Lasers, Light Beams and Light Pulses
We still use a classical wave description of light, but start in Sect. 1.1 with a brief introduction into the physics of lasers – certainly the most important tools of modern optics and spectroscopy. In Sect. 1.2 Gaussian light beams are explored, and their manipulation and measurement is illustrated. Section 1.3 gives a precise definition of polarization and describes some experimental tools for its characterization. Wave-packets are discussed in Sect. 1.4, with focus on short pulses as interesting examples from current research. Section 1.5 introduces “correlation functions” and describes methods for determining short pulse durations. Finally, in Sect. 1.6 we explore some characteristics of intense laser fields – a topic of great importance in present research – and thus transcend classical, linear spectroscopy.
KeywordsAutocorrelation Function Gaussian Beam Second Harmonic Generation Population Inversion Amplify Spontaneous Emission
Acronyms and Terminology
‘Ammonium dihydorgen phosphate’, crystal, birefringent, piezoelectric, used also in nonlinear optics.
‘Amplified spontaneous emission’, may occur in (long) optical amplifier media with high gain.
‘Beta barium borate’, crystal, birefringent, excellent nonlinear optical properties, piezoelectric.
‘Beam parameter product’, characterizing the quality of a laser beam (see Chap. 1, Eq. (1.69)).
‘Continuous wave’, (as opposed to pulsed) light beam, laser radiation etc.
‘Fabry-Pérot interferometer’, for high precision spectroscopy and laser resonators (see Sect. 6.1.2 in Vol. 1).
‘Free spectral range’, of an optical interferometer (see Sect. 6.1.2 in Vol. 1).
‘Fourier transform’, see Appendix I in Vol. 1.
‘Full width at half maximum’.
‘Left hand cicularly’, polarized light, also σ + light.
‘Multi-photon ionization’, ionization of atoms or molecules by simultaneous absorption of several photons.
‘Radio frequency’, range of the electromagnetic spectrum. Technically, one includes frequencies from 3 kHz up to 300 GHz or wavelengths from 100 km to 1 mm; ISO 21348 (2007) defines the RF wavelengths from 100 m to 0.1 mm; in spectroscopy RF usually refers to 100 kHz up to some GHz.
‘Right hand cicularly’, polarized light, also σ − light.
‘Second harmonic generation’, doubling of a fundamental frequency, for infrared or visible light typically by methods of nonlinear optics.
‘Transversally electric and magnetic’, modes of an electromagnetic wave.
‘Titanium-sapphire laser’, the ‘workhorse’ of ultra fast laser science.
‘Time of flight’, measurement to determine velocities of charged particles, and consequently their energies (if the mass to charge ratio is known) or their mass to charge ratio (if their energy is known).
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