Imperial College London

DrWilliamKerridge-Johns

Faculty of Natural SciencesDepartment of Physics

Imperial College Research Fellow
 
 
 
//

Contact

 

w.kerridge-johns

 
 
//

Location

 

640Blackett LaboratorySouth Kensington Campus

//

Summary

 

Publications

Publication Type
Year
to

20 results found

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.

Journal article

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.

Conference paper

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.

Journal article

Geberbauer JWT, Kerridge-Johns WR, Damzen MJ, 2020, Q-switched vortex laser using a Sagnac interferometer as an output coupler, Conference on Solid State Lasers XXIX - Technology and Devices, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X

Conference paper

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 ๐ฟ๐บ01modeto 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 ๐ฟ๐บ0๐‘™modes 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.

Journal article

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.

Journal article

Arbabzadah EA, Kerridge-Johns W, Thomas GM, Minassian A, Damzen MJet al., 2019, High efficiency TEM <inf>00</inf> diode end-pumped Alexandrite laser

Conference paper

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.

Journal article

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.

Journal article

Kerridge-Johns WR, Geberbauer JW, Volpini A, Damzen MJet al., 2018, Vortex laser output with a fundamental Gaussian internal mode using a sagnac interferometer

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.

Conference paper

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

Conference paper

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

Conference paper

Thomas GM, Minassian A, Kerridge-Johns W, Sheng X, Coney A, Damzen MJet 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

Conference paper

Kerridge-Johns WR, Damzen MJ, 2017, Vortex mode generation from coupled anti-resonant ring lasers

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.

Conference paper

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.

Journal article

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.

Journal article

Damzen MJ, Thomas GM, Teppitaksak A, Arbabzadah E, Kerridge-Johns W, Minassian Aet 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.

Conference paper

Arbabzadah E, Kerridge-Johns W, Thomas GM, Minassian A, Damzen MJet al., 2015, High efficiency TEM00 diode end-pumped Alexandrite laser, The European Conference on Lasers and Electro-Optics

Conference paper

Arbabzadah EA, Kerridge-Johns W, Thomas GM, Minassian A, Damzen MJet al., 2015, High efficiency TEM<inf>00</inf> diode end-pumped Alexandrite laser

Conference paper

Arbabzadah EA, Kerridge-Johns W, Thomas GM, Minassian A, Damzen MJet al., 2014, High efficiency TEM<inf>00</inf> diode end-pumped alexandrite laser

Conference paper

This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.

Request URL: http://wlsprd.imperial.ac.uk:80/respub/WEB-INF/jsp/search-html.jsp Request URI: /respub/WEB-INF/jsp/search-html.jsp Query String: respub-action=search.html&id=00639411&limit=30&person=true