Publications
45 results found
Battle RA, Chandran AM, Runcorn TH, et al., 2023, Mid-infrared difference-frequency generation directly pumped by a fiber four-wave mixing source., Opt Lett, Vol: 48, Pages: 387-390
We demonstrate a new, to the best of our knowledge, method of generating mid-infrared pulses by difference frequency mixing the Stokes pulse generated by four-wave mixing in a photonic crystal fiber with the remaining pump pulse. The Stokes pulses generated by four-wave mixing are inherently overlapped temporally and spatially with the pump pulse at the output of the fiber. Focusing this output into a nonlinear crystal phase matched for difference frequency generation between the pump and Stokes pulses results in a simple method of generating mid-infrared pulses. With a pump source at 1.064 µm, and a photonic crystal fiber engineered to generate Stokes pulses at approximately 1.65 µm, we generate 160 mW of mid-infrared light at approximately 3 µm through difference frequency generation.
Battle RA, Chandran AM, Runcorn TH, et al., 2022, Optical parametric amplification seeded by four-wave mixing in photonic crystal fibers, Conference on Nonlinear Frequency Generation and Conversion - Materials and Devices XXI at SPIE LASE Conference, Publisher: SPIE-INT SOC OPTICAL ENGINEERING, ISSN: 0277-786X
Chandran A, Battle RA, Murray RT, et al., 2021, Watt-level 743 nm source by second-harmonic generation of a cascaded phosphosilicate Raman fiber amplifier, Optics Express, Vol: 29, Pages: 41467-41474, ISSN: 1094-4087
We demonstrate a nanosecond pulsed 743 nm source through second-harmonic generation of a cascaded phosphosilicate Raman fiber amplifier system operating at 1485 nm. The amplifier is pumped by a 1240 nm phosphosilicate Raman fiber amplifier and seeded with a continuous-wave 1485 nm diode. This 1485 nm light is used for second-harmonic generation in periodically poled lithium niobate. Greater than 1 W of average power is generated at 743 nm with a corresponding pulse energy of 220 nJ at a repetition rate of 5 MHz. The source displays excellent beam quality (M2š„,š¦ ≤ 1.18) with ideal parameters for biomedical imaging applications.
Murray RT, Chandran AM, Battle RA, et al., 2021, Seeded optical parametric generation in CdSiP2 pumped by a Raman fiber amplifier at 124 µm, Optics Letters, Vol: 46, Pages: 2039-2039, ISSN: 0146-9592
We report a seeded optical parametric generator (OPG) producing tunable radiation from 4.2–4.6 µm. The seeded OPG employs a 13 mm long CdSiP2 (CSP) crystal cut for non-critical phase-matching, pumped by a nanosecond-pulsed, MHz repetition rate Raman fiber amplifier system at 1.24 µm. A filtered, continuous-wave fiber supercontinuum source at 1.72 µm is used as the seed. The source generates up to 0.25 W of mid-infrared (MIR) idler power with a total pump conversion of 42% (combined signal and idler).
Murray RT, Chandran AM, Battle RA, et al., 2021, Seeded optical parametric generation in CdSiP2 pumped by a nanosecond pulsed, MHz repetition rate Raman fiber amplifier at 1.24 µm, Nonlinear Frequency Generation and Conversion: Materials and Devices XX, Publisher: SPIE, Pages: 1-10
We report a CdSiP2 (CSP) based seeded optical parametric generator (OPG), emitting sub-nanosecond duration, 3 MHz repetition rate, wavelength tunable mid-infrared (MIR) light at 4.2-4.6 μm. We generate up to 0.25 W at 4.2 μm with a total pump conversion efficiency of 42%. The OPG is pumped by a 1.24 μm Raman fiber amplifier system. This is the first demonstration of pumping CSP with a Raman fiber source in this region, and we show that Raman fiber sources in the near-infrared (NIR) are ideal pump sources for non-critically phasematched (NCPM) CSP devices. Pumping CSP at 1.24 μm permits the use of NCPM whilst decreasing the negative effects of both two-photon absorption and linear absorption losses, when compared to conventional 1 μm pumping. This offers a potential advantage for MIR power scaling of CSP parametric devices due to a reduced thermal load in the crystal from residual pump absorption. The OPG is seeded with a continuous-wave fiber supercontinuum source emitting radiation in the 1.7 μm region, to lower the threshold pump intensity required for efficient conversion. NCPM and temperature tuning of the crystal allow for simple wavelength tuning of the idler radiation. We report on laser damage induced by elevated crystal temperatures, which we propose is linked to the decrease in CSP bandgap energy with increasing temperature.
Murray RT, Chandran AM, Battle RA, et al., 2021, CdSiP<inf>2</inf> based mid-infrared optical parametric sources pumped with Raman fiber amplifiers
CdSiP2 (CSP) is a nonlinear optical semiconductor which can phasematch pump wavelengths throughout the near-infrared (NIR) to generate mid-infrared (MIR) light through parametric three-wave mixing. In this work, we investigate the unique combination of NIR Raman fiber amplifiers around 1.24 µm and non-critical phasematching in CSP, to demonstrate tunable sources in the 4-5 µm MIR region.
Chandran AM, Battle RA, Murray RT, et al., 2021, 743 nm Source by SHG of a Cascaded Phosphosilicate Raman Fiber Amplifier
We demonstrate a nanosecond-pulsed 743 nm source by second harmonic generation of a cascaded phosphosilicate Raman fiber amplifier operating at 1485 nm. The source emits >1 W of 743 nm average power at a 5 MHz repetition rate.
Chandran A, Runcorn T, Murray R, et al., 2019, Nanosecond pulsed 620 nm source by frequency-doubling a phosphosilicate Raman fiber amplifier, Optics Letters, Vol: 44, Pages: 6025-6028, ISSN: 0146-9592
We demonstrate a nanosecond pulsed source at 620 nm with watt-level average power by frequency-doubling a 1240 nm phosphosilicate Raman fiber amplifier. A gain-switched laser diode operating at 1064 nm is amplified in an ytterbium fiber master oscillator power amplifier system and then converted to 1240 nm using a phosphosilicate Raman fiber amplifier with a conversion efficiency of up to 66%. The Raman fiber amplifier is seeded with a continuous-wave 1240 nm laser diode to obtain narrow-linewidth radiation, which is subsequently frequency-doubled in a periodically poled lithium tantalate crystal. A maximum average power of 1.5 W is generated at 620 nm, corresponding to a pulse energy of 300 nJ at a repetition rate of 5 MHz. The source has excellent beam quality (M2≤1.16) and an optical efficiency (1064 nm to 620 nm) of 20%, demonstrating an effective architecture for generating red pulsed light for biomedical imaging applications.
Chandran AM, Runcorn TH, Murray RT, et al., 2019, 620 nm source by second harmonic generation of a phosphosilicate raman fiber amplifier, Conference on Lasers and Electro-Optics (CLEO), Publisher: IEEE, ISSN: 2160-9020
We demonstrate a nanosecond-pulsed 620 nm source through frequency doubling a 1240 nm phosphosilicate Raman fiber amplifier. The source emits up to 213 mW of average power, and is repetition rate and pulse duration tunable.
Chandran AM, Runcorn TH, Tmurray R, et al., 2019, 620nm Source by Second Harmonic Generation of a Phosphosilicate Raman Fiber Amplifier
We demonstrate a nanosecond-pulsed 620 nm source through frequency doubling a 1240 nm phosphosilicate Raman fiber amplifier. The source emits up to 213 mW of average power, and is repetition rate and pulse duration tunable.
Woodward RI, Kelleher EJR, Runcorn TH, et al., 2019, Nanosecond to picosecond fiber bragg grating compression of giant-chirped pulses from an ultra-long mode-locked fiber laser
Runcorn TH, Murray RT, Kelleher EJR, et al., 2019, Watt-level, Duration-tunable Picosecond Source at 560 nm by Second-harmonic Generation of a Raman Fiber Laser
Gorlitz F, Guldbrand S, Runcorn T, et al., 2018, easySLM-STED: stimulated emission depletion microscopy with aberration correction, extended field of view and multiple beam scanning, Journal of Biophotonics, Vol: 11, ISSN: 1864-063X
We demonstrate a simplified setāup for STED microscopy with a straightforward alignment procedure that uses a single spatial light modulator (SLM) with collinear incident excitation and depletion beams to provide phase modulation of the beam profiles and correction of optical aberrations. We show that this approach can be used to extend the field of view for STED microscopy by correcting chromatic aberration that otherwise leads to walkāoff between the focused excitation and depletion beams. We further show how this arrangement can be adapted to increase the imaging speed through multibeam excitation and depletion. Fine adjustments to the alignment can be accomplished using the SLM only, conferring the potential for automation.
Runcorn TH, Murray R, Taylor JR, 2018, Highly efficient nanosecond 560 nm source by SHG of a combined Yb-Raman fiber amplifier, Optics Express, Vol: 26, Pages: 4440-4447, ISSN: 1094-4087
We demonstrate a nanosecond 560 nm pulse source based on frequency-doubling the output of a combined Yb-Raman fiber amplifier, achieving a pulse energy of 2.0 µJ with a conversion efficiency of 32% from the 976 nm pump light. By introducing a continuous-wave 1120 nm signal before the cladding pumped amplifier of a pulsed Yb:fiber master oscillator power amplifier system operating at 1064 nm, efficient conversion to 1120 nm occurs within the fiber amplifier due to stimulated Raman scattering. The output of the combined Yb-Raman amplifier is frequency-doubled to 560 nm using a periodically poled lithium tantalate crystal with a conversion efficiency of 47%, resulting in an average power of 3.0 W at a repetition rate of 1.5 MHz. The 560 nm pulse duration of 1.7 ns and the near diffraction-limited beam quality (M2≤1.18) make this source ideally suited to biomedical imaging applications such as optical-resolution photoacoustic microscopy and stimulated emission depletion microscopy.
Murray RT, Runcorn TH, Taylor JR, 2018, Fibre-based sources from the UV to mid-infrared
Extensive spectral and temporal versatility are achieved through the integration of nonlinear fibres and crystals with seeded master-oscillator power fibre amplifier configurations through diverse generation processes. Various schemes will be reviewed.
Runcorn TH, Gorlitz F, Murray RT, et al., 2017, Visible Raman-shifted Fiber Lasers for Biophotonic Applications, IEEE Journal of Selected Topics in Quantum Electronics, Vol: 24, ISSN: 1077-260X
The efficient nonlinear conversion of Yb-doped fiber laser systems using a combination of stimulated Raman scattering and second-harmonic generation is an effective method for developing sources for biophotonic applications in the yellow-green spectral region. In this paper, we review recent progress in the development of these sources, compare the relative benefits of differing source architectures and demonstrate STED microscopy using an exemplar source.
Runcorn TH, Murray RT, Taylor JR, 2017, High Average Power Second-harmonic Generation of a CW Erbium Fiber MOPA, IEEE Photonics Technology Letters, Vol: 29, Pages: 1576-1579, ISSN: 1041-1135
We report the generation of 28 W of 780 nm radiation with near diffraction limited beam quality (M²≤1.15) by frequency-doubling a continuous-wave (CW) erbium fiber master oscillator power amplifier (MOPA) system in a periodically poled lithium niobate crystal. The second-harmonic generation conversion efficiency reached 45% with no roll-off observed, suggesting that further power scaling should be possible with higher fundamental pump powers. The generated second-harmonic had a 3 dB spectral bandwidth of 0.10 nm. The presented architecture represents a simple and effective route to generating high-brightness radiation around 780 nm.
Murray RT, Runcorn TH, Guha S, et al., 2017, High average power parametric wavelength conversion at 3.31–3.48 μm in MgO:PPLN, Optics Express, Vol: 25, Pages: 6421-6430, ISSN: 1094-4087
We present results of high average power mid-infrared (mid-IR) generation employingsynchronized nanosecond pulsed ytterbium and erbium fiber amplifier systems using periodicallypoled lithium niobate. We generate greater than 6 W of mid-IR radiation tunable in wavelengthbetween 3.31–3.48μm, at power conversion efficiencies exceeding 75%, with near diffractionlimited beam quality (M2= 1.4). Numerical modeling is used to verify the experimental resultsin differing pump depletion regimes.
Woodward RI, Murray RT, Phelan CF, et al., 2017, Characterization of the second- and third-order nonlinear optical susceptibilities of monolayer MoS2 using multiphoton microscopy, 2D Materials, Vol: 4, ISSN: 2053-1583
We report second- and third-harmonic generation in monolayer MoS2 as a tool for imaging and accurately characterizing the material's nonlinear optical properties under 1560 nm excitation. Using a surface nonlinear optics treatment, we derive expressions relating experimental measurements to second- and third-order nonlinear sheet susceptibility magnitudes, obtaining values of $| {\chi }_{{\rm{s}}}^{(2)}| \ =2.0\times {10}^{-20}$ m2 V−1 and, for the first time for monolayer MoS2, $| {\chi }_{{\rm{s}}}^{(3)}| =1.7\times {10}^{-28}$ m3 V−2. These sheet susceptibilities correspond to effective bulk nonlinear susceptibility values of $| {\chi }_{{\rm{b}}}^{(2)}| =2.9\ \times {10}^{-11}$ m V−1 and $| {\chi }_{{\rm{b}}}^{(3)}| =2.4\times {10}^{-19}$ m2 V−2, accounting for the sheet thickness. Experimental comparisons between MoS2 and graphene are also performed, demonstrating ~3.4 times stronger third-order sheet nonlinearity in monolayer MoS2, highlighting the material's potential for nonlinear photonics in the telecommunications C band.
Runcorn T, Murray RT, Taylor JR, 2017, Microjoule Nanosecond 560 nm Source by SHG of a Combined Yb-Raman Fiber Amplifier, Pages: ATu1A-7
Murray RT, Runcorn T, Guha S, et al., 2017, Fibre MOPA Pumped MIR Parametric Wavelength Conversion, Pages: AM2A-1
Murray RT, Runcorn TH, Kelleher EJR, et al., 2016, Mid-Infrared Difference Frequency-Generation with Synchronized Fiber Lasers, Advanced Solid State Lasers
Murray RT, Runcorn TH, Kelleher EJR, et al., 2016, Watt-level Nanosecond 589 nm Source by SHG of a Cascaded Raman Amplifier, Advanced Solid State Lasers 2016
Murray RT, Runcorn TH, Kelleher EJR, et al., 2016, Highly efficient mid-infrared difference-frequency generation using synchronously pulsed fiber lasers, Optics Letters, Vol: 41, Pages: 2446-2449, ISSN: 1539-4794
We report the development of a high average power, picosecond-pulse, mid-infrared source based on difference-frequency generation (DFG) of two synchronous master oscillator power fiber amplifier systems. The generated idler can be tuned over the range 3.28–3.45 μm delivering greater than 3.4 W of average power, with a maximum pump to total DFG power conversion efficiency of 78%. The benefits of a synchronously pumped scheme, compared to CW seeding of DFG sources, are discussed.
Murray RT, Runcorn TH, Kelleher EJR, et al., 2016, Multi-Watt-level 3.28-3.45 μm difference frequency generation using synchronous fiber lasers
We report multi-Watt-level average power 3.28-3.45 μm difference frequency generation using two sychronous picosecond master oscillator power fiber amplifiers. Greater than 3.4 W of idler power is generated across the entire spectral tuning range.
Murray RT, Kelleher EJR, Runcorn TH, et al., 2015, Multi-Watt-level 3.28-3.45 um difference frequency generation using synchronous fiber lasers, Mid-Infrared Coherent Sources 2016
Woodward RI, Howe RCT, Runcorn TH, et al., 2015, Wideband saturable absorption in few-layer molybdenum diselenide (MoSeā) for Q-switching Yb-, Er- and Tm-doped fiber lasers., Opt Express, Vol: 23, Pages: 20051-20061, ISSN: 1094-4087
We fabricate a free-standing molybdenum diselenide (MoSe2) saturable absorber by embedding liquid-phase exfoliated few-layer MoSe2 flakes into a polymer film. The MoSe2-polymer composite is used to Q-switch fiber lasers based on ytterbium (Yb), erbium (Er) and thulium (Tm) gain fiber, producing trains of microsecond-duration pulses with kilohertz repetition rates at 1060 nm, 1566 nm and 1924 nm, respectively. Such operating wavelengths correspond to sub-bandgap saturable absorption in MoSe2, which is explained in the context of edge-states, building upon studies of other semiconducting transition metal dichalcogenide (TMD)-based saturable absorbers. Our work adds few-layer MoSe2 to the growing catalog of TMDs with remarkable optical properties, which offer new opportunities for photonic devices.
Runcorn TH, Murray RT, Kelleher EJR, et al., 2015, Duration-tunable picosecond source at 560 nm with watt-level average power, Optics Letters, Vol: 40, Pages: 3085-3088, ISSN: 0146-9592
A pulse source at 560 nm that is tunable in duration between 50 ps and 2.7 ns with >1 W of average power and near diffraction-limited beam quality is demonstrated. The source is based on efficient (up to 50%) second-harmonic generation in a periodically poled lithium tantalate crystal of a linearly polarized fiber-integrated Raman amplifier operating at 1120 nm. A duration-tunable ytterbium master-oscillator power-fiber amplifier is used to pulse-pump the Raman amplifier, which is seeded by a continuous-wave distributed-feedback laser diode at 1120 nm. The performance of the system using two different master oscillator schemes is compared. A pulse energy of up to 765 nJ is achieved with a conversion efficiency of 25% from the ytterbium fiber pump, demonstrating a compact and turn-key architecture for obtaining high peak-power radiation at 560 nm.
Runcorn T, Legg T, murray RT, et al., 2015, Fiber-integrated frequency-doubling of a picosecond Raman laser to 560 nm, Optics Express, Vol: 23, Pages: 15728-15733, ISSN: 1094-4087
We report the development of a fiber-integrated picosecond source at 560 nm by second harmonic generation of a Raman fiber laser. A picosecond ytterbium master oscillator power fiber amplifier is used to pulse-pump a Raman amplifier, which is seeded by a continuous wave distributed feedback laser diode operating at 1120 nm. The pulse train generated at 1120 nm is frequency-doubled in a fiber-coupled periodically-poled lithium niobate crystal module, producing 450 mW of average power at 560 nm with a pulse duration of 150 ps at a repetition rate of 47.5 MHz. The near diffraction-limited (M2 = 1.02) collimated output beam is ideal for super-resolution microscopy applications.
Woodward, Kelleher EJR, Runcorn TH, et al., 2015, Fiber grating compression of giant-chirped nanosecond pulses from an ultra-long nanotube mode-locked fiber laser, Optics Letters, Vol: 40, Pages: 387-390, ISSN: 1539-4794
We demonstrate that the giant chirp of coherent, nanosecond pulses generated in an 846 m long, all-normal dispersion, nanotube mode-locked fiber laser can be compensated using a chirped fiber Bragg grating compressor. Linear compression to 11 ps is reported, corresponding to an extreme compression factor of ∼100. Experimental results are supported by numerical modeling, which is also used to probe the limits of this technique. Our results unequivocally conclude that ultra-long cavity fiber lasers can support stable dissipative soliton attractors and highlight the design simplicity for pulse-energy scaling through cavity elongation.
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