A modular, compact and widely tunable laser system for the efficient generation of high peak and high average power ultrashort pulses. Peak power handling capability of fiber amplifiers is expanded by using optimized pulse shapes, as well as dispersively broadened pulses. Dispersive pulse stretching in the presence of self-phase modulation and gain results in the formation of high-power parabolic pulses. To ensure a wide tunability of the whole system, Raman-shifting of the compact sources of ultrashort pulses in conjunction with frequency-conversion in nonlinear optical crystals can be implemented, or an Anti-Stokes fiber in conjunction with fiber amplifiers and Raman-shifters are used. Positive dispersion optical amplifiers are used to improve transmission characteristics. An optical communication system utilizes a Raman amplifier fiber pumped by a train of Raman-shifted, wavelength-tunable pump pulses, to thereby amplify an optical signal which counterpropagates within the Raman amplifier fiber with respect to the pump pulses.

A MOPA laser system that includes a seed laser configured to output pulsed laser light, an amplifier configured to receive and amplify the pulsed laser light emitted by the seed laser; and a pump laser configured to deliver a pump laser beam to both the seed laser and the amplifier.

The invention relates to scanning pulsed laser systems for optical imaging. Coherent dual scanning laser systems (CDSL) are disclosed and some applications thereof. Various alternatives for implementation are illustrated. In at least one embodiment a coherent dual scanning laser system (CDSL) includes two passively modelocked fiber oscillators. In some embodiments an effective CDSL is constructed with only one laser. At least one embodiment includes a coherent scanning laser system (CSL) for generating pulse pairs with a time varying time delay. A CDSL, effective CDSL, or CSL may be arranged in an imaging system for one or more of optical imaging, microscopy, micro-spectroscopy and/or THz imaging.

Provided is a passive Q-switch laser device possessing a power density controller (15) making power density of excitation light from an excitation light source (14) equal to or greater than power density so that delay time required for reaching oscillation after start of excitation of a laser gain medium (12) becomes equal to or shorter than a laser upper energy level lifetime of the laser gain medium (12).

A gas detection system uses intracavity fiber laser absorption spectroscopy. The fiber laser is stabilized by a saturable absorber, and the sensitivity is enhanced by multiple circulations of amplified spontaneous emission light under threshold conditions, and multi-longitudinal mode oscillation of the laser.

The invention relates to scanning pulsed laser systems for optical imaging. Coherent dual scanning laser systems (CDSL) are disclosed and some applications thereof. Various alternatives for implementation are illustrated, including highly integrated configurations. In at least one embodiment a coherent dual scanning laser system (CDSL) includes two passively modelocked fiber oscillators. The oscillators are configured to operate at slightly different repetition rates, such that a difference f.sub.r in repetition rates is small compared to the values f.sub.r1 and f.sub.r2 of the repetition rates of the oscillators. The CDSL system also includes a non-linear frequency conversion section optically connected to each oscillator. The section includes a non-linear optical element generating a frequency converted spectral output having a spectral bandwidth and a frequency comb comprising harmonics of the oscillator repetition rates. A CDSL may be arranged in an imaging system for one or more of optical imaging, microscopy, micro-spectroscopy and/or THz imaging.

The present disclosure relates to the design of fiber frequency comb lasers with low carrier phase noise. Examples of these low carrier phase noise oscillators can be constructed from both soliton and dispersion compensated fiber lasers via the use of intra-cavity amplitude modulators such as graphene modulators. In low carrier phase noise dispersion compensated fiber frequency comb lasers, graphene and/or bulk modulators can further be used, for example, for phase locking of one comb line to an external continuous wave (cw) reference laser via high bandwidth control of the repetition rate of the comb laser via the graphene modulator. As a result a low phase noise radio frequency (RF) signal can be generated. In some implementations, a frequency comb exhibiting phase noise suppression of at least about 10 dB over a frequency range up to about 100 kHz is provided.

A passively mode-locking laser and corresponding method is described. The laser comprises a resonator (2) terminated by first (3) and second (4) mirrors and folded by a third (5) and fourth (6) mirror. The third mirror comprises a reflector (14) surmounted by a multilayer semiconductor gain medium (15) including at least one quantum well layer while the second mirror (4) comprises an intensity saturable mirror. The resonator is configured to provide a cross sectional area of an intra cavity resonating field on the intensity saturable mirror that is greater than or equal to a cross sectional area of the intra cavity resonating field on the multilayer semiconductor gain medium. This arrangement provides a passively mode-locking laser that exhibits increased stability when compared to those systems known in the art.

An optical window member includes an incident surface onto which a laser light is directed and an exit surface from which the laser light exits. At least one of the incident surface and the exit surface has a plurality of protrusions or recesses formed therein. An interval between centers of adjacent protrusions or adjacent recesses is shorter than or equal to a wavelength of the laser light.

A surface-emitting semiconductor laser system contains at least one MQW unit of at least three constituent QWs, axially separated from one another substantially non-equidistantly. The MQW unit is located within the axial extent covered, in operation of the laser, by a half-cycle of the standing wave of the field at a wavelength within the gain spectrum of the gain medium; immediately neighboring nodes of the standing wave are on opposite sides of the MQW unit. So-configured MQW unit can be repeated multiple times and/or complemented with individual QWs disposed outside of the half-cycle of the standing wave with which such MQW unit is associated. The semiconductor laser further includes a pump source configured to input energy in the semiconductor gain medium and a mode-locking element to initiate mode-locking.