Negative Group-delay-dispersion mirror (NGDD-mirror) multilayer structures include a generally-orderly arrangement of layers or groups of layers in which the function of certain individual layers or groups of layers can be recognized and defined. The structures are broadly definable as a rear group of layers which are primarily responsible for providing a desired reflection level and reflection bandwidth together with a low and smoothly varying reflection phase-dispersion, and a front group of layers which are primarily responsible for producing high reflection phase-dispersion necessary for providing a desired NGDD level and bandwidth. The front group of layers relies on multiple resonant trapping mechanisms such as two or more effective resonant-cavities, employing one or more sub-quarter-wave layers to shape the phase-dispersion for providing a substantially-constant NGDD. In certain embodiments of the structures, a base layer or substrate of a highly-reflective metal can be used to reduce the number of dielectric layers needed to provide high reflectivity.

A solid-state laser having an excitation light source, a lens system for focusing an excitation light produced from the light source, and a laser resonator which is laser-oscillated in response to the focused excitation light. The resonator includes only a gain medium and a solid-state medium having dispersion of a wavelength dependence opposite to that of the gain medium, and surfaces of the gain medium and the solid-state medium, which are respectively at opposite sides of opposing surfaces of the gain medium and the solid-state medium, are reflectively coated and act as mirror surfaces. At least one of the other surfaces of the gain medium and the solid-state medium, which ate positioned inside the resonator and are opposite to each other, is polished to a curved surface. The gain medium is excited by the focused excitation light so that the laser oscillation is made in the resonator.

In the wavelength-division-multiplexed optical transmission, laser diodes of the number of multiplicity are disposed as a light source to configure a transmitter. However, since this method requires a large number of light sources and highly precise wavelength control, a cost and an apparatus are increased. An ultrashort pulse solid-state laser is used as the light source of the transmitter and its wide spectrum is taken out by a splitter to be assigned to each channel, so that the number of light sources can be reduced greatly. The transmitter requires high repetition rate such as 2.4 GHz, 10 HGz and the like as the repetition rate of the ultrashort pulse solid-state laser, while by configuring the resonator only by two components as shown in FIG. 1, the high repetition rate can be attained. Since each channel is produced passively from the splitter, very precise wavelength management is not required. The light source is made small and the number thereof is reduced. Consequently, the whole apparatus is made small and a cost thereof is also reduced.

A mirror system for use in generating a short duration laser pulse is disclosed. The system includes first and second double-chirped mirrors disposed along an optical path within a cavity, where the second double-chirped mirror includes an additional phase-shifting layer as compared to the first double-chirped mirror. The additional phase-shifting layer causes the mirror system during use to produce a laser pulse that is characterized by oscillations in group delay substantially reduced in amplitude in comparison to oscillations in group delay for a pulse produced by the same system without the additional phase-shifting layer.

Systems, configurations and methods of using an ultrafast, self-starting, mode-locked laser are provided. The systems, devices and methods of using stable, self-starting mode-locked lasers, can be compact, use fewer optical elements and have energies sufficient for most micro-processing and micro-structuring applications. The large spectral bandwidth of ultra-short (femtosecond) laser pulses can be used in laser sensing applications, micro-machining, time-resolved experiments, where short-lived transient species can be observed in biological or chemical reactions. Terahertz radiation can be generated using ultrashort pulses and used for imaging applications.