High-energy nanosecond pulse extraction from a Tm-doped photonic crystal fiber laser emitting at 2050 nm with narrow linewidth.

A nanosecond-pulsed diode-pumped Tm-doped fiber laser (TDFL) operating at 2050 nm is reported based on a flexible photonic crystal fiber (PCF) with a core diameter of 50 µm. Analytical evaluation of reabsorption effects and optimization of the fiber length allow enhanced pulse energy extraction at long wavelengths. This enables the generation of Gaussian-shaped pulses with pulse energies of 1.

A Method to Correct the Temporal Drift of Single-Photon Detectors Based on Asynchronous Quantum Ghost Imaging.

Single-photon detection and timing has attracted increasing interest in recent years due to their necessity in the field of quantum sensing and the advantages of single-quanta detection in the field of low-level light imaging. While simple bucket detectors are mature enough for commercial applications, more complex imaging detectors are still a field of research comprising mostly prototype-level detectors. A major problem in these detectors is the implementation of in-pixel timing circuitry, especially for two-dimensional imagers.

Temperature investigation of low SWaP thulium-doped fiber lasers.

We investigate the temperature dependence of an in-band core-pumped thulium-doped fiber laser with a low SWaP (size, weight, and power) architecture. The temperature investigation is carried out both experimentally and numerically by a simulation model. We demonstrate experimentally that the investigated setup is resistant for temperatures till 353 K.

High average power Q-switched Ho:YAG laser with a single-line emission at 2122 nm.

We present an efficient Q-switched dual-crystal Ho:YAG laser resonator achieving an output power of 56 W at an incident pump power of 100.7 W with a slope efficiency of 64.4%.

3D quantum ghost imaging.

We present current results of a novel, to the best of our knowledge, type of setup for quantum ghost imaging based on asynchronous single photon timing using single photon avalanche diode (SPAD) detectors, first presented in [Appl. Opt.60, F66 (2021)APOPAI0003-693510.

Alignment-insensitive end-pumped continuous-wave crossed-Porro prism Ho:YAG laser.

A continuous-wave crossed-Porro prism Ho:YAG laser is presented and compared with a corresponding mirror resonator. A maximum output power of 30.7 W is reached with a slope efficiency of 67.

High-power continuous-wave Tm:Ho-codoped fiber laser operation from 2.1 µm to 2.2 µm.

A Tm:Ho-codoped free-space single-oscillator fiber laser is under investigation with special focus on the power scalability of emission wavelengths from 2.1 µm to 2.2 µm.

Fraunhofer Institute of Optronics, System Technologies and Image Exploitation: introduction to the focus issue.

This focus issue offers a glimpse into the breadth and depth of research in optics and image processing at the Fraunhofer Institute of Optronics, System Technologies and Image Exploitation (abbreviated Fraunhofer IOSB). The institute belongs to the Fraunhofer Society, which is Europe's largest organization for applied research. The society comprises 72 institutes spread throughout Germany as well as subsidiaries in several European countries, and the USA, UK, Chile and Singapore, each focusing on different fields of applied science.

Quantum ghost imaging using asynchronous detection.

We present first results of a novel type of setup for quantum ghost imaging based on asynchronous single photon timing using single photon avalanche diode (SPAD) detectors. This scheme enables photon pairing with arbitrary path length difference and does, therefore, obviate the dependence on optical delay lines of current quantum ghost imaging setups [Nat. Commun.

Nanosecond pulsed single-frequency two-stage holmium-doped fiber MOPA at 2054 nm and 2090 nm.

A single-frequency polarization-maintaining holmium-doped fiber master oscillator power amplifier operating at signal wavelengths of $2054\;{\rm nm}$ and $2090\;{\rm nm}$ is presented. The two-stage setup delivers up to $240\;{\rm W}$ peak power and $6.7\;\unicode{x00B5} {\rm J}$ pulse energy for a pulse width of $30.

Mid-infrared optical parametric oscillator pumped by a high-pulse-energy, Q-switched Ho:YAG laser.

A high-pulse-energy mid-infrared light source is presented, based on a zinc-germanium-phosphide optical parametric oscillator (ZGP OPO) pumped by an actively $Q$-switched high-pulse-energy ${{\rm Ho}^{3 +}}{:}{\rm YAG}$ laser. The ${{\rm Ho}^{3 +}}{:}{\rm YAG}$ pump laser source is capable of generating a pulse energy of 15 mJ from a single ${{\rm Ho}^{3 +}}{:}{\rm YAG}$ rod at room temperature at a pulse repetition frequency (PRF) of 700 Hz. A maximum power of 20.

High pulse energy ZnGeP OPO directly pumped by a Q-switched Tm-doped single-oscillator fiber laser.

A mid-infrared ${{\rm ZnGeP}_2}$ optical parametric oscillator pumped by a ${{\rm Tm}^{3 +}}$-doped fiber laser is reported, providing pulse energies of $230 \;\unicode{x00B5}{\rm J}$, pulse widths of 40 ns, and peak powers of ${\sim}6\;{\rm kW} $ with excellent efficiency and beam quality. The pump source is an actively $Q$-switched single oscillator optimized to generate high pulse energies.

Adaptable Shack-Hartmann wavefront sensor with diffractive lenslet arrays to mitigate the effects of scintillation.

Adaptive optics systems are used to compensate for distortions of the wavefront of light induced by turbulence in the atmosphere. Shack-Hartmann wavefront sensors are used to measure this wavefront distortion before correction. However, in turbulence conditions where strong scintillation (intensity fluctuation) is present, these sensors show considerably worse performance.

55 W actively Q-switched single oscillator Tm, Ho-codoped silica polarization maintaining 2.09 µm fiber laser.

A bidirectional 793 nm diode-pumped actively Q-switched Tm, Ho-codoped silica polarization-maintaining (PM) double-clad (DC) fiber laser is reported. With this fiber laser, 55 W of average output power with 100 ns pulse width at 200 kHz repetition rate and 2.09 µm wavelength is obtained.

Mid-infrared ZGP OPO with divergence compensation and high beam quality.

Divergence compensation, optimization of the optical-to-optical efficiency, and high beam quality of signal and idler beams of a high-energy mid-infrared ZnGeP (ZGP) optical parametric oscillator (OPO) have been demonstrated by use of a Galilean telescope inside the nonplanar fractional-image-rotation enhancement (FIRE) ring resonator. With a small variation of the distance between the lenses of the telescope, the divergences of signal and idler beams could be adjusted. Up to 36 mJ of mid-infrared pulse energy in the 3-5 µm wavelength range is obtained with 92 mJ of pump energy on crystal.

Improvement of the beam quality of a high-pulse-energy mid-infrared fractional-image-rotation-enhancement ZnGeP optical parametric oscillator.

The beam quality of a high-energy mid-infrared ZnGeP (ZGP) optical parametric oscillator has been improved by use of a negative lens inside the nonplanar fractional-image-rotation enhancement (FIRE) resonator compensating for the thermal lensing and gain guiding effects. With an f=-0.9  m CaF lens, the beam quality is 1.

Optical parametric generation by a simultaneously Q-switched mode-locked single-oscillator thulium-doped fiber laser in orientation-patterned gallium arsenide.

Optical parametric generation is demonstrated in orientation-patterned gallium arsenide, pumped by a novel single-oscillator simultaneously Q-switched and mode-locked thulium-doped fiber laser, downconverting the pump radiation into the mid-infrared wavelength regime. The maximum output energy reached is greater than 2.0 μJ per pump pulse.

High-pulse-energy mid-infrared fractional-image-rotation-enhancement ZnGeP optical parametric oscillator.

A high-energy mid-infrared ZnGeP (ZGP) optical parametric oscillator (OPO) based on the nonplanar fractional-image-rotation enhancement resonator pumped by a 2.05 μm Ho:YLF laser is presented. Up to 120 mJ pulse energy in a rotationally symmetric beam is generated in the 3-5 μm wavelength range at 1 Hz repetition rate.

High-peak-power single-oscillator actively Q-switched mode-locked Tm-doped fiber laser and its application for high-average output power mid-IR supercontinuum generation in a ZBLAN fiber.

A single-oscillator actively Q-switched mode-locked (QML) thulium-doped silica fiber laser is presented and used to pump a ZrF-BaF-LaF-AlF-NaF (ZBLAN) fiber for mid-infrared (mid-IR) supercontinuum (SC) generation. The fiber laser provided high-peak-power levels directly from the oscillator delivering single mode-locked pulse energies up to 48 μJ, being 2-4 orders of magnitude higher than conventional continuous wave mode-locked lasers. By pumping a ZBLAN fiber specially designed for high-output-power SC generation, 7.

Mid-infrared lasing from Ho(3+) in bulk InF(3) glass.

We report on an Ho:InF glass laser pumped by a Cr:LiSAF laser emitting at 889 nm. Ho:InF glass is a promising material for direct mid-infrared lasers around 4 μm. To evaluate the performances of this new material, we compared it to an Ho:BYF crystalline laser pumped by the same source.

Actively mode-locked Tm(3+)-doped silica fiber laser with wavelength-tunable, high average output power.

A diode-pumped, actively mode-locked high-power thulium (Tm)-doped double-clad silica fiber laser is demonstrated, providing an average output power in mode-locked (continuous wave) operation of 53 W (72 W) with a slope efficiency of 34% (38%). Mode-locking in the 6th-harmonic order was obtained by an acousto-optic modulator driven at 66 MHz without dispersion compensation. The shortest measured output pulse width was 200 ps.

6.5 W ZnGeP(2) OPO directly pumped by a Q-switched Tm(3+)-doped single-oscillator fiber laser.

An efficient actively Q-switched Tm-doped single-oscillator fiber laser based on a silica polarization-maintaining (PM) double-clad fiber provided average powers of 23 W at pulse widths of 65 ns at 40 kHz pulse repetition frequency. It was used to directly pump a ZnGeP optical parametric oscillator (OPO). Up to 6.

Mid-infrared rotated image singly resonant twisted rectangle optical parametric oscillator based on HgGa(2)S(4) pumped at 1064 nm.

We compare linear, planar ring, and rotated image singly resonant twisted rectangle (RISTRA) type nanosecond optical parametric oscillator cavities using HgGaS nonlinear crystal pumped by 8 ns pulses at 1064 nm from a low beam quality pump source. The input-output characteristics and the output idler beam quality at 6300 nm are compared for two values of the pump beam diameter presenting different cavity Fresnel numbers and magnitudes of the spatial walk-off effect due to birefringence. The RISTRA cavity ensures in all cases a circular output beam profile but is advantageous in terms of beam quality with respect to the planar ring only at a large pump beam diameter.

Laser action along and near the optic axis of a holmium-doped KY(WO₄)₂ crystal.

We demonstrate the first (to our knowledge) quasi-three-level conical refraction laser operating at 2 μm, with 1.6 W of output power at 2074 nm, using a holmium-doped KY(WO4)2 crystal. A maximum slope efficiency of 52% has been achieved, along the optic axis with respect to the absorbed pump power.

Lack of evidence for increased postoperative bleeding risk for dental osteotomy with continued aspirin therapy.

Objective: Dental osteotomy, the removal of an impacted, ankylosed, or severely destroyed tooth requiring an osteotomy, is more invasive than other minor dental procedures and therefore also has a higher bleeding risk. A considerable number of patients under antiplatelet therapy interrupt their therapy perioperatively, which, however, increases the risk of thromboembolism.

Study Design: This retrospective study assessed postoperative bleeding incidence for a total of 297 dental osteotomies with continued aspirin therapy, compared with that of 179 similar procedures on patients who were not on any anticoagulation or anti-platelet therapy.