Some Other Lasers and Laser Amplifiers

Abstract

We present further laser types: dye laser; chemical laser; X-ray laser; organic laser. And we discuss the principle of laser amplifiers. Another topic concerns optical damage.

Problems

16.1

Dye laser (length of the active medium 1 mm; beam diameter 0.2 mm; reflectivity of the output coupling mirror $R=0.7$; frequency 500 THz).

• (a) Determine the threshold condition.

• (b) Determine the output power at pumping 10 times above threshold.

16.2

Laser amplifier. To amplify femtosecond pulses emitted by a titanium-sapphire laser, an optical switch reduces the pulse repetition rate to 1 kHz. By passing through two amplifier stages (optically pumped titanium-sapphire crystals), each with a single path gain of 10, intense laser pulses are generated. Determine (by use of the data of Problem 13.2) the pulse power and the average power after amplification.

16.3

Momentum of a photon and radiation pressure.

• (a) When an atom at rest emits a photon, then the atom experiences a recoil. Estimate the velocity of a neon atom that was originally at rest and emitted a photon (wavelength 632 nm).

• (b) Estimate the average velocity of a spherical target (diameter 0.2 mm) consisting of frozen deuterium that absorbed an intense light pulse (energy 100 J, wavelength 1.05 $\upmu$m).

16.4

Radiation of a titanium sapphire laser amplifier system (pulse power 1 GW, wavelength 780 nm, pulse duration 100 fs) is focused to an area of diameter 10 $\upmu$m$^{2}$. Determine the intensity, the photon density, the energy density, the amplitude of the electric field in the focus.

16.5

Magnetic field of a light wave.

Determine for the example of the preceding problem the amplitude of the magnetic field of the electromagnetic wave in the focus. Compare the amplitude with Earth’s magnetic field. The amplitude of the magnetic field of a plane wave is $B_0 = (1/c)A$, where A is the amplitude of the electric field. The magnitude of Earth’s magnetic field on the surface ranges from 25 to 65 $\upmu$T.

16.6

Material processing .

The radiation of a high power laser with amplifier (pulse duration 1 ps, pulse power 1 MW, diameter 0.02 mm) is used to drill a hole in a metal foil (thickness 0.2 mm). How many shots are necessary?