bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Loss Slow-Wave Coplanar Strips and Coplanar Waveguides for Electro-Optic Modulators
Authors: Rahmatian F. , Kulpa A. , Jaeger N.A.F. , James R. , Bégin M. , Khazaei H.R. , Berolo E. , Gannouchi F.
Published: February 2023

Slow-wave (SW) coplanar electrodes can be used in compound semiconductor based electrooptic modulators to provide microwave/lightwave velocity matching and, therefore, make it possible to obtain modulators with wide bandwidths [1]-[3]. The microwave index for conventional, thin, coplanar electrodes on GaAs is ~2.6 whereas the effective index for the lightwave guided by typical AlGaAs/GaAs optical waveguides is in the range 3.2 - 3.4. Higher microwave indices (larger than 2.6) can be achieved by incorporating capacitive fins, and/or capacitive fins with pads on their ends, in the gaps between the coplanar electrodes [1],[3]. Here, we compare SW coplanar strips (SW-CPS) with SW coplanar waveguides (SW-CPW). Measurements on several SW-CPS and SW-CPW show that microwave indices close to, and even larger than, 3.4 can be achieved; i.e., both SW-CPS and SW-CPW are capable of achieving the necessary velocity-match condition. Other factors of interest are the characteristic impedance and the loss. SW-CPS and SW-CPW both can be designed to be 50Ω lines and their losses depend very much on their geometries.
Electrooptic effect in CdHgTe heterostructures in the 1.5 µm range
Authors: Mula Guido , Pelekanos N.T. , Gentile P. , Magnea N. , Pautrat J.L.
Published: February 2023

The increasing volume of dala transfer through optical telecommunication networks is demanding lugli efficiency optical switches (e.g. photorefractive devices) in the wavelength range of 1.5µm. Narrow gap semiconductors like cadmium mercury telluride (CMT) are natural candidates for realizing spatial holographic interconnect of optical fibers at the telecommunication wavelengths thanks to their possibility to cover the spectral range of interest. CMT heterostructures have also the advantage of being almost lattice matched to CdTe and Cd(0.96)Zn(0.04)Te substrates allowing the growth of almost strain free devices. In the present paper we report on room temperature transmission electromodulation in the wavelength range of 1.5µm of multiple quantum well (MQW) CMT heterostructures diodes.
Fibre lasers for surgery
Authors: Weber HP. , Lüthy W.
Published: February 2023

According to the absorption properties of tissue, a laser for microsurgery should emit radiation of 2.9 µm wavelength. This wavelength is absorbed in tissue within 1 µm and leads to evaporation with a minimum thermal damage in the walls of the incision. If monomode emission is used, the laser light can be focused to a very small spot. The resulting thin coagulation layer, however, cannot stop bleeding from larger vessels. For haemostasis a wavelength of 2 µm with a penetration depth of several hundred µm is preferable. For application in surgery therefore both wavelength 2 µm and 3 µm have to be available. These wavelengths can be generated in fibre lasers doped with Erbium for 3µm emission [1] or Thulium and Holmium for 2 µm emission [2]. Monomode fibre lasers are optically excited with a pump beam that has to be launched into the small rare earth- doped core of the fibre with a diameter of typically less than 10 µm. In view of this small target also the pump laser has to be operated in low transverse mode order or even in fundamental mode. For such a pump laser the available power is limited to about 1 Watt. In our experiments an output power of 158 mW has been reached for ZBLAN:Er3+ fibres [1] and 30 mW for silica:Tm:Ho fibres. These values were only limited by the available pump power. The output power of CW monomode fiber lasers, can be enhanced using a double clad fibre structure [3]. Double clad fibres can be excited with powerful multimode laserdiode arrays. An output power of several Watts has already been demonstrated in a Nd3+ doped double clad fibre [4,5].
Stimulated Raman amplification of femtosecond signals in H2, D2 and HD gases
Authors: Krylov V. , Rebane A. , Erni D. , OIlikainen O. , Wild U. , Bespalov V. , D.Staselko
Published: February 2023

Stimulated Raman scattering (SRS) is a well known method for frequency conversion of laser radiation including ultrashort pulses. Stimulated Raman amplification (SRA) or seed SRS has been studied with nano- and picosecond pulses. Here we report experiments on SRA by excitation with 350-fs-duration pulses at 390 nm wavelength in different gases.
Quantum Optics in Communications
Authors: Karlsson  , Goobar  , Björk
Published: February 2023

Over the last decade, there has been several demonstrations of applications of quantum optics for optical communication. Examples include low noise ”squeezed” light, low noise amplification and detection, and secure communications - quantum cryptography using Heisenberg’s uncertainty principle as the garantuee for the detection of unwanted eavesdroppers.
Quantum cryptography using frequency-division transmission of optical phase
Authors: Slutsky B. , Sun P. C. , Mazurenko Y. , Rao R , Fainman Y.
Published: February 2023

Quantum cryptography is a recently developed technique for secure communication based on the principles of quantum mechanics. It permits two parties, who share no secret information initially, to establish between themselves a shared secret sequence of bits and then communicate over an open channel.
Optical Transmission of Photonic Colloidal Crystals
Authors: Vos W. L. , van Kats C. M. , Megens M. , Boesecke P.
Published: February 2023

Currently, a great effort is put in making optical photonic crystals, i.e. 3D periodic composites of dielectric materials with a lattice parameter a of the order of visible wavelengths λ. This is driven by the goal to make optical band gaps, that are expected in suitable crystal structures for refractive index contrasts m > 2 [1], and photonic parameters - defined as the polarizibility per volume – Ψ=πα/v > 0.5 [2].
Diode-pumped 1.6 W cw Nd:YAG Laser at 1.444 µm
Authors: Heine F. , Ostroumov V. , Kretschmann H. , Huber G.
Published: February 2023

The 1.444 µm transition of Nd:YAG offers the possibility of a diode pumped[1], high power[2], scaleable eye-save laser. Due to the four level nature of this transition, the performance is not limited by thermal population of the lower laser level, as in Er3+- and Tm3+- lasers at 1.5 µm and 2 µm. respectively. Furthermore the inherent simplicity of diode pumped lasers offers considerable advantages over optical parametric oscillators operating in the near IR, when tuning of the wavelength is of minor interest.
Combining and Beam Shaping Technique for High Brightness Circular Symmetric Focusing of Several Laser Diode Bars
Authors: Khaleev M.M. , Mak A.A. , Mikhailov A.V. , Novikov G.E. , Orlov O.A. , Ustvueov V.L. , Hollemann G. , Voelckel H.
Published: February 2023

A number of applications, one of them being end-pumping of solid-state lasers, require tight focusing of several high power laser diode bars (LDBs) with maximum brightness and circular symmetry of radiation. Due to the high asymmetry factor of LDB output Q-wxθx/wyθx, where w and θ are half of the beam size and divergence angle along the corresponding axis respectively, the simple method to improve circular symmetry by beam packing along the fast y-axis1 is not successful and thus a special technique of beam shaping is required. Earlier reported beam shaping technique used for a single LDB2 is not effective in our case using several diode bars. In this paper we describe a novel technique of combining and beam shaping of a number of high-power LDBs so that an output beam with high brightness and improved circular symmetry is achieved (patent pending). Our approach is based on bulk-optics design offering in prospect cost effective industrial production and accepting LDBs with arbitrary emitter geometry.
Bleaching of the Cr4+ doped Q-switches in resonator during the laser operation.
Authors: Bufetova G.A. , Klimov I.V. , Nikolaev D.A. , Shcherbakov I.A. , Tsvetkov V.B.
Published: February 2023

The study of the Q-switch bleaching during the laser operation of flashlamp pumped Nd-lasers was done both with external probe beam technique and with intracavity beam splitting. The second method was used to determine the influence of the intracavity electromagnetic waves interference on the Q-switch bleaching. The pinhole was used to achieve TEM00 mode operation.
Thermal Considerations in Transverse Geometries for High Power Copper Vapour Laser Pumped Ti:sapphire Lasers
Authors: Wadsworth W.J. , Coutts D.W. , Webb C.E.
Published: February 2023

Copper vapour laser (CVL) pumped Titanium Sapphire lasers have proved to be excellent sources of high repetition rate tunable near infrared radiation. The CVL wavelengths at 511 nm and 578 nm are well matched to the absorption band of Ti:sapphire and CVLs are unique as pump lasers in that they operate at high repetition rate (2-24 kHz) and high average power (up to 500 W in a single unit). With low power CVLs (up to 10 W per crystal face) longitudinally pumped Ti:sapphire lasers have proved to be a robust and efficient, offering excellent beam quality, low threshold (<0.6 W), and slope efficiencies up to 30% [1,2,3,4] giving the highest output power to dale of 5 W at 780 nm[1].
Blue and Green Emitting Multilayer Organic Electroluminescent Devices
Authors: Böhler Achim , Ammermann Dirk , Dirr Siegfried , Kowalsky Wolfgang
Published: February 2023

Organic light, emitting diodes (OLEDs) [1] have attracted considerable attention over the last decade. Complex multilayer devices with separate electron transport, hole transport, and emitter layers allow to achieve bright emission at low turn-on voltages. However, stability and charge carrier injection efficiency need to be improved for long term operation in flat panel displays.
Etching Studies of Frequency Doubling Glass Systems
Authors: Lesche B. , Garcia F.C. , Hering E.N. , Valente L.C.G. , Margulis W. , Carvalho I.C.S. , Asseh A. , Laurell F.
Published: February 2023

It is possible to induce second order nonlinear effects in glass systems, such as fibres, films or bulk silica samples by recording a permanent electric field optically, or by poling the samples with high voltages and heat. Characterising the charge distribution is central to understanding the mechanisms involved. We recently imaged frequency doubling gratings in fibres previously prepared for SHG, by etched the fibres until close to the core. Due to the presence of charges, etching is nonuniform, and the period of the grating can be unambiguously identified. Here, we present a simple technique to determine the charge distribution in poled glasses with submicron resolution. An interference pattern was formed by the reflections of a HeNe beam on the faces of a 1 mm thick poled slice of SiO2(3 KV, 280 °C). One of the faces was etched in HF, while the other was used as a reference, and the intensity of one fringe was monitored in real time. The optical path of the light reflected off the surface being etched was altered. When the glass was not poled, the etching rate was constant and a periodic variation of the fringe intensity was seen. When the glass was poled, a strong frequency modulation was observed. Positive charge resulted in slower etching, and negative charge caused faster etching [1].
Quasi-Phase Matched Parametric Fluorescence in Periodically Electric-field Poled LiNbO3 waveguides
Authors: Elhadi K. , Sundheimer M. , Baldi P. , Aschieri P. , DeMicheli M. , Ostrowsky D. , Webjörn J.
Published: February 2023

Recent and significant advances in Electric-field poling of LiNbO3 have made Quasi-Phase Matching (QPM) of great interest especially for Optical Parametric Oscillators [1]. Realizing waveguides in such poled materials is a very attractive idea in order to benefit from the higher power confinement achievable in waveguide configuration. The measurement of parametric fluorescence is useful for predicting OPO operation since it allows measuring the d-coefficient and then the gain, the bandwidth, and the tuning curves of a resulting OPO device without the need for building a resonnator.
Simultaneous Two-Frequency Bunching in a Free-Electron Laser
Authors: Glotin F. , Jaroszynski D , Marconilié O , Ortega J. M. , Prazeres R.
Published: February 2023

Summary : The CLIO infrared free-electron laser (FEL) is used as an user facility(1) since 1993. CLIO spectral range spans 3 to 50 µm and its peak power is several MW in 0.2 to 5 ps long micropulses. It is based on a dedicated radiofrequency linear accelerator. The repetition rate of the micropulses can be varied from to 32 to 4 ns during 10 µs long macropulses (at up to 50 Hz) and average power up to a few Watts is achievable. About 2400 hours of laser beam time are produced annually, of which 1600 are dedicated to laser users and 800 to FEL physics and optimisation studies : ultrashort FEL pulses, 2-colors operation, undulator step tapering, harmonic generation, self amplified spontaneous emission (SASE) and Compton backscattering. The CLIO infrared free-electron laser (FEL) is used as an user facility(1) since 1993. CLIO spectral range spans 3 to 50 µm and its peak power is several MW in 0.2 to 5 ps long micropulses. It is based on a dedicated radiofrequency linear accelerator. The repetition rate of the micropulses can be varied from to 32 to 4 ns during 10 µs long macropulses (at up to 50 Hz) and average power up to a few Watts is achievable. About 2400 hours of laser beam time are produced annually, of which 1600 are dedicated to laser users and 800 to FEL physics and optimisation studies : ultrashort FEL pulses, 2-colors operation, undulator step tapering, harmonic generation, self amplified spontaneous emission (SASE) and Compton backscattering. The two-colors operation has been demonstrated for the first lime with an FEL<2)by using a very simple scheme : two undulators are used, instead of one, and they arc tuned to different resonnant frequencies. By varying these frequencies (i.e. the undulator magnetic gaps) one can vary independanlly the wavelength of the colors within the optical gain bandwidth. On CLIO, at a given electron energy, the 2-colors wavelengths can be separated by a factor of up to two, when using a hole as the laser cavity output coupler. It was easily verified that the 2 colors are occuring simultaneously during the 10 ps long macropulse. However, the frequency distribution inside the micropulse remained unknown. Recently, we have studied the distribution of the 2 colors within the micropulse, which is only a few picosecond long, by means of sum frequency generation in a Te crystal. The occurcncc of the 2 colors sum frequency show ■ that they are produced simultaneously by the electron beam circulating in the undulators. Therefore the resulting electron beam shape does not look like 2, or more, successive trains of regularly spaced pulses, one for each color; it exhibits a more complicated structure corresponding to the superposition of 2 pulse trains, each being at a different frequency, i.e. a 2-frequency bunching. Autocorrelation spectra of the sum frequency and of each, doubled, single frequency have been recorded in order to better understand the distribution of the different colors within the micropulsc.
Boosted Laser Output by Kinetics Enhancement in Copper Vapour Lasers
Authors: Withford Michael J , Brown D J W , Carman R J , Piper J A
Published: February 2023

Over recent years we have shown that we can engineer the kinetics of conventional high-temperature CVLs using hydrogen additives, thereby improving their performance. In particular, we have shown that we can improve the spatio-temporal output characteristics of small- amd medium scale CVL systems, improving both their raw output power [1],[2] and high beam quality extraction [3].
Electrogasdynamic CO lasers with combustion products - a new scientific direction to the creation of the industrial high-power lasers
Authors: Baranov I. Ya.
Published: February 2023

The advantages of the CO lasers, compared with the most commonly used high-power CO2 laser, are in higher stability of the output power, ability to use high-quality optical materials, higher intensity in the near-field and far-field zones, higher efficiency and radiation power.
Proton-implanted KNbO3 exhibits net photorefractive gain at telecommunication wavelengths up to 1550 nm
Authors: Brülisauer Simon , Fluck Daniel , Günter Peter , Beckers Lutz , Buchal Christoph
Published: February 2023

Photorefractive crystals such as KnbO3, BaTiO3, and Sr1-xBaxNb2O6 are very promising for all-optical signal processing. Attention has been drawn to the extension of the photorefractive response up to telecommunication wavelengths. Recently it was shown that ion-irradiation of KNbO3 and BaTiO3 improves photorefractive response time and gain due to a significant increase of the trap density compared to the virgin crystal 1,2. Quite large photorefractive gain at 830 nm was reported in He+ ion-implanted Fe-doped KNbO3 waveguides together with a significant decrease in the response time3.
Optical subtraction using double phase conjugate mirror in a photorefractive waveguide
Authors: Kamshilin Alexei A. , Raila Erik , Silvennoinen Raima , Jaaskelainen Timo
Published: February 2023

Among the different geometries of photorefractive phase conjugate mirrors, the double phase conjugate mirror (DPCM) has a remarkable feature that it can be recorded in a crystal by mutually incoherent laser beams. It is very convenient for practical applications allowing to design simple optical interferometric schemes that use two independent lasers, Light diffraction from the DPCM creates phase conjugate waves of both pump beams independently on the complexity of the wavefronts. A DPCM property to transform a speckle beam into a plane wave has been recently proposed for applications in fiber-optic sensors and in heterodyne detection of ultrasonic signals.
Efficient 1.2 W cw Green Generation from an Intracavity Frequency Doubled Diode Pumped Microchip Nd:LSB Laser
Authors: Ostroumov V. , Huber G.
Published: February 2023

Microchip intracavity frequency doubled lasers are the way to make solid state lasers stable, compact and cheap. In our experiments the chip set was formed by a 1 mm long Nd:LaSc3(BO3)4 (Nd:LSB) crystal in optical contact with a 1 mm long KTP crystal. Nd:LSB is an efficient laser material for intracavity doubled solid state lasers due to perfect crystal quality, broad absorption pump band and short absorption depth [1]. Under the longitudinally pumping arrangement the planar uniformity of the cavity is broken by the pump beam inducing thermal lens which stabilises the resonator.
Optical frequency mixing in a tunable Nd3+-doped fiber laser.
Authors: Mollier P. , Porte H. , Hauden J. , Goedgebuer J.P.
Published: February 2023

Summary not available.
Two-Dimensional Photonic Crystal Material in Fibre form
Authors: Knight J.C. , Birks T.A. , Atkin D.M. , Russell P. St. J.
Published: February 2023

Photonic crystals are formed of periodically structured dielectric material, the pitch or period of the structure being of the order of the optical wavelength. A novel property of photonic crystal materials is they can be designed so as to exhibit photonic bandgaps. i.e. frequency ranges in which there are no propagating modes in the material.1 Some interesting consequences of such photonic band gaps occur for waves propagating out-of-plane in two-dimensionally periodic materials. One possibility is to fabricate low-loss waveguides which guide solely by Bragg reflection.2 This could be done by using a 2-D structure which is effectively infinite in the third dimension, and which exhibits a bandgap in its transmission characteristics for waves which have a certain wavevector component β=k. along the structure. By purposefully introducing some kind of defect which is embedded in the crystal structure we can create a spatially localized region where such a wave can exist - a "defect stale" appears in the band structure of the material. Light in this defect state would be unable to leak away from the defect through the crystal material, but would travel along the defect with propagation constant β.
The Effect of Transport on High-Speed Dynamic Performance of Quantum-Well Semiconductor Optical Amplifiers
Authors: Annetts P. J. , Asghari M. , White I.H. , Whiteaway J.E.A. , Collar A. J.
Published: February 2023

The advances in semiconductor device integration have generated interest in the integration of semiconductor amplifiers with laser sources for communication applications. For example, the enhanced output power of optical laser modulator sources integrated with amplifiers can have appreciable benefit. In such structures however, care must be taken to ensure that power levels within the amplifier do not become sufficiently large for patterning in the amplifier to cause cither significant system amplitude distortion or chirp. For Multiple Quantum Well (MQW) devices, carrier transport effects must be considered in detail as the carrier population in the barrier level, changing in a different manner from that in the quantum wells, contributes both indirectly to the overall amplitude distortion imposed by the amplifier and directly to the chirp. This paper therefore reports a detailed study of the role of carrier transport in optical amplifiers operating al high power, at modulation rates in excess of 10 Gb/s. It is shown that transport effects can substantially alter the chirp of the device.
Perturbed Solitons in Birefringent Fibres
Authors: Darkins S.M. , Elgin J.N.
Published: February 2023

When an ultra-short pulse propagates down an anomolously dispersive birefringent, optical fibre, complex features develop which require explanation. These include the generation of soliton shadows, internal oscillation of the (vector) soliton, and an inelastic scattering between solitons with an accompanying generation of radiation. The purpose of this talk is to describe a perturbation theory based on inverse, scattering theory which admits useful application to the study of these, and other, observed features. The theory is first described, then applied to some of these problems and results compared with those presented elsewhere.
Lidar Studies of Air Aerosol Pollution
Authors: Yegorov A.D. , Perelman A. Ya.
Published: February 2023

The lidar equation involves the two unknown properties of the atmosphere. Appropriate ambiguity problem of interpreting lidar measurement data is known. To solve the problem the new unconventional remote sounding techniques, for measuring the atmosphere properties without. traditional "a priori" assumptions have been developed. The lidar locaton and the scattering volume location are considered as independent variables of the lidar equation in the unconventional form.
A Procedure for Processing Remote Sensing Data of Inhomogeneous Scattering Media under a Priori Unknown
Authors: Onoshko Dmitry Michailovich , Kugeiko Michail Michailovich
Published: February 2023

It is widely accepted that retrievals of optical characteristics play an important role at the lidar environmental monitoring. Many methods have been developed to retrieve optical characteristics (optical depth, attenuation coefficient, etc.) in the lidar measurements. In the most cases they use the local and integral calibrate value of defined optical characteristics and need therefore the additional measurements or expanding of measuring information. Of great interest to those studying is to extract the essential calibrate date along with processing lidar sensing data at the same measurement without any additional ones.
Potato Leaves Reflection Spectra Investigations with the Aim of Classification and Disease Diagnostics
Authors: Belyaev B.I. , Belyaev Yu.V. , Chumakov A.V. , Katkovsky L.V. , Kurikina T.M. , Nekrasov V.P. , Shuplyak V.I.
Published: February 2023

At present the urgent problem is the development of the methods of plant diagnostics, enabling to identify the initial forms of a potatoes for the selection and to diagnose illnesses at earliest vegetation stages. For the decision of this problem it is possible to use the methods and the equipment of the spectral analysis in visible and near IR-region. We have developed the methods of the measurement and processing of potato spectral characteristics in the field conditions. We have carried out the large series of measurements on the experimental fields of Potato Research Institute of Belarus.
Second-harmonic generation in Pr3+-doped gallium-lanthanum-sulphide glasses for optical fiber amplifiers at 1.3 μm
Authors: Vermelho M. V. D. , de Araujo M. T. , Gouvcia-Neto A. S. , Sombra A. S. B. , Medeiros Neto J. A.
Published: February 2023

Praseodymium-doped gallium-lanthanum-sulphide (Ga:La:S) glasses are one of the most promising candidates for fabrication of optical fiber amplifiers in the wavelength region of 1.3 μm, due to their low phonon-energy and high quantum efficiency as compared to fluoride glasses [1,2]. The experimental investigation of Ga:La:S glasses under conditions of high optical powers around 1.3 μm and 1.0 μm is important because nonlinear processes that might occur, arc undesirable nonlinear loss mechanisms in optical fiber amplifiers. In the experiment, at 1.319 μm the laser delivered 150 ps pulses at 100 MHz repetition rate in a 700 ns Q-switch envelope at 1.0 kHz frequency. For operation at 1.06 μm the laser generated 100 ps pulse at 100 MHz repetition rate. Our investigations were conducted utilising Pr3+-doped Ga:La:S glass samples prepared by melt quenching in the molar ratio of 70Ga2S3:30La2S3, with typical dopant concentration of 500 ppm/wt. Figure 1 shows a typical power spectrum of the second-harmonic signal at 660nm generated in a 3 mm thick sample of Pr3+-doped Ga:La.S glass for an average fundamental power of 200 mW at 1.319 μm. The spectral bandwidth of 0.24 nm indicates a parametric frequency doubling process. The spectral characteristics at 1.06 μm has basically shown the same features. Time measurements revealed that the Q-switch envelope at 660 nm had a duration of ~500 ns and the individual pulses had duration of less than 200 ps. The second-harmonic signal intensity as a function of fundamental power was analysed and the results are depicted in figure 2. As can be inferred from log-log plot of data, the signal intensity at 660 nm presented, as expected, a quadratic dependence on fundamental radiation intensity For the highest fundamental power of 350 mW utilised to pump the sample, as much as 70 μW average power at 660 nm was generated and a frequency doubling conversion efficiency of 0.02% was obtained. A praseodymium-free Ga:La:S sample was tested and we have also obsened frequency doubled light generated from it. However, the samples doped with praseodymium presented a higher conversion efficiency.
All-Optical Inverter using Negative Nonlinear Absorption Effect
Authors: Maeda Yoshinobu , Ikeda Seiichi , Migitaka Masatoshi
Published: February 2023

There has been considerable interest in all-optical devices for achieving the high-speed and parallel processing. Up to the present the amount of absorption in any absorption process has been considered to be proportional to the incident light intensity until in some cases saturation occurs [1]. Recently we observed experimentally negative nonlinear absorption (NNA) phenomena which cause transmission to decrease as the laser intensity increase and confirmed that the transmitted laser intensity with the variation of incident laser showed negative nonlinear (i. e. Maeda's effect) [2, 3]. In this report we demonstrate that the net quantity of light absorbed in an erbium doped yttrium aluminum garnet crystal can be a negative function of the incident laser intensity. The absorbing material has a four-level energy structure: absorption can occur between a ground level and an excited level and between two other excited levels. The input-output characteristic has a negative region due to the absorption between excited states.
A simple and compact Raman shifter for tunable narrowband IR radiation
Authors: Khanbekyan A. , Sarkisyan D. , van der Ham E.W.M. , Vrehen Q.H.F. , Eliel E.R.
Published: February 2023

Tunable infrared radiation can be generated from tunable visible radiation by a variety of nonlinear optical techniques such as parametric generation, difference frequency mixing and stimulated Raman scattering. The latter technique is attractive for its inherent simplicity since it is automatically phase matched in contrast to the parametric techniques that require the use of birefringent materials.
Computer Simulation of Dynamic Processes in Photorefractive Crystals
Authors: Kutuzov V. , Petnikova V.M. , Shuvalov V.V. , Vysloukh V.A.
Published: February 2023

For today, only the steady-state regimes of nonlinear interaction in photorefractive crystals (PRC) have been fully understood1. The transient and dynamic processes are much more complicated and have been analyzed in details only for the case with plane or quasi-plane waves2. In this paper, we present our last results in computer simulation of dynamic processes and spatial-temporal self-oscillations in PRC.
Nanosecond optical response to pulsed uv excitation in KNbO3
Authors: Ewart M. , Zgonik M. , Günter P.
Published: February 2023

Interband photoexcitation in photorefractive ABO3 perovskites has only recently attracted the attention of researchers. Band to band excitation of electrons can lead to fast photorefractive response times [1] and, through trapping, to the sensitisation of impurity levels in the band gap. Strong effects are observed that lead to cw photorefractive response times on the microsecond time scale [1]. Absorption changes at visible wavelengths induced by uv illumination have been observed in BaTiO3 [2].
The Influence of Different Dopands on the Photorefractive Properties of BTO Crystals
Authors: Riehemann S. , Rickermańn F. , von Bally G. , Egorysheva A. V. , Volkov V. V.
Published: February 2023

Sillenite type crystals like BSO, BGO, and BTO are well known for their large photoconductivity, but they also show very small electrooptic coefficients and a large optical activity. So the resulting diffraction efficiency is rather small. To overcome these disadvantages different dopands can be used. In this contribution we present investigations on BTO crystals doped with different contents of calcium, gallium, cadmium and vanadium.
Self-phase conjugation technique via four wave mixing of middle infrared radiation in a laser active medium
Authors: Ageichik A.A. , Kotyayev O.G. , Rezunkov Yu.A. , Safronov A.L. , Stepanov V.V.
Published: February 2023

As it is known, self-conjugation of the IR laser beam via Brillouin radiation stimulated scattering phenomenon is not realised because of some physical limits on radiation intensity which are the principal limitations, to the present time. That is why, one of the promising technique of phase conjugation of infrared radiation is a self-conjugation of a laser beam wavefront via four wave interaction in a nonlinear medium with feed-back loop (FWMF) [1]. Unlike conventional our wave mixing schemes, the FWMF self-conjugation is supposed to be realised without any additional beams pumping a phase conjugation mirror.
Nonlinear-Optic Process of Fourier Transformation
Authors: Mouradian L. Kh. , Papazian T.A. , Yavrian A.V. , Zohrabian A.V.
Published: February 2023

We propose an all-optic Fourier transformer which completely reproduces the field of input radiation by Fourier image of output. The latter will allow to register the temporal envelope of radiation by means of common spectrometric measurement. This performance is similar to the task of classic spectroscopy where instead of amplitude and phase registration of radiation complex field, the temporal and spectral distributions of intensity are measured by oscilloscope and spectrometer. Moreover, the proposed optical Fourier transformer solves the problem of direct phase measurements of ultrashort pulses, as well this problem is reduced to simplest one dimensional registration technique of beams spatial profile of phase.
Novel Quasi-Soliton Pulse Formation Mechanism by Slow Loss Saturation and Self-Phase Modulation in Solid-State Lasers
Authors: Mikhailov V.P. , Kalashnikov V.L. , Kalosha V.P. , Poloyko I.G.
Published: February 2023

An effective pulse formation in solid-state lasers is available through the wide variety of resonant and non-resonant optical nonlinearities, e. g. self-phase modulation, nonlinear optical Ken effect and self-focusing. An extremely short pulses have been achieved due to the femtosecond response of these third-order nonlinearities. It was shown that the start of ultra-short pulse generation may be provided by external disturbances of a laser system, for example, by modulation of cavity period, also without the traditional amplitude modulation. It seems that mode locking can be obtained "easier" than one used to think before. Here we have shown that the laser system, with self-phase modulation and energy saturation of losses, potentially possesses a nonlinear mode which can be excited under certain conditions, that results in generation of ultra-short pulse train without usual passive mode locking. This technique is very attractive for use of passive crystalline shutters (such as YAG, GSAG and firsterite) aimed to ultrashort pulse generation in all-solid-state lasers.
Polarization switching in a 633-nm He-Ne laser caused by injection locking
Authors: Ohta Tatehisa , Kubota Munechika , Harimoto Tsuneyasu , Ichii Mariko , Ichinose Takumi
Published: February 2023

Polarization switching by injection-locking was observed in a 633-nm single-mode He-Ne laser with internal-mirrors[1]. In this study, detailed switching characteristics are investigated for the single-mode and two-mode lasers respectively.
Very Low Switching Energy of Differential PnpN Optoelectronic Device Using Multiple Quantum Wells and Mirror Layers
Authors: Lee Jeong-Ho , Kim Byung-Gee , Choi Young-Wan
Published: February 2023

PnpN double-heterojunction optical thyristor (DHOT)1 has gained great attentions lately for its potential applications in optical digital systems with various advantages such as fast response, low switching energy, low power consumption, high contrast ratio, and possibility of 2-D integration. Also, there have been many reports showing various applications of DHOT, such as programmable logic array in optical parallel interconnection, optical thresholder in neural networks, and dynamic memories in optical computer.
All-Optical Piezoelectric-Barrier Quantum Well Modulator at 1.5μm
Authors: Pelekanos N.T. , Mula Guido , Magnea N. , Pautrat J.L.
Published: February 2023

We report early experimental results demonstrating a novel all-optical piezoelectric-barrier quantum well (QW) modulator. The device is designed such that an incident control laser beam strongly modulates the ground slate QW resonance of the heterostructure. Essential to this design is the fact that in strained semiconductor heterostructures grown along a polar axis (in our case [211]), the lattice-mismatch induced strain generates a large piezoelectric field along the growth axis [1].
Formation Of Silver Thin Films For Nonlinear Optics By Ion Synthesis In Viscous Organic Matrix
Authors: Stepanov A L , Abdullin S N , Khaibullin R I , Osin Yu.N , Khaibullin I B
Published: February 2023

The nonlinear-optical behavior of metall nanoclusters embedded in dielectric materials have attractive properties for applications in optical devices. This paper describes the fabrication of silver particles in polymer substrate. A metal/polymer class of materials, produced by ion synthesis of metal nanoparticles in the organic matrix, has been studied from the point of view of formation mechanisms of dispersions, microstructure and optical properties Some preliminary investigations of silver/epoxy composites formed by ion implantation were presented early1. Now metal dispersions were produced by high-dose implantation of silver ions in epoxy at the different stages of polymerization process and were thus depend on metal concentration and polymer viscosity ratio The composites were characterized by transmission electron microscopy, image analysis and linear optical absorption at room temperature The average particle size can be controlled by the properties of the organic substrate, concentration of the metal and processing The silver dispersions give rise to optical absorption at the plasmon wavelength in the visible spectra and maximum of absorption is correlated with filling factor and size of particles. It is shown that 5-20 nm spherical silver particles with narrow log-normal size distribution have taken in near-surface region of viscous epoxy. It was observed the considerable increasing of size distribution width of synthesized particles at change of viscosity of substrate from similar liquid to solid state. Structure of granular silver films were be saving a constant at different quantity of dispersed metal in glass polymer.
Diffraction of the Optical Second Harmonic in Polymer Films, Poled Periodically by an Electron Beam
Authors: Pinnow M. , Danz R.
Published: February 2023

Diffraction of light is a well known linear phenomena based on lattices with periodical phase or amplitude modulation of the incident radiation. We present investigations of a nonlinear optical lattice, diffracting not the incident but the second harmonic radiation, which is generated in a periodical poled thin polymer film.
Electron Beam Production of Phase Masks for Direct Writing of Photo-Induced Gratings
Authors: Liu X. , De La Rue R. M. , Krauss T. F. , Thoms S. , Hicks S. E. , Ailchison J. S. , Zhang L. , Williams J.A.R. , Bennion I.
Published: February 2023

Grating based components for integrated optics have long been recognised as potentially very important for the range of functions they enable. In 1978, Hill and co-workers reported the demonstration of gratings directly written into the core of a germanosilicate fibre, by interfering the counterpropagating beams from an Ar ion laser1. Since those initial observations fabrication techniques have been refined and improved to the point where gratings are now commercially available2
Chirped pulse interferometry.
Authors: Van'kov A.B. , Chizhov A.A. , Kozlov A.A. , Yashin V.E.
Published: February 2023

In last years CPA technique is widely used for amplification of short pulses. However chirped pulse has some additional interesting properties which can make it perspective for another applications. For example in paper[1] was demonstrated long range, high resolution laser radar using chirped pulse to avoid nonlinear effects in air. This scheme with compression of the pulses in final stage in our opinion is unreliable and expensive because it demands autocorrelator or streak-camera for measurements. We propose the simple and reliable scheme based on chirped pulse interferometry with no compression. Theoretical analysis shows that two chirped pulses interference leads to spectrum modulation of the output pulse according to sin-like law. Depth of modulation depends on the ratio of the input amplitudes and period is in inverse proportion to time delay between two pulses. Accuracy of this method improved with number of measured spectrum periods. To measure spectrum modulation it can be used spectrometer consisting of diffraction grating, lens and CCD-camera.
Diode Pumped Erbium-Ytterbium Microlasers
Authors: Laporta P. , Svelto O.
Published: February 2023

Laser oscillators based on Er3+-doped glasses and fibers have recently become the subject of great interest, in particular for their potential use in optical communication systems operating in the 1530-1560 nm region [1-2]. In the last few years, miniaturized, practical and efficient ErbiumYtterbium glass lasers, end-pumped at 980 nm by InGaAs semiconductor lasers, have been developed by our group [3-4]. These devices are based on a suitably codoped Erbium and Ytterbium phosphate glass, where the concentrations of both dopant ions have been optimized to enhance the absorption of the pump light in very short absorption lengths (200 μm to 2.5 mm) and to achieve low threshold pump powers and high slope efficiencies. The basic resonator structure is very short (a few mm) and compact. CW single-frequency operation may be achieved either by inserting an intracavity Fabry Perot etalon as the mode selecting element [4], or using a monolithic microchip cavity with a mode separation larger than the gain bandwidth of the laser medium [5].
Erbium 3-μm Lasers: Concepts of Energy Recycling
Authors: Pollnau M. , Lüthy W. , Weber H. P.
Published: February 2023

With rising power in cw and pulsed operation erbium 3-μm lasers work their way into a variety of applications in surgery. Despite the unfavorable ratio of upper-level to lower-level lifetime cw laser operation is achieved in fluoride host materials solely due to the small branching ratio on the laser transition [1]. CW output powers exceed 1 W in LiYF4 [2] and 150 mW in a ZBLAN fiber [3]. Owing to geometry and erbium concentration the population mechanisms are different in crystals and fibers [4]. These mechanisms determine different concepts of energy recycling in the mentioned materials.
Pr3+ Co-Doped 2.8-μm Erbium Fiber Laser
Authors: Pollnau M. , Schneider J. , Unrau U. B. , Lüthy W. , Weber H. P.
Published: February 2023

The erbium 2.8-μm ZBLAN fiber laser is a promising candidate for surgical applications. Owing to pump excited-state absorption (ESA) from the lower laser level and subsequent competitive lasing at 850 nm [1] the 2.8-μm laser usually saturates at some 15 mW output power. Recently a cascade-lasing method has been demonstrated that overcomes the saturation and 150 mW output power have been achieved [2]. However, this cascade laser is extremely difficult to adjust and requirements concerning the specifications of the mirror coatings are high.
Diode Pumped Quasi-cw Laser Performance at 3 μm in Er3+-Doped YAG and YLF Crystals
Authors: Jensen T. , Huber G. , Chai B.T. H.
Published: February 2023

We investigated the laser materials Er(50%):YAG at 2.94 μm and Er(15%):YLF at 2.81 μm. For the quasi-cw laser experiments we used a lens duct [1] for collecting the diode laser beams and imaging them longitudinally into the laser crystal (Fig. 1). The resonator consists of a thin incoupling mirror (AR 970 nm and HR 0.1% 2.8-3 μm) and a slightly curved output mirror. For the experiments with Er:YAG a rear mirror transmission of 0.2% and for Er:YLF of 2% was chosen. We coupled two water cooled SDL-6200 diode stacks into the lens duct, each consisting of five 1 μm × 10 mm arrays emitting around 970 nm and being supplied with micro- cylindrical lenses for the fast divergence direction. In the horizontal plane the light is focused to the exit face of the lens duct by the refraction of the entrance face. The slow axis divergence of about 10° in the vertical plane is guided to the exit face of the lens duct by total reflections at the side faces. The exit face has a side length of 1.5 mm. The transfer efficiency of the lens duct is about 90%.
Model of non-linear operation of a hollow-waveguide laser with Gaussian mirror.
Authors: Witoński Piotr , Szczepański Paweł , Adamowicz Tadeusz
Published: February 2023

Waveguide structures have become one of the most commonly used gas laser structures in many applications. Especially among different waveguide gas laser, CO2 lasers have been extensively investigated theoretically as well as experimentally (see, for example, [1] and its references). One of the most important problems which appear in analysis of waveguide lasers is quantity of generated output beam. However using Gaussian reflectivity mirror as transmission one make possible improve quantity of the beam.
All-Metal RF Excited Waveguide, Free Space And Planar CO2 LASERS
Authors: Lipatov N. I. , Mineev A. P. , Nefedov S. M. , Pashinin P. P.
Published: February 2023

Radio frequency (RF) excited waveguide, as well as free space carbon dioxide (CO2) lasers have received in the last years intensive development [1-4]. The waveguide CO2 lasers were improved from all-ceramic channel structures to metal-ceramic channel and planar ones, which supply better cooling of active laser medium and the most widely used now. But the selection of ceramic is very limited, or alumina, or oxide beryllium, which are expensive and the last besides toxic in operation.
Continuous-wave dye-laser-pumped KTP-OPO
Authors: Klein M. E. , Scheidt M. , Boller K.-J. , Wallenstein R.
Published: February 2023

Continuous wave optical parametric oscillators (OPOs) are of interest for the generation of widely tunable coherent radiation in the infrared. Of advantage are noncritically phasematched, pump-resonant OPOs based on the nonlinear material KTP These devices have been pumped by a Ti:sapphire laser [1] and - because of their low threshold power - even with diode lasers [2]. In addition, dye lasers may be considered as suitable pump sources for such OPOs. This is because they provide tunable narrowband radiation at shorter wavelengths with output powers of up to 2W in nearly diffraction limited beams.
Two 40 Khz Repetition Rate Independently Tunable, Synchronised Femtosecond Pulses Generated In The Visible Using Optical Parametric Amplifiers
Authors: Towrie M. , Matousek P. , Parker A. W. , Taday F.P. , Toner W. T.
Published: February 2023

Many time-resolved spectroscopy techniques require two broadly and independently tunable, synchronised light pulses. Recent advances in short pulse laser technology and non-linear crystal materials have lead to rapid development of optical parametric oscillators (OPOs) and travelling wave optical parametric amplifiers (OPAs) capable of meeting these requirements. Our aim was to develop a multi-kilohertz repetition rate OPA system for femtosecond/picosecond, pump and probe time-resolved absorption and resonance Raman spectroscopies. We believe this work reports, for the first time, on synchronously pumped travelling wave OPAs. The design similar to that described in [1] was adopted for the development of the OPAs.
The relative signs of the nonlinear coefficients of KTP
Authors: Anema A. , Rasing Th.
Published: February 2023

Various authors have measured the values of the nonlinear optical d-coefficients of KTP and also tried to give an answer about the relative signs of these coefficients. We want to point out that, in our opinion all the signs are the same.
The nonlinear optical properties of KTA
Authors: Anema A. , Isaenko L. , Rasing Th.
Published: February 2023

Since the discovery of the promising nonlinear optical (nlo) properties of KTA (larger d-coefficients and spectral range than KTP) there has been some confusion about the precise nlo coefficients.
Kerr-Lens Modelocked Cr:LiSAF Femtosecond Laser Pumped By The Diffraction Limited Output Of a 670nm Laser Mopa System
Authors: Robertson A. , Knappe R. , Boller K-J. , Wallenstein. R.
Published: February 2023

The modelocked, all-solid-slate laser, based on the material Cr:LiSAF, has reccnlly been established as an excellent source of femtosecond pulses [l]. As well as exhibiting an extremely wide emission bandwidth (780nm to 950nm) necessary for the production of ultra-short pulses, the material is amenable to pumping with the new generation of AlGaInP laser diodes which provide an output which matches the red absorpion region of Cr:LiSAF (640nm to 680nm). The use of semiconductor laser pumping is often bcntficial when using solid state laser materials, resulting in more stable, compact, and efficient systems, as compared to their ion-laser-pumped counterparts.