Laser Operation of Tm: LuAG Single-Crystal Fiber Grown by the Micro-Pulling down Method

Single crystals fiber (SCF) of LuAG doped with 2.0 at.% thulium has been grown by using micro-pulling down (µ-PD) technique. A continuous-wave output power of 2.44 W was achieved with a slope efficiency of 11.7% using a 783-nm diode laser as pump source. The beam quality factors M2 were 1.14 and 1.67 in the x and y directions, respectively. This is, to the best of our knowledge, the first report on the Tm:LuAG SCF laser. Using ray tracing analysis, the influence of laser performance by the pump intensity distribution in the SCF was also studied.

Purely Gain-Coupled Distributed-Feedback Bragg Semiconductor Laser Diode Emitting at 770 nm

The transition lines of Mg, K, Fe, Ni, and other atoms lie near 770 nm, therefore, this spectral region is important for helioseismology, solar atmospheric studies, the pumping of atomic clocks, and laser gyroscopes. However, there is little research on distributed-feedback (DFB) semiconductor lasing at 770 nm. In addition, the traditional DFB semiconductor laser requires secondary epitaxy or precision grating preparation technologies. In this study, we demonstrate an easily manufactured, gain-coupled DFB semiconductor laser emitting at 770 nm. Only micrometer scale periodic current injection windows were used, instead of nanoscale grating fabrication or secondary epitaxy. The periodically injected current assures the device maintains single longitudinal mode working in the unetched Fabry–Perot cavity under gain coupled mechanism. The maximum continuous-wave output power reached was 116.3 mW at 20 °C, the maximum side-mode-suppression ratio (SMSR) was 33.25 dB, and the 3 dB linewidth was 1.78 pm.

The Interband Cascade Laser

We review the history, development, design principles, experimental operating characteristics, and specialized architectures of interband cascade lasers for the mid-wave infrared spectral region. We discuss the present understanding of the mechanisms limiting the ICL performance and provide a perspective on the potential for future improvements. Such device properties as the threshold current and power densities, continuous-wave output power, and wall-plug efficiency are compared with those of the quantum cascade laser. Newer device classes such as ICL frequency combs, interband cascade vertical-cavity surface-emitting lasers, interband cascade LEDs, interband cascade detectors, and integrated ICLs are reviewed for the first time.

35 W continuous-wave Ho:YAG single-crystal fiber laser

We report on a high-power Ho:YAG single-crystal fiber (SCF) laser inband pumped by a high-brightness Tm-fiber laser at 1908 nm. The Ho:YAG SCF grown by the micro-pulling-down technique exhibits a propagation loss of $0.05\pm 0.005~\text{cm}^{-1}$ at $2.09~\unicode[STIX]{x03BC}\text{m}$ . A continuous-wave output power of 35.2 W is achieved with a slope efficiency of 42.7%, which is to the best of our knowledge the highest power ever reported from an SCF-based laser in the 2 $\unicode[STIX]{x03BC}\text{m}$ spectral range.

Efficient 1 µm Laser Emission of Czochralski-Grown Nd:LGSB Single Crystal

A 5.0-at.% Nd-doped La0.64Gd0.41Sc2.95(BO3)4 (Nd:LGSB) borate laser crystal was successfully grown by the Czochralski method, for the first time to our knowledge. The spectroscopic properties of the grown crystal are discussed and 1 µm laser emission, under end-pumping with a fiber-coupled diode laser at 807 nm, is reported. A c-cut Nd:LGSB medium yielded 1.35 W continuous-wave output power at 0.63 overall optical-to-optical efficiency, with respect to the absorbed pump power, together with the high 0.68 slope efficiency. With an a-cut Nd:LGSB sample, 0.81 W output power at 0.52 optical-to-optical efficiency was obtained. The laser emission performances under quasi-continuous wave pumping are presented as well, for both c-cut and a-cut crystals. Passive Q-switching was investigated with a semiconductor saturable absorber mirror (SESAM). Laser pulses with 2.2 µJ energy and 32.8 ns durations were recorded from a-cut Nd:LGSB. The average output power reached 0.36 W at 1.55 W absorbed pump power. Passive mode-locking with SESAM was achieved in a long Z-type resonator. Ultrashort pulses with 0.19 W average power, 1.63 nJ energy, and 1.43 ps pulse duration, at 118 MHz repetition rate, are demonstrated for the a-cut Nd:LGSB medium.

OPTIMIZATION OF CO2 LASER PARAMETERS FOR WOOD CUTTIOPTIMIZATION OF CO2 LASER PARAMETERS FOR WOOD CUTTING

By taking advantage of the best characteristics of wood, modern production methods can offer hard wearing and ecological solutions in industrial construction, house building, machinery construction, furniture manufacturing, transport and many other industries. Laser cutting process is an alternative choice to prepare the final shape of wood parts. Materials like wood have good laser light absorption of wavelength 10600 nm. In this paper a CO2 laser system with a maximum continuous-wave output power of 150 W is described and used in studying laser cutting process of wood materials. Cut depth is evaluated with variation of values of laser power and cutting speed. Additionally, optimal values of parameters for laser cutting of different wood plate thicknesses are determined and graphs are created showing the results.