Showing papers by "IPG Photonics published in 2019"

Super-octave longwave mid-infrared coherent transients produced by optical rectification of few-cycle 2.5-μm pulses

Abstract: Femtosecond laser sources and optical frequency combs in the molecular fingerprint region of the electromagnetic spectrum are crucial for a plethora of applications in natural and life sciences. Here we introduce Cr2+-based lasers as a convenient means for producing super-octave mid-IR electromagnetic transients via optical rectification (or intra-pulse difference frequency generation, IDFG). We demonstrate that a relatively long, 2.5 μm, central wavelength of a few-cycle Cr2+:ZnS driving source (20 fs pulse duration, 6 W average power, 78 MHz repetition rate) enabled the use of highly nonlinear ZnGeP2 crystal for IDFG with exceptionally high conversion efficiency (>3%) and output power of 0.15 W, with the spectral span of 5.8–12.5 μm. Even broader spectrum was achieved in GaSe crystal: 4.3–16.6 μm for type I and 5.8–17.6 μm for type II phase matching. The results highlight the potential of this architecture for ultrafast spectroscopy and generation of broadband frequency combs in the longwave infrared.

Octave-spanning Cr:ZnS femtosecond laser with intrinsic nonlinear interferometry

Abstract: We report a few-cycle, super-octave, polycrystalline Cr:ZnS laser system with 4 W power at 78 MHz repetition rate, where all of the necessary optical signals for the measurement of the carrier–envelope offset frequency are generated intrinsically.

Middle-IR frequency comb based on Cr:ZnS laser.

Abstract: We report, to the best of our knowledge, the first fully referenced Cr:ZnS optical frequency comb. The comb features few cycle output pulses with 3.25 W average power at 80 MHz repetition rate, spectrum spanning 60 THz in the middle-IR range 1.79–2.86 µm, and a small footprint (0.1 m2), The spectral components used for the measurement of the comb’s carrier envelope offset frequency were obtained directly inside the polycrystalline Cr:ZnS laser medium via intrinsic nonlinear interferometry. Using this scheme we stabilized the offset frequency of the comb with the residual phase noise of 75 mrads.

Visible-near-middle infrared spanning supercontinuum generation in a silicon nitride (Si3N4) waveguide

Abstract: We demonstrate the generation of a supercontinuum spanning more than 1.5 octaves over the 1.2–3.7 µm range in a silicon nitride waveguide using sub-40-fs pulses at 2.35 µm generated by a 75 MHz Kerr-lens mode-locked Cr:ZnS laser.

The tectonics and active faulting of Haiti from seismicity and tomography

Abstract: Oblique convergence of the Caribbean and North American plates has partitioned strain across a major transpressional fault system that bisects the island of Hispaniola. The devastating M W 7.0, 2010 earthquake that struck southern Haiti, rupturing an unknown fault, highlighted our limited understanding of regional fault segmentation and its link to plate boundary deformation. Here we assess seismic activity and fault structures across Haiti using data from 33 broadband seismic stations deployed for 16 months. We use traveltime tomography to obtain relocated hypocenters and models of V p and V p /V s crustal structure. Earthquake locations reveal two clusters of seismic activity. The first corresponds to aftershocks of the 2010 earthquake and delineates faults associated with that rupture. The second cluster shows shallow activity north of Lake Enriquillo (Dominican Republic), interpreted to have occurred on a north-dipping thrust fault. Crustal seismic velocities show a narrow low-velocity region with an increased V p /V s ratio (1.80-1.85) dipping underneath the Massif de la Selle, which coincides with a southward-dipping zone of hypocenters to a depth of 20 km beneath southern Haiti. Our observations of seismicity and crustal structure in southern Haiti suggests a transition in the Enriquillo fault system from a near vertical strike-slip fault along the Southern Peninsula to a southward-dipping oblique-slip fault along the southern border of the Cul-de-Sac-Enriquillo basin. This result, consistent with recent geodetic results but at odds with the classical seismotectonic interpretation of the Enriquillo fault system, is an important constraint in our understanding of regional seismic hazard.

Multi-octave visible to long-wave IR femtosecond continuum generated in Cr:ZnS-GaSe tandem.

Abstract: We report a technique for generation of broad and coherent femtosecond (fs) continua that span several octaves from visible to long-wave IR parts of the spectrum (0.4–18 µm). The approach is based on simultaneous amplification of few-cycle pulses at 2.5 µm central wavelength at 80 MHz repetition rate, and augmentation of their spectrum via three-wave mixing in a tandem arrangement of polycrystalline Cr:ZnS and single crystal GaSe. The obtained average power levels include several mW in the 0.4–0.8 µm visible, 0.23 W in the 0.8–2 µm near-IR, up to 4 W in the 2–3 µm IR, and about 17 mW in the 3–18 µm long-wave IR bands, respectively. High brightness and mutual coherence of all parts of the continuum was confirmed by direct detections of the carrier envelope offset frequency of the master oscillator.

Relaxation study of pre-densified silica glasses under 2.5 MeV electron irradiation.

Abstract: We examined the “relaxation properties” of pre-densified synthetic fused silica glass under 2.5 MeV electron irradiation. The densification of the glass was either obtained by hot compression (5 GPa-350 °C and 5 GPa-1000 °C) or via a thermal treatment increasing its fictive temperature (Tf = 1050, 1250 and 1400 °C). Under irradiation, the pre-densified silica glasses exhibit a relaxation of their macroscopic density with increasing integrated dose. Density was reduced for hot compressed silica and increased for Tf samples with different relaxation rates but it is remarkable that all sample densities follow a trend towards the same equilibrium value around 2.26 for a dose larger than 10 GGy despite a different final topology. After irradiation of hot compressed silica, the Raman spectra display a significant increment of 4 and almost 3-membered rings whereas they exhibit a glass density reduction; demonstrating that a D2 band increase cannot be considered as an absolute marker of the glass compaction. The correlation between density and D2 intensity remains valid until silica density remains lower than 2.26. In contrast, the FWHM of the main band peaking at 440 cm−1 appears to remain correlated to the silica glass density for all investigated samples.

NRZ, Duobinary, or PAM4?: Choosing Among High-Speed Electrical Interconnects

Abstract: Over the last several decades, the increasing data traffic in telecom, datacom, and high-performance computing has led to multi-gigabytes-per-second data transmission speeds in multiservice switches (MSSs), such as core routers and cross-connect switches [1]. A particularly challenging problem in this regard is the transmission of high-speed electrical data through the backplane in MSSs due to the high attenuation of current backplane materials and the limited bandwidth of backplane connectors [2].

System Design for High-Capacity Unrepeatered Optical Transmission

Abstract: By basing the figure of merit on the joint evaluation of signal bit error rate and optical signal-to-noise ratio, the design of single-carrier 400 G unrepeatered optical systems using remote optically-pumped amplifiers with dedicated delivery fiber is discussed and analyzed in this paper. Simulation results show very good agreement with experimental measurements, proving the effectiveness of the proposed approach in critical transmission situations.

A 43.6-dB SNDR 1-GS/s 3.2-mW SAR ADC With Background-Calibrated Fine and Coarse Comparators in 28-nm CMOS

Abstract: This paper presents a 1-GS/s 3.2-mW 8-bit successive approximation register (SAR) analog-to-digital converter (ADC) using background-calibrated coarse and fine comparators. A coarse and fine comparator scheme is proposed for the bit cycling procedure of MSBs and LSBs to reduce the power consumption. By employing a capacitive digital-to-analog converter (DAC) with redundancy, the decision errors of the coarse comparators due to the thermal noise can be tolerated. Therefore, coarse comparators can have relaxed noise constraint and consume low power. In addition, a novel background calibration method is proposed to align the offsets between different comparators using a reference comparator. This background calibration technique requires no additional bit cycle for comparator calibration, thus improving the ADC’s conversion speed. The prototype ADC is implemented in a 28-nm CMOS technology and achieves an effective number of bits of 6.95 b (signal to noise and distortion ratio (SNDR) of 43.6 dB) near Nyquist frequency with the figure of merit (FOM) of 25.87 fJ/conversion-step. To the best of authors’ knowledge, this ADC achieves the highest SNDR among all single-channel SAR ADCs reported that operate above 1 GS/s.

High Precision SEIS Calibration for the InSight Mission and Its Applications

Abstract: Part of the InSight mission, the SEIS instrument (Seismic Experiment for Interior Structures), is planned to arrive on Mars in November 2018. In order to prepare its future recordings on the red planet, special attention was directed towards calibrating the seismometer in-situ on the Martian surface. Besides relative calibrations, we studied the possibility of actively calibrating the two kinds of seismometers onboard SEIS, the Very Broad Band seismometers (VBB) and the Short Period seismometers (SP) and extended the analysis towards a possible absolute calibration. For that purpose, we developed additional noise models at low frequency and elaborate on how they will be sensed by the seismic sensors from long-period data recorded by the seismometer. Such work will improve SEIS capabilities to unveil the inner structure of Mars by checking SEIS well-being and with applications such as gravimetry with the main Phobos tide. The current calibration procedure is planned to take one hour to calibrate the VBB sensors using the SP sensors, and determine the VBB gain with an accuracy of 0.4%, good enough to resolve the state of the Martian core.

Characterization of high-harmonic emission from ZnO up to 11 eV pumped with a Cr:ZnS high-repetition-rate source.

Abstract: We report the measurement of high-order harmonics from a ZnO crystal with photon energies up to 11 eV generated by a high-repetition-rate femtosecond Cr:ZnS laser operating in the mid-infrared at 2–3 μm, delivering few-cycle pulses with multi-watt average power and multi-megawatt peak power. High-focus intensity is achieved in a single pass through the crystal without a buildup cavity or nanostructued pattern for field enhancement. We measure in excess of 108 high-harmonic photons/second.

1.5-mJ Cr:ZnSe Chirped Pulse Amplifier Seeded by a Kerr-Lens Mode-Locked Cr:ZnS oscillator

Abstract: We report a 1-kHz, 1.5 mJ Cr:ZnSe chirped pulse amplifier with 140 fs pulse width, 9.5 GW peak power at 2.4 µm central wavelength. The amplifier is seeded with a commercial few-cycle Cr:ZnS oscillator.

Where does a volcano break? Using self-potential reiteration to forecast the precise location of major destructive events on active volcanoes: the case study of the Piton de la Fournaise 2007 caldera collapse

Abstract: In April 2007, the Dolomieu caldera collapse was one of the most outstanding events of the last few decades at Piton de la Fournaise volcano. Forecasting the occurrence of such a destructive event is difficult but since then, the development of tools and monitoring networks has improved our knowledge of the dynamics of volcano instability. However, the precise location of volcano failure is still hard to constrain. In this paper, we show that reiteration of self-potential (SP) measurements taken at a one meter step-size along a 440-m-long profile prior to caldera collapse brings valuable insights on the most instable areas around the Dolomieu crater. SP signal dynamic reveals information not visible on one single SP acquisition. In particular, the SP dynamic highlights the presence of low cohesion/low strength materials at depth despite a lack of surface expression. Our survey at Piton de la Four-naise showed that preferential failure area can be precisely identified, at the meter scale. These results highlight the relevance of SP reiteration measurements as a tool for locating instabilities in both volcanic and non-volcanic environments.

Simulation of the 2004 tsunami of Les Saintes in Guadeloupe (Lesser Antilles)

Abstract: Subduction zones are areas with significant tectonic activity, complex fault systems, volcanic edifices and growth of islands. Earthquakes in this context are associated with sudden subsidence or uplift of the sea floor with the potential to trigger landslides and tsunamis. A tsunami initiated by a megathrust earthquake can generate strong currents, and is able to carry massive quantities of sediments. The inhabited islands and coasts near subduction areas are threatened by those destructive earthquakes and tsunamis. The arc of the Lesser Antilles which formed due to the plunge of the Atlantic oceanic plate under the Caribean plate, is one of them. The tsunamigenic earthquakes in this region are rare, poorly documented and the only available data are qualitative (observations of coseismic displacement, intensity of the damages). Quantitative data is lacking as no seismograms or tide-gauge were set up before 1968. This lack of data increases the uncertainty on the existent fault models and the shortness of the catalog of seismicity does not enable a good analysis of the recurence cycle of the megathrust earthquakes. The most recent tsunamigenic earthquake occured in 2004 in the area of Les Saintes normal fault system. This Mw6.3 earthquake generated small waves with 2m of run-up in several bays of Les Saintes, a group of island in the South of Guadeloupe. A recent survey done on the fault scarp revealed important coseismic displacement at the surface which had not been predicted in the seismic source models resulting from the joint inversion of teleseismic and GPS data. Tsunami simulations of those different models of fault enable the calculation of the associated time arrivals and water heights of the waves. Compared to the reported observation, those results give complementary informations and additional constrains on the source parameters.

Performing submarine field survey without scuba gear using GIS-like mapping in a Virtual Reality environment

Abstract: Geomorphological and geological studies of the seafloor benefit today from both ROV exploration and from acquisition of high resolution bathymetric data. Although both represent significant improvements to study submarine domains, the understanding of the studied objects is made more difficult than on land given the limited visual perception provided by the ROV camera due to the attenuation of light in the water and the need to use artificial illumination. Likewise, mapping can be performed using GIS software for digital elevation models and its derivatives (e.g. slope or shade raster), mostly in a 2D map view only. So, the submarine studies lack the field survey stage performed in classical onshore works that allows clear visualization and appreciation of the studied objects.Our aim is to develop a solution allowing the visualization of Digital Elevation Models (DEM) and 3D models derived from Structure-from-Motion (SfM) within a virtual reality environment, and to use these data for geomorphological and geological analysis. For this, we use an Oculus Rift headset, Touch controllers, and the Unity game engine, with GIS-like interaction capabilities.The free and open Unity package that we are developing allows, at this stage, data visualization and working at a 1:1 scale in a georeferenced system. The user can therefore move freely within a 3D immersive environment that includes custom topographic data. For quantitative observations, we develop tools (ruler, compass) allowing measurements similar to those performed during geomorphological or geological field work. We also add the possibility to map objects. Digitizing in 3D is achieved with a laser pointed towards the data, providing great precision. The user can thus create pseudo shapefiles using the same three graphic primitives, and that are compatible with standard GIS software. Beside these functionalities, we also implement a spatial user interface displaying help and information and a teleportation tool preventing motion sickness.The users that have tested this solution are enthusiastic and agree that it helps to better appreciate and understand the shape and geometry of the studied objects. It was also used to present and explain 3D models of outcrops to master students. Further developments will port the solution for other headsets, facilitate the data import (e.g., standard file formats for 3D objects and DEMs), create and manage of multiple layers of shapefiles, and include multiplayer online gaming capabilities to allow remote co-working with colleague(s) at other distant locations, or a whole classroom.

New self-starting mode locked laser with active phase control

Abstract: We report on a commercial laser system based on a Yb fiber oscillator with cross-filter mode lock (CFML) mechanism that is integrated with a programmable pulse shaper. The laser is self-starting and stable in a wide temperature range, 15- 50°C, resilient to vibrations and shock. It can serve as a seed for high-power femto- and pico- second systems or be implemented as a standalone unit, as illustrated in this paper. The master oscillator is outputting strongly chirped pulses, with the spectrum centered at 1030 nm and having the full bandwidth of up to 90 nm. It operates at 11 MHz repetition rate, with the pulse energy of at least 10 nJ at the output. When equipped with an additional power amplification module, the oscillator yields the same spectral output and repetition rate, but the pulse energy can be increased up to 400 nJ. The laser output is fully coherent, and pulses are compressible down to the transform limit (TL). For demanding femtosecond applications, the laser system is being configured with a static grating compressor and a compact spectral phase shaper. The pulse shaper utilizes a liquid-crystal spatial light modulator for active phase control which enables high-finesse pulse compression as well as arbitrary manipulation of the pulse waveform. With the use of the pulse shaper, the oscillator output is compressed down to 57 fs, which is within 7% from the TL pulse duration, 53 fs, calculated from the experimental laser spectrum.

Mid-IR Optical Parametric Oscillator Based on Periodically Polled LiNbO 3 Pumped by Tm 3+ :Lu 2 O 3 Ceramic Laser

Abstract: Optical parametric oscillator based on a periodically poled MgO:LiNbO3 crystal pumped by a repetitevely pulsed Tm3+:Lu2O3 ceramics laser at 1966 nm was studied. The OPO average output power up to 530 mW at wavelength of 3.7–4.2 μm was achieved at the ceramics laser power of 7.9 W. The optical-to-optical efficiency of OPO energy conversion was up to 6.7%, and the slope efficiency was up to 8%.

Actively Q-switched Tunable Narrowband 2 μm Tm:YAP Laser Using a Transversally Chirped Volume Bragg Grating

Abstract: A pulsed, narrow-linewidth, wavelength-tunable Tm:YAP laser was realized. 1 kHz stable operation with 200 μJ, 50 ns pulses is reported. Spectrum was narrowed to 0.2 nm and tuned from 1940 to 1960 nm with a transversally chirped volume Bragg grating.

Ultrafast mid-IR sources based on polycrystalline Cr:ZnS/Se and their spectral broadening using supercontinuum generation in silicon nitride waveguides (Conference Presentation)

Abstract: Kerr-lens mode locked lasers based on polycrystalline Cr:ZnS and Cr:ZnSe have come of age and, arguably, represent the most viable route for generation of ultra-short pulses in the range 2–3 μm. Developed designs of Kerr-lens mode locked oscillators feature high efficiency and provide access to few-cycle MIR pulses with Watt-level power in a very broad range of pulse repetition rates. However, currently available dispersive mirror coatings limit spectral coverage of these oscillators to below one octave hampering their conversion to frequency combs via frequency envelop offset frequency (fceo) control and stabilization. Supercontinuum (SC) generation using photonic waveguides is a promising approach for spectral broadening of pulsed coherent sources at low pulse energies and small footprint. Among many materials promising for this application stoichiomentric Si3N4 (SiN) holds a unique place due to its high nonlinearity, CMOS compatible fabrication process, and spectral coverage over visible-middle-infrared (MIR) range. In the current paper we experimentally demonstrate the generation of a supercontinuum spanning more than 1.5 octaves over 1.2-3.7 um range in a silicon nitride waveguide using sub-40-fs pulses at 2.35 um generated by 75 MHz Cr:ZnS laser. The coupling efficiency was about 16%, which corresponds to 0.56nJ pulse energy and 12.4 kW peak power. We also have observed that threshold for SC generation was about 50 mW of incident power that corresponds to 2.4KW peak power. The demonstrated coherent 1.5 octaves spanning bandwidth is ideal for self-referenced f-2f detection of the fceo. In addition, this represents a promising broadband coherent source for dual comb spectroscopy.

A 2.35-{\mu} {m} Pumped Subharmonic OPO Reaches the Spectral Width of Two Octaves in the Mid-IR

Abstract: We used an orientation-patterned gallium phosphide (OP-GaP) crystal combined with an ultrafast $2.35-\mu \text{m}$ pump (1.2W, 79 MHz, 62 fs) to demonstrate a subharmonic sync-pumped OPO with an instantaneous output spectrum of $3-12.5\ \mu \text{m}$.

Yb-Fiber Laser Pumped Optical Parametric Sources Using LBO Crystals

Abstract: Green-pumped OPG/OPAs and OPO using non-critical phase-matching in LBO are investigated at various pulse durations from 1ps to 13ns. The OPAs and OPO achieve similar conversion efficiencies of ∼50% providing up to 25W output power.

Focus issue introduction: advanced solid-state lasers.

Abstract: This joint issue of Optics Express and Optical Materials Express features 28 state-of-the-art articles written by authors who participated in the international “Advanced Solid State Lasers” conference, held in Boston November 4–8, 2018. This review provides a summary of these articles that cover the spectrum of solid state lasers from materials research to sources and from design innovation to applications.

Broadband Randomly Phase Matched OPO Using a Thin 0.5-Mm ZnSe Ceramic and a Dispersion-Free Cavity

Abstract: We used a 0.5-mm randomly-phase-matched ZnSe polycrystal pumped by femtosecond 2.35-μm pulses and achieved a 3.2-9-μm-wide spectrum with 53-mW output power in a dispersion-free OPO cavity consisting of gold-coated mirrors and a pump injector. © 2019 The Author(s)

System and Method for Visualizing Laser Energy Distributions Provided by Different Near Field Scanning Patterns

Abstract: A system and method may be used to visualize laser energy distributions within one or more laser movements generated by a scanning laser processing head. The system and method determine laser energy distributions at a plurality of locations within the laser movement(s) based at least in part on received laser processing parameters and laser movement parameters. A visual representation of the laser energy distributions may then be displayed to allow the user to visualize and select or define the appropriate pattern and parameters for a laser processing operation. The visualization system and method may be used to predict actual laser energy distributions in a laser processing operation by visualizing the laser energy distributions before the laser processing operation and/or to troubleshoot a laser processing operation by visualizing the laser energy distributions after the laser processing operation.

5-Octave Laser Source Based on Cr: ZnS-GaSe Tandem

Abstract: We report laser architecture that enables generation of coherent femtosecond continua that span from visible to long-wave IR (0.5-18 μm), and features: high power (4W), high repetition rate (80 MHz), and intrinsic nonlinear interferometry. © 2019 The Author(s)

Focus issue introduction: advanced solid-state lasers

Abstract: This joint issue of Optics Express and Optical Materials Express features 28 state-of-the-art articles written by authors who participated in the international “Advanced Solid State Lasers” conference, held in Boston November 4–8, 2018. This review provides a summary of these articles that cover the spectrum of solid state lasers from materials research to sources and from design innovation to applications.

2-cycle Cr:ZnS Laser with Intrinsic Nonlinear Interferometry

Abstract: We demonstrate a fs laser architecture that enables the direct measurement of the laser’s carrier envelope offset frequency. A multi-Watt source is arranged as a full-repetition-rate polycrystalline Cr:ZnS MOPA and covers 3-octaves (0.4–4.2 µm).