Abstract: A passively mode-locked solid-state laser is designed to emit a continuous-wave train (51, 52) of electromagnetic-radiation pulses, the fundamental repetition rate of the emitted pulses exceeding 1 GHz, without Q-switching instabilities. The laser includes an optical resonator (3.1), a solid-state laser gain element (2) placed inside the optical resonator (3.1), a device (1) for exciting said laser gain element (2) to emit electromagnetic radiation having the effective wavelength, and a device (4) for passive mode locking including a saturable absorber. The laser gain element (2) is a laser material with a stimulated emission cross section exceeding 0.8×10?18 cm2 at the effective wavelength, and is made of Nd:vanadate. The saturable absorber (4) is preferably a semiconductor saturable absorber mirror (SESAM) device. Even higher repetition rates are achieved by operating the laser in the soliton regime. For use in fiber-optical telecommunication, the laser wavelength is preferably shifted to 1.

Abstract: According to the invention, a semiconductor saturable absorber mirror device for reflecting at least a proportion of electromagnetic radiation of essentially one given optical frequency impinging on said device, comprises a substrate with a Bragg reflector, and on top of this Bragg reflector a layered structure with at least one layer with saturably absorbing semiconductor material. A low index dielectric coating layer is placed on said outermost surface of said structure. The Bragg reflector and said layered structure are designed in a manner that the field intensity of radiation of said given frequency takes up a maximum at or near the interface between said structure and said dielectric material. The thickness of said dielectric coating layer may be varied and may for example be a quarter of a wavelength of said electromagnetic radiation in the dielectric material.

Abstract: A multiplexer for producing an output continuous-wave train of electromagnetic radiation pulses from an input continuous-wave train of electromagnetic radiation pulses is disclosed, the pulse repetition frequency of the output train of pulses exceeding the pulse repetition frequency of the input train of pulses. The time domain multiplexer comprises a planar lightwave integrated circuit (PLC) at least two integrated beam couplers and at least two intermediate integrated waveguide paths arranged between said beam couplers, the optical lengths of said two waveguide paths being different. The optical beam path difference is chosen and said time beam couplers are designed in a manner that said device is for multiplexing trains of electromagnetic pulses with an input pulse repetition frequency exceeding 1 GHz into at least one train of electromagnetic pulses with an output pulse repetition frequency being larger by a factor N≧2.

Abstract: An optically pumped laser with an Er:Yb: doped solid state gain element is disclosed, which is passively mode-locked by means of a saturable absorber mirror. The laser is designed to operate at a fundamental repetition rate exceeding 1 GHz and preferably at an effective wavelength between 1525 nm and 1570 nm. Compared to state of the art solid state pulsed lasers, the threshold for Q-switched-mode-locked operation is substantially improved. Thus, according to one embodiment, the laser achieves a repetition rate beyond 40 GHz. The laser preferably comprises means for wavelength tuning and repetition rate locking.

Abstract: According to the invention, a semiconductor saturable absorber mirror device for reflecting at least a proportion of electromagnetic radiation of essentially one given optical frequency impinging on said device, comprises a substrate with a Bragg reflector, and on top of this Bragg reflector a layered structure with at least one layer with saturably absorbing semiconductor material. A low index dielectric coating layer is placed on said outermost surface of said structure. The Bragg reflector and said layered structure are designed in a manner that the field intensity of radiation of said given frequency takes up a maximum at or near the interface between said structure and said dielectric material. The thickness of said dielectric coating layer may be varied and may for example be a quarter of a wavelength of said electromagnetic radiation in the dielectric material.

Abstract: An optically pumped laser with an Er:Yb: doped solid state gain element is disclosed, which is passively mode-locked by means of a saturable absorber mirror. The laser is designed to operate at a fundamental repetition rate exceeding 1 GHz and preferably at an effective wavelength between 1525 nm and 1570 nm. Compared to state of the art solid state pulsed lasers, the threshold for Q-switched-mode-locked operation is substantially improved. Thus, according to one embodiment, the laser achieves a repetition rate beyond 40 GHz. The laser preferably comprises means for wavelength tuning and repetition rate locking.

Abstract: Essentially non-linear optical material characteristics of a semiconductor material grown at low temperatures can be significantly improved by the following measures: Doping with foreign atoms and/or additional thermal annealing. If, for example GaAs grown at 300° C. is doped with Be to a concentration of 3·1019 cm−3, then the response time is reduced from 480 fs (curve 1.1) to 110 fs (curve 3.1), without the absorption modulation being reduced by this or the non-saturable absorption losses being increased. Semiconductor materials, during the production of which at least one of the above measures was implemented, manifest influenceable, in particular short response times as well as simultaneously high absorption modulations and low non-saturable absorption losses. For this reason, they are eminently suitable for non-linear optical applications, such as optical information processing, optical communication or ultrashort laser pulse physics.

Abstract: An optically pumped laser with an Er:Yb: doped solid state gain element is disclosed, which is passively mode-locked by means of a semiconductor saturable absorber mirror. The laser is designed to operate at a fundamental repetition rate exceeding 1 GHz and preferably at an effective wavelength between 1525 nm and 1570 nm. Compared to state of the art solid state pulsed lasers, the threshold for Q-switched-mode-locked operation is substantially improved. Thus, according to one embodiment, the laser achieves a repetition rate beyond 40 GHz. The laser preferably comprises means for wavelength tuning and repetition rate locking.

Abstract: A “low field enhancement” (LFR) semiconductor saturable absorber device design in which the structure is changed such that it has a resonant condition. Consequently, the field strength is substantially higher in the spacer layer, resulting in a smaller saturation fluence and in a higher modulation depth. However, the field in the spacer layer is still lower than the free space field or only moderately enhanced compared to the field in the free space. According to one embodiment, the absorber device is a Semiconductor Saturable Absorber Mirror (SESAM) device. In contrast with SESAMs according to the state of the art, a structure including the absorber and being placed on top of a Bragg reflector is provided, which essentially fulfills a resonance condition whereby a standing electromagnetic wave is present in the structure. In other words, the design is such that the field intensity reaches a local maximum in the vicinity of the device surface.

Abstract: A passively mode-locked solid-state laser for emitting a continuous-wave train of electromagnetic-radiation pulses, the fundamental repetition rate of the emitted pulses exceeding 1 GHz, without Q-switching has an optical resonator, a solid-state laser gain element placed inside the optical resonator, an exciter for exciting said laser gain element to emit electromagnetic radiation having the effective wavelength, and a saturable absorber for passive mode locking. The laser gain element preferably consists of a laser material with a stimulated emission cross section exceeding 0.8×10−18 cm−2 at the effective wavelength. Typically, the laser gain element is made of Nd:vanadate. The saturable absorber is preferably a semiconductor saturable absorber mirror device. The laser is simple, robust, compact, efficient, and low-cost.