336 results found
Geberbauer J, Kerridge-Johns W, Damzen M, 2021, > 30 W vortex LG₀₁ or HG₁₀ laser using a modetransforming output coupler, Optics Express, ISSN: 1094-4087
High-power vortex light generated directly from lasers will help drive theirapplications in material processing, optical manipulation, levitation, particle acceleration, andcommunications, but limited power has been achieved to date. In this work, we demonstraterecord vortex average power of 31.3 W directly from a laser, to the best of our knowledge,using an interferometric mode transforming output coupler to convert a fundamental modeNd:YVO4 laser into a LG01 vortex output. The vortex laser was Q-switched with up to 600 kHzpulse rate with a high slope efficiency of 62.5% and an excellent LG01 modal purity of 95.2%.We further demonstrate > 30W laser power in a high quality HG10 mode by simple adjustmentof the output coupler. Experimental investigations of varying output coupling transmission arecompared with theory. This successful implementation of the interferometric output coupler ina high power system demonstrates the suitability of the mode transforming method for robustturn-key vortex lasers with high efficiency and high modal purity, with scalable power andpulse rate.
Kerridge-Johns WR, Jaillot J-B, Damzen MJ, 2021, Sampling a vortex from a Gaussian beam using a wedge-plate shearing interferometer, Applied Optics, Vol: 60, Pages: 3510-3510, ISSN: 1559-128X
Many vortex-generation techniques have been developed to address a range of potential applications, exploiting their unique amplitude and phase profiles and their possession of orbital angular momentum. In this work, we present what may be the simplest method of vortex beam generation, requiring only a wedged optic: the wedge-plate shearing interferometer (WPSI). We show that the WPSI can reflect a first order Laguerre–Gaussian vortex beam (LG01) with a theoretical purity of >99% from an input fundamental Gaussian beam, with 98% LG01 purity experimentally demonstrated. We demonstrate 1% power conversion with a route to 14%. The monolithic WPSI is a simple, compact, and highly stable device, which can operate at any wavelength that the material is transparent to. We anticipate that it will be useful where sampling a robust, high-purity vortex beam from a Gaussian laser beam is required, including low-cost vortex generation for metrology or education.
Coney A, Damzen M, 2021, High-energy diode-pumped alexandrite amplifier development with applications in satellite-based lidar, Journal of the Optical Society of America B: Optical Physics, Vol: 38, Pages: 209-219, ISSN: 0740-3224
Efficient, wavelength-tunable diode-pumped alexandrite laser systems offer the potential for a more versatile, satellite-based lidar source compared to fixed wavelength Nd:YAG systems and non-space compliant lamp-pumped alexandrite. In this paper, we develop a strategy to enable the high-energy operation required for atmospheric lidar based on an efficient diode-pumped Master-Oscillator Power-Amplifier (MOPA) system design. A novel multi-pass ‘diamond’ slab amplifier geometry is introduced alongside the experimental results of the world’s first diode-pumped alexandrite amplifier producing a gain of 2.13 in a demonstration system. A diode-pumped Q-switched alexandrite oscillator is presented with a record-highest pulse energy of 3.80 mJ. Detailed optimisation of a two-stage amplifier design is studied numerically and maximised with temperature, wavelength and pump pulse duration to produce 50 mJ pulse energy. This forms part of an optimised alexandrite MOPA design capable of high pulse energy, showing the future potential of diode pumped alexandrite for satellite-based atmospheric lidar.
Kerridge-Johns WR, Jaillot J-B, Damzen MJ, 2020, Shear plate Interferometer for complex angular momentum field generation, Frontiers in Optics, Publisher: OSA, Pages: 1-1
We show that a shear plate interferometer can generate high purity complex angular momentum states and is simple, cheap, compact, and could operate in wavelength regions where optics for conventional techniques are not available.
Sathian J, Abadi MM, Damzen MJ, et al., 2020, Communication characteristics of high-brightness light sources based on luminescence concentration
Communication characteristics of high-brightness solid-state light sources based on luminescence concentration generated using blue emitting InGaN light emitting diode arrays are demonstrated here for the first time. The proposed device is used as a transmitter in visible light communications, and its performance is evaluated.
Damzen M, Sathian J, Tawy G, et al., 2020, Non-astigmatic Alexandrite ring laser design with wavelength-tunable single-longitudinal-mode operation, Journal of the Optical Society of America B: Optical Physics, Vol: 37, Pages: 2185-2192, ISSN: 0740-3224
This work presents a study of a fully nonastigmatic design of a single-longitudinal-mode, wavelength-tunable, unidirectional alexandrite ring laser cavity and assessment of its performance compared to more complex laser design requiring astigmatism compensation. A “displaced mode” nonastigmatic laser cavity design eliminating astigmatic cavity elements is developed around an alexandrite crystal end-pumped by a low-brightness, high-power red diode laser pump system. Single-longitudinal-mode, continuous-wave operation is demonstrated with output power of 700 mW with an excellent TEM00 mode (M2<1.1) across a wide pump power range. Wavelength tuning from 748–773 nm is produced using a birefringent filter plate. The nonastigmatic alexandrite laser design achieves better spatial quality and resilience to maintain TEM00 operation across wide variation in pump-induced lensing compared to the astigmatic design. To the best of our knowledge, this is the first wavelength-tunable, single-longitudinal-mode operation of a unidirectional alexandrite ring system in a fully nonastigmatic cavity regime.
Tawy G, Minassian A, Damzen M, 2020, High-power 7.4W TEM00 and wavelength-tunable Alexandrite laser with novel cavity design and efficient fibre-coupled diode-pumping, OSA Continuum, Vol: 3, Pages: 1638-1649, ISSN: 2578-7519
We report significant improvement in the performance of TEM00 alexandrite laser operation by employing high power fibre-coupled red diode pumping, novel cavity design, and active direct Shack-Hartmann wavefront sensor measurement of pump-induced lensing. We demonstrate 12.7 W of laser power in low-order (𝑀2∼5) mode operation from a compact double-end-pumped cavity, and with novel cavity design, a record power of 7.4 W in TEM00 operation with excellent beam quality (𝑀2≤1.1). With single-end pumping, laser power of 4.7 W (𝑀2∼1.3) was achieved with slope efficiencies as high as 54.9 %; a record efficiency for red-diode-pumped alexandrite. Using a birefringent filter, continuous laser wavelength tuning from 725-808 nm is achieved in diffraction-limited TEM00 mode, with laser power of 4.7 W at 765 nm, and >1 W across 730-805 nm, which is a higher tunable power than any other directly diode-pumped vibronic laser, to the best of our knowledge.
Geberbauer JWT, Kerridge-Johns WR, Damzen MJ, 2020, Q-switched vortex laser using a Sagnac interferometer as an output coupler, Solid State Lasers XXIX - Technology and Devices, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, Pages: 1-10, ISSN: 0277-786X
Vortex lasers are an attractive prospect for efficient generation of high-quality beams in compact, environmentally robust, and turnkey systems. We demonstrate conversion of a Q-switched, diode-pumped Nd:YVO4, TEM00 Gaussian laser into a vortex laser source by replacing the output coupling mirror by a vortex output coupler (VOC) based on an imbalanced Sagnac interferometer. The Q-switched VOC laser generated a vortex output with 5.1 W average power, slope efficiency of 46% at 150 kHz pulse repetition rate, only marginally lower than the 5.4 W and 49% slope efficiency of the plane mirror laser. Vortex handedness was switchable with a single VOC control without loss of vortex power. In both handedness cases the vortex mode quality was assessed to be excellent by detailed analysis of vortex phase profile and propagation characteristics and comparison to an ideal vortex. The power scaling potential of the VOC was demonstrated in a higher power cavity, achieving a vortex output power of 14.3 W and a slope efficiency of 55%. Further investigation verified the ability for the VOC laser to self-mode-filter the intracavity mode, showing maintenance of high TEM00 quality even after introducing deliberate mode to pump size mismatch, when the equivalent plane mirror laser becomes multimode. This work highlights the potential of the VOC as a simple route to high powered structured light sources using just standard high-power handling mirror components and its self-mode-filtering property to compensate intra-cavity spatial mode degradation when power-scaling.
Geberbauer J, Kerridge-Johns WR, Damzen MJ, 2020, Q-switched laser with self-mode-filtering interferometric vortex output coupler, OSA Continuum, Vol: 3, Pages: 204-213, ISSN: 2578-7519
Vortex lasers are an attractive prospect for efficient generation of high-quality beams in compact, environmentally robust, and turnkey systems. We demonstrate conversion of a Q-switched, diode-pumped Nd:YVO4, TEM00 Gaussian laser into a vortex laser source by replacing the output coupling mirror by a vortex output coupler (VOC) based on an imbalanced Sagnac interferometer. The Q-switched VOC laser generated a vortex output with 5.1 W average power, slope efficiency of 46% at 150 kHz pulse repetition rate, only marginally lower than the 5.4W and 49% slope efficiency of the plane mirror laser. Vortex handedness was switchable with a single VOC control without loss of vortex power. In both handedness cases, the vortex mode quality was assessed to be excellent by detailed analysis of the vortex phase profile and propagation characteristics and comparison to an ideal vortex. Further investigation verified the ability for the VOC laser to self-mode-filter the intracavity mode, showing maintenance of high TEM00 quality even after introducing deliberate mode to pump size mismatch, when the equivalent plane mirror laser becomes multimode. This work highlights the potential of the VOC as a simple route to high powered structured light sources using just standard high-power handling mirror components and its self-mode-filtering property to compensate intra-cavity spatial mode degradation when power-scaling.
Tawy G, Damzen MJ, 2020, Ultra-compact > 100kHz Q-switched Alexandrite lasers, Conference on Solid State Lasers XXIX - Technology and Devices, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Tawy G, Wang J, Damzen MJ, 2020, Thermal and population induced lensing in Alexandrite lasers, Conference on Laser Resonators, Microresonators, and Beam Control XXII, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Tawy G, Damzen MJ, 2020, Narrow linewidth tunable and dual wavelength compact Alexandrite laser, Conference on Solid State Lasers XXIX - Technology and Devices, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Damzen M, Kerridge-Johns W, Geberbauer J, 2019, Vortex mode transformation interferometry, Journal of Optics, Vol: 22, Pages: 1-9, ISSN: 1464-4258
Whilst many techniques exist for generation of an optical vortex, there remains a need for new devices and methods that can also provide vortex generation withhigher powers, greater flexibility of wavelength, and generation beyondthe lowest-order Laguerre-Gaussian 𝐿𝐺01modeto address a broader range of practical applications.This work revealshow an all-mirror based interferometricmode transformation system can provide these propertiesincludingrevealing, for the first time,the generation ofa much richer set of vortex mode patterns than might have been thought possible previously.Anew developed theoreticalformulation, confirmed with excellent agreement by experimental demonstrationsin an imbalanced Sagnac interferometer,showsinterferometric transformation is possible for all orders of Laguerre-Gaussian 𝐿𝐺0𝑙modes into a rich set of high quality higher-order vortex and vortex superposition. The interferometric approachis shown to be configurabletoincrease or decrease vorticity. The new mathematical formulation provides the ability to perform a fullmodal power analysis of both the mode-transformed transmitted vortex and the complementary reflected beam at the Sagnac beamsplitter port.A discussion is made on the origin of the orbital angular momentum transferred to the vortex output from the Sagnac beamsplitter.
Tawy G, Wang J, Damzen M, et al., 2019, Pump-induced lensing effects in diode pumped Alexandrite lasers, Optics Express, Vol: 27, Pages: 35865-35883, ISSN: 1094-4087
It is essential to understand the pump-induced lensing and aberration effects in solid-state lasers, such as Alexandrite, since these set limits on laser power scaling whilst maintaininghigh spatial TEM00beam quality. In this work, we present direct wavefront measurements ofpump-induced lensing and spherical aberration using a Shack-Hartmann wavefront sensor, for thefirst time, in a diode-pumped Alexandrite laser, and under both non-lasing and lasing conditions.The lens dioptric power is found to be weakly sub-linear with respect to the absorbed pumppower, and under lasing, the lensing power is observed to decrease to60 %of its non-lasingvalue. The results are inconsistent with a thermal lens model but a fuller theoretical formulationis made of a combined thermal and population lens model giving good quantitative agreementto the observed pump power dependence of the induced-lensing under non-lasing conditionsand the reduced lensing under lasing conditions. The deduced value for the difference inexcited to ground state polarizability is consistent with prior measurement estimates for otherchromium-doped gain media. The finding of this paper provide new insight into pump-inducedlensing in Alexandrite and also provides a basis for a fast saturable population lens mechanism toaccount for self-Q-switching observed recently in Alexandrite laser systems.
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.
Sathian J, Tawy G, Shen X, et al., 2019, Compact Non-Astigmatic Alexandrite Ring Laser with Unidirectional Single-Longitudinal-Mode operation, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Tawy G, Wang J, Damzen MJ, 2019, Population Lensing in Alexandrite Lasers, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Tawy G, Damzen MJ, 2019, Tunable and Dual Wavelength Alexandrite Laser Using the Crystal Birefringence, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Sathian J, Minassian A, Alford NM, et al., 2019, Enhancing Performance of Ce:YAG Luminescent Concentrators for High Power Applications, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Sathian J, Tawy G, Sheng X, et al., 2019, Compact non-astigmatic alexandrite ring laser with unidirectional single-longitudinal-mode operation
Progress in single frequency and precise wavelength tunable lasers are essential to address future demands in high resolution spectroscopy, metrology and quantum technology systems. Alexandrite lasers with wide tunability in near-IR spectral region when pumped by low cost red diodes provide a good prospect as a cost effective precision laser source. This was demonstrated in our earlier work  using a tunable single-frequency bow-tie cavity with Brewster-cut Alexandrite crystal. The astigmatism of the Brewster cut gain medium and need for angled curved mirrors for astigmatic compensation, whilst being well established [2,3] also places some complexity on the design and can be compromised by astigmatic thermal lensing . Here we report the investigation and successful operation of a non-astigmatic compact design of a unidirectional wavelength tunable Alexandrite ring laser with single frequency operation.
Sathian J, Minassian A, Alford NM, et al., 2019, Enhancing performance of Ce:YAG luminescent concentrators for high power applications
High power scaling of an LED pumped luminescent concentrator (LC) can address significant excitation and illumination applications, including laser pumping and medical light therapy [1-3]. However, heat deposited into the luminescent material is critical and was already a serious issue in our prior systems  where forced air cooling of the Ce:YAG LC light-guide was employed but limited power and/or duration of operation. Here we report the successful demonstration of a temperature controlled Ce:YAG LC pumped with blue InGaN LEDs.
Sathian J, Lian W, Minassian A, et al., 2019, Brightness-enhanced solid-state light sources: From kaleidoscope effect to uniform illumination
Luminescent concentrators (LCs) are systems that can increase the brightness of lambertian light sources such as an LED. Applications considered for LED-pumped LCs include laser pumping, general lighting and medical illumination [1-3]. Most studies consider the output power, spectrum and efficiency of the LC system. Here we explore the spatial nature of the output of the LCs under both laser and LED illumination.
Tawy G, Wang J, Damzen MJ, 2019, Population lensing in alexandrite lasers
Alexandrite (Cr3+:BeAl2O4) is a vibronic laser at 701-858 nm. Its excellent thermo-mechanical properties and high energy storage make it an ideal high power and high energy Q-switched source with recent development in mJ-level red-diode-pumped Alexandrite oscillators and amplifiers [1-3]. Further power scaling of these systems is limited by thermal lensing which has yet to be addressed in great detail. In this work we present experimental and finite element analysis (FEA) results on the investigation of thermal lensing in a red-diode-pumped Alexandrite laser. Differences in the thermal lensing power for non-lasing and lasing conditions are attributed to a 'population lens' effect. In a separate study stable self-Q-switching (SQS) is observed in an Alexandrite laser cavity containing only the gain medium where the SQS loss mechanism is attributed to the population lens.
Sathian J, Lian W, Minassian A, et al., 2019, Brightness-Enhanced Solid-State Light Sources: From Kaleidoscope Effect to Uniform Illumination, Conference on Lasers and Electro-Optics Europe / European Quantum Electronics Conference (CLEO/Europe-EQEC), Publisher: IEEE
Thomas GM, Minassian A, Damzen MJ, 2019, Directly diode-side-pumped alexandrite slab lasers in the bounce geometry and optical vortex generation
Arbabzadah EA, Kerridge-Johns W, Thomas GM, et al., 2019, High efficiency TEM <inf>00</inf> diode end-pumped Alexandrite laser
Tawy G, Damzen MJ, 2019, Tunable and dual wavelength alexandrite laser using the crystal birefringence
Red-diode-pumped Alexandrite lasers has proven to be an efficient method of generating light in the near infrared with broad tunability from 714 to 818 nm recently demonstrated . Conventionally, tunable Alexandrite lasers have used wavelength selective elements such as birefringent filters or external gratings [1, 2]. In this work wavelength tuning is obtained by exploiting the birefringence of the crystal to use the crystal itself as the wavelength selective element, greatly simplifying the cavity and reducing innecessary loss components.
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
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.
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