Steering Laser-Produced THz Radiation in Air with Superluminal Ionization Fronts

Area of Science:

• Physics
• Optics
• Electromagnetism

Background:

• Terahertz (THz) radiation generation in air using ultrashort laser pulses is a known phenomenon.
• Controlling the emission direction of THz radiation has been a challenge for practical applications.

Purpose of the Study:

• To demonstrate controllable steering of THz radiation generated in air.
• To explore the use of the flying focus technique for directional control of THz emission.
• To establish a well-separated and adjustable THz source for potential applications.

Main Methods:

• Utilizing focused ultrashort laser pulses to generate THz radiation in air.
• Employing the flying focus technique to manipulate the ionization front's speed and direction.
• Analyzing the emission angle of the generated THz radiation relative to the laser propagation axis.

Main Results:

• Demonstrated successful steering of pulsed THz radiation to large angles, including the backward direction.
• Showed that the flying focus technique effectively controls the ionization front, dictating the THz emission angle.
• Confirmed that the THz source is well separated from the intense laser pulse.

Conclusions:

• The flying focus technique provides precise angular control over laser-induced THz radiation in air.
• This method establishes a versatile and adjustable THz source with significant potential for remote sensing and spectroscopy.