Cladding Pumped Thulium-Ytterbium Short Pulse Fiber Lasers

Abstract

This chapter describes double clad fiber along with cladding pump technique in which pump light is coupled in the inner cladding of fiber thereby interacting with doped core through total internal reflection. Lasers operating in continuous wave mode have limited output power. Their output power can be enhanced to a great extent by concentrating the available energy in a single or in a periodic sequence of optical pulses. This is achieved by Q-switch and modelock techniques. Q-switched and modelocked lasers can be real-ized by active and passive means. Active technique is based on active loss modulation by using mechanical, electro-optic or acousto-optic based modulators. However, such techniques require complicated electronic circuits and have limited gain bandwidth. The attention then moves towards the passive technique which is low cost, compact in size, gives reliable operation without high voltages and provides simple cavity design without need for external electronics. Passive technique employs a saturable absorber, based on materials like carbon nanotubes, graphene, molybdenum di-sulfide etc. A brief descrip- tion of pulsed fiber lasers and solitons in view of modelocking are described in the text. Moreover examples of Q-switched and modelocked lasers are also presented by using Thulium-Ytterbium co-doped double clad fiber. A cladding pump technique is employed for the purpose.