Different Ways of Operating a Laser

Abstract

In this chapter, we describe techniques used to operate lasers as continuous wave lasers or as pulsed lasers—in the next chapter we will treat femtosecond lasers.

Problems

12.1

Resonance condition for a planparallel plate. Derive the resonance condition (12.1) for a planparallel plate. [Hint: Determine the difference of the optical path of a beam directly reflected at the surface of the plate and a beam reflected at the backside of the plate.]

12.2

Michelson interferometer. A Michelson interferometer operates with a parallel laser beam (wavelength $\lambda = 580$ nm; $P_0$ = power of the laser radiation).

• (a) Calculate the intensity I(x) at the detector for a length difference x when one arm has the length L and the other arm the length $L + x$.

• (b) Determine the path difference $\delta x$ for values of x in the interval $x_0 \le x \le x_0+\lambda$ for $x_0 = 1$ km that leads to the largest signal-to-noise ratio for the signal.

• (c) Estimate the change of the signal if one of the arms changes its length by $\delta L/L = 10^{-15}$ and the other arm by $\delta L/L = -10^{-15}$. [Hint: The beam splitter in the Michelson interferometer splits an incident electromagnetic field into two fields.]

12.3

It is possible to reduce suddenly the reflectivity of the output mirror of a laser . Show, qualitatively, that this “cavity dumping” results in a much stronger laser pulse than without cavity dumping.