Photoluminescence Lasers

The first laser did not actually use visible light, but microwave radiation, and hence it was termed a maser. This device was developed by Charles H. Townes (b. 1915) in 1953, and in 1964 he shared the Nobel Prize in Physics with Nikolay 

Basov (1922-2001) and Aleksandr Prokhorov (1916-2002), two Russian physicists who independently discovered how to produce continuous output, something that Townes was unable to do. The three were cited for fundamental work in the field of quantum electronics, which has led to the construction of oscillators and amplifiers based on the maser-laser principle [29]. Since that time, many different types of lasers were developed—gas, solid-state, fiber, semiconductor, dye, etc.— and they have found use in hundreds of applications in virtually every field of endeavor such as the military, industry, law enforcement, medicine, entertainment, and basic research [29]. 

---

Serpone N. and Pelizzetti E. (1986), Fundamental studies into the primary events in photocatalysis employing CdS and Ti02 semiconductors. Photoluminescence, laser flash photolysis, and pulse radiolysis , in Homogeneous and Heterogeneous Photocatalysis, Pelizzetti E. and Serpone N., eds., Reidel Publ. Co., Dordrecht, The Netherlands, pp. 51-90. 

Interestingly, it has been argued that nanoparticulate formation might be considered as a possibility for obtaining new silicon films [379]. The nanoparticles can be crystalline, and this fact prompted a new line of research [380-383], If the particles that are suspended in the plasma are irradiated with, e.g., an Ar laser (488 nm), photoluminescence is observed when they are crystalline [384]. The broad spectrum shifts to the red, due to quantum confinement. Quantum confinement enhances the bandgap of material when the size of the material becomes smaller than the radius of the Bohr exciton [385, 386]. The broad PL spectrum shows that a size distribution of nanocrystals exists, with sizes lower than 10 nm. 

The photoluminescence measurements of Thewalt et al. (1985) were performed at 4.2 K with 200 mW of 514.5 nm excitation from an Ar-ion laser in a 4 mm-diameter spot. The spectrum was analyzed with a double-grating spectrometer using a cooled photomultiplier operating in the photon-counting mode. 

Li G, Mianami N (2003) Increase of photoluminescence from fullerenes-doped poly (alkyl methacrylate) under laser irradiation. Journal of Photoluminescence 104 207. 

Ohno T, Matsuishi K, Onari S (1997) Effects of laser irradiation on photoluminescence of C-60 single crystal with/without air exposure. Solid State Communications 101 785-789. 

Figure 1.8 A schematic diagram showing the main elements for measuring photoluminescence spectra. The excitation can also be produced using a laser instead of both a lamp and an excitation monochromator.

Photoluminescence spectroscopy provides information on the composition of the painting surface and the presence of retouchings and overpainting. This technique has progressively evolved using laser sources, giving rise to laser-induced fluorescence (LIP) spectroscopy [35]. 

Experimental technique used during these investigations is usual for Raman scattering and photoluminescence spectroscopy. For luminescence excitation He-Cd, He-Ne, and Ar+ ion lasers were used. The exciting light power not exceeds 25 mW in all experiments. 

The technique of up-conversion photoluminescence allows one to record the transient PL of a system at the temporal resolution of the laser pulse. It is used to study very fast processes below the picosecond time domain. A typical set-up for this experiment is shown in Fig. 3. The sample is excited at frequency uq by a femtosecond laser pulse and its PL at ujj- is mixed with that of an optically... 

---