1,721,049 research outputs found
Dielectric solid-state planar waveguide lasers: a review
No full textThis review takes a look at the historical development of the dielectric planar waveguide laser leading to key state-of-the-art technologies which fall within this broad subject area. Discussed herein are many of the advantages offered by the waveguide geometry such as; high optical-gain and thus low threshold-power requirements, suitability for quasi-three-level laser transitions, integration with functional devices on single substrates, guided spatial-mode control, and its considerable immunity to thermal effects and external environmental conditions. A detailed snapshot is made of many active host media for which there has been reported laser action in the planar waveguide geometry, covering many of the major rare-earth-ion transitions. Several fabrication techniques are highlighted and appraised for their applicability to different host media, touching on their benefits and drawbacks. Challenges and future prospects for these lasers are considered
Planar waveguide lasers: pros and cons of the architecture in the middle
No full textThe performance of dielectric planar-waveguide lasers has had a chequered history, often overshadowed by other laser architectures, and/or application oriented fabrication research. In this presentation I will review some of the interesting highlights for this unique laser geometry, and attempt to give a balanced view as to their relative advantage and disadvantages with respect to other laser architectures. In the process I will discuss several of the research firsts demonstrated in the ORC at Southampton University, highlighting the key parameters that allowed them to be attained. The talk will culminate with a discussion of a recent world-record 100W result for a 946nm Nd:YAG planar waveguide laser, and where to next for power-scaling this challenging laser system
Planar waveguides, a power scaling architecture for low-gain quasi-four-level lasers
No full textLimited by pump brightness and high thermal-loading density, low-gain lasers suffering reabsorption losses have an ally in planar waveguides for efficient power scaling. Current performance and future prospects are presented for this laser architecture
Cryogenically cooled 946nm Nd:YAG laser
No full textWe present the first multi-Watt demonstration of a diode pumped cryogenically cooled Nd:YAG operating on the 946nm, 4F3/2 to 4I9/2 transition. Preliminary results at LN temperature produced 3.8W of output power for 20.7W of incident pump power and a slope efficiency of 28%
Power and radiance scaling of a 946 nm Nd:YAG planar waveguide laser
No full textWe present a diode-end-pumped Nd:YAG planar waveguide laser operating on neodymium's quasi-four-level transition at a wavelength of 946 nm. Two modes of operation are described: a high-power multi-mode monolithic cavity generating 105 for 210 W of incident pump power with a slope efficiency of ~54%, and secondly, a high-radiance configuration employing an external stable resonator producing a maximum output power of 29.2 for 86.5 W of incident pump-power, with a slope efficiency of 33%. The output beam quality values of the external cavity were M2 of 3.2 by 2.4, leading to a maximum radiance of 0.43 GW cm-2 sr-1
End-pumped passively Q-switched Yb:YAG double-clad waveguide laser
No full textWe present a diode- pumped, double-clad Yb:YAG waveguide laser that maintains an integrated section of Cr4+:YAG saturable absorber for passive Q switching. Using two 4W polarization-coupled, broad-stripe diode-pumped lasers, we obtained 30µJ pulses of 16ns duration at repetition rates of as much as 77 kHz. The slope efficiency was ~50% with respect to absorbed pump power, with a maximum output average power of 2.3 W and a peak power of ~18 kW. The output beam was single lobed, with M2 values as great as 1.5 x 1.3 . We also demonstrate a passively Q-switched Nd:YAG waveguide laser of similar design, operating at 1064 µm and 946 nm
Excited-state absorption measurement of Tm<sup>3+</sup>-doped crystals
No full textThe excited-state absorption (ESA) spectra from the long-lived 3F4 energy-level of several crystals doped with trivalent thulium (Tm3+) ions have been measured using a pump-probe technique employing high-brightness narrowband (FWHM ~15 nm) light emitting diode (LED) as the probe. Our aim is to determine the strength of ESA channels at wavelengths addressable by commercially available laser diodes around 630-680 nm, pivotal for building waveguide upconversion lasers. The favorable lifetime of the 3F4 energy-level and negligible ground-state absorption for the red-wavelength second-step excitation, ensures a direct and efficient excitation route for a dual-wavelength pumping scheme of the thulium ion, which will enable blue-green laser emission from its 1G4 manifold.ESA measurements in the red spectral region were conducted at room temperature utilizing the pump-probe technique. The advantage of the LED probe over a broadband incandescent lamp is that stimulated-emission at the probe wavelength can be eliminated, simplifying the analysis of the measurement and the determination of the magnitude of the ESA cross-section. Four Tm-doped crystalline hosts Y3Al5O12 (YAG), YAlO3 (YAP), LiYF4 (YLF), and KYGdLu(WO4)2 (KYGdLuW) were investigated, with polarized ESA spectra measured for the non-isotropic samples. Excitation of the Tm3+ ions into the intermediate 3F4 manifold was achieved via non-radiative and cross-relaxation energy transfer from the 3H4 manifold, pumped by a current-modulated fibre-coupled GaAs laser diode operating at ~790 nm. To ensure that ESA at all wavelengths of interest were resolved, the LED's spectra were tuned via the modulated drive-current amplitude and junction temperature. As such, with direct pump and probe modulation, we eliminated the need for mechanical choppers, simplifying the optimization of frequency-resolved ESA measurements needed to isolate the other possible ESA transition (3H4 to 1D2). Vastly improved ESA spectra have been obtained with respect to those reported in the literature
Power-scaling Nd:YAG's quasi-four-level transition
No full textIncreasing the output power of Nd:YAG's 4F3/2 to 4I9/2 quasi-four-level transition is attractive for providing a high-radiance source with a wavelength below 1 micron for applications at the life sciences interface, ranging and sensing, or as a vital element for next-generation display technologies, when frequency converted into the blue-green part of the visible spectrum. Reabsorption losses at the lasing wavelength combined with a relatively low stimulated emission cross-section and competition with the much stronger 1.06 micron transition, demands a configuration with high pumping intensity, comparable to the pump saturation intensity at 808nm, to achieve efficient operation. However, even with the availability of increasingly bright diode-lasers, the thermal deficit of the excitation cycle and the thermo-optic properties of the YAG host medium currently limit the achievable output power at 9xx nm. Presented here is a double-clad planar-waveguide Nd:YAG laser, operating at a lasing wavelength of 946nm with an output power in the 100W regime and better than 50% optical to optical conversion efficiency. The enhanced thermal management characteristics of the waveguide structure have enabled power-scaling well beyond that possible in a bulk laser configuration. These advantages and further power-scaling possibilities will be discussed
Managing thermal effects in high-power solid-state lasers
No full textThe performance and power levels from solid-state laser have escalated dramatically in recent years, primarily associated with increasing efficiency and brightness of diode-laser pump sources. This has led to a similar increase in the thermal load within the solid-state gain medium itself, a by-product of the excitation cycle, which has had to be managed appropriately to continue to achieve increasing output powers. Choosing the right gain media, its geometry, and the cooling method have all been critical parameters in this complex interplay between light and heat. In this presentation, we will discuss the recent progress in solid-state laser performance; the role fibre lasers have played and make comparisons with other laser architectures. Of particular interest to this forum is the thermal management constraints and where we are in terms of fundamental limits for these systems. It will be demonstrated that we are indeed very close to the limits already, where novel approaches and engineered materials will be paramount for future power scaling potential
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