Fiber-coupled Laser Diode Research Articles

Suppression of parasitic oscillations in a core-doped ceramic Nd:YAG laser by Sm:YAG cladding

The onset of parasitic oscillations limits the extraction efficiency and therefore energy scaling of Q-switched lasers. A solid-state laser was end pumped with a fiber-coupled diode laser and operated in q-cw as well as in passively Q-switched operation. For Q-switched operation, we demonstrate the suppression of parasitic oscillations in a core-doped ceramic Nd:YAG laser by Sm:YAG cladding.

Er:YAG fiber-shaped laser crystals (single crystal fibers) grown by micro-pulling down: Characterization and laser operation

Er 3+ doped Y 3Al 5O 12 (Er:YAG) single crystal fibers, with a diameter of 800 μm and a length up to 80 cm, were grown by the micro-pulling-down technique. The structural and optical characterization of these fibers shows a perfect single crystalline structure and a very high optical quality suitable for laser operation. With 6 cm long samples, we demonstrated a continuous wave laser delivering an output power of 950 mW for a pump power of 36 W coming from fiber-coupled laser diodes emitting at 1532 nm. To our knowledge, this is the first laser ever achieved with directly grown Er:YAG single crystal fibers.

Studying the Thermal Effects on Operation and Wavelength Stability of High Power Fiber Coupled Diode Lasers operating at 808 nm and 975 nm

Studying the Thermal Effects on Operation and Wavelength Stability of High Power Fiber Coupled Diode Lasers operating at 808 nm and 975 nm

Focus on lasers and imaging

Focus on lasers and imaging

Characterization of seeds with different moisture content by photoacoustic microscopy

Photoacoustic (PA) technique has important applications for material characterization and nondestructive evaluation of opaque solid materials. PA microscopy allows the acquisition of information of samples with inhomogeneous structures as agricultural seeds. A determining factor for seed safe storage is their moisture content. Seeds stored at high moisture content exhibit increased respiration, heating, and fungal invasion resulting in poor seed vigor and viability. Low moisture content, in the seed to be stored, is the best prevention for these problems. In this study, Photoacoustic Microscopy (PAM) was used to characterize seeds with different moisture content. In the PAM experimental setup the photoacoustic cell and its sensor, an electret microphone, are mounted on an x-y stage of mobile axes, with spatial resolution of 70 μm. The excitation light source is a fiber coupled laser diode, at 650 nm wavelength, modulated in intensity at 1 Hz of frequency, by the reference oscillator of a lock-in amplifier. By using a microscope objective the laser beam was focused on the seed surface. The resolution was enough to obtain differences in the obtained images, which are dependent on the moisture content. This method, to study differences in the seed moisture content, is nondestructive and could be useful for a sustainable Agriculture.

High-efficiency diode-pumped femtosecond Yb:YAG ceramic laser

A highly efficient diode-end-pumped femtosecond Yb:yttrium aluminum garnet (YAG) ceramic laser was demonstrated. Pumped by a 968 nm fiber-coupled diode laser, 1.9 W mode-locked output power at a repetition rate of 64.27 MHz was obtained with 3.5 W absorbed pump power, corresponding to a slope efficiency of 76%. Our measurement showed that the pulse duration was 418 fs with the central wavelength of 1048 nm.

Conductively cooled 250-Hz single frequency Nd:YAG laser

A conductively cooled, laser diode (LD) end-pumped, injection-seeded single frequency Nd:YAG laser is designed and implemented. The laser utilizes Nd:YAG rod as gain medium and compact dual-end-pumping arrangement using two fiber-coupled LDs with a maximum output of 150 W. The optimized ramp-fire technique is applied to build reliable single longitudinal mode oscillating. The laser is capable of producing a 10-mJ Q-switched pulse with 13-ns pulse width at 1064 nm at a pulse repetition rate of 250 Hz. The output beam qualities M2 of approximately 1.19 and 1.22 in horizontal and vertical directions are detected, respectively.

绕纤法分析光纤耦合输出半导体激光器的光束质量

绕纤法分析光纤耦合输出半导体激光器的光束质量

Spectroscopic properties of Tm, Ho:LiLuF4

LiLuF4 single crystals co-doped with thulium (5%) and holmium (0.5%), having large size, intact shape, and high optical quality, are successfully grown by the Czochralski technique. Absorption and fluorescence spectra of the crystal are measured. The absorption spectrum shows that the main absorption band locates at near 686 and 792 nm and the fluorescence spectrum peaks at 2.05 µm. At room temperature, the as-grown Tm, Ho: LiLuF4 single crystals are end-pumped by a fiber-coupled laser diode system with pumping wavelength of 795 nm under CW operations. A power of 50 mw continuous laser output at 2.05 µm wavelength is achieved. Meanwhile an obvious green light is detected.

880 nm半导体激光主动照明光纤耦合模块

880 nm半导体激光主动照明光纤耦合模块

Room temperature operation of 2-μm microchip Tm,Ho:Lu2SiO5 laser

Room temperature operation of a c-cut microchip Tm,Ho:Lu2SiO5 laser end-pumping by a fibercoupled laser-diode is reported. A 4.03 W incident pump power is used to generate a maximum laser output of 98 mW, representing 2.43% optical-to-optical conversion efficiency and a 4.38% slope efficiency corresponding to incident power. In the experiment, the oscillating wavelengths shifting from 2.084 to 2.089 μm has been observed and approximately 10 mW single 2.087 μm wavelength oscillation has been obtained by changing the pump power to 1.43 W and the position of the pump focus.

Continuous wave and AO Q-switch operation of a b-cut Tm,Ho:YAP laser with dual wavelengths pumped by a laser diode of 792 nm

Continuous wave (CW) and AO Q-switch operation of a b-cut Tm,Ho:YAP laser with dual wavelengths were reported in this paper. In the temperature of 77 K, the b-cut Tm,Ho:YAP crystal was double endpumped by a 7.21-W fiber-coupled laser diode (LD) at the center wavelength of 792 nm. A 1.17-W Q-switch output power was acquired at pulse repetition frequency (PRF) of 10 kHz, corresponding to an effective optical-optical conversion efficiency of 25.9% and an effective slope efficiency of 31.5%. The energy per pulse of 0.46 mJ in 100 ns was achieved at 2.5 kHz with the peak power of 4.6 kW.

Laser characteristics of 2-µm microchip Tm,Ho:Lu2SiO5 laser

Cryogenic temperature operation of a 〈010〉-cut microchip Tm,Ho:Lu2SiO5 laser end-pumping by a fiber-coupled laser-diode is presented. A 2.73 W absorbed pump power is used to generate a maximum laser output of 470 mW, representing a 17.2% optical-to-optical conversion efficiency and a 61.7% slope efficiency corresponding to absorbed power. In the experiment, the oscillating wavelength shifting from 2.03 to 2.08 µm has been observed and a single 2.03 µm wavelength oscillation has obtained. To our knowledge, this work is the first time to investigate the Cryogenic temperature operation of microchip Tm,Ho:Lu2SiO5.

Digital imaging measurement of dense multiphase flows in industrial processes

This paper presents a submersible imaging system for investigations of multiphase flows in various industrial applications. Our objective is to visualize and online monitor complex multiphase flows that take place in industrial process devices (e.g., reactors, channels and flotation tanks) of chemical and paper industries. The system presented, including a laptop computer, CCD camera and pulsed, optical fibre-coupled diode laser, is designed for industry-scale, in situ measurements of dispersed phase particle properties (size, shape and velocity). The system has been successfully tested in a waste water dissolved air flotation (DAF) tank, in a white water de-aeration channel, in a deinking flotation cell Metso OptiCell and in a plastic bead production reactor, where the hot and pressurized plastic bead production process is monitored through a submersed pipe. New image processing techniques and system modifications are presented based on the test experiences.

Compact diode end-pumped c-cut Tm,Ho:YAlO3 laser

Cryogenic temperature operation of a c-cut Tm(5%),Ho(0.3%):YAlO3 laser end-pumping by a fiber-coupled laser-diode is reported. A 2.55 W incident pump power is used to generate 160 mW of laser output, representing a 7.1% optical-to-optical conversion efficiency respect to the incident pump power. In the experiment, three wavelengths—2.04, 2.10, and 2.13 µm oscillation have been observed simultaneously, which is agreement with the inherent a-axis polarization fluorescence spectra of Tm,Ho:YAlO3. Also single wavelength oscillation performance has been observed which is centered at 2.13 µm.

Fabrication and characterization of a design optimized SU-8 thermopile with enhanced sensitivity

In the infrared wavelength region, thermopiles are an important type of detector. A major advantage of thermopiles is their non-cooling requirement. Depending on the applied absorption layer, their responsivity is often rather flat within a large wavelength region. This work presents the fabrication and characterization of a sensitivity and design optimized thermopile detector with a 4 µm self-supported SiO2/SU-8 membrane. The structure consists of 240 series interconnected thermocouple junctions obtained by metal evaporation and lift-off. Two metal combinations have been evaluated, namely, nickel/titanium and aluminium/bismuth. Series resistances of 76 kΩ and 283 kΩ were measured for the Ni/Ti thermopile and the Al/Bi thermopile respectively. For the Al/Bi thermopile a responsivity of 60 V W−1 was achieved using a 1.56 µm fibre coupled diode laser with a power of 3.5 mW. Using a white light source with a radiation flux of 0.45 W mm−2 a voltage response of 68 V mm2 W−1 was measured for the Al/Bi thermopile. The time constant of the characterized detectors was calculated to be 70 ms, using the pulsed IR laser.

Yb-doped Lu 3Al 5O 12 fibers single crystals grown under stationary stable state for laser application

Undoped and Yb-doped Lu 3Al 5O 12 fibers single crystals have been grown by micro-pulling-down (μ-PD) technique. The crystals fibers diameter is determined by the melt meniscus section formed by the crystallization surface. Melt behaviours in the molten zone, meniscus length and thermal gradient have been studied by Ircon optical pyrometer and CCD camera. The longitudinal segregation coefficient ( k) of the dopant (Yb 3+) was measured by optical fluorescence and inductively coupled plasma (ICP). For laser measurement, the crystal fiber is longitudinally pumped by a fiber-coupled laser diode emitting a maximum output power of 100 W at 940 nm and the obtained result is encouraging.

Stable single-frequency output at 201 μm from a diode-pumped monolithic double diffusion-bonded Tm:YAG nonplanar ring oscillator at room temperature

We demonstrate a monolithic double diffusion-bonded monolithic Tm:YAG nonplanar ring laser pumped by a fiber-coupled laser diode. Up to 867 mW single-frequency output at 2.01 microm was obtained from the Tm:YAG system at room temperature, with a slope efficiency and an optical-optical efficiency of 31.6% and 19.2%. The power stability of the single frequency laser was 0.32% within 30 min.

Crystal growth, spectroscopic and laser properties of Tm:LuAG crystal

Tm:Lu3Al5O12 (Tm:LuAG) crystal was grown by the Czochralski method. The segregation coefficient was measured by Inductively Coupled Plasma Atomic Emission Spectrometer. The cell parameters were analyzed with X-ray powder diffraction experiments. The absorption and fluorescence spectra of Tm:LuAG crystal at room temperature were investigated. With a 20 W fiber-coupled diode laser as pump source, the continuous-wave (CW) laser action of Tm:LuAG crystal was demonstrated. The maximum output power at 2020 nm was obtained to be 3.04 W, and the slope efficiency was 25.3%.

Laser–fibre vibrometry at 1550 nm

This paper presents new solutions for laser vibrometry, which are based on fibre vibrometry in the third telecommunication window. The scattered laser beam from a vibrating object is guided by a fibre collimator and coherently detected through heterodyning it with an acousto-optical frequency-shifted reference beam. The concept of measuring vibration parameters from many points of the vibrating object has been inspired by wavelength division multiplexing (WDM) in fibre telecommunications. The N-independent WDM separated 15XX nm fibre-coupled laser diodes (used for optical fibre telecommunications) form a system of sources for multipoint vibration measurement according to the rule ‘one wavelength–one point’.