Dysprosium (III) ion doped fluoride glass fibre lasers have been demonstrated to generate mid-infrared coherent light with operating wavelength beyond 3000 nm. These devices can also generate mid-infrared optical pulses using both gain and Q-switching. Thus, potentially dysprosium (III) ion doped fluoride glass fibre lasers have many potential commercial applications. In this study, we perform numerical analysis of mid-infrared pulse generation by dysprosium (III) ion doped fluoride glass fibre lasers that operate in a pulsed regime using Q-switching. The results obtained using the developed dynamic numerical model are compared with the measurements. The comparison enables explanation of the experimentally observed trends and helps better understanding of the principles of the fibre laser operation.

A realisation of a Q-switched Tm3+-doped fibre laser operating at 1.96 mu m wavelength is reported. The Tm3+-doped fibre was fabricated using a novel multi-ring modified chemical vapour deposition-chelate doping technique (MCVD-CDT) technology. The developed laser emits pulses at a repetition rate of 3 kHz with an energy of 84 mu J and a duration of 272 ns, which corresponds to a peak power of 309 W. The experimental results confirm that the fabricated Tm3+-doped multi-ring, large mode area fibre is a promising candidate for developing high-energy Q-switched lasers operating near 2 mu m wavelength.

Rare-earth ion doped, silica glass, optical fibre amplifiers have transformed the world by enabling high speed communications and the Internet. Fibre lasers, based on rare-earth ion doped silica glass optical fibres, achieve high optical powers and are exploited in machining, sensing and medical surgery. However, the chemical structure of silica glass fibres limits the wavelength of laser operation to < 2.5 µm, which excludes the mid-infrared longer wavelength range of 3–50 µm. Rare-earth ion doping of fluoride glasses enables manufacture of fibre lasers up to a limiting 3.92 µm wavelength, but the fluoride glass chemical structure again prevents operation at longer wavelengths. Optical fibre lasers that are constructed from different rare-earth ion doped chalcogenide glass fibres will potentially operate across the 4–10 µm wavelength range, where suitable high-power lasers currently do not exist. We present a short review here of our recent work in achieving first time, continuous wave, mid-infrared fibre lasing beyond 5 μm wavelength in Ce 3+ -doped selenide chalcogenide fibre. We place this disruptive breakthrough into the wider fibre laser context, and also present the unprecedented advances in new cross-sector applications that will be enabled by mid-infrared fibre lasers in the 4–10 µm wavelength range. To surpass the few mW power output of the Ce 3+ -doped chalcogenide glass fibre lasing achieved to date, the glass quality of the doped chalcogenide fibres must now be improved, similar to the challenges originally facing the first glass fibre lasers based on silica.

Chalcogenide selenide glass fibres have been demonstrated to be well suited for realising lasers operating beyond 5000 nm wavelength with output powers exceeding 100 mW in CW. These devices have many potential commercial applications because they can be in principle tuned over a wide range of wavelengths and can also be potentially made to generate short optical pulses. Therefore in this paper we use a numerical model to study the energy level population dynamics in terbium doped chalcogenide selenide glass fibre under pulsed pumping. The results obtained further the understanding of major dynamic processes governing a mid-infrared pulse generation by a chalcogenide selenide glass host.

A laboratory realization of an actively Q-switched Dy3+-doped fluoride fiber laser operating near 3.0 mu m is reported. Two laser cavities were realized: one based on 1000 ppm Dy3+:ZBLAN fiber and one on 2000 ppm Dy3+:ZBLAN fiber. With the laser cavity based on 1000 ppm Dy3+:ZBLAN fiber a record high peak power of 200 W was achieved with 17 mu J pulse energy and 84.5 ns pulse duration. Moreover, a record short pulse duration of 74 ns was achieved using Q-switched laser cavity composed of 2000 ppm Dy3+:ZBLAN fiber.

Nanoplasmonics as enabler of room-temperature quantum nanophotonic networks (Invited), Ortwin Hess Coffee break (11:00 -11:20) Track 1 -Room 2.1 Track 2 -Room 2.2 Track 3 -Room 2.3 Track 4 -Room 3.1 Track 5 -Room 3.2 Track 6

We provide measurements to support our earlier report of continuous wave fiber lasing in a small core Ce3+-doped selenide chalcogenide SIF (step index fiber) of core: Ge-As-Ga-Se chalcogenide glass, doped with 500 ppmw (parts-per-million by weight) of cerium (III). In-band pumping of Ce3+ in fiber, bulk glass and ground glass geometries, at 4.15 mu m wavelength, gives MIR (mid-infrared) photoluminescence spanning 3.40-5.80 mu m wavelength, corresponding to the 2F5/2 <- 2F7/2 electronic emission transition due to Ce3+. Room temperature emission and MIR absorption spectra together enable interpretation of the manifold energies of the first excited state and there is potential for occupied Stark levels in the ground state at room temperature. Both 'tau rad' (PL lifetime) and 'trise' (rise-time through 10% to 90% of maximum PL intensity) are determined: for ground glass at 4.60 mu m wavelength, the best decay fit comprises a primary, and perhaps secondary, lifetime for ground glass of 3.5 ms, and 1.2 ms, and PL rise time of 3.9 ms.

Pulsed fluoride glass fibre based lasers have many potential important applications in materials processing, medicine and defence. At present a number of continuous wave fluoride glass fibre lasers is offered commercially. However, there is still a large scope for the development of pulsed lasers. Therefore, in this contribution we give an up-to-date review of the recent progress in the development of gain switched and Q-switched fluoride glass fibre lasers. Also, we present new experimental results on dysprosium ion doped Q-switched fluoride glass fibre lasers.

We review here our recent work in achieving mid-infrared (MIR) fibre lasing beyond 5 µm wavelength in Ce 3+ -doped selenide-chalcogenide fibre, as well as the observed photoluminescence in samples of the same composition but in particulate and bulk glass form as well as unstructured fibre and in the SIF (step index fibre) in which fibre lasing took place.

In this contribution a comprehensive spectroscopic study of Dy3+ doped fluoroindate glass samples and glass fiber is presented. The mid-infrared (MIR) emission from DyF3 doped bulk glass samples (0.2, 0.4, 0.8, 1.2, 1.4, 1.6 mol.%) is investigated when pumping at 1320 nm. A broadband mid-infrared emission spanning from 2800 nm to 3500 nm with 0.88 ms emission lifetime of the 6H13/2 level in 0.2 mol.% glass sample was observed. Also 0.2 mol.% of DyF3 doped fluoroindate glass fiber was drawn and its photoluminescence properties were studied showing the emission spectrum to 3500 nm and the 6H13/2 level lifetime of 0.91 ms. The results obtained show that fluoroindate glass is a good candidate for further development of tunable fiber lasers and broadband mid-infrared spontaneous emission fiber sources.

“ M id- I nfra R ed ( MIR ) fiber photonics” is an important emerging technology worldwide. The MIR spectral region (3 μm wavelength) offers great potential for molecular sensing systems that will translate across sectors from security to healthcare; MIR laser cutting and welding at new wavelengths of soft materials will include medical surgery of human tissue. Chalcogenide glasses present windows within the 1–20 μm region and chalcogenide glass optical fibers are suitable for routing MIR light and as active laser sources. Chapter 8 is a critical review of the last 10 years’ research on lanthanide-ion doped chalcogenide bulk glasses and fibers up to, and including, the advent of bulk glass lasing, at >5 μm, in 2020 and 2021. Photoluminescent behavior is critically analyzed, including absorption and emission cross-sections, lifetimes, branching ratios of praseodymium, dysprosium, terbium and samarium ions doped into a variety of chalcogenide glass hosts. Potential electro-optic traps in chalcogenide glass hosts, as well as optical traps, are discussed for the first time.

Mid-infrared lasers operating near 3 µm are a subject of considerable research effort in recent years. The main reason is the broad range of potential applications for such sources in the field of medicine, environmental monitoring and free space communication. For many applications pulsed mid-infrared light sources with high output energy, short pulse duration (to reduce the impact of thermal background) and good pulse-to-pulse stability are preferred. A promising candidate for such pulsed light sources is a mid-infrared fiber laser realised using fluoride glass fibers doped with rare earth ions (for example erbium or dysprosium). In this contribution pulsed operation was obtained by implementing the Q-switching technique in a laser setup consisting of a fluoride fiber pumped with near infrared laser diodes. The obtained pulses have output energy above 100 µJ, with pulse width below 50 ns and repetition rate in the kilohertz range.

Multicomponent glass optical fibers are being developed for mid-infrared (MIR) fiber lasers for beyond 4 microns' wavelength for: narrow-band biomolecular sensing; medical laser surgery at new, long wavelengths and for pulsed-seeding of long-wavelength, fiber MIR-supercontinua for compact systems for broad-band MIR medical-sensing and hyperspectral imaging.

A practical realization of a diode pumped actively Q-switched Er 3+ -doped fluoride fiber laser operating near 2.78 μm is reported. For the repetition rate of 100 Hz stable 26 ns pulses with an energy of 330 μJ and peak power of 12.7 kW are demonstrated. The laser performance is tested against variations in pump power, repetition rate and active fiber length.

In this contribution, a comprehensive experimental study of photoluminescence from Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber samples is discussed. The selenide-chalcogenide multimode fiber samples co-doped with 500 ppm of Pr3+ ions and 500 ppm of Dy3+ ions are prepared using conventional melt-quenching. The main objective of the study is the analysis of the pumping wavelength selection on the shape of the output spectrum. For this purpose, the Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber samples are illuminated at one end using pump lasers operating at the wavelengths of 1320 nm , 1511 nm and 1700 nm. The results obtained show that the Pr3+/Dy3+ ion co-doped selenide-chalcogenide multimode fiber emits photoluminescence spanning from 2000 nm to 6000 nm. Also it is demonstrated that, by varying the output power and wavelength of the pump sources, the spectral shape of the emitted luminescence can be modified to either reduce or enhance the contribution of radiation within a particular wavelength band. The presented results confirm that Pr3+/Dy3+ co-doped selenide-chalcogenide multimode fiber is a good candidate for the realization of broadband spontaneous emission fiber sources with shaped output spectrum for the mid-infrared wavelength region.

S. Sujecki, L. Sojka, E. Beres-Pawlik, R. Piramidowicz, H. Sakr, Z. Tang, E. Barney, D. Furniss, T.M. Benson, A.B. Seddon Department of Telecommunications and Teleinformatics, Faculty of Electronics, Wroclaw University of Science and Technology, Wyb. Wyspianskiego 27, 50-370 Wroclaw, Poland George Green Institute for Electromagnetics Research, the University of Nottingham, University Park, NG7-2RD, Nottingham, UK Institute of Microelectronics and Optoelectronics, Warsaw University of Technology Nowowiejska 15/19, 00-665 Warsaw, Poland

In this contribution experimental investigation of acousto-optically Q-switched erbium-doped fluorozirconate fiber laser is presented. Under the repetition rate of 1 kHz laser produces pulses with the shortest duration of 20 ns and the maximum pulse energy of 180 μJ, corresponding to a maximum peak power of 9 kW.

Mid-infrared (MIR) direct fiber lasers beyond 4 mu m wavelength will deliver optimum beam quality of bright, spatially and temporally coherent light, routeable in MIR fiber-optics. They are being developed for applications including narrow-band biomolecular sensing, medical laser surgery at new, long wavelengths and for pulsed seeding of long-wavelength MIR-supercontinua in MIR glass fiber for all-fiber, compact systems for broad-band MIR medical sensing and hyperspectral imaging. Low phonon energy, selenide chalcogenide glasses are the optimum glass host for lanthanide ion doping for emission across the 3 to 10 mu m wavelength MIR region. Here, we report our recent advances including: > 1 mW incoherent emission in the 4-5 mu m wavelength region and demonstration of gain beyond 4 mu m in Pr3+ doped chalcogenide glass fiber, and proposed quasi three-level lasing beyond 4 mu m in Tb3+ doped chalcogenide glass fibers. Encouragingly, since 2020, lasing in both Pr3+ and Tb3+ selenide chalcogenide bulk glasses has been reported. Our overall goal is for new portable, MIR spectroscopic systems based on chalcogenide optical fibers for in vivo sensing, imaging and treatment in healthcare, including for early diagnosis of disease.

This Letter, to the best of our knowledge, reports mid-infrared fiber lasing beyond 5 µm at room temperature for the first time, Ce3+-doped, chalcogenide glass, step index fiber employed in-band pumping with a 4.15 µm quantum cascade laser. The lasing fiber is was 64 mm long, with a calculated numerical aperture of 0.48 at the lasing wavelengths. The core glass was Ge15As21Ga1Se63 atomic % (at. %), doped with 500 parts-per-million-by-weight Ce, with a 9 µm core diameter. The cladding glass was Ge21Sb10Se69 at. % with a 190 µm outer diameter. As pump power increases continuous wave lasing corresponding to the 2F7/2→2F5/2, transition in the Ce3+ ion occurs at 5.14 µm, 5.17 µm, and 5.28 µm.