An ion-exchanged thulium-doped germanate glass channel waveguide laser operating near 1.9 micron

Solid-state lasers operating in the eye-safe region near 2 micron are of considerable interest owing to various application areas such as remote sensing, spectroscopy and LIDAR. Thulium-based gain media have several attractive features including a broad emission bandwidth, a broad absorption band near 800 nm that can be diode pumped and the possibility of obtaining a quantum efficiency of up to 200% due to the process of cross-relaxation. Guided-wave devices can offer additional advantages of compactness and integration, as well as lower thresholds and high slope efficiencies if low propagation losses can be obtained. Such devices, when combined with integrated saturable absorber elements, can also be passively modelocked to generate femtosecond pulses with multi-GHz repetition rates

Towards high-power multi-GHz waveguide lasers

There has been a growing interest in the development of laser sources with high (>GHz) pulse repetition rates owing to their potential applications in areas such as nonlinear microscopy, optical sampling, frequency metrology, optical communications, optical arbitrary waveform generation and for the calibration of astronomical spectrographs (astro-combs). Ultrafast lasers based on low-loss waveguide geometry offer a combination of features (low-threshold operation, high efficiency and moderate non-linearities) which make them attractive for development of compact, low-cost, multi-GHz femtosecond sources

PbSe quantum dots grown in a high-index low-melting-temperature glass for infrared laser applications

PbSe quantum dots (QDs) were grown in high-refractive-index low-melting-temperature lead-phosphate glass. QDs with various sizes ranging from 2 nm to 5.3 nm were grown by controlling the growth parameters, heat-treatment temperature and time. The corresponding room-temperature exciton absorption was tuned within the infrared region from 0.93 µm to 2.75 µm. Photoluminescence was measured for samples with absorption peaks above 0.95eV. Real time quantum dot growth was demonstrated by monitoring the evolution of exciton absorption with temperature and time duration. As a demonstration of the use of QDs in laser applications, the saturation fluence (Fsat) of one of the QDs was evaluated and found to be ~2.1 µJ/cm2 at 1.2 µm

Fundamentally mode-locked Yb³⁺ doped glass waveguide lasers with repetition rate of up to 15.2 GHz

Ultrafast lasers with multi-GHz repetition rates can have applications in areas such as biophotonics, optical frequency metrology, optical sampling, optical communications and as astro-combs. Ultrafast waveguide lasers with monolithically integrated saturable absorber elements are very promising candidates for multi-GHz operation, benefiting from a low-threshold mode-locked operation and high efficiency due to the small guided mode size and consequent strong saturation of both gain medium and saturable absorber. One of the most attractive features of such devices is their compactness and compatibility with integrated optics technology

Low-threshold, mirrorless emission at 981nm in an Yb,Gd,Lu:KYW inverted rib waveguide laser

In this work, we demonstrate 3-level laser operation in a Yb,Gd,Lu:KYW waveguide laser fabricated by combination of liquid phase epitaxy and Ar+ ion beam milling. Laser emission was observed at 981 nm with an absorbed threshold power of 23 mW and a slope efficiency of 58% without the use of any mirrors. With an HR/6%T cavity, the threshold was reduced to 13 mW. The output was single mode with beam radii of 4.8 µm and 3 µm in the in-plane and out-of-plane direction respectively. Laser emission was also observed at 999.8 nm with a threshold of 8 mW by using mirrors favouring the 999.8 nm transition and forming an HR/5%T cavity

Synthesis, structural, thermal and optical studies of inorganic-organic hybrid semiconductors, R-PbI₄

Wide varieties of naturally self-assembled two-dimensional inorganic-organic (IO) hybrid semiconductors, (4-ClC6H4NH3)2PbI4, (C6H9C2H4NH3)2PbI4, (CnH2n-1NH3)2PbI4 (where n = 12, 16, 18), (CnH2n-1NH3)2PbI4 (where n = 3, 4, 5), (C6H5C2H4NH3)2PbI4, NH3(CH2)12NH3PbI4, and (C4H3SC2H4NH3)2PbI4, were fabricated by intercalating structurally diverse organic guest moieties into lead iodide perovskite structure. The crystal packing of all these fabricated IO-hybrids comprises of well-ordered organic and inorganic layers, stacked-up alternately along c-axis. Almost all these hybrids are thermally stable up to 200 °C and show strong room-temperature exciton absorption and photoluminescence features. These strongly confined optical excitons are highly influenced by structural deformation of PbI matrix due to the conformation of organic moiety. A systematic correlation of optical exciton behavior of IO-hybrids with the organic/inorganic layer thicknesses, intercalating organic moieties, and various structural disorders were discussed. This systematic study clearly suggests that the PbI layer crumpling is directly responsible for the tunability of optical exciton energy

Ion-exchanged Tm³⁺:glass channel waveguide laser

Continuous wave laser action around 1.9 µm has been demonstrated in a Tm3+ - doped germanate glass channel waveguide laser fabricated by ion-exchange. Laser action was observed with an absorbed power threshold of only 44 mW and a slope efficiency of up to 6.8% was achieved. Propagation loss at the lasing wavelength was measured and found to be 0.3 dB/cm. We believe this to be the first ion-exchanged Tm3+-doped-glass waveguide laser

Waveguide lasers in (Yb,Nb):RbTiOPO₄

In this paper we present lasing results with a planar (Yb,Nb):RbTiOPO4 waveguide device. We also demonstrate channel waveguiding in an ion-beam etched (Yb,Nb):RbTiOPO4 thin film for the first time with a loss of 2.4 dB/cm. To reduce the losses, a study of reactive ion etching of RbTiOPO4 was carried out resulting in structures with a surface roughness of 6.6nm and an etch rate of 13nm/minute

Growth of PbSe quantum dots within high-index lead-phosphate glass for infrared saturable absorbers

PbSe quantum dots (QDs) were grown in high-refractive-index low-melting-temperature lead-phosphate glass. The lowest energy exciton transition of the QDs was tuned over a wide range within the infrared spectral region (0.93-2.75µm) by a controlled heat treatment. The measured QD radius ranged between 2 and 5.3nm, with a time (t) dependence of t0.29 for long dwelling times during the heat treatment, indicating that the QD growth mechanism tends to follow Lifshitz-Slyozov-Wagner theory. The QD saturable absorber behavior at 1.2µm had a measured saturation fluence of ~2.1µJ/cm2

Graphene Q-switched mode-locked and Q-switched ion-exchanged waveguide lasers

In this paper, we present the use of mono-layer graphene saturable absorbers to produce Q-switched and Q-switched mode-locked operation of Yb and Yb:Er-doped phosphate glass waveguide lasers, respectively. For the 1535-nm wavelength Yb:Er laser, the Q-switched pulses have repetition rates up to 526 kHz and contain mode-locked pulses at a repetition frequency of 6.8 GHz. The measured 0.44 nm bandwidth should allow pulses as short as ~6ps to be generated. Maximum average output powers of 27 mW are obtained at a slope efficiency of 5% in this mode of operation. For the 1057-nm-wavelength Yb laser, Q-switched pulses are obtained with a repetition rate of up to 833 kHz and a maximum average output power of 21 mW. The pulse duration is found to decrease from 292 ns to 140 ns and the pulse energy increase from 17 nJ to 27 nJ as the incident pump power increases from 220 to 652 mW