bluuebunny/crossref_metadata_2025 huggingface dataset:
Sub-picosecond gain and amplified spontaneous emission spectroscopy on semiconductor optical amplifiers.
Authors: de Boer A. P. , Christianen P. C. M. , Tolstikhin V. I. , van de Roer T. G. , de Vrieze H. M. , Maan J. C. , Rasing Th.
Published: February 2023

A full understanding of the response of the carrier distribution to the strong internal optical fields in semiconductor lasers and in semiconductor optical amplifiers (SOA’s) is necessary to exploit these components for all optical data processing to their greatest extent. Especially in the field of wavelength conversion, based on cross gain modulation (XGM) in an SOA, it would push the limits of modulation speed of these devices.
VULCAN : A versatile ultra high power Nd:Glass laser system
Authors: Winstone T B , Danson C N , Allott R , Booth G , Collier J , Damerell A , Edwards C B , Frackiewicz A , Flintoff P , Hancock S , Harman M , Hatton P , Hawkes S , Hutchinson M H R , Hernandez-Gomez C , Leach J , Lester W , Neely D , Notley M , Pepler D A , Reason C , Rodkiss D A , Ross I N , Walczak J , Wellstood R , Wyatt R W W , Wyborn B
Published: February 2023

The VULCAN high power laser system is an eight beam Nd:glass (1.053 μm) system capable of delivering pulse lengths of 300 ps - 10 ns and energies of 250 J per beam (at 1 ns) on six 108 mm diameter beams and 500 J per beam (at 1 ns) on two 150 mm diameter backlighter beams. Furthermore VULCAN in high power mode is capable of single pulse powers in excess of 35 TW in pulses as short as 700 fs using the chirped pulse amplification (CPA)1 technique. CPA avoids the non-linear effects of propagating an ultrashort pulse through the amplifier glass by stretching the pulse prior to amplification.
High-Energy Heavy-Ion Irradiation into Bulk Gaas for Sub-Picosecond Wide-Band Efficient Saturable Absorbers
Authors: Mangeney J. , Stelmakh N. , Alexandrou A. , Shen A. , Lourtioz J-M. , Thierry-Mieg V. , Oudar J-L.
Published: February 2023

The technique of high-energy ion irradiation is an interesting alternative to low-temperature epitaxy for reducing the absorption relaxation time in semiconductor materials. The possibility of creating defects of particular structures by heavy-ion irradiation was suggested as early as in 1980, but experimental works[1] only gave indirect indications of this possibility. To our knowledge, there are no comparative measurements of irradiated materials directly showing the particular properties of heavy-ion irradiation for applications to fast and efficient saturable absorbers.
Optical Parametric Chirped Pulse Amplifiers for the Generation of Extremes in Power. Intensity and Pulse Duration
Authors: Ross I. N. , Matousek P. , Towrie M. , Langley A. J. , Collier J. L. , Danson C. N , Neely D. , Osvay K.
Published: February 2023

We have investigated the possibility of using optical parametric amplifiers (OPA) as optical parametric chirped pulse amplifiers (OPCPA), in which energy from a narrow bandwidth pump source is efficiently transferred to a chirped signal pulse prior to its recompression (1).
Excited state absorption, loss and gain measurements in the Nd3+ doped ZBLAN and BIG fluoride laser glasses
Authors: Doualan J.L. , Adam J.L. , Girard S. , Landais J. , Moncorgé R.
Published: February 2023

Nd3+ doped optical fibers are interesting medium for both laser emission and amplification in the near infrared. The stimulated transitions start from the 4F3/2 level. However higher energy levels above 4F3/2 can absorb and perturb the emissions. This process is especially probable in glasses whose the disordered structure is responsible for the inhomogeneous broadening of the transitions. Therefore it's very interesting to know the effect of these excited state absorptions (ESA) on the stimulated emissions (SE). The experiment are done on Nd3+ ions in bulk ZBLAN (Zr-Ba-La-Al-Na) and BIG (Ba-In-Ga) fluoride glasses[l]. We use a pump probe technique to measure directly the ESA and SE cross sections from the 4F3/2 level. A Ti:sapphire laser pumps the 4F3/2 level and a white lamp probes the transmission from 0.82 to 1.44 µm. The spectrum is calibrated to the ground state absorption cross section of the transition 4I9/2 → 4F3/2 For the 4F3/2 → 4i13/2 SE, the amplification range is reduced to the longer wavelength part of the transition, over 1.31µm (fig.). On the contrary, the 4F3/2 → 4I11/2 transition around 1.05 µm is not perturbed by ESA.
Tropospheric ozone, nitrogen dioxide and sulphur dioxide measurements in the ultraviolet range using the differential absorption LIDAR technique.
Authors: Molero F. , Jaque F.
Published: February 2023

A ground-based differential absorption LIDAR system has been development and using in several field tests. The system is based on the well-established configuration of a Nd:YAG laser pumping a dye laser, working in the ultraviolet spectral range with the following characteristics: Emission of 8 mJ/pulse laser radiation at the spectral range 290-310 nm (Dye: Rh 610) and 20 mJ/pulse in the range 430-460 nm (Coumarin 450), divergence ≤0,1, linewidth, 2,5 cm-1 and beam diameter of 50 mm.
TEA CO2 dial station for atmospheric water and pollutants measurements
Authors: Bellecci C. , Gaudio P. , Valentini M. , Martellucci S. , Aversa P. , Caputi G. , De Donato R. Zoccali F.
Published: February 2023

Among the differential techniques of remote sensing employed to study the atmosphere and it’s composition, the dial is one of the most powerful, mainly in the detection of concentration of the gas traces. This technique, as known, is based on the knowledge of the interaction between the laser radiation and the molecular compound in studying. In particular it needs, with high precision, the value of the absorption coefficients for the defined wavelengths used in carrying the measurements out.
Continuously Pumped YAG:Nd Scanlaser with Intracavity Plzt-Based Spatial-Time Light Modulator
Authors: Alekseev V. N. , Grigorjev K. V. , Kotylev V. N. , Liber V. l. , Talalaev V. G.
Published: February 2023

Intracavity electrically-controlled scanning of laser radiation direction is a promising method of the non-mechanic laser beam sending to the given space point. In paper [1,2] the application PLZT-based electrically-controlled spatial-time light modulator (STLM) for scanning of the YAG:Nd laser and Cu vapor laser radiation was given for the first time.
Advanced Liquid Crystal Display backlighting for portable personal electronic devices
Authors: Gibson D R , Hanney M J , Lewis R. J. , Garin G , Ruh R
Published: February 2023

Uniform, high efficiency and miniaturized liquid crystal display (LCD) backlights are required for installation in portable personal electronic devices. Display miniaturisation, resolution and colour requirements require enhancement in backlight illumination level and uniformity, higher efficiency/ reduced number of light sources and reduced size.
Output Power Stabilization of Cascaded Raman Fiber Lasers
Authors: Riedel P. , Onishchukov G. , Shipulin A. , Peschel U. , Lederer F.
Published: February 2023

We propose a simple and effective method to stabilize the output power of a cascaded Raman fiber laser at variations of the pump power. It has been demonstrated theoretically and experimentaly for a three stage cascaded Raman converter of 1.06 µm down to 1.24 µm which is necessary as a pump source for Raman amplification in the 1.3 µm communication window [1].
Electro-optic modulation in quantum wells in transverse and longitudinal strong electric fields
Authors: Vorobjev L.E. , Zibik E.A. , Titkov I.E. , Firsov D.A. , Shalygin V.A. , Towe E. , Nashchokina O.N. , Saydashev I.I.
Published: February 2023

Electro-optic modulation in transverse (perpendicular to the layers) and longitudinal (parallel to the layers) electric fields was studied in simple rectangular and asymmetric tunnel-coupled GaAs/AlGaAs quantum wells (QW). The investigated phenomena can be used for fast amplitude and phase light modulation.
The Role of Partial Illumination in Metal-Semiconductor-Metal Photodetectors (MSM-PD)
Authors: Hassan M. A. , Vickers A. J. , Wilson S. P. , Walker A. B.
Published: February 2023

GaAs metal-semiconductor-metal photodetectors (MSM-PD) have shown great promise for optoelectronics integrated circuit applications, particularly in telecommunications, due to their high speed response, low dark current of 30pA leading to very low noise, and high quantum efficiencies of up to 90%. Their simple planar structure with a capacitance in the fF regime leads to extremely low RC times and large bandwidths (375GHz).
Optical System for the early detection of cancer
Authors: Mckechnie Tracy , Jahan Ali , Cuschieri Alfred , Sibbett Wilson , Padgett Miles
Published: February 2023

We report a novel optical system for detecting early-stage cancerous tissue in the upper Gastrointestinal Tract. This system uses a differential fluorescent signature to distinguish between healthy and cancerous tissue. The fluorescent marker used in this study is 5-aminolaevulinic acid which is metabolised at tissue level to produce protoporphyrin IX(PpIX). The absorption of PPIX peaks at 405nm, while its emission is characterised by a bimodal distribution predominantly at 630nm.
Octupolar Crystalline Structures for Quadratic Nonlinear Optics : A Dual Crystal and Propagative Engineering Approach
Authors: Tballad V.R. , Brasselet S. , Desiraju G.R. , Zyss J.
Published: February 2023

Crystal engineering is increasingly turning towards functional materials. Octupolar . NLO active substances are expected to overcome many of the disadvantages posed by dipolar species. While octupolar non-linearity has been demonstrated at the molecular level, its demonstration in supramolecular crystalline systems remains a challenge. Trigonal, non- centrosymmetric assemblies of trigonal molecules lead to supramolecular octupolar networks. However, most trigonal molecules do not assemble into trigonal networks. In this work, the principles of crystal engineering have been used in the carry-over of molecular symmetry into the crystals structures of six related compounds. Supramolecular retrosynthesis of a trigonal network based on herringbone interactions leads to 2,4,6-triaryloxy-l,3,5-triazines as the starting materials. Six triazines are analyzed and their molecular non-linearities are measured by HLS experiments.
Conjugated Dendrimers for Colour Control in Light-emitting Diodes
Authors: Halim M. , Samuel I.D.W. , Pillow J.N.G. , Burn P.L.
Published: February 2023

We report a novel molecular engineering approach to organic materials for LEDs based on dendrimers. The molecules consist of a conjugated core, conjugated linkers, and surface groups, as illustrated schematically in figure 1. The conjugated core and linkers control the electronic properties, whilst the surface groups control the processing properties. This is a very attractive feature as it should enable electronic and processing properties to be optimised independently, in contrast to linear polymers where substitution can affect both.
Recent Developments on Solid State Laser Materials.
Authors: Shestakov A. V.
Published: February 2023

Bring results of complex studies in the field of making the new materials for solid state lasers and methods of their preparation, executed at last years in Russia by several scientific groups. Studies were conduct in following directions:- Elaboration of disordered oxide crystalline materials co-doped by rare earth ions for efficient solid state lasers working in self-modelocking regime under semiconductor diode pumping.
Quantum Technologies.
Authors: Rarity J.G.
Published: February 2023

Could we send information encoded in single photons possibly exploiting the wave particle duality inherent in quanta? Could we even build arbitrary processors using single quanta to encode bits of information? Within this talk I would hope to introduce you to the area of quantum information which is largely a theoretical preserve at the moment. There are however various experimental in-roads into this area, the most notable being secure key exchange using quantum cryptography.
Emission Direction Modulation of Diode Lasers
Authors: Gornik E. , Finger N. , Köck A.
Published: February 2023

We present a surface emitting GaAs/AlGaAs laser diode beam steering device using the surface mode emission (SME) technique [1], The SME laser diode is based on a conventional GaAs/AlGaAs double-heterostructure grown by MOCVD. The crucial difference to a conventional laser diode is a surface-relief grating (period I., grating vector kg=2π/L) covered with a semitransparent AuZnAu-film and a photoresist layer forming a surface waveguide. This structure supports a TE0-mode which can be excited by the laser light propagating in the active region via one grating vector according to klaser-ke=kTE0. The TE0-mode propagates in the surface-waveguide and emits via one grating vector into air with a well-defined angle α =arcsin(neff-2λ/L) where neff is the effective refractive index of the laser diode and λ the emission wavelength. The TE0-mode in turn emits back into the active region providing a wavelength selective feedback resulting in a single-mode operation.
Range finding module design with a combined actively and passively Q-switched microchip laser
Authors: Hansson B. , Arvidsson M
Published: February 2023

Microchip lasers is a growing and maturing field of diode pumped solid state lasers. Passively Q-switched microchip lasers are now commercial The excellent beam quality and the high efficiency of the microchip laser makes it ideal for many applications For range finding however there is a need for low jitter in time between the pulses to achieve good measuring accuracy. Work has been done to stabilise passively Q-switched lasers, by modulation of the pump light to the passively Q-switched laser[1] However, the jitter is still to large for many applications and to solve this we have reported presently on a combined actively and passively Q-switched laser[2]. In this novel design the jitter is dramatically reduced to less than 100 ps compared to 10-100 ns in a passively Q-switched laser
High Efficiency Microcavity LEDs
Authors: Bockstaele R. , Depreter B. , Blondelle J. , Dhoedt B. , Moerman I. , Demeester P. , Van Daele P. , Baets R.
Published: February 2023

By placing the active layers of a LED into a microcavity, the spontaneous emission in the direction perpendicular to the mirrors of the cavity can be much enhanced, leading to a much higher efficiency, better spectral purity and a narrower beam emission profile compared to classical LEDs. The principle of microcavity-LEDs and experimental results on GaAs-based and InP-based microcavity-LEDs will be presented.
Novel Approach to Transverse Mode Control in VCSELs
Authors: Greally M J G , Adams M J
Published: February 2023

A theme of current VCSEL research is the quest for single-transverse mode operation, especially at high power levels. Monomode output is required for many VCSEL applications using both free-space propagation and the superior fibre-coupling properties of VCSELs. The oxide aperture approach has been remarkably successful in this respect, and a record single-mode power of 4.8 mW has been reported. Here we investigate the potential of a somewhat simpler approach - that of patterning the top reflector in a VCSEL in order to obtain sufficient waveguiding to confine a single transverse mode.
Room temperature generation of amplitude squeezed light from 1550 nm distributed feedback semiconductor laser
Authors: Jérémie F. , Chabran C. , Gallion P.
Published: February 2023

The control of the quantum state of light has recently been studied extensively, aiming at the achievement of ultra-low noise below the shot noise limit. Several experiments showed that amplitude squeezing could be achieved in constant-current-driven semiconductor lasers. However, the generation of amplitude-squeezed light from distributed feedback semiconductor lasers (DFB) has been up to now considerably less successful than that from Fabry-Perot devices. Simulations indicate that DFB structures with high coupling coefficient length product kL are unlikely to be good sources of squeezed light, because of the evanescence of the optical fields along the grating [1]. They also show, that for low kL values the lowest achievable intensity noise depends on the structure of the laser diode and can be higher than expected from the laser quantum efficiency alone.
Realisation of Multi-Wavelength Phased Array Laser by Hybrid Coupling of Active and Passive Waveguide Chips
Authors: Van Thourhout D. , Van Caenegem T. , Vanwassenhove L. , Moerman I. , Van Daele P. , Baets R. , Herben C.G.P. , Leijtens X.J.M. , van Uffelen J.W.M. , Smit M.K.
Published: February 2023

For many novel integrated WDM-devices such as multi-wavelength lasers (MWL), the integration of passive waveguides and active devices is required. Several techniques such as butt coupling, shadow mask growth or selective area growth have been proposed for realising monolithic integrated photonic integrated circuits (PIC). Whatever integration scheme is used, it requires a lot more processing steps compared to the realisation of a standard laser or a passive waveguide device. As a consequence the fabrication of PICs is much more time consuming and expensive at the development stage, which leads to long iteration cycles to realise optimised devices. Moreover, since the passive devices are often rather big, it is generally not possible to put many variations of the device on one wafer. We propose and demonstrate a hybrid solution that allows to test and evaluate new devices, using a standardised array of amplifier stripes and a passive waveguide chip coupled together on an optical bench. This approach allows for rapid testing and optimisation of new passive waveguide designs as part of an active device. To avoid reflections at the passive-active interface amplifiers and passive wave guides are angled at the facet and a standard AR-coating is applied.
Characteristics of linearly chirped and functionally apodised phase mask and reflection spectra of UV written fibre gratings
Authors: Liu X. , Aitchison J. S. , Thoms S. , De La Rue R. M. , Everall L. A. , Williams J. A. R. , Bennion I.
Published: February 2023

Complex filters are required for functions such as gain flattening and side-lobe suppression in wavelength division multiplexed optical communication systems. The phase mask technique for fibre grating production provides a reliable and flexible route to achieve this [1-2]. Side lobes and noise effects caused by sudden changes in the optical geometry along the fibre axis [3] can be largely eliminated by apodising the grating along its axis during UV exposure [4]. We have previously reported the design and fabrication of geometrical apodisation and chirp in electron beam written phase masks [5]. Here, we describe the characteristics of these phase masks with various apodisation functions and the reflection spectra of the resulting fibre gratings.
WDM networking: lessons from ACTS OPEN field trials
Authors: Chbat M. , Goedsvang P. , Jourdan A. , Leclert A. , Olsen T.
Published: February 2023

The ACTS OPEN project aims at the assessment of the feasibility of an Optical Pan-European overlay Network (OPEN), interconnecting major European cities by means of a mesh of high-capacity optical fibre links cross-connected through transparent photonic nodes, making an extensive use of WDM for both transmission and networking. Two cross-border field trials have been scheduled to assess this concept:

• The first one, linking Oslo in Norway (N) with Hjerring and Thisted in Denmark (Dk) via a mix of terrestrial (G.652) and submarine (G.653) types of fibre has been carried out from October to December 1997.

• The second one, linking Paris in France (F) with Brussels in Belgium (B), via a terrestrial standard fibre cable will be initiated February 1998.
A Fully Automated Diode Laser Based Difference Frequency Spectrometer Tunable from 12-16 μm
Authors: Putnam Roger S. , Lancaster David G.
Published: February 2023

The generation of tunable narrow-band light in the mid-infrared region is of considerable interest in pollution monitoring, remote sensing and trace gas detection. Nonlinear difference frequency mixing (DFM) is one of several techniques which allow access to the important 3-20 μm region, where many molecules have fundamental absorptions. Recent advances in single longitudinal mode high-power diode-laser technology, coupled with new developments based on periodic poling of non-linear crystals and improved growth techniques for birefringently phasematched crystals (such as GaSe), has made DFM a promising approach for a compact broadly tunable, narrowband infrared source. A judicious selection of pump laser wavelengths and non-linear crystals will allow most of the mid-infrared spectral region to be accessible by DFM. Our approach involves DFM of two high power single longitudinal mode diode lasers in the non-linear crystal, GaSe. We combine the broad tuning-range of the diode lasers with the extended critical phasematching range of GaSe to produce a widely tunable system with which we have implemented computer controlled diode frequency tuning, automatic crystal angle positioning, and automatic alignment of the pump beams into the crystal.
The Influence of Energy-Transfer Upconversion on Thermal Lensing in End-Pumped Nd:YLF and Nd:YAG Lasers
Authors: Hardman P. J. , Pollnau M. , Clarkson W. A. , Hanna D. C.
Published: February 2023

Nd:YLF and Nd:YAG are two of the most commonly used solid state laser crystals because of their qualities both spectroscopically and thermo-mechanically. However, scaling these lasers to higher powers has been hindered by thermal lensing problems. We have found that under different schemes of operation, e.g. CW versus Q-switched, the heat load and consequent thermal lensing may vary significantly. The mechanisms underlying this difference must be thoroughly understood and controlled if optimum design for efficient operation is to be achieved.
Determination of thermal lensing in pulsed Cr:YAG lasers
Authors: Diettrich Jan C , White Richard T , McKinnie Iain T , Warrington Don M
Published: February 2023

Broadband tunable solid state lasers in the 1300-1600 nm spectral region are required for applications in remote sensing, eyesafe optical ranging and communication. However, with Cr:YAG, the most promising tunable laser material in this region1, acute problems of output energy saturation, rollover in efficiency and thermal limitations have been observed. These problems have been attributed to ground state bleaching, pump and laser excited state absorption (ESA) and thermal lensing. Here we report, to our knowledge, the first measurements of thermal lens strength in Cr: YAG. Focal lengths have been determined under a range of pump conditions with a conventional low Cr4+ concentration (0.2at.%) rod, and with a new heavily-doped (0.3at.%) rod. These results have been incorporated in a dynamic spatio-temporal model of gain-switched Cr:YAG lasers. The good agreement which has been obtained between model predictions and experimental results confirms the role of both thermal lensing and parasitic ESA loss processes in the saturation, rollover and instability problems. Results of the model have been used to maximise Cr:YAG output at a range of pump repetition rates, and can be used to optimise cavity design for specific rod parameters and pump fluence.
38W Nd:YAG slab laser partially end pumped by a stack with 3 diode laser bars
Authors: Wu Nianle , Xu Jiandong , Giesekus J. , Liao Yan , Du Kerning , Loosen P. , Poprawe R.
Published: February 2023

To scale the output power of diode pumped solid state lasers at high beam quality, high efficiency and low cost, we have developed a novel slab laser concept /1,2/, which consists of slab-shaped crystal with only two polished faces for passing pumping and laser beam. The slab crystal is end pumped by a stack consisting of 3 diode laser bars and mounted in a water-cooled brass heat sink with two large faces serving as thermally conducting surfaces. The pumped volume underfills the slab volume and has a rectangular cross section. Hybrid resonator, which is stable in the plane of the small dimension and unstable in the plane of the large dimension, was used for diffraction-limited beam quality at high efficiency. Unlike in the conventional slab laser design, in which the laser beam takes zigzag path inside the slab crystal, in our design the laser beam goes straight through the slab. This leads reduced crystal cost and possibility of parasitic oscillation.
Efficient Polarised Output from an End-Pumped Multirod Variable-Configuration Resonator
Authors: MacDonald Michael P. , Graf Thomas , Balmer Juerg E. , Weber Heinz P.
Published: February 2023

The variable-configuration multirod resonator (VCR)1 consists of three Nd:YAG rods in a folded cavity so that each rod is end pumped by a fibre coupled diode laser. The VCR can be constructed with a total cavity length as short as 64 cm, in a square measuring 12 cm by 20 cm, and gives a high power fundamental mode output, with a very high efficiency (slope efficiency of 51% and optical efficiencies as high as 37%). It is capable of running in either Fabry-Perot or ring configuration1. In the case of the Fabry-Perot resonator, the output consists of two orthogonally polarised components and in the ring resonator the output consists of two circularly polarised components with opposite sense. We discuss here, techniques that can be used to obtain linearly polarised output from the VCR whilst maintaining the exceptional qualities of the VCR. Of the seven or more configurations constructed, the three most significant are shown in Fig. 1.
Novel Gas Sensor Based On Difference Frequency Mixing Using All Fiber Beam Delivery
Authors: Lancaster D.G. , Curl R.F. , Tittel F.K. , Goldberg L. , Koplow J.
Published: February 2023

Tunable infrared laser absorption spectroscopy has proven to be a powerful technique for accurately determining the real time concentrations of trace pollutants in both point monitoring and open path configurations (1). For the detection of molecules including many of the common pollutants, and most of the hydrocarbons, the key spectral region for absorption spectroscopy is in the mid-infrared (3-5 μm).
Erblum-doped fiber laser with a frequency-shifted feedback: Oscillation characteristics and application to optical reflectometry
Authors: Yoshida Masato , Nakamura Koichiro , Miyahara Toshiharu , Ito Hiromasa
Published: February 2023

In the frequency-shifted feedback (FSF) laser, a frequency shift is imposed on a intracavity light field by feedback of the first order diffracted light of an acoustooptic modulator (AOM). There have been several reports on this type of laser with an erbium-doped fiber (EDF) as a gain medium for an electronic tuning of the oscillation wavelength and unidirectional oscillation [1]. Here we report the first obsrevation of a chirped frequency comb output from the EDF-FSF laser and its application to optical reflectometry.
Efficient Raman shifting of tunable LiF:F2+ laser radiation into 1.3-1.4 μm region
Authors: Basiev T.T. , Doroshenko M. E. , Zverev P.G. , Sigachev V.B.
Published: February 2023

A-number of scientific and industrial applications (for instance in the field of telecommunication) require radiation sources with rather wide tunability within the 1.3 μm range. LiF crystals with stable F2- color centers have proved to be efficient source of widely tunable radiation which can be shifted to the desired region by means of Raman converters. In this report the barium nitrate Ba(NO3)2 Raman laser, pumped by tunable LiF:F2- color center (CC) laser was investigated For tuning range broadening the CC laser was pumped by passively Q-switched Nd:YLF laser with shorter oscillation wavelength (1.047 μm).
Analysis and Performance of A Tunable Intracavity Pumped Cr:Forsterite Laser
Authors: Skórczakowski Marek , Jankiewicz Zdzislaw
Published: February 2023

A saturable absorber (SA) operating both as a laser and as an intracavity Q-switch for its pump laser medium (LM) is analyzed. This analysis is performed in terms of dimensionless normalized functions and laser parameters. According to the theoretical predictions there is an optimal value of SA normalized pumping rate m2σ1a/σ2e ensuring maximal efficiency of the SA intracavity pumped laser; where m is a magnification of an intracavity expander, σ1a - SA absorption cross section, σ2e - LM emission cross section. This optimal value depends on the initial losses distribution (as it is seen in Fig 1) but does not almost depend on the initial gain. It corresponds with inefficient passive Q-switching case when the most amount of energy stored in LM is absorbed by SA.
Stimulated emission in solid-state laser powders: effects of density, external mirror, and seeding
Authors: Noginov M. A. , Egarievwe S. U. , Noginova N. , Wang J. C.
Published: February 2023

A stimulated emission without cavity in pulverized solid-state luminophosphors was first reported in 1986 by Markushev et al. [1] who observed a dramatic narrowing of Nd luminescence line (4F3/2-4I11/2) when the pumping energy exceeded some critical threshold level; at the same time a series of subnanosecond emission pulses at 1.06 μm appeared in response to a single 30 ns pumping pulse. In several publications gain+scattering media were proposed to be used for express testing of novel solid-state laser materials, interial confinement laser fusion, holography, and in Identification of Friend and Foe devices. These and other applications stimulated our interest to further studies of powder lasers. In the present paper we report the effects of the medium volume density, external seeding, and external mirror on stimulated emission in powders and ceramics.
Polarization dynamics of Nd: YAG laser with weakly anisotropic Fabry-Perot cavity
Authors: Khandokhin P. , Mamaev Yu. , Milovsky N. , Ovchinnikov E. , Shirokov E.
Published: February 2023

A major factor in the dynamical behavior of solid-state lasers with a weakly anisotropic cavity is a collective interaction of all longitudinal modes of one polarization with the total ensemble of modes of the orthogonal polarization. Our analysis of the dynamics of the polarization modes[1] demonstrates that along with the well-known in-phase relaxation oscillations of laser modes at frequency Ω0 the system possesses relaxation oscillations at lower frequencies Ω1, and Ω2<Ω1 which belong to the antiphase dynamics of polarization modes.
Modeling of diode pumped high power Nd:YAG laser- a comparison with experimental results
Authors: Schmidt G. , Wester R. , Hoffmann D. , Hobein B. , Treusch H.G. , Loosen P. , Poprawe R.
Published: February 2023

The laser beam propagation in high power Nd:YAG lasers is strongly distorted by the laser rod which not only acts as an aberrated lens but also mixes the two transverse field components by stress induced birefringence (fig 1). For the simulation of laser beam propagation in diode-pumped high power Nd:YAG lasers we have set up a model which includes all physical effects relevant in the high power region including transversal field component mixing. Beam propagation is computed by solving the 2D Fresnel integral, beam amplification is modeled using gain sheets and thermal lensing and stress induced birefringence is taken into account by a Jones matrix sheet. The 2D Jones matrix field is calculated using the temperature T and stress distribution o inside the laser rod and the relation between T, σ and the laser rod indikatrix.
Pulse Train Laser driving the Photocathode of the TTF Linear Accelerator
Authors: Will I. , Liero A. , Sandner W.
Published: February 2023

We describe the Nd:YLF laser system, which generates pulse trains consisting of 800 individual picosecond pulses spaced by 1.0 microsecond (see records below taken with time scales of 100 μs/div (upper) and 1 μs/div (lower image)). Each of the individual "micropulses" contains an energy of 0.2 mJ. Consequently, the total energy of the pulse trains, which are generated with 10 Hz repetition rate, amounts to 0.18 J.
High-power cw transversally diode-pumped Nd:YAG rod laser with hexagonal core passively high repetition Q-switched by F2:LiF crystals
Authors: Lucianetti A. , Muller N. , Weber R. , Papashvili A. , Konyushkin V. A. , Basiev T. T. , Weber H. P.
Published: February 2023

Longitudinally diode laser-pumped solid-state lasers have been demonstrated to achieve high efficiency with a F2-:LiF passive Q-switch [1]. As power scaling possibilities of end-pumped configurations are limited by the thermally induced stress fracture of the laser material, transversal pumping schemes are the system of choice to achieve high average powers. The use of composite laser rods consisting of a hexagonal Nd:YAG core surrounded by an undoped YAG is expected to improve the relatively poor beam quality typical for side pumped solid-state lasers.
Laser-induced bulk damage of various types of silica glasses with fundamental and higher harmonics of Nd:YAG laser
Authors: Yoshida K. , Ochi K. , Kuzuu N. , Yoshida H. , Kamimura T.
Published: February 2023

Silica glasses can be used as optical materials for high-power lasers, because they have no internal absorption in a wide range of wavelength from ultraviolet to near-infrared, and extremely small defects such as inclusion and bubbles[1]. There are two groups : synthetic fused silica (SFS) and fused quartz (FQ) produced by melting natural quartz powder.
Refinement of the dispersion equations of the nonlinear biaxial crystals KTiOAsO4, RbTiOAsO4 and CsTiOAsO4. Method and measurements.
Authors: Fève J.P. , Boulanger B. , Rousseau I. , Ménaert B. , Marnier G.
Published: February 2023

In a recent work. Roberts proposed a method for the improvement of the dispersion equations of uniaxial crystals[1], starting from precise and numerous refractive indices measurements, and from reliable phasematching data.
Large Rare-Earth Pentaphosphate Laser Crystals Growth by Modified High Temperature Solution Method
Authors: Chen H.C. , Han J.R. , Liu Y.G. , Chen F. S. , Lu B.S.
Published: February 2023

Rare-earth pentaphosphates belong to the class of pure or stoichiometric laser media, exhibiting a concentration of active ions of the order of 1022cm-3. From 1974 H.G. Danielmeyer to 1995 F. Kaczmarek, they were all using the large container to grow rare-earth pentaphosphate crystals. Unfortunately, the crystals were always obtained in small size with plate-like shapes because of the strong evaporation caused by strong convection in the large growth system.
Ultimate light intensities in multilayer optical coatings with inhomogeneous microstructure
Authors: Gruzdeva Anastasia S. , Gruzdev Vitali E.
Published: February 2023

Laser-induced damage (LID) of optical coatings is the most important reason limiting output power and energy of laser systems. Developing of manufacturing technology has resulted in increasing of LID thresholds by decreasing of absorbing microinclusions, so, problem of possible mechanisms of LID in low-absorbing materials has become important.
Optical Limiting Properties of New Modified Fullerene
Authors: Sahraoui B. , Kityk I. , Phu X. Nguyen , Hudhomme P. , Gorgues A.
Published: February 2023

Optical limiting is a new field of applications for nonlinear organic materials. In particular, the strong two-photon absorption of organic crystals and organic dyes could be used for the design of laser protection devices in the visible spectral range.
Transverse Spatial Beam Control in Quadratic Nonlinear Materials
Authors: Cerioni R. , Dekker J. , Sibilia C. , Bertolotti M.
Published: February 2023

Recently a great interest has been given to the propagation of self-guided beams or spatial solitary waves in quadratic media [1-2]. Here we consider stationary fields propagation in a planar waveguide with quadratic nonlinearity in the configuration of second-harmonic amplification (Type I interaction (eoo)). A numerical study of the propagation of intense beams in a quadratic non-linear material is presented, when a second harmonic amplification process occurs.
Aperiodic quasi-phase-matching as a method to reduce switching intensity in devices based on second order cascading
Authors: Saltiel S. , Koynov K. , Fejer M.
Published: February 2023

The combination of two novel techniques second order cascading [1] and quasi phase matching [2] (QPM) can yield to solutions for construction small, low power operated, all-optical switching devices. Important parameters in this devices are the switching intensities Iπ/2 and Iπ necessary for obtaining nonlinear phase shift (NPS) with amount of π or π/2, correspondingly. Here we show that one way to reduce the parameters Iπ/2and Iπ is to use aperiodic quasi-phase matched structure. We investigated the NPS obtained by the fundamental beam involved in the process of second harmonic generation in second order material for which the normalized phase mismatch satisfy where ki=2πni/λi (i=ω,2ω), p is a coefficient and Kgrat(z) = 2π/Λgrat(z) with Λgrat being the grating period.
10 W average power at 8.5 kHz from a copper vapour laser pumped Ti:sapphire laser
Authors: Wadsworth W.J. , Coutts D.W. , Webb C.E.
Published: February 2023

Copper vapour laser (CVL) pumped Ti: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 and medium power CVLs (up to 18 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% giving the highest output power to date of 6.2 W at 6.2 kHz at 780 nm (1).
Closed-Loop Active Alignment for Free-Space Optical Interconnects
Authors: Yang Tsung-Yi , Gourlay James , Walker Andrew C.
Published: February 2023

Providing free-space optical interconnects and the integration of a 2-D optoelectronic interfaces with silicon chips (smart-pixels) can allow many advantages over convention interconnects. However, the introduction of free-space optics brings new technological difficulties for the system designer, mainly concerned with the system packaging. Active alignment is an important design option to achieve realistic low-cost free-space optical interconnects [1].
Alignment Tolerant Microchannel Relay Systems: Broken Symmetry Interconnects
Authors: Robertson Brian , Miller J. Mike , McCarthy Angus , Tooley Frank A. P.
Published: February 2023

In the following paper we describe the optical design of an alignment tolerant microchannel free-space interconnection scheme developed for photonic backplane applications. Implementing a free-space backplane that will be competitive with conventional electronic systems will be a challenging task. The interconnection links must be compact enough to meet current printed circuit board (PCB) pitch standards, typically of the order of 25mm. In addition, the interconnect must be rugged enough to be unaffected by external operating conditions such as temperature variations and vibrations. These factors place exacting demands on the optical and optomechanical design of the interconnect.
Photoacoustic Depth Profiling of Layered Samples
Authors: Kopp C. , Niessner R.
Published: February 2023

Our experimental setup of time-resolved photoacoustic spectroscopy is presented in Fig. 1. This device was used to analyse absorption profiles of thin films Aquatic samples with varying absorption coefficients confined between thin glass plates, strong absorbers immersed in water and sandwiches of thin plastic films were build up to investigate the resolution of this measurement technique with well defined layered samples According to these samples it was possible to resolve layers of at least 100 pm thickness, with minimal absorption coefficients of about 1 - 2 cm−1
High-repetition rate femtosecond laser system tunable near 200 nm
Authors: Petrov V. , Rotermund F.
Published: February 2023

High-repetition rate femtosecond pulses in the 200-nm spectral region are very interesting for dynamic studies of adsorbates on metal surfaces and are advantageous over using longer wavelengths with multiphoton processes or lower repetition rate amplifiers since the latter can cause surface damage. Generation of the fourth harmonic (FH) of mode-locked Ti:sapphire lasers seems at present to be the most straightforward method to create a high-repetition rate short pulse laser source near 200 nm. Previous experiments on frequency quadrupling resulted in average powers on the 10 mW level in the picosecond regime [1], but in the femtosecond regime only attempts near 205 nm have been reported where the output power levels were not sufficient for any temporal characterization. [2] Here we report for the first time to our knowledge efficient FH pulse generation in the femtosecond regime below 205 nm. The shortest wavelength achieved is 193.7 nm.
A versatile angular shearing interferometer for measurement of spatial coherence
Authors: Coutts David W
Published: February 2023

Shearing interferometry provides a very convenient method of measuring the spatial (transverse) coherence of optical beams. A wavefront folding interferometer produces an interferogram with shear varying from zero up to the full beam width, however such an interferometer is not ideal for measurement of sources having very low transverse coherence, and measures the second order degree of coherence in only one spatial dimension. In this paper an angular/rotary shearing interferometer for measurement of spatial coherence is presented. The interferometer (shown schematically in the figure) is analogous to that proposed by Armitage and Lohmann [1] for use in measurement of aberrations in optical elements. The plane mirror of one arm of a Michelson type interferometer is replaced by a pair of 45° mirrors such that the return beam is laterally displaced. A second beamsplitter is inserted to recombine this beam with the reference and form the interferometer output. Such an interferometer represents a very convenient and easily aligned wavefront folding interferometer in its own right. Insertion of an image rotating dove prism as indicated in the figure converts the wavefront folding interferometer into an angular (rotary) shearing interferometer, where the shear varies from zero in the centre of the interferogram to a maximum at the edge. For a dove prism rotation angle θ (where θ = 0 is defined as the reflecting hypotenuse of the prism being vertical) a shear angle of 2θ is produced in the interferogram. The shear produced at distance r from the centre of the interferogram is therefore 2r sinθ. For small θ, very low shears and hence low spatial coherence values can be measured, and for θ =90° the maximum shear corresponds to the full beam diameter. An angular shear also enables coherence measurement of beams with anisotropic (with respect to angular co-ordinate) coherence. Note that polarisation rotation within the dove prism can be compensated using quarter wave ‘polarisation coupling’ [1], however the amount of polarisation rotation/introduced elipsicity produced by the dove prism is in practice very small [2].
A 10kHz 100mW Cerium LiCAF laser pumped by the sum frequency mixed output of a copper vapour laser
Authors: McGonigle A.J.S. , Coutts D.W. , Webb C.E.
Published: February 2023

In recent years there has been considerable progress in the operation of tunable uv solid state lasers based on trivalent cerium doped fluoride crystals, most notably Ce:LiCAF, Ce:LiSAF and Ce:LiLuF. The pump bands for cerium doped fluorides are in the 250-290nm spectral region, thus requiring a deep uv pump laser. Typically frequency quadrupled Nd:YAG lasers are used to pump Ce:LiCAF and Ce:LiSAF, and KrF excimer lasers for pumping Ce:LiLuF. These pump lasers generally only give short pulses (<20 ns) at PRFs of tens of hertz, thus limiting their suitability for pumping high pulse repetition rate cerium lasers. However recently kHz PRF cerium lasers have been developed using a 10ns frequency quadrupled Nd:YVO4 pump laser [1].
Upconversion Fluorescence and Lasing in Pr,Yb-doped Host Lattices
Authors: Sebald K. , Kück S. , Heumann E. , Sandrock T. , Groß R. , Möbert P. , Huber G.
Published: February 2023

It has been shown that Pr,Yb-doped YLiF4 (YLF) is a suitable upconversion laser material. Under excitation with a Ti:sapphire laser tuned to an emission wavelength of about 830nm, 75mW of red output on the transition Pr3+(3P0) →Pr3+(3F2) at 639.5nm were obtained. Experimental observations indicate that an avalanche process is the main upconversion mechanism leading to population of the 3PJ multiplets of Pr3+.The metastable intermediate energy level required for upconversion is the Pr3+(1G4) multiplet [1].Recently a significant improvement of red output in YLF was achieved by optimizing the Pr- and Yb- concentration. The best composition was Pr(3%),Yb(5%):YLF. Moreover green and yellow upconversion lasing have been demonstrated. Since the host lattice YAlO3 (YAP) has turned out to be a good material for laser crystals [2], YAP doped with various concentrations of Pr and Yb have been investigated for a similar upconversion mechanism. Spectroscopic measurements were carried out on Czochralski-growm crystals, with melt compositions Pr(0.5%),Yb(5%):YAP, Pr(0 75%),Yb(5%):YAP and Pr(0.8%),Yb(5%):YAP. The respective dopant concentrations refer to the Y sites.
Measurement of gain spectra in as-grown and intermixed GaAs/AlGaAs quantum well lasers
Authors: Blay C.L. , Laughton F.R. , Hobbs L. , Marsh J.H.
Published: February 2023

Selective area quantum well intermixing (QWI) has recently emerged as a powerful technique for the monolithic integration of optoelectronic devices, such as lasers, modulators and waveguides. Monolithically-integrated multiple-wavelength lasers for use as wavelength division multiplexing sources have been demonstrated in both GaAs/AlGaAs and InP/InGaAsP material systems, using one-step techniques to achieve varying degrees of intermixing across a sample. In order to design and optimise such devices, it is necessary to understand the effect of QWI on the semiconductor’s complex dielectric coefficients. Of particular interest are the changes in gain spectra caused by the intermixing process. Theoretical predictions of gain spectra as a function of the degree of intermixing have been made [1], but to date there have been no corresponding experimental measurements. Using the method of Blood et al. [2], gain spectra have been measured in as-grown and intermixed GaAs/AIGaAs quantum well lasers.
Ultralow-noise Battery Operated Passively Modelocked Cr3+:LiSAF laser
Authors: Hopkins J-M. , Valentine G.J. , Sibbett W , Aus der Au J , Morier-Genoud F. , Keller U , Valster A
Published: February 2023

The combination of a GaAs semiconductor saturable absorbing mirror (SESAM)1 and a low-threshold laser geometry2 has allowed the efficient production of stable low-noise femtosecond pulses. The highly asymmetric 4-mirror Cr3+LiSAF laser was pumped by 2 polarisation-combined narrow-stripe AlGaInP laser diodes each providing a maximum available power of 40mW incident on the crystal facet. The cw oscillation threshold of the laser was 16mW and the pulse repetition frequency was 153MHz. When output coupling through a high reflecting (HR) end mirror, the laser produced stable, sub 70 fs transform limited pulses at an average output power of 1mW. Modelocking could be sustained with pump powers as low as 21 mW.