Gigatera Ag

Spectra Physics Lasers, Inc.

Time-Bandwidth Products Ag

Intel Corporation

Ursula Keller

Kurt J Weingarten

Gabriel J Spuehler

Nicolai Matuschek

Lukas Krainer

Ruediger Paschotta

Franz X K&auml;rtner

Rüdiger Paschotta

Ian A Young

Markus Haiml

Rudiger Paschotta

Guenter Steinmeyer

Silke Schön

Juerg Aus Der Au

Dirk H Sutter

Lukas Gallmann

Heiko Unold

David Stephen Thomas

Reto Haering

Uwe Siegner

A surface emitting laser (SEL) with an integrated absorber. A lower mirror and an output coupler define a laser cavity of the SEL. A monolithic gain structure positioned in the laser cavity includes a gain region and an absorber, wherein a saturation fluence of the absorber is less than a saturation fluence of the gain region.

Surface emitting laser with an integrated absorber

A passively mode-locked solid-state laser is designed to emit a continuous-wave train () 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 (), a solid-state laser gain element () placed inside the optical resonator (), a device () for exciting said laser gain element () to emit electromagnetic radiation having the effective wavelength, and a device () for passive mode locking including a saturable absorber. The laser gain element () is a laser material with a stimulated emission cross section exceeding 0.8&#xd7;10cmat the effective wavelength, and is made of Nd:vanadate. The saturable absorber () 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 1.5 &#x3bc;m by use of an optical parametric oscillator. The laser is simple, robust, compact, efficient, and low-cost. It generates a relatively large average power of 100 mW and higher, which is useful for a number of optical probing and detection applications, in a beam () that is substantially a fundamental spatial mode.

High-repetition-rate passively mode-locked solid-state laser

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 passively mode-locked optically pumped semiconductor vertical-external-cavity surface-emitting laser (OPS-EXSEL) is disclosed. The laser is mode locked by a semiconductor saturable absorber mirror (SESAM) which forms part of an external cavity. Both the beam-quality limitations of edge-emitting lasers, and the power restrictions of electrically pumped surface-emitting lasers are overcome. The laser uses a semiconductor wafer in which a stack of quantum wells is grown adjacent to a single Bragg-mirror structure. Light from one or more multi-mode high-power diode lasers is focused onto the face of the wafer and pumps the wells by absorption in the barrier regions. The area of the laser mode on the active mirror can be about 10 times larger than the mode area on the facet of an edge-emitting laser, offering scope for the generation of high average power and large pulse energy. At the same time the external cavity enforces fundamental mode operation in a circular, near-diffraction-limited beam. With the laser, sub-picosecond pulse durations are achievable by eliminating coupled cavity effects and by external pulse compression. Band-gap engineering can be used to shape the pulses, or even integrate gain and saturable absorption within the same wafer. Thus, rugged, efficient pulsed laser sources with high average power in a nearly diffraction-limited beam, sub-picosecond pulse durations and multi-GHz repetition rates, which operate in a broad range of wavelengths accessible by bandgap engineering are made possible.

Passively mode-locked optically pumped semiconductor external-cavity surface-emitting laser

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&deg; C. is doped with Be to a concentration of 3&middot;10 cm , then the response time is reduced from 480 fs (curve ) to 110 fs (curve ), 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.

Optically nonlinear semiconductor material and a method for the production thereof

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.

Semiconductor saturable absorber mirror

The invention is a double chirped mirror and a method of constructing a double chirped mirror for a frequency range of electromagnetic radiation, comprising specifying a design including a plurality of layers, the plurality of layers being transparent to the electromagnetic radiation and having refractive indices which vary between layers in the plurality of layers, and wherein for a first set of layers the optical thickness of alternate layers in the set of layers varies monotonically and the total optical thickness of a layer and the two adjacent half layers in the set of layers varies monotonically. The design is optimized by adjusting the optical thickness of layers in the plurality of layers.

Double chirped mirror

The dielectric and/or semiconductor device influences the dispersion of electromagnetic radiation within a given spectral range. It comprises a substrate being essentially transparent to said electromagnetic radiation. The substrate has a first surface for incoupling said electromagnetic radiation into said substrate, and a second surface. The device further comprises a reflective multilayer structure on said second surface, said multilayer structure providing a controlled dispersion characteristic upon reflection of said electromagnetic radiation, e.g., a chirped mirror. The device is arranged in such a way that there is essentially no interference of electromagnetic radiation propagating in the direction of said multilayer structure and electromagnetic radiation reflected by said multilayer structure. An antireflection coating may be provided on the first surface of the substrate. With this device, oscillations in the group delay dispersion can almost completely be avoided.

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Zurich, Switzerland

Ursula Keller