 ps [2]. Because oxygen itself may alter the material properties in addition to damaging the crystal, we have studied the photoresponse of Si-implanted SOS. The transport properties as a function of device gap length and bias voltage were measured. Raman scattering and resistivity measurements were made to characterize the material and were compared with the photoconductivity data.
High-Frequency Laser Modulation
Authors: Olshansky Robert
Published: February 2023

The commercial application of high speed laser diodes and modulators to lightwave systems is restricted by the limited availability of time-division multiplexing (TDM) circuitry at data rates above 2 Gb/s. The multiplexing of modulated microwave subcarriers is a promising new approach for circumventing this TDM bottleneck and for exploiting the full bandwidth capability of lightwave components.
Tunneling Dynamics and Resonant Coupling of Electrons in GaAs/AlAs Coupled Double Quantum-Well Structures under Electric Fields
Authors: Matsusue T. , Tsuchiya M. , Sakaki H.
Published: February 2023

Resonant tunneling(RT) phenomenon in double-barrier(DB) heterostructure[1,2] has a conceptual similarity to a transmission of optical waves in Fabry-Perot (FP) resonator and involves time delay. Its dynamics should be investigated since they limit the ultimate speed of RT devices. Such a study will also clarify similarities and differences between electronic and optical waves. In our previous work[3], we investigated the tunneling escape process of electrons from AlAs/GaAs/AlAs DBRT structures. The measured escape rate was well explained by the idealized theory of FP-like model, which predicts the tunneling escape time τ in DBRT structures is given by |t| 2vk/Lw, when |t|2 <<1, where t is the transmission coefficient through the barrier, vk is the group velocity of electrons and Lw is the well width. This predicted escape time is equal to the one calculated by the sequential tunneling model, suggesting that the tunneling escape time is not strongly dependent on the coherency of electron waves. This simple relation may not hold for the tunneling process between quantum wells(QW), where resonant coupling effect plays a more sophisticated role. To clarify the resonant tunneling phenomena between QWs, we report, in this paper, our study on electron dynamics in several different double GaAs QW structures separated by thin AlAs barrier, where the coupling condition between QWs was varied by electric fields. Tunneling process was studied at ~20K by measuring time resolved photoluminescence (PL). Picosecond pulses of a mode-locked dye laser were used to generate electron hole pairs in QWs, and the subsequent PL from particular QWs was monitored by a streak camera to determine the time variation of electron density in the QWs. Note that the electrons are lost either by recombination (radiative[4] and nonradiative) and/or by tunneling process. Since the mass of heavy hole is quite heavy, hole tunneling can be neglected at least in the initial phase of tunneling.
Observation of Low-Power-Level Picosecond Pulses Using Single-Photon Counting Techniques
Authors: Hamana M. , Kimura A. , Umeda T. , Cho Y. , Kanda M.
Published: February 2023

Picosecond measurement capability using low power-level pulses from semiconductor lasers based on a combination of nonlinear process and single-photon counting technique was tested and the preliminary result showed sensitivities of μW range.
Differential Sampling with Picosecond Resolution Using Bulk Photoconductors
Authors: Paslaski J. , Yariv A.
Published: February 2023

A photoconductive sampling technique is demonstrated whose resolution is independent of carrier lifetime and is in principle limited only by the RC charging time of the photoconductor.
Ultrafast Optical Studies of Tunneling and Perpendicular Transport in Semiconductor Microstructures
Authors: Oberli D. Y. , Shah Jagdeep , Deveaud B. , Damen T. C.
Published: February 2023

Ultrafast optical techniques provide a powerful means of investigating the dynamics of carrier transport and tunneling in semiconductor microstructures. We present a brief review of the basic concepts and various all-optical techniques. We then discuss our results on the direct determination of the dynamics of perpendicular transport using subpicosecond luminescence spectroscopy. Finally, we discuss our recent results on the direct determination of resonant and non-resonant tunneling times in asymmetric double quantum well structures.
Role of Electron–Electron Scattering on the Ultrafast Relaxation of Hot Photoexcited Carriers in GaAs
Authors: Kann M. J. , Ferry D. K.
Published: February 2023

The femtosecond relaxation of photoexcited carriers in semiconductors is investigated by the use of ensemble Monte Carlo calculations coupled with a molecular dynamics approach for the carrier-carrier interaction, to probe various scattering mechanisms and the dynamic screening of hot carriers in semiconductors. The results indicate that the initial rapid relaxation occurs on a time scale of tens of femtoseconds in GaAs decreasing with increasing carrier density.
Mobility and Lifetime Measurements on PECVD and Type IIa Diamond
Authors: Kania Don , Landen Otto L. , Pan Lawrence , Pianetta Piero , Ravi K. V.
Published: February 2023

Photoconductivity measurements were used to get carrier lifetimes and mobilities in three forms of diamond: (i) natural type IIa diamond, (ii) synthetic high-pressure, high-temperature bulk diamond, and (iii) plasma enhanced chemical vapor deposited polycrystalline diamond film. Signals were generated by picosecond ultraviolet laser pulses. We find that the lifetimes of carriers generated in both the thin film and the type IIa diamonds are in the range of 100 to 600 ps, varying from sample to sample. In the thin film material, a much longer lifetime component is also observed on some samples and is attributed to the diamond-like carbon transition layer found in these samples. The data also suggests a grain size dependence in the lifetimes. In the synthetic bulk diamond, there was no fast component and the lifetimes were on the order of 4 ns. Mobilities in the thin film and type IIa were also comparable (around 10 to several hundred cm2/V-s), while in the synthetic bulk material, mobilities were around 30 cm2/V-s.
Terahertz Time-Domain Transmission of Superconductors
Authors: Nuss Martin C. , Mankiewich Paul M. , O’Malley Megan , Goossen Keith W. , Roskos Hartmut , Tell Ben , Bhushan Manjul
Published: February 2023

The optoelectronic generation and coherent detection of extremely short electrical pulses with bandwidths in excess of several THz1,2 have made possible to study materials and electronic transport phenomena in a previously hardly accessible region of the electro-magnetic spectrum. These electrical pulses can be propagated in free space and collimated as well as focussed like optical pulses using lenses and mirrors.2 The extremely high signal-to-noise ratio of the electrical pulses generated by the photoconductive dipole antennas together with the phase sensitive detection scheme outperforms conventional Fourier-transform infrared spectrometers in the terahertz range by a large margin. Here, we use collimated terahertz radiation from photoconductive dipoles to study the electronic response of the Cooper pairs and of thermally excited quasiparticles in thin superconducting films. Historically, far-infrared studies of superconductors have been a crucial factor for the theoretical description of superconductivity and the agreement of these studies with BCS theory has been seen as a validity proof of the BCS theory.3-5
Triggering with Subpicosecond Jitter Using Resonant Tunneling Diodes
Authors: Özbay E. , Bloom D.M.
Published: February 2023

Resonant tunneling diodes (RTD's) with their superior high frequency characteristics, are attractive for high speed applications. As RTD's have terminal characteristics very similar to the Esaki Tunnel Diode, all current high speed applications of Esaki Tunnel Diode are good candidates for the use of new tunneling device. One such application is in high frequency trigger circuits.
Femtosecond Monolithic CPM Quantum-Well Lasers
Authors: Wu M. C. , Chen Y. K. , Tanbun-Ek T. , Logan R. A.
Published: February 2023

Monolithicly integrated mode-locked semiconductor lasers are compact and stable sources of ultrashort optical pulses.1−7 Their applications include multi-hundred Gbit/sec time-division multiplexed communication systems, ultra-high speed electro-optic sampling systems, soliton transmission in optical fibers, and generation of millimeter and sub-millimeter waves. The fully integrated optical cavities not only eliminate the tedious optical alignment processes in the mode-locked semiconductor lasers using external cavities and bulk optics, they also suppress the undesired multiple pulse output generated by residue intra-cavity reflections. The first sub-picosecond pulses from integrated mode-locked lasers were generated with a novel monolithic colliding pulse mode-locked (CPM) quantum-well lasers.6,7
Large Aperture Photoconducting Antennas
Authors: Auston D.H. , Zhang X.-C. , Froberg N. , Hu B.B. , Darrow J.
Published: February 2023

We describe a novel optoelectronic technique to generate and detect THz electromagnetic waves by using large-aperture planar photoconducting antennas and antenna arrays. This appoach is an effective method of producing directional and steerable sub-millimeter wave pulses.
Display of Microwave Waveform Via a Low Frequency Replica Using an Optical Phase-Locking and Sampling Technique
Authors: Li Ming G. , Huang Sheng-lung L. , Lee Chi H. , Hung Hing-Loi A.
Published: February 2023

Waveform measurement and dispay are very important for characterizing oscillator, amplifier or other device output performance. At frequencies below 400 MHz, conventional real time oscilloscope is the usual means to study this kind of waveform, while above 400 MHz, sampling scope takes this place. At present, conventional RF/microwave sampling scope has a maximum bandwidth of 20 GHz. A superconductive sampling scope, (by Hypres, PSP-1000) has extended the bandwidth up to 70 GHz, but this instrument is designed to operate at cryogenic temperature, cooled with liquid helium during normal operation.
All-optical micro wave gain measurements on MMIC amplifiers
Authors: Weingarten Kurt J. , Riaziat Majid
Published: February 2023

All optical swept-frequency measurement of the gain of two types of microwave integrated circuits, a feedback amplifier and a distributed amplifier, was demonstrated. A diode laser excited an on-chip photodetector and the circuit response was measured with electro-optic sampling. The only physical contact probes were DC bias probes for the circuit and the on-chip MSM photodetector. The optically measured gains compared favorably to independent network analyzer measurements using contact probing. The integrated photodetector needed for signal generation is process compatible with MMIC technology, occupies a small space on the wafer, and requires no additional processing steps. Since the yield of the photodetector is very high compared to the MMICs, the all optical test is potentially a practical and low cost approach for RF monitoring of circuits.
The Temperature Dependence of the Resonant Tunneling Process
Authors: Bar-Joseph I. , Gedalyahu Y. , Yacoby A. , Woodward T.K. , Chemla D.S. , Sivco D.L. , Cho A.Y.
Published: February 2023

The nature of a resonant tunneling process that involves inelastic scattering events is of a wide interest lately1–3. In this paper, we investigate the influence of inelastic scattering by measuring the tunneling characteristics at various temperatures. We show that the stored charge and the transit time are not sensitive to a large temperature change.
Competition Between Tunneling and Exciton Formation of Photoexcited Carriers in Asymmetric Double Quantum Wells
Authors: Kuhl J. , Strobel R. , Eccleston R. , Köhler K.
Published: February 2023

Time-resolved photoluminescence (TRPL) spectroscopy has been utilized by various groups to determine resonant and nonresonant tunneling times of electrons as well as of holes in asymmetric double quantum well (ADWQ) structures /1-4/. The main disadvantage of the TRPL method arises from the fact that it is impossible to measure electron and hole tunneling times simultaneously or to determine hole tunneling times directly in the absence of an electric field. These drawbacks are inherent to the linear TRPL technique since the photoluminescence (PL) decay time of the narrow quantum well (QWn) depends only on the tunneling time of the carrier type which tunnels faster.
Design and Construction of Holographic Optical Elements for Optical Photonic Switching Applications
Authors: Taghizadeh M.R. , Redmond I.R. , Walker A.C. , Smith S.D.
Published: February 2023

There has been a lot of interest in the possibility of the application of two-dimensional arrays of intrinsic optical bistable elements for cross-point switching in telecommunication systems and optical signal processing.
Optical Amplifiers for Photonic Switches
Authors: Jopson R. M. , Eisenstein G.
Published: February 2023

Although semiconductor optical amplifiers1,2,3,4 hold the promise of allowing lossless switch design, current optical amplifiers have properties that render them unusable in many applications. Two problems currently limiting their use are rapid Fabry-Perot variations in the gain spectra and bidirectionality of the gain. The figure below schematically illustrates the gain spectrum of a semiconductor optical amplifier. It can be seen that the broad (≈70-nm) semiconductor gain spectrum is multiplied by a rapidly varying Fabry-Perot spectrum. (The spacing between the Fabry-Perot peaks in the figure has been increased for illustrative purposes). Semiconductor optical amplifiers are usually made by putting an anti-reflective coating on the facets of a laser diode. It is the residual refectivity of the amplifier facets that causes Fabry-Perot resonances in the gain spectrum. The amplitude of this variation is determined by the product of the amplifier chip gain and facet reflectivity while the optical length of the amplifier waveguide determines the separation between the peaks. Since optical amplifiers typically have Fabry-Perot periods of 1.3 nm, it can be seen that there are actually around 50 Fabry-Perot periods within the material gain bandwidth rather than the 7 illustrated in the figure. While is possible to obtain high gain from an amplifier with strong Fabry-Perot resonances, the use of such an amplifier obviously presents wavelength control problems to the switch designer. Other less obvious problems in amplifiers with strong Fabry-Perot structure are: 1) the locations of the Fabry-Perot peaks are strongly temperature dependent, 2) the location and gain of the peaks are sensitive functions of the bias current of the amplifier, 3) they have more cross-talk and lower saturated output power than amplifiers with a smooth gain spectrum, and 4) the backward reflected gain is comparable to the forward gain. Given these problems, it is unlikely that amplifiers with large Fabry-Perot resonances will be of much use in photonic switching systems.
170ps Fast Switching Response in Bistable Laser Diodes with Electrically Controlled Saturable Absorber
Authors: Tomita Akihisa , Ohkouchi Shunsuke , Suzuki Akira
Published: February 2023

There has been great interest in optical data switching technology to meet increasing demand for massive data processing. Optical bistable devices have been considered as key elements for the optical data switching. Among the optical bistable devices, is a tandem electrode bistable laser diode (we will abbreviate this to BS-LD here). The BS-LD has various advantages over other optical bistable devices, such as large optical gain, high ON/OFF contrast, large optical output, and wide wavelength range for trigger light. The feasibility of BS-LDs as optical switching elements has been shown in 256Mb/s optical time division switching experiment1. The main factor limiting the BS-LD switching speed was the turn-off time rather than the turn-on time, as seen in most semiconductor optical bistable devices2. In order to achieve much faster switching operation in BS-LDs, it is necessary to reduce the turn-off time.
Physical And Optical Properties of Cd(Se, S) Microcrystallites in Glass
Authors: Hall D.W. , Borrelli N.F.
Published: February 2023

Since the demonstration of degenerate four-wave mixing in 'sharp-cut' filter glasses by Jain and Lind [1], considerable effort has been expended to understand the linear and nonlinear optical properties of glasses containing small amounts of Cd(Se,S) microcrystallites. This class of materials is promising for all-optical photonic switching devices: good optical quality samples are available, waveguide structures can be made using conventional ion-exchange techniques, the location of the absorption edge can be varied by composition changes across a wide range of wavelengths, and photo-recovery times on the order of ~ 10 ps have been reported [2,3]. Additional scientific interest in these materials comes from the observation of optical effects due to three-dimensional quantum confinement of photo-generated carriers [4] in specially treated samples.
Photonic Time-Division Switching Technology
Authors: Goto Hirokazu
Published: February 2023

With growing interest in visual information services, substantial needs for broadband communications networks are increasing. Optical switching systems are expected to have advantages over conventional electronic switching systems for use in switching broadband optical signals. Space-division, wavelength-division and time-division switching networks will be used in optical switching systems. Compared with the two other switching networks, the time-division switching network has an inherent advantage in providing a good match with existing time-division optical fiber transmission systems. This paper describes the principles and the present state of optical time-division switching technology. Further studies are also discussed.
Optical Logic and Switching Using Solitons
Authors: Doran N J , Wood David
Published: February 2023

Solitons occur in optical fibres with the propagation of short pulses in the negative group velocity dispersion regime. Solitons have the important property of dispersionless propagation and also behave in many respects as single entities. Nonlinear devices designed for optical switching respond to local intensities and thus do not function efficiently for typical ultrashort pulse envelopes. The device described here exploits the ’particle’ nature of solitons to produce excellent switching characteristics for entire pulses and also serves to illustrate the necessity for using solitons as the essential ’bits’ in ultrafast optical devices.
Switching Requirements for Broadband-ISDN
Authors: Fundneider O.
Published: February 2023

Telephone, telex and data networks today span the whole world and enable any parties to communicate with each other regardless of distance or time. In spite of their efficiency, these networks have one basic shortcoming: they are service-dedicated networks. A special terminal, a special network and a special service is required for each type of Information. The users of the communication networks, however, would like to be able to use all types of information in one session.
Optoelectronic Hybrid Switching
Authors: MacDonald R.I.
Published: February 2023

Optical methods have proved extremely successful for signal transmission and have very quickly formed the basis for a maturing industry. Other applications of optics to informatics are less natural. For example, it has been recognised that wideband transmission implies a future need for wideband switching, but the development of optical switches has proved difficult. Similarly the concept of optical computing may have great promise, but its present state is very primitive.
High-Speed Δβ-Reversal Directional Coupler Switch
Authors: Alferness R.C. , Buhl L.L. , Korotky S.K. , Tucker R.S.
Published: February 2023

Waveguide electro-optic directional coupler crosspoints find use in many applications including modulators and switches for optical fiber communication.[1] Recently there has been significant progress in titanium-diffused lithium niobate (Ti:LiNbO3) devices in both of these areas.[2],[3] To date, however, the emphasis of the device performance for modulation has been speed, drive voltage, and insertion loss; whereas, for switching it has been level of integration crosstalk, and insertion loss. Presently, for example, the switch arrays can be reconfigured only relatively slowly (0.1-1 GHz) and are appropriate for space division switching applications. However, optical switches capable of low crosstalk at reconfiguration rates above 1 GHz are important for time-division switching applications such as optical time-division multiplexing (OTDM).[4] The requirements for use in modulation and switching are, in fact, not necessarily conflicting. In this paper we describe a directional coupler crosspoint structure designed specifically for switching at multi-gigahertz reconfiguration rates with low ( < -20 dB ) crosstalk in both switch states.
Optical Digital Computers
Authors: Huang Alan
Published: February 2023

Summary not available.
Velocity-Matched Ti:LiNbO3 Switch for 16 Gb/s Optical Time-Division Multiplexing
Authors: Veselka J. J. , Korotky S. K.
Published: February 2023

We demonstrate a Ti:LiNbO3 switch at 1.3 μm wavelength that is optimized for 8 GHz operation using velocity-matching via periodic-phase-reversal. Crosstalk values of ≤-20 dB at 8 GHz were achieved for both switch states with a low drive power of 193 mW.
Relationship between the Hardware Required for Photonic Switching and Optical Computing Based on Free-Space Digital Optics
Authors: Hinton H. S.
Published: February 2023

This paper will review the optical hardware required for both photonic switching and optical computing systems based on free-space digital optics.
Optical Parallel Processor for Control of Photonic Switching Networks
Authors: Blumenthal Daniel J.
Published: February 2023

Given the extremely high channel bandwidth of photonic switching networks, the performance in terms of throughput and delay is greatly affected by the bandwidth and architecture of the control system. A parallel optical pipelined architecture can perform the complex crosspoint control of specific switch structures while maintaining the high throughput and bandwidth of pipelined processing. It is shown that the overall switch throughput and delay under centralized processing and control at very high data rates approaches that of distributed control, limited only by the propagation delay of the switch and the bandwidth of the processor. The performance of an integrated-optic tree switch controller is discussed and evaluated in terms of optical implementation and system optical efficiency.
Reduction of the Voltage-Length Product for a Y-branch Digital Optical Switch
Authors: Okayama H. , Ushikubo T. , Kawahara M.
Published: February 2023

The waveguide type optical switches which operate through modal evolution have attracted much attention by their digital response against applied voltage [1]. The most basic form of this switch is the Y-branch optical switch. Most of the devices reported used straight waveguides to form the Y-branch. Some devices with curved waveguides (shaped branch) were reported recently [2][3]. However, the structure was optimized only for a specific drive voltage and crosstalk. In this report we propose structures which are optimized for a wide range of drive voltages.
Photonic Switching Device by Integration of Heterojunction Phototransistor and Laser Diode
Authors: Noda Susumu , Takayama Toru , Shibata Kimitaka , Sasaki Akio
Published: February 2023

There is an increasing interest in optical information processing and optical computing. In the fields, various optical functional devices such as a photonic switch and an optical amplifier are greatly demanded. Thus far, we have demonstrated that these optical functional devices can be achieved by the vertical and direct integration of electronic and optical devices such as a heterojunction phototransistor (HPT) and a light-emitting diode (LED).[1,2] Since the optical device at the output side was an LED, the optical gain and the output power were small. To improve the optical gain, a laser diode (LD) must be utilized for the optical device. Furthermore, the additional attractive features due to the lasing oscillation can be expected.
High-speed Wavelength Switching Experiment for Wavelength-Division and Time-Division Hybrid Switching Networks using LiNbO3 Fabry-Perot Tunable Wavelength Filters
Authors: Nishio M. , Urino Y. , Kouta H. , Kondo M. , Suzuki S.
Published: February 2023

Wavelength-division (WD) and time-division (TD) hybrid switching networks are expected to be one of the strong candidates for future broadband ISDN (B-ISDN) H4 signal (around 150 Mbps) STM switching networks[1]. In these switching networks, high-speed wavelength switching operation of tunable wavelength filters is necessary. Recently, to confirm the feasibility of an 8 WD and 4 TD hybrid switching network to cater for 100 Mbps signals, a wavelength switching experiment was demonstrated with a TD multiplexed signal in a byte-interleaved signal form with 6.7-nsec guard-time. Wavelength switching within the guard-time was accomplished[2], by using a phase-shift-controlled DFB LD tunable wavelength filter[3]. However, a bit-interleaved signal form is more suitable for the hybrid switching network than that of a byte-interleaved signal form, because of the amount of hardware required for the time switch, used for the hybrid switching networks. To employ the bit-interleaved signal form, improvement in the wavelength switching time is required for tunable wavelength filters. Wavelength switching in times of 1 nsec has been reported, using a DFB LD tunable filter[4]. However, this type of filter with wavelength tuning principles based on the effective refractive index change due to the carrier injection effect, lacks the possibility of achieving less than 1-nsec wavelength switching time. This is mainly due to the value of the carrier life time.
Design Issues in Free-Space Optical Interconnection of Switching Systems
Authors: Tooley Frank A. P.
Published: February 2023

The recent development of large two-dimensional arrays of digital, optically bistable devices has facilitated the construction of test-bed, free-space switching systems1,2. This paper discusses aspects of the design and operation of these systems. Free-space switching systems may ultimately provide larger interconnection density than conventional electronic techniques. It is proposed that they therefore provide the switching fabric. The fabric is the part of the switch which routes data from the input to the required output. The input to the switch is not in a format suitable to send directly to the fabric. It includes the routing information required by the computer controlling the switch, the path hunt processor, and signalling protocol information that must be extracted and processed. The input data must also be re-synchronized and bit-aligned. Therefore, the operating wavelength of the fabric is unconstrained. It does not need to match the transmission wavelength. Similarly, with demultiplexing, the fabric data rate does not need to match the transmission data rate. Each array of logic gates provides data regeneration in a manner similar to electronic gates. Thus, although the devices must switch states at the fabric data rate, high output contrast is not required. Any comparison with systems using data ‘transparent’ devices, such as lithium niobate waveguides, is complicated since they operate as relational rather than logical devices.
Large arrays of symmetric self electro-optic effect devices
Authors: Chirovsky L. M. F. , Focht M. W. , Freund J. M. , Guth G. D. , Leibenguth R. E. , Przybylek G. J. , Smith L. E. , D’Asaro L. A. , Lentine A. L. , Novotny R. A. , Buchholz D. B.
Published: February 2023

For optical processing to become a reality, large arrays of optical processing gates are required with low energies and fast switching speeds. Arrays of symmetric self electro-optic effect devices (S-SEEDs) with as many as 2048 devices (64 x 32) have been made using batch fabrication procedures that process an entire wafer of devices at once [1,2]. In this paper we describe the extension of that work to arrays with 8192 devices (128 x 64) and 32768 elements (256 x 128). We also demonstrate 8 x 16 arrays of symmetric SEED modulators [3] with individual electrical access to the devices. The performance and uniformity of the arrays are more than acceptable to continue systems experiments with these types of devices.
Integrated self electro-optic effect device photonic switching nodes
Authors: Lentine A. L. , Chirovsky L. M. F. , Focht M. W. , Freund J. M. , Guth G. D. , Leibenguth R. E. , Przybylek G. J. , Smith L. E. , D’Asaro L. A. , Miller D. A. B.
Published: February 2023

The division between optical processing and electronic processing with optical interconnections can be a fuzzy one at best. Because of the limited functionality acheivable in "all-optical" logic gates, a growing interest is seen in "optical" processing elements made using optoelectronic devices with greater functionality [1]. Large scale integrated optoelectronic chips of quantum well self electro-optic effect devices (SEEDs) have been made [2,3] with fast switching times and low operating voltages and energies. The processing elements in these chips, the symmetric SEEDs (S-SEEDs) [4], have limited processing capabilities, in that they are set-reset latches and can be made to perform logic functions by pre-setting the device to a given state. We can, in theory, achieve arbitrary logical functionality by using a separate group of quantum well detectors configured similar to the field effect transistors in CMOS and NMOS circuits to drive a S-SEED configured as an output modulator [5]. These devices have many desirable qualities including, time sequential gain, effective input-output isolation, signal level and timing regeneration, wavefront quality restoration, and operation over decades in power levels due to the differential nature of the devices. In this paper, we describe the first integrated arrays of these devices, with each device or processing element having the functionality required to implement photonic switching nodes. Since these arrays were made using the same batch fabrication procedures that have yielded the large S-SEED arrays [6], we feel that the capability now exists to make large scale optoelectronic circuits of arbitrary functionality.