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Explanatory Notes
¹⁾ laser (acronym from Light Amplification by Stimulated Emission of Radiation) – a device for the creation, amplification, and transmission of a narrow, intense beam of coherent light.
²⁾ plasma – a state of matter similar to gas in which a certain portion of the particles are ionized.
Section 1
TEXT COMPREHENSION QUESTIONS
1.1. Issues for Discussion

1. 
   What is proposed as a means of controlling the envelope propagation velocity of a laser pulse in a plasma?
   
2. 
   Characterise a superluminous pulse as viewed by the authors of the article.
   
3. 
   Under what conditions does the acceleration of the group velocity of a superluminous laser pulse become possible?
   
4. 
   What scientific theories serve as the basis of the hypothesis suggested?
   
5. 
   What physical property of the pulse predetermines the fact that the phase velocity of the accelerating field will be at the design speed in an active-plasma medium?
   
6. 
   What is the role of the preexcited active medium in increasing the overall pulse speed and which components of the pulse structure are affected by it?
   
7. 
   Why is the acceleration of the group velocity said not to violate the theory of relativity?
   
8. 
   Which element of the pulse structure already contains information about the pulse and in what way is this information extracted?
   
9. 
   Under what physical condition will the peak of the pulse travel to the edge of the pulse?
   
10. 
    What are the three main spheres of application of the process of effective acceleration of the photon group velocity and the recovery of laser energy loss by the active medium? Comment on each of them.
    
11. 
    Enumerate and disclose the essence of the three conditions to be met to accelerate the pulse envelope to the design speed and retain a stationary structure.