Gigatera Ag

Time-bandwidth Products Ag

Gabriel J Spuehler

Ursula Keller

Kurt J Weingarten

Lukas Krainer

Ruediger Paschotta

Rudiger Paschotta

Juerg Aus Der Au

David Stephen Thomas

A pulsed solid-state thin-disk laser comprises an optical resonator and a solid-state laser gain medium placed inside the optical resonator. The laser gain medium is in the shape of a thin plate or layer with two end faces, the extension of the end faces being greater than a thickness of said plate or layer measured in a direction perpendicular to one of the end faces. One of the end faces comprises a cooling surface, via which the laser gain medium is cooled. A pumping source is provided for exciting the laser gain medium to emit electromagnetic radiation. The thin-disk laser further comprises means for passive mode locking placed inside the optical resonator. The mode-locking means are preferably a semiconductor saturable absorber mirror (SESAM). The laser offers a high average power, a good beam quality, short pulses and a high efficiency. Problems such as thermal lensing, Q-switching instabilities and damages of the mode-locking means are avoided. Moreover, the output power of the laser is scalable, i.e., may be increased without increasing the above-mentioned problems.

Mode-locked thin-disk laser

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.

Semiconductor saturable absorber device, and laser

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.

Pulse-generating laser

A &ldquo;low field enhancement&rdquo; (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.

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Zurich, Switzerland

Gabriel J Spuehler