307 results found
Damzen M, Tawy G, Wang J, Pump-induced lensing effects in diode pumped Alexandrite lasers, Optics Express, ISSN: 1094-4087
Tawy G, Damzen M, 2019, Tunable, dual wavelength and self-Q-switched Alexandrite laser using crystal birefringence control, Optics Express, Vol: 27, Pages: 17507-17520, ISSN: 1094-4087
We present a red-diode-pumped Alexandrite laser with continuous wavelength tunability, dual wavelength and self-Q-switching in an ultra-compact resonator containing only the gain medium. Wavelength tuning is obtained by varying the geometrical path length and birefringence by tilting a Brewster-cut Alexandrite crystal. Two crystals from independent suppliers are used to demonstrate and compare the performance. Wavelength tuning between 750 and 764 nm is demonstrated in the first crystal and between 747 and 768 nm in the second crystal. Stable dual wavelength operation is also obtained in both crystals with wavelength separation determined by the crystal free spectral range. Temperature tuning was also demonstrated to provide finer wavelength tuning at a rate of −0.07 nm K −1. Over a narrow tuning range, stable self-Q-switching is observed with a pulse duration of 660 ns at 135 kHz, which we believe is the highest Q-switched pulse rate in Alexandrite to date. Theoretical modelling is performed showing good agreement with the wavelength tuning and dual wavelength results.
Kerridge-Johns W, Geberbauer JWT, Damzen M, 2019, Vortex laser by transforming Gaussian mode with an interferometric output coupler, Optics Express, Vol: 27, Pages: 11642-11650, ISSN: 1094-4087
Generation of vortex beams directly from the laser source can be limited in power and efficiency, or to specific pump sources and gain media. Here, we propose a new high power and high efficiency vortex laser methodology with interferometric mode transformation as output coupling, which uses high power handling and low loss optics that have wavelength versatility. Experimental demonstration is made in a diode-pumped Nd:YVO4 laser using an imbalanced Sagnac interferometer as output coupler producing high quality vortex output beams (M2 = 2.07) with fully selectable control of handedness whilst the intracavity mode is maintained as a fundamental Gaussian. Vortex output power >3W is produced with only small reduction in efficiency compared to the equivalent TEM00 laser. Continuous variation of vortex output coupling transmission and the quality of the vortex is investigated experimentally showing good agreement with theory. This work reveals a new approach to high power structured laser radiation direct from the source through interferometric spatial mode transformations.
Thomas GM, Minassian A, Damzen MJ, 2019, Directly diode-side-pumped alexandrite slab lasers in the bounce geometry and optical vortex generation
Teppitaksak A, Thomas GM, Damzen MJ, 2019, Gain-switched diode laser seeding of ultra-high-gain Nd: YVO <inf>4</inf> bounce amplifier system as a versatile pulsed laser source
Arbabzadah EA, Kerridge-Johns W, Thomas GM, et al., 2019, High efficiency TEM <inf>00</inf> diode end-pumped Alexandrite laser
Kerridge-Johns W, Damzen MJ, 2018, Vortex laser from anti-resonant ring coupled cavities, Optics Express, Vol: 26, Pages: 32839-32846, ISSN: 1094-4087
Optical vortex Laguerre-Gaussian (LG0l) modes have wide-ranging applications due to their annular spatial form and orbital angular momentum. Their direct generation from a laser is attractive, due to the pure and high-power modes possible; however, previous demonstrations have had limited ranges of applicability. Here, we propose and implement direct LG0l vortex mode generation with an anti-resonant ring (ARR) coupled laser cavity geometry, where the gain medium inside the ARR is shared between two laser cavities. This generation uses standard wavelength-insensitive optical components, is suitable for high peak and average power levels, and could be applied to any bulk gain medium in pulsed or continuous wave regimes. This work demonstrates the technique with a diode end-pumped Nd:YVO4 gain medium. From 24 W of pump power, 8.9 W LG01 and 4.3 W LG02 modes were generated, all with high mode purity and pure handedness. The LG01 mode handedness was controlled with a new technique.
Sheng X, Tawy G, Sathian J, et al., 2018, Unidirectional single-frequency operation of a continuous-wave Alexandrite ring laser with wavelength tunability, Optics Express, Vol: 26, Pages: 31129-31136, ISSN: 1094-4087
High resolution spectroscopy, metrology and quantum technologies (e.g. trapping and cooling) require precision laser sources with narrow linewidth and wavelength tunability. The widespread use of these lasers will be promoted if they are cost-effective, compact and efficient. Alexandrite lasers with a broad tuning band pumped efficiently by low-cost red diodes are a potential candidate, but full performance as a precision light source has not been fully achieved. We present in this work the first continuous-wave (CW) and single-frequency operation of a unidirectional diode-end-pumped Alexandrite ring laser with wavelength tunability. An ultra-compact bow-tie ring cavity is developed with astigmatic compensation and a novel ‘displaced mode’ design producing CW output power > 1 W in excellent TEM00 mode (M2 < 1.2) when using a low brightness pump (M2 ≥ 30). Wavelength tuning from 727 - 792 nm is demonstrated using a birefringent filter plate. This successful operation opens the prospects of precision light source applications.
Kerridge-Johns WR, Damzen MJ, 2018, Temperature effects on tunable CW Alexandrite lasers under diode end-pumping, Optics Express, Vol: 26, Pages: 7771-7785, ISSN: 1094-4087
Diode pumped Alexandrite is a promising route to high power, efficient and inexpensive lasers with a broad (701 nm to 858 nm) gain bandwidth; however, there are challenges with its complex laser dynamics. We present an analytical model applied to experimental red diode end-pumped Alexandrite lasers, which enabled a record 54 % slope efficiency with an output power of 1.2 W. A record lowest lasing wavelength (714 nm) and record tuning range (104 nm) was obtained by optimising the crystal temperature between 8 °C and 105 °C in the vibronic mode. The properties of Alexandrite and the analytical model were examined to understand and give general rules in optimising Alexandrite lasers, along with their fundamental efficiency limits. It was found that the lowest threshold laser wavelength was not necessarily the most efficient, and that higher and lower temperatures were optimal for longer and shorter laser wavelengths, respectively. The pump excited to ground state absorption ratio was measured to decrease from 0.8 to 0.7 by changing the crystal temperature from 10 °C to 90 °C.
Thomas G, Minassian A, Damzen MJ, 2018, Optical vortex generation from a diode-pumped alexandrite laser, Laser Physics Letters, Vol: 15, ISSN: 1612-2011
We present the demonstration of an optical vortex mode directly generated from a diode-pumped alexandrite slab laser, operating in the bounce geometry. This is the first demonstration of an optical vortex mode generated from an alexandrite laser or from any other vibronic laser. An output power of 2 W for a vortex mode with a 'topological charge' of 1 was achieved and the laser was made to oscillate with both left- and right-handed vorticity. The laser operated at two distinct wavelengths simultaneously, 755 and 759 nm, due to birefringent filtering in the alexandrite gain medium. The result offers the prospect of broadly wavelength tunable vortex generation directly from a laser.
Coney AT, Minassian A, Damzen MJ, 2018, High-energy diode-pumped alexandrite oscillator and amplifier development for satellite-based LiDAR
© OSA 2018. Development of a Q-switched diode-pumped Alexandrite oscillator producing 3.8mJ pulse energy is described with wavelength and temperature optimisation of a diode-pumped Alexandrite slab amplifier as part of a future Alexandrite design for satellite-based lidar.
Kerridge-Johns WR, Geberbauer JW, Volpini A, et al., 2018, Vortex laser output with a fundamental Gaussian internal mode using a sagnac interferometer
© OSA 2018. We experimentally demonstrate a simple technique to convert any linear laser cavity into an optical vortex source using a Sagnac interferometer as an output coupler. No specialist optics are needed, the vortex has controlled handedness.
Parali U, Sheng X, Minassian A, et al., 2017, Diode-pumped Alexandrite laser with passive SESAM Q-switching and wavelength tunability, Optics Communications, Vol: 410, Pages: 970-976, ISSN: 0030-4018
We report the first experimental demonstration of a wavelength tunable passively Q-switched red-diode-endpumped Alexandrite laser using a semiconductor saturable absorber mirror (SESAM). We present the results ofthe study of passive SESAM Q-switching and wavelength-tuning in continuous diode-pumped Alexandritelasers in both linear cavity and X-cavity configurations. In the linear cavity configuration, pulsed operation upto 27 kHz repetition rate in fundamental TEM00 mode was achieved and maximum average power was 41 mW.The shortest pulse generated was 550 ns (FWHM) and the Q-switched wavelength tuning band spanned wasbetween 740 nm and 755 nm. In the X-cavity configuration, a higher average power up to 73 mW, and obtainedwith higher pulse energy 6.5 J at 11.2 kHz repetition rate, in fundamental TEM00 mode with excellent spatialquality M2 < 1.1. The Q-switched wavelength tuning band spanned was between 775 nm and 781 nm.
Sheng X, Parali U, Thomas GM, et al., 2017, Passively SESAM Q-switched Red-Diode-Pumped Alexandrite Laser, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Kerridge-Johns WR, Damzen MJ, 2017, Tunable CW Alexandrite Lasers and Fundamental Limits of Efficiency, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Coney AT, Thomas GM, Minassian A, et al., 2017, High-Energy Diode-Pumped Alexandrite Laser Development for Remote Sensing, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Thomas GM, Minassian A, Kerridge-Johns W, et al., 2017, High power and high energy diode-pumped Alexandrite lasers, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Kerridge-Johns WR, Damzen MJ, 2017, Anti-Resonant Ring Laser Cavities, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Damzen MJ, Thomas GM, Minassian A, 2017, Diode-side-pumped Alexandrite slab lasers, Optics Express, Vol: 25, Pages: 11622-11636, ISSN: 1094-4087
We present the investigation of diode-side-pumping of Alexandrite slab lasers in a range of designs using linear cavity and grazing-incidence bounce cavity configurations. An Alexandrite slab laser cavity with double-pass side pumping produces 23.4 mJ free-running energy at 100 Hz rate with slope efficiency ~40% with respect to absorbed pump energy. In a slab laser with single-bounce geometry output power of 12.2 W is produced, and in a double-bounce configuration 6.5 W multimode and 4.5 W output in TEM00 mode is produced. These first results of slab laser and amplifier designs in this paper highlight some of the potential strategies for power and energy scaling of Alexandrite using diode-side-pumped Alexandrite slab architectures with future availability of higher power red diode pumping.
Kerridge-Johns WR, Damzen MJ, 2017, Vortex mode generation from coupled anti-resonant ring lasers
© OSA 2017. Vortex modes with controllable handedness were generated by coupling two laser cavities through a common Nd:YVO4 gain medium inside an anti-resonant ring. This design is applicable to both isotropic and anisotropic gain media.
Parali U, Thomas GM, Minassian A, et al., 2017, Wavelength tunable passively Q-switched Alexandrite laser with direct diode-pumping at 635 nm, 5th International Conference on Photonics, Optics and Laser Technology (PHOTOPTICS), Publisher: SCITEPRESS, Pages: 82-89
We report on a wavelength tunable passively Q-switched Alexandrite laser directly red-diode-pumped at 635 nm. Passive Q-switching was achieved with a semiconductor saturable absorber mirror (SESAM) and wavelength tuning with a birefringent tuner. The pulse repetiton rate was variable on the pump power and wavelength and a maximum 27 kHz rate was achieved in fundamental TEM00 mode. The maximum average output power obtained was 41 mW. The Q-switched wavelength tuning band was studied between 740 nm and 755 nm. To the best of our knowledge, this is the first time that tunable TEM00 passive Q-switched operation of a diode-pumped Alexandrite laser has been achieved. The results obtained in this study can be significantly further optimised for performance. A new cavity configuration for this optimisation is described. Future work is expected to lead to the development of higher power, more efficient tunable passive Q-switched (and potentially passive mode-locked) diode-pumped Alexandrite la (More)
Thomas GM, Minassian A, Sheng X, et al., 2016, Diode-pumped Alexandrite lasers in Q-switched and cavity-dumped Q-switched operation, Optics Express, Vol: 24, Pages: 27212-27224, ISSN: 1094-4087
We present the first study of Q-switched Alexandrite lasers under continuous-wave diode-pumping with operation up to 10 kHz repetition rates in TEM00, with spatial quality M2 1.15. With a pulsed-diode dual-end-pumped design, pulse energy is scaled to a record level of 3 mJ. We also demonstrate, for the first time, cavity-dumped Q-switching of diode-pumped Alexandrite lasers under continuous-wave and pulsed diode-pumping, up to 10 kHz. Pulse energy of 510 μJ is demonstrated with 3 ns pulse duration and 170 kW peak power, in TEM00 with M2 < 1.2. Second harmonic generation of the cavity-dumped Q-switched pulses was used to generate UV wavelength 379 nm with conversion efficiency of 47 %.
Kerridge-Johns WR, Damzen MJ, 2016, Analytical model of tunable Alexandrite lasing under diode end-pumping with experimental comparison, Journal of the Optical Society of America B, Vol: 33, Pages: 2525-2534, ISSN: 0740-3224
An analytical model is formulated to support understanding and underpin experimental development of laser action in the promising diode end-pumped Alexandrite system. Closed form solutions are found for output power, threshold, and slope efficiency that for the first time incorporate the combined effects of laser ground state absorption and excited state absorption (laser ESA), along with pump excited state absorption (pump ESA), in the case of an end-pumping geometry. Comparison is made between model predictions and experimental results from a fiber-delivered diode end-pumped Alexandrite laser system, showing the impact of wavelength tuning, crystal temperature, laser output coupling, and intracavity loss. The model is broadly applicable to other quasi-three-level lasers with combined laser and pump ESA. A condition for bistable operation is also formulated.
Arbabzadah EA, Damzen MJ, 2016, Fibre-coupled red diode-pumped Alexandrite TEM00 laser with single and double-pass end-pumping, Laser Physics Letters, Vol: 13, ISSN: 1612-202X
We report the investigation of an Alexandrite laser end-pumped by a fibre-coupled red diode laser module. Power, efficiency, spatial, spectral, and wavelength tuning performance are studied as a function of pump and laser cavity parameters. It is the first demonstration, to our knowledge, of greater than 1 W power and also highest laser slope efficiency (44.2%) in a diode-pumped Alexandrite laser with diffraction-limited TEM00 mode operation. Spatial quality was excellent with beam propagation parameter M 2 ~ 1.05. Wavelength tuning from 737–796 nm was demonstrated using an intracavity birefringent tuning filter. Using a novel double pass end-pumping scheme to get efficient absorption of both polarisation states of the scrambled fibre-delivered diode pump, a total output coupled power of 1.66 W is produced in TEM00 mode with 40% slope efficiency.
Loiko PA, Arbabzadah EA, Damzen MJ, et al., 2015, Judd-Ofelt analysis and stimulated-emission cross-sections for highly doped (38 at%) Er:YSGG laser crystal, Journal of Luminescence, Vol: 171, Pages: 226-233, ISSN: 1872-7883
Stimulated-emission cross-section spectra are determined for the ~1.5 μm and 3 μm transitions of Er3+ ions in YSGG crystal. For the 4I11/2→4I13/2 channel, the maximum stimulated-emission cross-section σSE is 0.43×10−20 cm2 at 2797.1 nm. For the 4I13/2→4I15/2 channel, σSE=1.20×10−20 cm2 at 1532.8 nm. Due to the reabsorption loss, laser operation is expected at ~1644 nm. Radiative lifetimes of all excited states of the Er3+ ion from 4I13/2 to 2H9/2 and probabilities of radiative transitions from these states are determined using the Judd–Ofelt theory. Radiative lifetimes of the 4I13/2 and 4I11/2 excited states for Er3+ ions in YSGG are 7.73 ms and 9.75 ms, respectively. Non-radiative decay is analyzed for lower excited-states of Er3+ ions in YSGG.
Kerridge-Johns WR, Damzen MJ, 2015, Analysis of pump excited state absorption and its impact on laser efficiency, Laser Physics Letters, Vol: 12, ISSN: 1612-202X
Excited state absorption (ESA) is a process that occurs in many laser gain media and can significantly impact their efficiencies of operation. In this work we develop a model to quantify the effect of ESA at the pump wavelength on laser efficiency, threshold and heating. In an analysis based on the common end pumped laser geometry we derive solutions and analytical expressions that model the laser behaviour. From these solutions we discuss the main parameters affecting efficiency, such as the laser cavity loss, pump ESA cross section and stimulated emission cross section. Methodologies are described to minimise the impact of pump ESA, for example by minimising cavity loss. It is also shown that altering the pumping geometry can significantly improve performance by improved distribution of the population inversion. Double end pumping can approximately halve the effect of pump ESA compared to single end pumping, and side pumping also has the potential to arbitrarily reduce its effect.
Thomas GM, Minassian A, Teppitaksak A, et al., High Energy Q-switching and Cavity Dumped Q-switching of a Diode-pumped Alexandrite Laser, Advanced Solid State Lasers
Thomas GM, Damzen MJ, Next generation space and airborne laser technology - plenary, SpaceLab 2015
Damzen MJ, Thomas GM, Teppitaksak A, et al., 2015, Diode-Pumped Alexandrite Laser—a new prospect for Remote Sensing, 11th Conference on Lasers and Electro-Optics/Pacific Rim, Publisher: IEEE
Tunable-wavelength diode-pumped Alexandrite laser operation includes highest power > 26W (end-pumped rod); > 12W (side-pumped slab); and first Q-switched operation with pulse energy ~ 1mJ at kHz repetition rate, as development for space lidar application.
Teppitaksak A, Thomas GM, Damzen MJ, 2015, Gain-switched diode laser seeding of ultra-high-gain Nd: YVO 4 bounce amplifier system as a versatile pulsed laser source, The European Conference on Lasers and Electro-Optics, Publisher: OSA Publishing
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