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Josephson effects
Published in J. R. Waldram, Superconductivity of Metals and Cuprates, 2017
This remarkable ability of current-fed weak links to transfer energy efficiently from one frequency to another has been employed in various devices, such as frequency multipliers, mixers and parametric amplifiers (Section 18.11). A parametric amplifier, for instance, is a device which needs a reactive parameter such as a capacitance or an inductance whose value can be modulated by applying a strong signal to it. Such a device may be realized in various ways using weak links. One method is to use a weak link with a d.c. current bias I0 smaller than its critical current. From (6.3) we see that the current bias establishes a corresponding equilibrium phase ϕ0. If we now consider small departures from equilibrium, we find on differentiating (6.3) that
Photoelectron angular distributions from resonant two-photon ionisation of adiabatically aligned naphthalene and aniline molecules
Published in Molecular Physics, 2021
Jacqueline Arlt, Dhirendra P. Singh, James O. F. Thompson, Adam S. Chatterley, Paul Hockett, Henrik Stapelfeldt, Katharine L. Reid
A schematic of the laser set-up is shown in Figure 1(a). Both laser beams originate from the same pulsed Ti:Sapphire laser system (customised Solstice ACE, model 80L-35F-1K-HP-T Spectra-Physics, 1 kHz, 6 W, 40 fs). A part of the uncompressed 800 nm output of the laser system provides the alignment beam. These laser pulses have a duration of 110 ps (FWHM, see Figure 1(c) for pulse profile) and a pulse energy up to 700 µJ. The beam used to ionise the molecules is obtained from an optical parametric amplifier (TOPAS, model TP8U1, Light Conversion, pumped by 3 mJ from the compressed output of the Ti:Sapphire laser system) and subsequent nonlinear optical processes. The TOPAS idler output at ∼2215 nm is frequency-mixed with an 800 nm beam from the Ti-Sapphire laser in a 0.5-mm thick BBO crystal to generate a visible beam at ∼588 nm.
Piloted Liquid Spray Flames: A Numerical and Experimental Study
Published in Combustion Science and Technology, 2020
Yejun Wang, Salar Taghizadeh, Anurag S. Karichedu, Waruna D. Kulatilaka, Dorrin Jarrahbashi
The experimental configuration for CO fs-TPLIF measurements, as shown on the left side of Figure 1, has been described in detail elsewhere (Wang, Jain, Kulatilaka 2019; Wang and Kulatilaka 2017). Briefly, it consists of a regeneratively amplified, Ti:sapphire laser system (Spectra Physics, Model: Solstice Ace), which generates 800-nm output beam with approximately 80-fs full-width at half-maximum laser pulses at 1-kHz repetition rate. Then the output laser beam was passed through an optical parametric amplifier (OPA) and a frequency-mixing module (Light Conversion Model: TOPAS Prime Plus with a NirUVis UV extension module) to generate 230.1-nm UV radiation with approximately 40 μJ/pulse laser energy. Several UV fused silica 45° dielectric laser mirrors and a f = + 200 mm plano-convex lens were used to guide the UV laser beam and focus it onto the probe region. The fluorescence signal was collected at a normal direction to the excitation beam path with a 50-mm-focal-length, f/1.2 camera lens coupled through a 36-mm extension lens tube for sufficient magnification, and then imaged onto an intensified CCD (ICCD) camera (Princeton Instruments, Model: PIMax 4). To reduce C2 Swan bands and background interferences, a narrowband pass filter (Thorlabs, Model: FB450-10) and 10-ns detection gate were used for quantitative CO concentration measurements in these piloted liquid-spray flames (Wang and Kulatilaka 2017).
Ultrafast Electron–Phonon Coupling at Metal-Dielectric Interface
Published in Heat Transfer Engineering, 2019
Qiaomu Yao, Liang Guo, Vasudevan Iyer, Xianfan Xu
A Ti-Sapphire amplified femtosecond laser is used to generate laser pulses with 100 fs pulse width, central wavelength at 800 nm, and repetition rate of 5 kHz. A collinear pump and probe technique is used by dividing the laser beam into a relatively weak probe beam and higher power pump beam. The pump beam is focused to a 29.8 μm radius on the sample. The probe beam is sent to an optical parametric amplifier (OPA), which generates tunable wavelengths with nonlinear processes. The output from the OPA is fixed at the 490 nm wavelength in order to reduce the effect of non-thermalized electrons as discussed above. The probe spot radius is 13.8 μm, smaller than half of the pump spot radius. A computer-controlled mechanical delay stage is used to adjust the time delay between the pump and the probe beams in femtosecond time step.