The resonant laser ionisation uses the fact that each element has specific frequencies to absorb and emit light. By choosing the correct resonance it is possible to excite and ionise only the desired element. The line width has to be in the range of a few gigahertzes 5 GHz to cover the Doppler broadening and level splitting. For this purpose a laser light source with the right attributes is needed. With the development of the Titanium Sapphire laser a new widely tuneable laser light source is available. The standard wavelength range reaches from 650 nm up to 1100 nm. Those properties make the laser perfect for the resonant laser ionisation. This book describes the necessary theory to setup such a laser and to determine its properties. Those are investigated during miscellaneous experiments and presented along with the design work on a Z-Resonator Titanium-Sapphire Laser. This book will be a useful tool to every one determining laser parameters and working with the resonant laser ionis