Publications
9 results found
Temel T, Murray RT, Wang L, et al., 2024, Narrowband-seeded PPLN non-resonant optical parametric oscillator, Optical Materials Express, Vol: 14, Pages: 889-889
<jats:p>A PPLN non-resonant optical parametric oscillator injection-seeded by narrowband sub-100-mW CW radiation at the signal wavelength produces > 3 W idler average power at 2376 nm for a 20-kHz repetition rate, with a sub-2-nm spectral linewidth. The maximum quantum efficiency reaches 39.5%, roughly 1.4 times higher compared to narrowband operation achieved with a volume Bragg grating at the same pump level. Seed levels as low as 40 mW are sufficient to produce the desired spectral narrowing effect.</jats:p>
Battle RA, Chandran AM, Runcorn TH, et al., 2023, Mid-infrared difference-frequency generation directly pumped by a fiber four-wave mixing source, OPTICS LETTERS, Vol: 48, Pages: 387-390, ISSN: 0146-9592
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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 (M2𝑥,𝑦 ≤ 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.
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.
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.
Andrew Y, Bähner JP, Battle R, et al., 2019, H-Mode Power Threshold Studies on MAST †, Plasma, Vol: 2, Pages: 328-338
Analysis of the L–H and H–L transition power thresholds (Pth) and pedestal parameters are presented for the mega ampere spherical tokamak (MAST). The dependencies of Pth on the average, core plasma electron density, X-point height, and plasma current are described. Increasing X-point distance from the divertor floor over 10–12 cm is found to increase Pth by a factor of three, while X-point heights greater than this have no further influence. The X-point height dependence of Pth is also observed to be sensitive to the plasma current. An Ip decrease from 0.77 MA to 0.65 MA, is observed to lower Pth by a factor of three across the X-point height scan and increases the maximum X-point height at which Pth stops increasing by 3 cm. Finally, a comparison of the experimental results with the predictions by the finite beta drift wave model is made, which provides a reasonable condition for the transition into and out of the H-mode.
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