bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel Experimental and Theoretical Results on the Pulse Poling Mechanism of Second Order Nonlinear Optical Polymers
Authors: Michelotti Francesco , Toussaere Eric , Zyss Joseph
Published: February 2023

Electrode poling of a crosslinkable electrooptic polymer was investigated upon application of cw and pulsed electric fields. The measurements were carried out on Red Acid Magly polymer, which is a crosslinkable extension of the currently used Disperse-Red 1 MMA side chain polymer1. Thin solid films were produced by spin coating on ITO coated glass substrates and then cladded with two adjacent gold electrodes. The ITO and gold layers were used both as poling and modulating electrodes throughout the measurements. Poling was obtained contemporarly in both zones by applying a cw electric field (130 V/µm) between ITO and one first electrode and a square wave electric field

(

E
p

miax

=
100
 
V
/
μ
m
,

E
p

min

=
0
 
V
/
μ
m
,
v
=
1
Hz

)

between ITO and the second electrode. Temperature was high enough to initiate the crosslinking process (Tp=130°C) and the time sufficiently long to saturate it2.
Ba2ErCl7 - a New Upconversion Material Emitting in the Near UV Region
Authors: Egger Ph. , Rogin P. , Riedener T. , Wickleder M. S. , Güdel H. U. , Hulliger J.
Published: February 2023

Most of the upconversion lasers implemented so far are based on rare earth doped oxide or fluoride crystals as well as fluoride glass fibers [1]. However, lower phonon energies of chloride and bromide materials, leading to less efficient multiphonon relaxation, are supposed to bring laser action within easier reach. Indeed, materials such as cs3er2cl9 [2] exhibit enhanced upconversion efficiencies. Unfortunately, such compounds are (in some cases extremely) sensitive to moisture. New materials that would combine efficient upconversion and stability to withstand storage, processing and operation under moderately dry conditions are subject to be found. In addition to other promising host lattices, we developed Ba2ErCl7 [3], recently reported by Japanese industrial researchers [4]. This compound shows bright greenish and white luminescence upon excitation around 800 nm and 980 nm, respectively. On the other hand, sensitivity to moisture turned out to be less critical than observed for e.g. Cs3Er2Cl9.
Ultra high power CO2-lasers with coaxial electrodes and fast gas flow
Authors: Schuöcker Dieter , Bohrer Markus , Braunsteiner Arnold , Schröder Kurt
Published: February 2023

Fast flow RF-excited CO2-Lasers with coaxial electrodes have been shown to be very well suited for the generation of ultra high beam power up to 100 kW with a moderate plasma volume and satisfactory beam quality. A detailed analysis demonstrated that the latter beam power can be reached, if four discharge modules with an outer diameter of 40 cm and a length of 80 cm are optically connected in series in one common resonator. These modules must be energized each by 180 kW RF power and independently cooled by a fast gas flow of 10 m3/s.
The effect of the discharge frequency on the performance of RF excited CO2 waveguide lasers
Authors: Witteman W.J. , Ochkin V.N. , Ilukin B.I. , Kochetov I.V. , Peters P.J.M. , Udalov Yu.B. , Tskhai S.N.
Published: February 2023

It is well-known that the highest continuous power generation of CO2 lasers, about 20 W per cm3 active medium is obtained with RF discharges in waveguides. For that reason a detailed study of the physics of RF discharges as a function of frequency, gas density and power dissipation in CO2 laser gas mixtures is a challenge. Compared with the longitudinal dc discharges the RF discharges are transversal and mainly characterized by the sheath formation and the oscillating amplitudes of the discharge electrons which causes a part of the electrons to disappear into the electrodes. From a simple theory one finds that the thickness of the sheath decreases with density and frequency. However, the absence of quantitative values of the sheaths and electron behaviour and their relations with other parameters of the discharge and the laser prevented the understanding of experimental results and adequate predictions of the performance.
Narrow gap slab discharges for fast axial flow lasers
Authors: Betterton J G , Baker H. J.
Published: February 2023

In recent years, narrow electrode gap. area scalable discharges produced by transverse RF excitation have given major increases in power density for diffusion cooled CO2, CO and Xe lasers, with hybrid resonators, such as the stable/waveguide-unstable configuration giving high beam quality [1]. Fast flow gas lasers produce higher total power, but operate at lower power density, limited by gas flow and discharge stability effects. In this paper, we investigate the narrow gap, slab RF discharge with fast axial gas flow as a route to high pressure, high power density, continuously operating gas lasers.
The Analysis of Particulate matter (PM10) with special reference to diesel particles in the Plymouth atmosphere
Authors: Dye A.L. , Rhead M.M. , Trier C.
Published: February 2023

Summary not available.
Residual fluorescence anisotropy: A probe of two photon excitation with resonance energy migration
Authors: Andrews David L. , Allcock Philip
Published: February 2023

Recent studies of resonance energy transfer have extended the early works of Perrin and Galanin to include, not only the residual anisotropy following near zone Förster-type energy transfer, but also the retardation effects manifest in the long range radiative results [1,2]. In this paper we report new theoretical results for two photon fluorescence migration in a two-component system, determining the residual fluorescence anisotropy at both the long and short range asymptotes. In employing a two level approximation for the polar centre we are able to obtain tractable results for the fluorescence anisotropy ratios, in a form that resembles Perrin’s (single centre) result.
Ultraviolet induced photochromic and photorefractive effects in BaTiO3
Authors: Ross G. W. , Moniemezzani G. , Bemasconi P. , Zgonik M. , Günter P.
Published: February 2023

It is known that the optical properties of oxide crystals, such as BaTiO3, LiNbO3 and KNbO3, are strongly influenced by the presence of impurity levels in the bandgap of the material. The distribution and population of these levels have been the focus of much recent research into the tailoring of photorefractive materials to respond to near infrared wavelengths compatible with compact solid-state laser diodes [1]. The impurity levels must have a sufficiently high occupation to provide significant absorption at a wavelength of interest. However, in thermal equilibrium most levels are not occupied by an excitable charge carrier and therefore do not contribute directly to the optical nonlinearity. The creation of a nonequilibrium state by optical illumination may produce a more convenient charge distribution in the material band gap levels.
Stabilization of the phase conjugate reflectivity in photorefractive four-wave mixing
Authors: SHIMURA Tsutomu , NAKAMURA Atsushi , KURODA Kazuo , WAKIMOTO Hiroyuki , TSUKAKOSHI Mikiro
Published: February 2023

Phase conjugate reflectivity of the photorefractive four-wave mixing system is usually quite unstable and it is serious issue for practical use of these systems. The cause of this instability is mainly combination of the fluctuation of the phases of input signal and pump beams and the slow response time of the photorefractive crystal. When all input beams in the four-wave mixing system are mutually coherent and the phases of the input beams are not stable, four kinds of gratings are compete each other and the phase conjugate output becomes quite unstable. To avoid this problem, we can make one of the pump incoherent to the signal and another pump1. The phase conjugate output is, however, still unstable due to the rewriting of the grating caused by the fluctuation of the phase of the input beams. In this paper, we report our feedback system to stabilize the power of the phase conjugate output from the four-wave mixing system by controlling the phase of the signal beam. In this system, we detect the phase difference between signal and forward pump beam with lock-in amplifier and control the phase of the signal with a piezoelectric mirror to stabilize the phase difference.
Phase aberration correction of laser optical system via dynamic holography
Authors: Ageichik A.A. , Kotyayev O.G. , Rezunkov Yu.A. , Safronov A.L. , Stepanov V.V.
Published: February 2023

To correct complex optical system aberrations a number of phase conjugation techniques are widely developed, for the present time. The phase conjugation, used for imaging telescope systems, is found to improve of a system resolution and to compensate for stress- and heat -induced aperture aberrations during an observation of remote objects. The main PC techniques are based on four wave mixing of radiation in a nonlinear medium or on self-conjugation of observed signal. However, every PC method operates under limiting conditions. For example, self-conjugation technique is limited in a signal threshold level that restricts imaging telescope system sensibility. In the case of FWM technique use, the input radiation coming from a remote object must be coherent to a laser radiation pumping the PC mirror.
Self-Starting Kerr-Lens Mode-Locked Nd:YAG-Laser
Authors: Henrich B. , Beigang R.
Published: February 2023

Kerr-lens mode-locking (KLM) of solid state lasers is a very powerful method to generate ultrashort light pulses. Pulses as short as 8.5 fs have been obtained directly from a Kerr-lens mode-locked Ti:sapphire laser [1]. In this contribution we report on a self-starting KLM end-pumped Nd:YAG laser.
Laser Remote Sensing of Phytoplankton
Authors: Chernyavskaya Elina A.
Published: February 2023

Quantitative measurements of the photosynthetic activity of the sea phytoplankton are very important now.
Pulse poling of second order nonlinear optical polymers
Authors: Miclielotti Francesco , Garofolo Andrea , Bertolotli Mario , Toussaere Eric , Zyss Joseph
Published: February 2023

We report on the investigation the electric field poling of side-chain Disperse Red 1-MMA polymer1. Thin solid films were produced by spin coating on ITO coated glass substrates and then cladded with a gold electrode. The ITO and gold layers were used both as poling and modulating electrodes throughout the measurements2. Electrode poling was performed by applying either cw or pulsed electric fields between the electrodes of the sandwich structure.
Organic Electroluminescent Devices Using Rare-Earth Complex Thin Films
Authors: Dirr S. , Johannes H.-H. , Ammermann D. , Böhler A , Kowalsky W
Published: February 2023

Organic light emitting diodes |1| using fluorescent dyes show visible light emission with spectral bands of about 80 nm. The color perception by the human eye is therefore insatisfactory for display applications. Filters or microcavities may reduce this problem, however, they are not practicable for low-cost, fabrication. To overcome these disadvantages, rare-earth complexes with luminescent bandwidths of about 5 to 10 urn have been developed |2|. For green and red electroluminescent devices thin films of the complexes europiuni-tris(l-thenoyl-3-trifiuoracetona1.e)-1.10-phenanthroline (Eu(TTFA)3Phen) and terbium-tris(l-acetyl-3-acctonate)-1.10-phenanthroline (Tb(ACAC)3 Phen) have been prepared. Our first realized organic light emitting diodes with the europium complex as emitter exhibit nearly monochromatic red light with a luminance of 2cd/m2 and drive voltages of about 5 V.
The Analyse of Optical Field-Equations in Stochastic Media and the Solving of Inverse Scattering Problem
Authors: Iftimia N. , Babin V. , Iftimia Ileana
Published: February 2023

The paper analyse the propagation of optical field (in approximation of a plane wave) in a turbulent medium. We will determinate the distribution of intensity and reflection coefficient by considering the situation described in the figure 1.
High Power (55 W CW) Surface Emitting 0.8μm GaAlAs/GaAs Laser Diodes
Authors: Peyrot C. , Vassilakis E. , Marquebielie G.
Published: February 2023

High power Monolithic Surface Emitting Laser sources operating at 808 nm are very Interesting tor applications such as high duty cycle (20 to 30%) or CW mode sources for pumping Nd: YAG rods or slabs because of their brightness (10° × 15°) and their high optical power density.
Experimental characterization and theoretical modelling of a diode laser oscillator amplifier system with a near diffraction limited output of 2.85 W
Authors: Beier B. , Gehrig E. , Boller K.-J. , Wallenstein R.
Published: February 2023

Near infrared diode lasers are compact laser sources of high efficiency. Diode laser radiation with diffraction limned divergence are generated by single stripe diode lasers with limited output power (P < 100 mW) or by high power oscillator-amplifier systems as demonstrated e.g. by a 5.25 W tapered diode laser-system [1].
Multiplex coherent anti-Stokes Raman spectroscopy using a pulsed optical parametric oscillator: comparison of broadband and two-colour techniques
Authors: Baxter G. W. , Haub J. G. , Orr B. J.
Published: February 2023

Coherent anti-Stokes Raman spectroscopy (CARS) is a form of nonlinear-optical spectroscopy that is useful for spectroscopic sensing of high-temperature media. Earlier research1 evaluated optical parametric oscillator (OPO) devices as an alternative to dye lasers in providing tunable coherent light for this purpose. Further development of the OPO CARS theme follows demonstrations2,3 of how to control the optical bandwidth and output wavelengths of a pulsed OPO with a passive ring cavity, injection-seeded by a single-mode external-cavity diode laser (ECDL). We have succeeded in injection seeding a single pulsed OPO at two separate optical frequencies that fall within its intrinsically broad optical bandwidth, using a pair of ECDLs. This OPO-based strategy enables single-shot, two-colour multiplex CARS measurements4 that can be used for combustion diagnostics, as has previously been demonstrated with dye-laser sources.5
Two is enough: dynamics of a two modes laser for intracavity laser absorption
Authors: Lacot E. , Stoeckel F. , Romanini D. , Kachanov A.
Published: February 2023

Ideal intracavity laser absorption spectroscopy (ICLAS) can be explained as a competition of individual modes of a highly broadband laser sharing the same homogeneous gain medium without any coupling between each other. In such a case, a narrow spectral absorption appearing in time on the envelope of the spectrum follows the classical Lambert-Beer absorption law with an equivalent absorption path Leq=c.tg. [1]. The limitation of the sensitivity is theoretically due to the spontaneous emission and the absorbance stops to grow for a typical time τsp of one second for solid state lasers, which correspond to an equivalent absorption path of 300,000 km [2]. Experimentally the saturation of the sensitivity appears for a much shorter time τNL which decreases when the pump power increases. This suggest that non linear coupling between modes exists and play an important role in the spectro-temporal dynamics [3,4].
Coherent Das Lidar System for Pollutants Monitoring
Authors: Iftimia N. , Strzelec M. , Kopika M. , Spanulescu I. , Babin V. , Ersen S.
Published: February 2023

Based on differential absorption and scattering technique, the presented lidar-system use as emitter a tunable CO2 laser. The laser beam is emitted, alternatively, at two frequencies v1 and v2, in a sufficiently narrow spectral interval, to can assume that the volume extinction coefficients of atmosphere (due to aerosol and molecular scattering) are constant. The control of emitted lines is made using a computer controlled step motor system that rotates the diffracting grating of the laser resonator. To measure the range and velocity of pollutant clouds, the laser beam is acousto-opticaly modulated using the "chirp" technique. This principle was described in a previous paper [1].
Gain and performance of a transverse RF excited cw atomic xenon waveguide laser
Authors: Blok F.J. , Tskhai S.N. , Udalov Y.B. , Peters P.J.M. , Witteman W.J.
Published: February 2023

We have recently shown the first good laser performance of a continuous wave Ar:He:Xe laser with RF excitation1. The laser can deliver a cw output power in excess of 1 W. This output comes mainly from two wavelengths2: 2.03 µm and 2.65 µm. A key parameter for laser-action is the gain. We measured the gain on these two wavelengths in a waveguide of dimensions 2 × 10 × 50 mm3, a gas mixture of Ar:He:Xe (60:40:0.5) and an excitation frequency of 112 MHz. The gas pressure was varied from 80 to 360 mbar and power deposition into the plasma is up to 400 W.
Conjugated cavity with the wide field of vision
Authors: Kornev A.F. , Pokrovsky V.P. , Stoupnikov V.K. , Venediktov V.Yu.
Published: February 2023

In the Fig. 1 is shown the optical system (relay 1:1) which can be used in wide field of vision laser amplifiers or conjugated laser cavities [1]. Specific feature of such a system is scanning by the narrow beam with the small own numerical aperture across the wide field of vision: the total field of vision of the active element in terms of diffraction limited angles is determined by the relation of the angular range of beam steering to the angle of its diffraction limited divergence.
Light Beams Propagation in Angular Mirror-Symmetrical Structures
Authors: Rudnitsky A.S. , Titov A.D.
Published: February 2023

The angular mirror-symmetrical structures are formed by the intersecting planes directed at π/s angles (s - is the integer). Part of them may be classified by the proper- ties of their reflection matrices: The angular mirror-symmetrical structures which realize back reflecting opera- tion (1) present the following trihedral angles: 1) (π/2,π/2,π/2s, when s=1 it’s the well- known cube-corner reflector); 2) (π/2,π/3,π/4); 3) (π/2,π/3,π/5).
Stimulated Raman Spectroscopy as a Probe of Silica Network Distortion Due to the Rare-Earth ION Inclusion or Formation of Photoinduced Colour Centers in an Optical Fiber Core
Authors: Solovjov V.V. , Alexandrov I.V. , Nesterova Z.V. , Petrovskii G.T. , Nolan D.A.
Published: February 2023

A few years ago a spectroscopic aspect of stimulated Raman scattering (SRS) in optical fibers was established1. It is well-known, that in bulk nonlinear media the intense light wave is parametrically instable. As a consequence the SRS excitation may occur, but the most intensive vibration has a lowest SRS threshold and determines the spectral content of secondary radiation only. Due to the long interaction distance in an optical fiber even a small amount of scattered centers which include the bonds with enough hyperpolarizabilities takes part in the SRS process. Early the effective SRS by the local native microdefects and by the ones due to the dopant inclusion in silica network was observed1. Later the SRS spectroscopic studies were spreaded on the colour photoinduced centers, which determined an effective second harmonic generation in silica fiber core2.
Optimization of transversely pumped planar waveguide dielectric lasers
Authors: Malinowski Michal , Mossakowska-Wyszyńska Agnieszka , Piramidowicz Ryszard , Szczepański Paweł , Tyszka-Zawadzka Anna , Frukacz Zygmunt , Pracka Izabela
Published: February 2023

The research and development of diode pumped solid state lasers is stimulated by rational prospect for achieving significantly higher laser performance in one or more key characteristics (e.g., operating wavelength, tunability, efficiency, beam quality, and average power) based on major innovations in laser materials as well as devices geometries. Especially, the rare earth planar lasers and amplifiers have recently received growing attention. The claims made on their behalf are that they provide relatively easily produced sources and amplifiers operating at wavelengths that to both current and projected future requirements, in fields such as telecommunications, optical data processing, sensing and spectroscopy. Moreover, the waveguide lasers offer several advantages giving rise to low threshold, high slope efficiency and stability.
VCSEL’s dynamics beyond the rate-equation approximation
Authors: Logvin Y.A. , Loiko N.A. , Turovets S.I. , Spencer P.S. , Shore K.A.
Published: February 2023

Recent advances in semiconductor growth technology have permitted the development of novel microcavity laser sructures whose characteristic dimensions d are of order the optical wavelength λ. It is to be expected that the operating characteristics of such microcavity lasers will exhibit novel features which depend upon the device geometry. The aim of this work is to develop a microscopic model of VCSELs which takes into account BOTH the realistic geometry, (very thin active layer), and the evolution of material variables in framework of Maxwell-Bloch equations.
Passive Q-Switching and Frequency Stabilization of CW YAG:Nd Laser by Molecular Cesium Vapour
Authors: Pokhsrarian Karen , Petrossian Karina , Petrossian Henry , Sarkisyan David
Published: February 2023

For passive Q-switching of cw YAG:Nd lasers the dye solutions and LiF:F2- crystals are used usually. At cw operation, espacially at high average output power the thermal properties of passive cell is to be taken account. Here we report of molecular cesium Cs2 vapour usage for Q-switching and frequency stabilization of the cw YAG:Nd laser.
Short-term Stability Measurement of Motor-driven Polygon Mirror Scanners in Laser Printers
Authors: Ishihara Shuichiro , Jablonski Richard , Kubo Takahiro
Published: February 2023

Motor-driven polygon mirror scanners are commonly used for beam deflection in laser printers, digital copy machines, bar code readers, laser micrometers, etc. The performance of scanners highly effects the positioning accuracy of laser beam and thus the performance of OA equipment. In practice, the stability of laser scanners is determined by the accuracy of polygon mirror and its drive. At present, in low profile, low cost compact scanners, a motor-driven polygon mirror scanner with built-in drive control circuit is used, and its stability is estimated by the dynamic characteristics measurement equipment.
Tentative of Realization of New Silicon-Integrated Interferometric Microvibration Sensor with Piezoelectric Amplitude Modulation
Authors: Gorecki Christophe , Chollet Franck , Kawakatsu Hideki , Fujita Hiroyuki
Published: February 2023

The approach of microsensing based on integrated optics is very attractive because of the intrinsic features: insensitivity to electromagnetic noise, and ability for non-contact measurements. Fabrication of these devices in silicon-based technology has a lot of follows advantages: good mechanical behavior, availability in large size, low cost of silicon wafers, possibility to hybridize laser diodes directly on the substrate, efficient coupling between optical fibers and silica waveguide, and possible association on the same chip of microinterferometers with other optical components as lenses or beamsplitters. Heterodyne technique can he achieved in an optical waveguide via phase modulation. Usually, this is obtained by altering the refractive index of the guiding region. The induced grating structure causes diffraction of the guided optical wave, resulting in modulation. In silicon, this effect is not possible via electro-optic techniques because of the passive nature of this crystalline material. On the other hand acoustic waves can be used to generate the desired grating pattern in the index profile It is caused by mechanical strain produced by the passage of an acoustical-strain wave. The resulting index variation is periodic, with a wavelength equal to that of the acoustic wave We propose to obtain this effect by deposit of a piezoelectric thin-film transducer on the silicon waveguide.
A new lateral shearing Interferometer for testing silicon microlenses
Authors: Schreiber H. , Schwider J.
Published: February 2023

Shearing interferometers have a growing range of applications especially in the field of optical testing /1/ We propose a new type of lateral shearing interferometer /2/ based on two Ronchi gratings in series. We use this set-up because it has several advantages which make it very suitable for measurements e.g. of silicon lenses in the near IR region. The set-up /3/ consists of two Ronchi gratings in series with suppressed zero orders. The main advantage of this set-up is that the interferometer is very easy to adjust. The important parameters like amount of phase shift of shear can easily be controlled. The phase shift can be adjusted by moving the second grating laterally with respect to the other and the amount of shear can be adjusted by changing the longitudinal distance of the gratings. For the whole measurement of a wavefront two orthogonal partial derivatives can easily be obtained by rotating the two gratings together through 90 degrees.
Novel concepts of distributed temperature fiber sensors based on Brillouin scattering
Authors: Czarske J.W. , Freitag I. , Tünnermann A.
Published: February 2023

Distributed fiber sensors based on Brillouin scattering are of great interest, e.g. for the temperature monitoring over long distances at installed current cables, pipelines, tunnels, mines or buildings [1]. Recently realized Brillouin temperature sensors achieve the promising results of 51 km sensing length, 5 m spatial resolution and 1° temperature resolution [2]. However, the application area of this sensor is limited, since it operates on both fiber ends and exhibits high technical efforts. In order to enhance the application potential of Brillouin sensors, one-end measuring techniques were realized, but these systems involve complicated optoelectronic elements (EOM [3], AOM [4]), allowing a laser frequency shift of the Brillouin frequency shift. In this contribution we present novel concepts on Brillouin fiber temperature sensing, which enable one-end measurement without having to use an external frequency shift element. The general sensing mechanism of the presented temperature sensors is the excitation of stimulated Brillouin scattering and the measurement of the temperature dependent Brillouin frequency shift. In principle, the spatial resolution can be achieved by the (i) OTDR (optical time domain reflectometry) or the (ii) OFDR (optical frequency domain reflectometry) technique.
Lateral Carrier Profile for Mesa-structured InGaAs/GaAs Lasers
Authors: Torre M. S. , Esquivias I. , Czotscher K. , Weisser S. , Romero B. , Ralston J. D. , Larkins E. , Benz W. , Rosenzweig J.
Published: February 2023

Lateral carrier diffusion and carrier recombination at external surfaces are limiting mechanisms in the performance of laser devices with small lateral dimensions i e ultra-low threshold lasers, ultra hisgh-speed laser, and etched-pillar VCSEL's. Spatial effects also play an important role in the behaviour of broad-area high power lasers.
Modified Grating Resonator with Uniform Output Beam
Authors: Yepishin V.A. , Maslov V.A. , Militinskiy I.M. , Svich V.A. , Topkov A N.
Published: February 2023

The modified grating resonator with flat reflectors and a phase corrector of finite aperture have been designed to produce lowest-loss mode with uniform output field distribution by means of absorbing (or phase-shifting) masks made on one of the cavity mirrors. This mode is named Fourier-mode because its field distribution functions at the mirrors are similar to the Fourier transforms of each other.
Analytical Unit for Laser-Induced Fluorescence Flame Characterization Using the LiCaAlF6:Ce3+ Tunable UV Laser
Authors: Dubinskii M. A. , Misra P. , Abdulsabirov R. Yu , Korableva S. L. , Naumov A. K. , Semashko V. V.
Published: February 2023

As shown in [1], by choosing the OH radical as the primary species for microgravity combustion studies and a tunable LiCaAlF6:Ce3+ (LiCAF:Ce) laser as a laser-induced fluorescence (LIF) excitation source for LIF-based analytical unit for in-space/in-flight flame characterization, the weight-dimension characteristics of the unit (including the tunable UV laser and the PMT-detection system) can be minimized, which is extremely important for such applications.
High-power multirod Nd:YAG laser end pumped by multiple diode lasers
Authors: Graf Th. , Balmer J. E. , Weber R. , Weber H. P.
Published: February 2023

End pumping of solid-state lasers with high-power diode lasers has become a standard method to produce fundamental-mode laser radiation with high efficiency. The scaling of end-pumped, single-rod, fundamental-mode lasers to higher powers, however, very soon borders on principal limitations due to thermally induced beam distortions. A general relation between the minimum of the mode radius ωmin in the crystal rod and the range of the dioptric power ΔD of the thermal lens for which the resonator is stable, has been derived in ref. [1], For fundamental-mode operation in the whole stable region the effective pump spot has always to be smaller than the fundamental mode The possibility to enlarge the stability range with symmetric multirod Fabry-Perot resonators is discussed in ref [2]. We have found that a further enlargement of the stability range can be achieved with a ring cavity, where the stability region is given by the dotted area in fig. 2.
Spaceborne Lidar Mission, Past and Future
Authors: Werner Christian
Published: February 2023

Laser rangefinders and atmospheric lidars use the same techniques. A short laser puls is transmitted and the reflected or scattered light is detected. Range resolved information of the targets or scatters is the output. To illustrate the use the mission, an example for a ground based system is given: A mission scenario on the highways is a good example. A policeman uses a handheld (Binocular type in size) laser radar to control the distance and speed of cars. Additional a video camera provides the police with the necessary information on the kind of car, the driver and the licence plate.
New Mim Diode Device for IR Measurement
Authors: Avetisyan Yu. H. , Demirkhanyan B. B. , Kocharian K. N.
Published: February 2023

For the measurement of laser spectrum a method, based on the detection of laser radiation by quadratic photoreceivers is widely used. In this case well known difficulties arise, which are conditioned by the necessity to carry out the measurement in the very wide frequency range and up to dc.
Tropospheric Wind Profiling with Doppler LIDAR
Authors: Roths J. , Klein V. , Hilber B. , Heilmann R.
Published: February 2023

A coherent Doppler LIDAR system for remote sensing of atmospheric winds has been developed by Kayser-Threde GmbH. The system is devoted for meteorological airport surveillance and for atmospheric research studies. A diode- pumped Tm:YAG laser system generates eye-safe laser pulses with 3 mJ output energy, 600 nsec duration (full width half maximum FWHM) at a pulse repetition frequency (PRF) of 100 Hz. The q-switched laser is operating single longitudinal mode at 2.02184 µm wavelength, where atmospheric attenuation due to molecular absorption is low. This is achieved by injection seeding the pulsed laser with an etalon-tuned, cw Tm:YAG laser. A 10 cm aperture, offaxis Dall-Kirkham telescope is employed to expand the transmitted laser beam and to receive the atmospheric backscatter signal. This coherent LIDAR system is housed in a mobile 20’ container. On its roof, a computercontrolled, two axis mirror system is installed which allows scanning the laser beam in elevation and azimuth with a resolution of 0.1 degrees on each axis. Thus, the full hemisphere above and around the LIDAR station can be probed. The Doppler shifted frequency of the received radiation is measured using a heterodyne detection scheme and employing the cw laser as local oscillator.
Lidar Investigation of Air Quality over Complex Terrain
Authors: Kolev I. , Savov P. , Parvanov O.
Published: February 2023

The information about the atmospheric processes in the mountain valleys is important especially in the cases when industry exists there. Since the mountain-valley circulation is of local wind nature (closed cycle) the aerosol pollution is transported from one place to another inside the valley (i.e. the pollution remains in the valley). The essential parameter of the planetary boundary layer which effects the aerosol concentration is the mean height of the mixing layer.
Near Field Optical Microscopy
Authors: Courjon D.
Published: February 2023

Near field microscopy is about ten years old. Unlike Scanning Tunneling Microscopy, its progress has been slow and somewhat erratic. Today, we can consider that this new tool is mature enough to be used in a few routine surface characterization procedures.
Quantum Computing
Authors: Zoller P.
Published: February 2023

In this tutorial we review basic ideas of quantum computing, from quantum bits and state entanglement to quantum gates and quantum networks [1]. In addition, we give an overview over possible physical implementations of quantum gates[2-6], with emphasis on quantum optical systems: this includes ion traps [2,3], and cavity QED in the optical and microwave domain [4-6], Fundamental problems of building quantum computers, in particular the decoherence problem, and error correction schemes for quantum memory elements [7] and quantum gates [8] will be discussed. We conclude with a critical evaluation what should be expected from quantum computing ideas in terms of applications in physics (quantum optics) and mathematics within the nest few years.
High repetition rate excimer laser directly pumped by a sliding discharge
Authors: Bashkin V.K. , Treshchalov A. B.
Published: February 2023

Sliding discharge along the surface of dielectric is a relatively new source for the excitation of high-pressure gas mixtures. Up to now this type of the discharge was used as a preionizer in CO2 and excimer lasers [1] and also for direct pumping of N2 [1] and HF [2] lasers. In this work, to the best of our knowledge, we report for the first time about direct excitation of excimer laser gas mixtures by a high current sliding discharge. Lasing with the pulse energy of 0.12 mJ and repetition rate up to 1kHz has been obtained for XeCl and KrF excimers without special gas circulation.
Temperature Stabilized Multi-FBG Package With Zero-Wavelength Shift
Authors: Pan J. J. , Shi Y. , Ma P. , Li S. X.
Published: February 2023

FBGs have been widely used in DWDM devices with a channel spacing of 0.4 nm [1,2]. This requires a high λ accuracy and stability. However, the low temperature coefficient (TC) of 0.011 nm/°C of FBG cannot meet the requirements of DWDMs and other applications. In this paper, a specially designed multi-FBG temperature stabilized package is developed with precise control of center λ and a low TC. Design structure, tuning mechanism, measurement technique, experimental results and reliability of the multi-FBG package are presented.
Low coherence interferometry using coherent function synthesis
Authors: Teramura Y , Suzuki K , Suzuki M , Kannari F
Published: February 2023

Low coherence interferometry (LCI) is a noninvasive sensing method that provides depth information with high resolution and high sensitivity When the coherence of broadband incoherent light is modified by the same spectral modulation technique utilized in femtosecond pulse shaping1, one can achieve more functional sensing. In this paper, coherent function synthesis by manipulating the spectral phase of low coherence light in the frequency domain and its application in a reflectometry are described.
Near Infrared Photorefraction In Reduced Rh-Doped KNbO3
Authors: Medrano Carolina , Ewart Michael , Biaggio Ivan , Ryf Roland , Günter Peter
Published: February 2023

Potassium niobate (KNbO3) remains the subject of considerable interest for several applications involving the photorefractive effect. During the past, materials development efforts have focused on increasing the sensitivity at near-infrared wavelengths and on decreasing the photorefractive response time1,2. The main approach to optimize near-infrared sensitivity has been the introduction of suitable dopants in the energy band gap to provide impurity centers necesary for photoexcitation. Rh was selected among a group of dopants as the most efficient impurity to increase the photorefractive sensitivity at near-infrared wavelengths2. In order to optimize photorefractive recording times, in-situ high-temperature reduced Rh-doped KNbO3 crystals were grown. In this work, we performed optical and photorefractive characterization in the reduced samples at 860 and 1064 nm wavelengths. The photorefractive performance is compared with the non-reduced rhodium-doped crystals, as well as other photorefractive crystals.
Investigation of Intensity Noise in a Diode-Pumped Tm-Ho:YAG Laser
Authors: Taccheo S. , Sorbello G. , Longhi S. , Svelto C. , Laporta P.
Published: February 2023

Laser intensity stability is of great interest for system design in metrology, sensor applications [1], and optical communications [2] to improve detection sensitivity and overall system performance. In this work we focus our attention on and experimentally investigate the physical mechanisms through which external noise sources induce intensity noise in a singlefrequency Tm-Ho:YAG laser to be used as local oscillator for 2-µm coherent LIDAR applications.
Broadly Tunable Laser Spectrometer for Trace Gas Detection Based on Critically Phase-Matched Difference-Frequency Generation in Bulk LiNbO3
Authors: Seiter M. , Keller D. , Sigrist M.W.
Published: February 2023

The selective and sensitive detection of trace gases in multicomponent gas mixtures by means of absorption spectroscopy requires narrowband continuously tunable laser sources. Using a cw External Cavity Diode Laser (ECDL), tunable between 795 and 825 nm as pump wave, and a diode-pumped monolithic cw Nd:YAG laser at 1064 nm as signal wave, we produce narrowband (a few MHz) mid infrared laser light between 3.16 and 3.67 μm by Difference-Frequency Generation (DFG) in bulk LiNbO3. Many compounds of interest (CH4, H2CO, …) show characteristic strong absorptions in this fundamental wavelength region. A multipass cell employed as a gas chamber with an effective path length of 36 m is used in combination with sensitive IR detectors for recording absorption spectra. True multicomponent capability of such a laser spectrometer requires a broad, narrowband, continuous tunability in the mid-IR.
A pulsed, injection-seeded optical parametric oscillator system based on periodically poled lithium niobate for high-resolution spectroscopy
Authors: Baxter G. W. , He Y. , Orr B. J.
Published: February 2023

Optical parametric oscillator (OPO) and amplifier (OPA) devices are recognised as versatile coherent tunable spectroscopic sources. This is borne out by our previous work on OPOs based on bulk (3-barium borate (BBO) [1] and lithium niobate (LNB) [2], in which tunability and optical bandwidth are achieved by injection seeding with single-mode tunable diode lasers (TDL). We now report a new modular spectroscopic system, as depicted in Figure 1: a TDL-seeded OPO based on periodically poled lithium niobate (PPLN) plus a bulk-LNB OPA.
Speckle Pattern Correlation in Fluid Mediums in the Quantum Limited Detection Regime
Authors: Grasso Robert J. , Mui Peter H. , Amore Scott J. , Weiss David H. , Jilting Adam N. , Savoie Matthew , Temple Paul
Published: February 2023

Northrop Grumman reports on a program utilizing autodyne detection for correlating speckle patterns in a quantum limited detection regime. Experiments performed verify this approach for sensing changes within a fluid medium. Light backscattered from particles located at random positions within a fluid medium interferes to produce speckle patterns; the motion from these particles is manifested as a time variation in the speckle patterns.
An Integrated Optic Approach to 10μm LIDAR
Authors: Jenkins R M , Devereux R W J , Blockley A F
Published: February 2023

The paper describes a novel integrated optics approach to coherent 10.6μm LIDAR systems. The concept is based on using hollow waveguides to guide light between components located in a common dielectric substrate. The concept, referred to as Hollow Waveguide Integrated Optics (HOW-IO), has advantages in relation to achieving and maintaining good coherent mixing efficiencies and has the potential to: reduce size, increase ruggedness and lower manufacturing costs. The figure shows a plan view photograph of a HOW-IO interferometer subsystem which we have realised in practice. The integrated components and interconnecting waveguides are clearly visible. The subsystem was formed in a 180×190×20mm polycrystalline alumina substrate using a computer controlled milling machine. Polycrystalline alumina was chosen as the substrate and lid material because its optical properties, in conjunction with waveguides of appropriate cross section, allow the realisation of low attenuation coefficients at 10.6μm.
Measuring mutual coherence of speckle-like beams using adaptive photodetectors
Authors: Arroyo L.M. , Rodríguez P. , Stepanov S.
Published: February 2023

Knowledge of the mutual coherence of two interfering beams plays a fundamental role in some applications, such as laser ranging and optical coherence tomography (OCT). Severe problems arise, however, when one (or both) of the beams is speckle-like aberrated. One promising possibility to overcome this problem (and to deal with the speckle-like wavefronts) is by means of dynamic holography, and, in particular, by the so-called adaptive photodetectors based on the photo-EMF effect [1].
Comprehensive Evaluation of A Photorefractive Two Beam Coupling Novelty Filter
Authors: Delaye Philippe , Roosen Gérald
Published: February 2023

A novelty filter is a image pre-processing element that is sensitive only to the new features in a scene. It is thus perfectly adapted to the detection of an objet appearing and moving in a complex scene. Different architecure where proposed to implement a novelty filter with a photorefractive crystal [1]. Among these different set-ups the simplest one is based on photorefractive two beam coupling. A signal beam carrying the image interferes with a pump beam in a high gain photorefractive crystal. An energy transfer occurs through two beam coupling that causes a strong attenuation of the stationnary signal beam. As soon as an objet appears in the image the condition for the attenuation of the beam disappears and ligth passes immediatly at the position of the object, and only there, until a new grating is written and restores attenuation. We use and characterize this device with the final goal of detecting very small moving object, with a very small contrast compared to the background.
Amplitude and Phase Characterisation of Femtosecond Pulses in a Photodiode-Based Autocorrelator
Authors: Baltuška Andrius , Pshenichnikov Maxim S. , Wiersma Douwe A.
Published: February 2023

Second-order autocorrelation of ultrashort laser pulses by using two-photon-induced photocurrent in semiconductors offers several advantages compared with traditionally employed combination of a second harmonic (SH) crystal and a photomultiplier tube. A low-priced commercially available photodiode [1] allows to overcome principal drawbacks of SH-based autocorrelation: limited phase-matching bandwidth and wavelength-dependent sensitivity of the light detector leading to a spectral filtering effect, pulse broadening due to crystal bulk dispersion, low conversion efficiency which decreases with increase of SH bandwidth, high cost and manufacturing problems associated with thin SH crystals. A significant advantage of incorporating a semiconductor photodiode into autocorrelation measurements is that the desired two-photon response and the transformation of light into electric current are combined into a single solid-state device. It has been shown recently that for the vast majority of practically realisable pulses the complete phase and amplitude information could be rapidly recovered from the autocorrelation trace and the pulse spectrum by means of a two-stage iterative algorithm [2]. In this contribution we demonstrate that due to absence of spectral filtering effect and high dynamic range of quadratic response to the incident intensity in a GaAsP photodiode [1], correct retrieval of temporal profile and phase from autocorrelation and spectrum can be achieved for ultrashort laser pulses with bandwidths as large as 130 nm and pulse energies as low as several pJ.
Wave-Front Correction of Femtosecond TeraWatt Laser using a Deformable Mirrors
Authors: Druon Frédéric , Chériaux Gilles , Maksimchuk Anatoly , Mourou Gérard
Published: February 2023

Chirped Pulse Amplification (CPA) allowed the development of ultrashort, high intensity lasers. For many applications, laser users are interested in reaching the highest intensity focused on target. Often neglected, the spatial quality of the beam is crucial in this regard(1). Wave-front distortions can significantly affect this spatial quality and thus severely reducing the attainable focused intensity. In fact, the wave-front of multi-Terawatt lasers, because of thermal effects and the size of optical elements, features sizeable distortions. The correction of the wave-front and a better confinement of the energy is thus a solution much less expensive than adding one more amplifier stage to the laser chain to actually obtain the same peak intensity. To quantify this decrease in the peak focused intensity, we use the normalized Strehl intensity which is the ratio of the peak intensity at focus of a beam with a distorted wave-front to that of the same beam without distortions. We present, in this paper, the wave-front correction of a femtosecond TeraWatt CPA lasers using an Achromatic Three-Wave Lateral Shearing Interferometer (ATWLSI)(2) and a deformable mirror.
Laser forming of metals using few-watt Nd:YAG lasers
Authors: Namba Y. , Yamaguchi T.
Published: February 2023

Laser forming is defined as a metal forming process by thermal stresses under laser irradiation without an external force exerted to materials.1 The cw high power CO2 laser of 1.5 kW was used for this new metal forming technology.1 This paper deals with the possibility of laser forming using low power lasers.
Q-switched microlaser with Nd:La3Ga5,5Nb0.5O14 active medium
Authors: Batay L. E. , Gribkovskii V. P. , Demidovich A. A. , Kaminskii A. A. , Kuzmin A. N. , Ryabtsev G. I. , Strek W.
Published: February 2023

LD pumped solid state lasers are very attractive for producing of compact systems with different special lasing regimes. In this connection disordered crystals with Ca-gallogermanate structure are one of the most appropriate laser materials with broad (about 4 nm) lasing spectum [1]. Previously it was shown that Nd:La3Ga5.5Nb0.5O14 crystal like other crystals of Ca-gallogermanate group has unique combination of their physical properties [2]. In this research characteristics of LD pumped Q-switched short crystal Nd:La3Ga5.5Nb0.5O14 laser are presented.
High resolution Real-Time 3-D Imaging through Scattering media using Photorefractive Holography with Multiple Quantum Well devices
Authors: Tziraki M. , Jones R. , French P. M. W.
Published: February 2023

Imaging through tissue using ballistic light is important for medical applications such as diagnosing and/or monitoring skin cancer and other dermatological conditions. Various techniques have been demonstrated including confocal imaging, time gating and coherence gating (e.g. OCT ) which may provide 3D images, pixel by pixel and so having long acquisition times. Our “whole-field” imaging technique, using photorefractive holography, is being developed for “in vivo” applications where rapid image acquisition is a priority. It is related to coherence gating techniques such as optical heterodyne detection, electronic and light-in-flight holography, but differs in that it is, to first order, insensitive to an incoherent diffuse light background.