Final Examination - Design of Lasers and Systems | ECEN 4843, Exams of Electrical and Electronics Engineering

Download Final Examination - Design of Lasers and Systems | ECEN 4843 and more Exams Electrical and Electronics Engineering in PDF only on Docsity! ECEN4813 Final Examination Spring 2003 Name: _________________________________ Team: ____________________________________ You are a scientist who has been working on developing a new gain medium for a laser. This material is a burdalyte crystal doped with a small amount of Saturinium ions. After many months of work you have succeeded in growing a crystal you think you can use to build a laser. You have a lot of data available from measurements you made on the laser crystal. At this point you will start to design and build the laser. Your goal is to design and build the most efficient laser possible that has a minimum beam divergence. The following pages contain data about the laser crystal and the mirrors and pump sources that you have available in the lab. Laser Crystal Data: • Burdalyte has a refractive index of 1.5. • Saturnium ions have the property that the degeneracies of all energy levels are equal g0 = g1 = g2 = g3. • Faces are AR coated with reflectance of 0.1% • Dimensions of laser crystal are 0.3×0.3×1.0 cm. Energy Level Diagram: The laser crystal has the energy level diagram shown below. There is one broad band and three narrow ones. There are three radiative transitions (radiative transitions emit or absorb light when an electron changes level) and three non-radiative transitions (ones which don’t emit or absorb light). The lifetimes of the non-radiative transitions are shown in the diagram below. The radiative transitions are not shown here. Measured Absorption Spectrum: This is the power absorption of the crystal as a function of wavelength. The transition corresponding to each absorption peak is shown in the boxes. The measured FWHM of the absorption peak is also shown. E3 E2 E1 E0= 0 eV E ne rg y τ = 0.5 µs τ = 1 µs τ = ∞ forbidden E ne rg y 200 300 400 500 Wavelength (nm) α (λ ) ( cm -1 ) 1 2 3 4 0→2 0→1 0→3 5 nm 1 nm 1 nm α (λ ) ( cm -1 ) 1 2 3 4