The present invention is an improved modelocked laser comprising an optical gain medium and an optical cavity including a self-tuning saturable reflector incorporating one or more quantum wells. In the improved laser, the self-tuning saturable reflector comprises a first Bragg grating having a reflection spectrum broader than the spectrum of desired lasing and an additional Bragg reflector for light in the spectral region of lasing to provide self-starting and stable operation without mechanical tuning. The Bragg reflectors are preferably semiconductor quarter wave reflector stacks, and the saturable absorber is one or more quantum wells within the outer stack. The invention also encompasses the new saturable reflector used in such lasers.

A mode-locking device for a laser operating at a defined wavelength, has a substrate, transparent to the defined wavelength, with a front side for receiving, incident radiation and a back side. An anti-reflection coating is formed on the front side to minimize reflection loss at the defined wavelength. A quantum well structure is arranged on the back side. A high reflectance structure is arranged behind the quantum well structure in such a way that an electric field peak in the incident radiation lies coincides with that of the quantum well structure. This device offers a more reliable and less costly approach for the production of non-linear mirrors since the layers of the dielectric stack do not have to be formed by epitaxial deposition.

The solid state laser comprises a laser gain medium (1), pumping means for pumping the laser gain medium, and a laser cavity having a first end (3) and a second end (17), wherein the laser gain medium is at, or in the vicinity of, said first end (3) of said cavity. A semiconductor saturable absorber mirror (SESAM) can be placed at the second end (17) of the cavity. The laser gain medium can comprise at least one face for receiving pumping energy from the pumping means, the face being made reflective at a laser frequency of the laser, so that it can form the first end of the laser cavity. The resulting setup used for generating femtosecond laser pulses.

A self starting, self mode-locked laser is disclosed that utilizea gain saturation lens and an optical Kerr lens to start and to sustain passive mode locking. The laser consists of a resonant cavity which has a saturable gain medium and an optical Kerr lens medium. The laser cavity is described such that the loss modulation induced by the gain saturation lens is cascaded to that of the optical Kerr lens to start the mode locking process, while the loss modulation of the Kerr lens maintains the mode locking. The self mode locking operation restores automatically without any additional induction mechanism, after the pump laser beam or the laser cavity is blocked and then unblocked. In a preferred embodiment, the laser includes a resonant cavity , a Ti:sapphire crystal which produces both the gain saturation lens and the optical Kerr lens, a prism pair for ultra-short pulse operation, and a slit for laser bandwidth control and wavelength tuning. This laser can produce stable pulses shorter than 100 femtosecond.

A device for generating tunable light pulses has a non-linear optical fiber. The optical spectrum of femtosecond light pulses can be modified by this optical fiber, taking advantage of solitonic effects. In order to make available such a device, which makes it possible to vary the pulse energy and the wavelength of the light pulses independently of one another, an optical compressor precedes the non-linear optical fiber.