1. Lasers and their applications in chemistry Dr Dean Venables (G16)

2. Course outline Part (1) looks at what lasers are and how they work 1 test and 1 assignment What is a laser? What are its properties? How does a laser work? What molecular transitions produce laser operation? How are these practically realised? What are some common types of laser? Part (2) looks at several applications of lasers in chemistry Laser spectroscopy

3. References (These are all available in the library) More advanced texts on lasers and their applications: Milonni, Eberly, Lasers Siegman, Lasers Silfast, Laser Fundamentals Telle, Urena, Donovan, Laser Chemistry: Spectroscopy, Dynamics, and Applications Demtröder, Laser Spectroscopy: Basic Concepts and Instrumentation Basic overview of lasers: Atkins, de Paula, Physical Chemistry Hollas, Modern Spectroscopy

4. 1.1 Lasers – an introduction What is a laser? “LASER”: Light Amplification by the Stimulated Emission of Radiation “A laser is a device that amplifies light and produces a highly directional, high intensity beam that most often has a very pure frequency or wavelength” [Silfast]

5. Lasers have unique characteristics as light sources: Other properties: Pulsed or continuous operation Tunable Polarised light Directionality Monochromaticity Coherence Brightness

6. Video: Applications of lasers Why are these properties useful? CharacteristicAdvantageApplications High powerMultiphoton process Improved signal High scattering intensity Nonlinear spectroscopy Improved sensitivity Raman scattering MonochromaticHigh resolution State selection Spectroscopy Isotope separation Collimated beamLong path lengthsSensitivity CoherentInterference between separate beamsCARS PulsedPrecise timing of excitation Pump-probe studies Relaxation processes Energy transfer Fast reactions

7. 1. Gain medium 2. Laser pumping energy 3. High reflector 4. Output coupler 5. Laser beam Principal components of a laser

8. Preconditions for laser operation “Population inversion” - consider populations of and transitions between energy levels in molecules in the gain medium (1) Optical cavity - look at the physical design of a laser – cavity formed by the high reflector (3) and output coupler (4) 1. Gain medium 2. Laser pumping energy 3. High reflector 4. Output coupler 5. Laser beam

9. A short sketch of laser history 1917: Einstein – stimulated absorption and emission of light 1954: Charles Townes and Schawlow – maser, prediction of the optical laser Nobel Prize (1964) 1960: Theodore Maiman – first demonstration of a laser: Ruby laser Rapid progress in the 1960s: 1961: first gas laser, first Nd laser 1962: first semiconductor laser 1963: CO 2 laser (IR)