![]() The tunable laser light source ( C-WAVE) is based on Optical Parametric Oscillator (OPO) technology. In contrast to the fixed wavelength laser above, a tunable source of cw laser light was also used to investigate how the Brillouin signals varied with wavelength. The wavelength and power level is well suited for spectroscopy of magnons in metallic ferromagnets such as permalloy. In addition, the linewidth of the laser must be very narrow (70 dB and 200 mW output power was used ( Cobolt Calypso 491 nm). In order to expose the resulting weak Brillouin signals, the laser line must have typically better than 70 dB side mode suppression, and in some cases as good as 100 dB. The resulting photon to phonon/magnon interaction results in a very weak Brillouin signal typically in the low frequency GHz region in relation to the incident laser light. The term Brillouin light scattering refers to the nonlinear optical creation of an acoustic phonon or a magnon. Characterization of laser sources for Brillouin scattering Both fields of research promise to play important roles in future generations of computation devices. These are used in spintronics and magnonics, new approaches to use magnetic effects in computing to overcome limitations of the current CMOS (Complementary Metal Oxide Semiconductor) architecture. In this post, we discuss the laser characteristics needed for Brillouin spectroscopy and show that this technique can be used to characterize the magnetic properties of ferromagnetic thin films. This puts even higher demands on the spectral purity and linewidth of the incident laser light in order to reveal the very weak Brillouin signal, when compared with Raman spectroscopy. Although the physical processes of both can be compared up to a certain degree, the big difference is that the Brillouin signal lies in the GHz region and the Raman signal in the THz region in relation to the incident laser light. While Raman spectroscopy reveals the structure or chemical composition, Brillouin spectroscopy provides information on a larger scale such as the elastic or magnetic properties. In particular, two common nonlinear inelastic scattering methods, Raman and Brillouin scattering, both give important insight into the physical properties of the material under investigation. Nonlinear optical effects are exploited in a wide range of technologies. Imaging of hidden objects and indentification of dangerous materials. ![]()
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