Studying and understanding the world that surrounds us has been one of the main driving forces for scientific research. Identifying the particles and elements constituting the universe and determining their structure and behavior are tasks yet in progress, and of great interest for humankind. The study of matter interaction with different physical phenomena has enabled the development of the current physics models and technologies. Light has been a key source for the study of these physical phenomena, particularly since the invention of the laser. The present thesis entails the study and the application of nonlinear optical methods to produce laser light for spectroscopy and metrology, which are two of the most important techniques to gain insight on the properties of matter at atomic and molecular scales. Widely tunable lasers are pivotal tools for spectroscopy, such as in the resonance ionization and nuclear spectroscopic experiments. In this work, we have developed a tunable diamond Raman laser capable of fulfilling the requirements for such applications. We prove that it can produce pure ion beams efficiently by emitting tunable light in the hard-to-access visible spectral range (400-650 nm). Moreover, our device constitutes a simple add-on solution that can be easily integrated in established laser infrastructures, extending their capabilities to virtually any spectral range of interest. The study is accompanied by mathematical models and simulation tools for the design of GHz-class linewidth and efficient Raman lasers: these include a simulator based on steady-state stimulated Raman scattering equations, a higher Stokes order generation and polarization state simulator, and a photo-ionization model that considers the impact of laser spectral features on the ionization efficiency. In this regard, we also proposed a diamond Raman z-fold cavity with the potential of achieving higher ionization efficiency levels. The generality of the proposed tools further supports the design and optimization of Raman-based laser sources in a variety of fields of application. Perhaps, the main limitation of our lasers is in the need of specialized multi-layer reflective coatings. With the aim of granting an alternative all-diamond solution, we have evaluated the performance of laser produced metasurfaces, which can be beneficial for extending the wavelength reach at ever higher power densities.