More Like this

1. All-Solid State Iron Resonance Lidar for Measurement of Temperature and Winds in the Upper Mesosphere and Lower Thermosphere

   Collins, R; Li, J; Wiliams, B; Kaifler, B; Thorsen, D (October 2022, 30th International laser radar Conference (ILRC-30))

   The Arctic atmosphere and subauroral region are a natural laboratory for understanding plasma-neutral and dynamical coupling in the atmosphere and geospace. During geomagnetically active periods the auroral electrojet and auroral precipitation are overhead at the High-Frequency Active Auroral Research Program (HAARP) facility in Gakona, Alaska (62°N, 145°W) and facilitate active experiments. Iron resonance lidar systems are uniquely suited for these active investigations as naturally occurring iron layers extend from the upper mesosphere to the middle thermosphere (~70-150 km). A novel lidar system has been demonstrated at the German Aerospace Center using an Nd:YAG laser that operated at a minor line at 1116 nm and was tripled to the iron resonance line at 372 nm. This prototype laser was fully solid-state without liquid dyes or flashlamps and with diode pumping. We are developing a lidar system based on this prototype system that can operate robustly at the remote location of HAARP. We will employ a diode-pumped Nd:YAG laser with second and third harmonic generation. The laser will be injection-seeded by a tunable diode laser allowing the laser to frequency scan the iron line. The laser pulse spectra will be recorded on a shot-by-shot basis using an etalon imaging system with a spectral reference. The lidar system is will operate at 372 nm, with a pulse repetition rate of 100 pps, a pulse energy of 30 mJ, and a 0.9-m diameter telescope. We present the system specifications and the expected performance of the system. 

   more » « less
2. Development of an All-Solid-State Iron Resonance Temperature Lidar

   Li, Jintai; Roddewig, Michael R; Kumar, Vishnu R; Collins, Richard L; Williams, Bifford P (June 2024, EPJ Web of Conferences)

   The coupling between the neutral and ionized atmosphere is important to improve our understanding of the dynamics of the upper atmosphere and thus improving the prediction of space weather. The Arctic atmosphere is a natural laboratory for understanding these processes. The High-frequency Active Auroral Research Program (HAARP) facility located in Gakona Alaska hosts many scientific instruments that can be used for active experiments. An all-solid state Iron Resonance Temperature Lidar system is under development to be deployed at HAARP to enrich the capability of the HAARP facility. We present recent developments of this lidar system. Progress has been made on the development of the transmitter, and the etalon-based laser frequency monitoring system. We are modifying a commercial Nd:YAG laser to operate at 1116 nm. We have achieved broadband lasing at 1116 nm with 1mJ at 100 Hz in long-pulse mode. The 1116 nm laser will be Q-switched and injection seeded to yield narrowband high power emission. The light will then be tripled to 372 nm and serve as the lidar transmitter. Using a frequency-lock Rb laser, we demonstrate accurate monitoring of the laser’s frequency differences when locked to different Doppler free features with errors <1 MHz. This will support the measurement of temperature with this lidar. 

   more » « less
3. On the use of ELF/VLF emissions triggered by HAARP to simulate PLHR and to study associated MLR events

   https://doi.org/10.1186/s40623-021-01551-9  

   Parrot, Michel; Němec, Frantisěk; Cohen, Morris B.; Gołkowski, Mark (December 2022, Earth, Planets and Space)

   Abstract A spectrogram of Power Line Harmonic Radiation (PLHR) consists of a set of lines with frequency spacing corresponding exactly to 50 or 60 Hz. It is distinct from a spectrogram of Magnetospheric Line Radiation (MLR) where the lines are not equidistant and drift in frequency. PLHR and MLR propagate in the ionosphere and the magnetosphere and are recorded by ground experiments and satellites. If the source of PLHR is evident, the origin of the MLR is still under debate and the purpose of this paper is to understand how MLR lines are formed. The ELF waves triggered by High-frequency Active Auroral Research Program (HAARP) in the ionosphere are used to simulate lines (pulses of different lengths and different frequencies). Several receivers are utilized to survey the propagation of these pulses. The resulting waves are simultaneously recorded by ground-based experiments close to HAARP in Alaska, and by the low-altitude satellite DEMETER either above HAARP or its magnetically conjugate point. Six cases are presented which show that 2-hop echoes (pulses going back and forth in the magnetosphere) are very often observed. The pulses emitted by HAARP return in the Northern hemisphere with a time delay. A detailed spectral analysis shows that sidebands can be triggered and create elements with superposed frequency lines which drift in frequency during the propagation. These elements acting like quasi-periodic emissions are subjected to equatorial amplification and can trigger hooks and falling tones. At the end all these known physical processes lead to the formation of the observed MLR by HAARP pulses. It is shown that there is a tendency for the MLR frequencies of occurrence to be around 2 kHz although the exciting waves have been emitted at lower and higher frequencies. Graphical Abstract 

   more » « less
4. Sub-picosecond timing jitter between optically synchronized femtosecond and picosecond laser systems

   https://doi.org/10.1088/1361-6501/acc41b  

   Jiang, Zhenfei; Strycker, Benjamin; Hand, Lucian; Adamonis, Jonas; Yi, Zhenhuan; Sokolov, Alexei; Scully, Marlan (March 2023, Measurement Science and Technology)

   Abstract Synchronized optical pulses are widely used. We report here characterization and measurement of synchronized femtosecond and picosecond pulses from a Ti:Sapphire laser (nominally 800 nm) and a Nd:YAG laser (1064 nm), respectively. Synchronization is achieved by utilizing soliton self-frequency shift in a photonic-crystal fiber that allows the 800 nm femtosecond oscillator to seed the third-harmonic generation (355 nm) of picosecond regenerative amplifier. The relative timing jitter between the amplified femtosecond and the third-harmonic generation of picosecond pulses is (710 ± 160) fs, which is only (1.17 ± 0.26)% of the picosecond pulse duration. This work paves way for applications in stimulated Raman scattering spectroscopy and amplification. 

   more » « less
5. Boosting the efficiency of high harmonic amplification by modulating a plasma-based X-ray laser with the second harmonic of the fundamental frequency laser field

   Khairulin, I.R.; Antonov, I.R.; Kocharovskaya, O. (October 2021, International conference on Ultrafast Optical Science)

   Attosecond pulses formed by high order harmonics (HHs) of an infrared (IR) laser field is a powerful tool for studying and controlling ultrafast dynamics of electrons in atoms, molecules and solids at its intrinsic time-scale. However, in the X-ray range the energy of attosecond pulses is rather limited. Their amplification is an important but very challenging problem since none of the existing amplifiers can support the corresponding PHz bandwidth. In our previous work [1] we proposed a method for the attosecond pulse amplification in hydrogen-like active medium of a recombination plasma-based X-ray laser dressed by a replica of the fundamental frequency IR field used for the HH generation. Due to the IRfield-induced sub-laser-cycle Stark shift and splitting of the lasing energy levels the gain of the active medium is redistributed over the combination frequencies, separated from the resonance by even multiples of the frequency of the IR field. If the incident HHs forming an attosecond pulse train are tuned in resonance with the induced gain lines and the active plasma medium is strongly dispersive for the modulating IR field, then during the amplification the relative phases of harmonics and (under the optimal choice of the IR field strength) the shape of the amplified pulses will be preserved. In the present work we show the possibility of boosting the efficiency of HH amplification by modulating the active medium of an X-ray laser with the second harmonic of the fundamental frequency IR field. We show that under the action of a laser field (with arbitrary frequency) the gain redistribution occurs not only over the even combination frequencies discussed in [1], but also over the odd frequencies separated from the resonance by odd multiples of the laser frequency. Besides, nearly half of the medium gain is contained in the even induced gain lines, and nearly half in the odd. If the modulating field is the second harmonic of the IR field, used for the generation the HHs and attosecond pulses, then the seeding HHs can be tuned in resonance with both even and odd gain lines simultaneously, which will make the overall gain much higher as compared to the previously considered case of the fundamental frequency modulating field (when only the even gain lines play the role). By the example of the C5+ X-ray laser with 3.38 nm wavelength of the inverted transition we show the possibility of increasing the efficiency of 430 as pulse amplification by 8.5 times when the active medium is modulated with the second harmonic of the fundamental frequency IR field with wavelength 2.1 µm. 

   more » « less