1,721,046 research outputs found
Blue laser light from infra-red laser diodes
No full textDespite the breathtaking progress of semiconductor diode laser technology in recent years there is still no such thing as a diode that emits blue light. A great deal of research effort is therefore being put into schemes for efficiently converting the near-infrared output from the best available diodes into green and blue coherent radiation. Recently Bill Kozlovsky and Bill Lenth of the IBM Almaden Research Center, California, USA, reported a result which represents the current high-water mark in this field. In collaboration with scientists at the IBM Zurich Research Laboratory they succeeded in generating 41 mW of blue laser light by using a nonlinear crystal to double the frequency of infrared radiation emitted by a GaAlAs diode laser
Optical-fiber lasers exploit new techniques and materials
No full textProgress in fiber laser research around the world is accelerating as the implications of new materials and fabrication techniques begin to be felt. With the appearance of the fiber grating reflector the potential versatility of the spectrally broad emission characteristic of glass fibers can at last be exploited, in compact and rugged narrow linewidth sources at wavelengths precisely selected over a wide band. Fiber lasers are no longer restricted to low power operation; the cladding-pumping technique enables light from high power pump sources which are not diffraction-limited to be used efficiently, converted to output which may be multiwatt and enhanced in brightness by more than two orders of magnitude. Moreover. rare-earth-doped fluoride glass fiber is now commercially available from both Le Verre Fluoré, France, and Galileo Electro-Optics, MA; this is a "low-phonon-energy" alternative to silica, which offers many more metastable energy levels and laser transitions over a larger spectral range. Fluoride fibers have lased at blue and even ultraviolet wavelengths when pumped by longer-wavelength sources in upconversion lasing schemes
Passively modelocked surface-emitting semiconductor lasers
No full textThis paper will review and discuss pico- and femtosecond pulse generation from passively modelocked vertical–external-cavity
surface-emitting semiconductor lasers (VECSELs).We shall discuss the physical principles of ultrashort pulse generation in these lasers, considering in turn the role played by the semiconductor quantum well gain structure, and the saturable absorber. The paper will analyze the fundamental performance limits of these devices, and review the results that have been demonstrated to date. Different types of semiconductor saturable absorber mirror (SESAM) design, and their characteristic dynamics, are described in detail; exploring the ultimate goal of moving to a wafer integration approach, in which the SESAM is integrated into the VECSEL structure with tremendous gain in capability. In particular, the contrast between VECSELs and diode-pumped solid-state lasers and edge-emitting diode lasers will be discussed. Optically pumped VECSELs have led to an improvement by more than two orders of magnitude to date in the average output power achievable from a passively modelocked ultrafast semiconductor laser
Laser ions ring local modes first
No full textWe tend to think that lasers only produce light. In many solid-state lasers, however, just as much energy ends up as vibrations of the laser crystal as emerges in the laser beam. These vibrations are crucial to the operation of the laser because they carry excess energy away from the ion that produces laser emission. But we do not know how the ion transfers this energy into the lattice, in particular how each ion is able to release energies many times greater than those typical of thermal vibrations. Experiments by Dana Calistru and colleagues at City College in New York have now provided new insights into this mechanism that could lead to improved materials for solid-state lasers
Erbium doped fluorozirconate fibre laser operating at 1.66 and 1.72µm
No full textPulsed laser emission at 1.66 and 1.72µm has been observed in a multimode fluorozirconate fibre doped with erbium under excitation at 514nm. The threshold absorbed pump power for laser oscillation was measured as 90mW
Ion-exchanged Nd:glass tapered waveguide laser
No full textWe report an efficient (>40% slope) and low threshold (~10mW) ion-exchanged Nd:glass tapered waveguide laser with near-diffraction-limited output. This structure is compatible with high-power, broad-stripe, diode pumping
Wetting-layer-pumped continuous wave surface emitting quantum dot laser
No full textWe report a continuous wave 1 μm laser based on InAs Stranski-Krastanov quantum dots (SK-QD) which is optically pumped on a wetting layer absorption band at 915 nm. The slope efficiency of this laser relative to absorbed pump power was measured to be 56% with wetting layer pumping, 1.75 times larger than when pumped with 830 nm light absorbed into the barriers between the SK-QD layers. Compared to barrier pumping, wetting layer pumping benefits from a smaller quantum defect, with less heat deposited in the active region, at the expense of weaker pump absorption in the thin (~1 nm) wetting layer. When a 50 μm thick intracavity diamond heatspreader was contacted to the optically pumped gain structure, a 10-fold increase in output power, up to 2.25W, was obtained in the barrier pumped case. A much smaller 2-fold increase in power, to a maximum of 0.35 W, was seen for the wetting layer pumped case. The diamond heatspreader is more effective in removing heat from the active region, where it is deposited by barrier pumping, than from the substrate, which absorbs residual pump radiation in the barrier pumping case. A gain sample with a doubly periodic DBR to back reflect pump radiation, will allow the full potential of wetting layer pumping to be realised, both by increasing pump absorption due to the double pass through the active region, and by localising heat generation in the active region.</p
Dataset for Continuous Repetition Rate Tuning from 960 MHz to 1.72 GHz of a sub-300 femtosecond Mode-Locked Semiconductor Disk Laser
No full textDataset supports:
Chen Sverre, T. et al (2018). Continuous repetition rate tuning from 960 MHz to 1.72 GHz of a sub-300 femtosecond mode-locked semiconductor disk laser. Applied Physics Letters, 113(16), [161106].
Vertical External Cavity Surface Emitting semiconductor Lasers rely on Semiconductor Saturable Absorbing Mirrors for mode-locking, allowing laser cavities to be designed far from stability limits. We have harnessed this feature to study repetition rate tunability. The cavity element separations were determined by a coded cavity design protocol based on cavity round trip matrix calculations. We produced a sub-300-fs near transform-limited pulse train with a repetition rate of 0.96 MHz - 1.72 GHz, at 1035 nm and average power of 50 mW.</span
Ion-exchanged tapered waveguide laser in neodymium-doped BK7 glass
No full textWe report what is to our knowledge the first operation of a planar dielectric tapered-waveguide laser. The waveguide laser is fabricated by potassium-ion exchange in Nd3+ -doped BK7 glass and consists of a single-mode channel waveguide of a few micrometers' width followed by a linear taper up to a broad region with a width of 180µm. A slope efficiency of 42% is found both in the tapers and in standard channel waveguides fabricated upon the same substrate, indicating that the tapers and the channels have similar internal losses; hence the low-loss nature of the tapered beam expansion. The output from either end of the tapered structure is found to be nearly diffraction limited
Continuous wave holographic laser resonators using degenerate four-wave mixing in a diode bar side-pumped Nd:YVO<sub>4</sub> amplifier
No full textDegenerate four-wave mixing techniques used to produce self-adaptive laser resonators based on diffraction from a gain grating have shown considerable promise for correction of distortion in high-average-power solid-state laser systems, as well as for spectral and temporal control of the laser radiation [1-4]. In these systems, the gain grating is formed by spatial hole burning caused by interference of coherent beams in the laser amplifier and modulation of the population inversion. The gain grating formation can be used for phase conjugation by using the amplifier in a four-wave mixing geometry [2], for self-pumped phase conjugation by using an input beam in a self-intersecting loop geometry [3] and for formation of a self-starting adaptive oscillator by providing additional feedback from an output coupler and requiring no external optical input. Experimental demonstrations have been performed successfully in several laser systems including flashlamp-pumped and quasi-c.w. pumped neodymium-doped amplifiers [1,2], in laser-pumped titanium-doped sapphire [4] and CO2 lasers. We present for the first time, demonstration of a continuous-wave self-adaptive holographic laser resonator. The operation is based on the very high reflectivities (>800%) [5] and more recently (>10,000%) of a gain grating formed in a diode-bar side-pumped Nd:YVO4 amplifier. We have subsequently modelled the FWM interactions and have found good agreement with experimental results. This resonator has been shown to correct for severe phase distortions introduced inside the loop. An output of ~1 W has so far been achieved, future steps include an additional power amplifier incorporated into the resonator loop geometry to give an expected multi-watt operation with a midterm goal of 10 W
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