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- X-Ray – Anatoly’s paper.
- LWI.
- Various particles after laser passes – figures.
- Discussion with yushan.
- How to eliminate collision.
- 找Anatoly写论文去.
- Setup
- Laser system
- KML System
- Tarlas system – Weifeng’s Thesis
- Image system
- Syncronization
- Laser system
- Theory
- Experiment
- Linebroanding analysis
- Yoav’s code – work on this.
- Probably write my own code.
To make an X-ray laser at 58nm. ionization-recombination
The ion-electron recombination occurs on a time scale faster then 1 ps which creates $Li2+$ (He-like) ions in highly excited states (large principle quantum number n). By collisions atoms are transferred to states with smaller n on a few ps time scale. For proper density population inversion between the level n = 2 and the ground state (n = 1) is created for 10 − 100 ps. This results in lasing on the wavelength of the n = 2 to n = 1 transition (13.5nm) which is measured by a spectrometer.
- XUV
cold plasma 1-2ev
Usually, the gain medium of a laser works on the basis of a population inversion. In the 1990s, however, it was shown that optical amplification and consequently lasing without inversion are possible by using an additional optical or microwave field which induces a quantum coherence in the atoms of the gain medium. The basic idea is to provide two different pathways for atoms to get from the ground state to the excited state – a direct one and another one via a third energy level –, and to induce a quantum coherence, so that the quantum-mechanical probability amplitudes for both processes cancel. In effect, this suppresses the reabsorption and thus makes it possible to obtain gain even with a small population in the upper state.
In principle, lasing without inversion could help, e.g., in realizing lasers operating on very short wavelengths, where a population inversion is difficult to achieve.
The idea: Pump atoms into dark state, then emission from |1> can exceed absorption from ground states.
In physics, atomic coherence is the induced coherence between levels of a multi-level atomic system sometimes observed when it interacts with a coherent electromagnetic field.
The Rabi frequency for a given atomic transition in a given light field gives the strength of the coupling between the light and the transition. Rabi flopping between the levels of a 2-level system illuminated with resonant light, will occur at the Rabi frequency. The Rabi frequency is a semiclassical concept as it is based on a quantum atomic transition and a classical light field.
The brightness of an Atomic spectral line emitted by atoms in a gas (or plasma) can be proportional to the gas’s temperature, pressure or a weighted sum of both.
a low power 2 Hz Nd/YAG laser (100 mJ, 5ns) was focused with an f/6 lens.
After a few hundred nsec delay (varied between 300 and 1000 ns), the Ti:sapphire 250 fs laser was fired, whose energy is 50 − 60 mJ in a repetition rate 2 Hz. This femto-second laser was tightly focused with the same f/6 lens onto the plasma at the entrance of the microcapillary providing a power density close to 2×1017 W/cm2.
was directed to the microcapillary by a near 100reflectivity mirror, M1, and the femto-second laser beam was directed by directed by a mirror, M2 which is transparent for the 1.06 μm wavelength of the Nd/YAG laser. From the output spectra, we could see the soft X-ray lasing.
Purpose: Verify
Gaussian broadening refers to broadening effects in spectral lines, these can be produced by Doppler broadening and natural broadening.
- Natural
- Doppler
- Collision
Verify population on 2