Danmarks Tekniske Universitet

Forskningscenter Riso

Peter Eskil Andersen

Paul Michael Petersen

Ole Bjarlin Jensen

Anders Overgaard Bjarklev

Andreas Tycho

André Müller

Ole Jensen Bjarlin

Anders Kragh Hansen

Andrea Tycho

The present invention relates to an apparatus comprising a diode laser () providing radiation in a first wavelength interval, a radiation conversion unit () having an input and an output, the radiation converter configured to receive the radiation in the first wavelength interval from the diode laser at the input, the radiation conversion unit configured to convert the radiation in the first wavelength interval to radiation in a second wavelength interval and the output configured to output the converted radiation, the second wavelength interval having one endpoint outside the first wavelength interval. Further, the invention relates to a method of optically pumping a target laser () in a laser system, the laser system comprising a laser source providing radiation at a first frequency, the laser source being optically connected to an input of a frequency converter, the frequency converter configured to convert the radiation at the first frequency to a second, different frequency, the target laser arranged in optical communication with an output of the frequency converter, the method comprising the steps of emitting radiation from the laser source, receiving the radiation at the frequency converter, converting the radiation from the first frequency to the second frequency in the frequency converter, and providing the radiation at the second frequency at the target laser so that the target laser is optically pumped.

Laser system with wavelength converter

A laser apparatus generating frequency converted light. Embodiments of the laser apparatus described herein apply a cascade of nonlinear frequency mixer for sum frequency generation (SFG) or difference frequency generation (DFG) between two frequency components of a spectrally combined laser beam with at least two spectral components originating from two respective laser sources, SFG of two frequency components beams offers up to a factor of four amplification of output power over SHG of a single laser beam.

Laser apparatus with cascade of nonlinear frequency mixers

A method of controlling beam quality and stability of a laser apparatus, the laser apparatus comprising, a diode laser () providing first radiation of at least a first wavelength, and a frequency conversion unit () configured to frequency-convert the first radiation from the diode laser and to output the frequency-converted radiation (), the frequency-converted radiation having at least a second wavelength different from the first wavelength, the diode laser () comprising at least a first and a second section (), a first contact () for injecting a first current (I) into the first section (), a second contact () for injecting a second current (I) into the second section (), and means for controlling a temperature of the diode laser; wherein the method comprises monitoring a first parameter indicative of the power content of a dominant lobe of the first radiation; iteratively determining a combination of respective values of the first current, the second current and the temperature at which combination of respective values the monitored first parameter and a stability parameter indicative of a fluctuation over time of the monitored first parameter each fulfills a respective predetermined optimization criterion; and setting the first current, the second current, and the temperature to the determined combination of respective values.

The present invention relates to an apparatus comprising a diode laser () providing radiation in a first wavelength interval, a radiation conversion unit () having an input and an output, the radiation converter configured to receive the radiation in the first wavelength interval from the diode laser at the input, the radiation conversion unit configured to convert the radiation in the first wavelength interval to radiation in a second wavelength interval and the output configured to output the converted radiation, the second wavelength interval having one end point outside the first wavelength interval. Further, the invention relates to a method of optically pumping a target laser () in a laser system, the laser system comprising a laser source providing radiation at a first frequency, the laser source being optically connected to an input of a frequency converter, the frequency converter configured to convert the radiation at the first frequency to a second, different frequency, the target laser arranged in optical communication with an output of the frequency converter, the method comprising the steps of emitting radiation from the laser source, receiving the radiation at the frequency converter, converting the radiation from the first frequency to the second frequency in the frequency converter, and providing the radiation at the second frequency at the target laser so that the target laser is optically pumped.

The present invention relates to an apparatus for optical coherence reflectometry, in particular for optical coherence tomography, wherein the apparatus for optical coherence reflectometry comprises a wavelength scanning laser source for providing a light signal, and splitting means for dividing said light signal into a sample light field and a reference light field, wherein the sample light field is directed to the sample being measured, and the light reflected from the sample is amplified without correspondingly amplifying the light reflected in the reference light field. Thereby, it is possible to direct substantially all light energy from the first reflected light field to the detectors, and to obtain fully the utilization of the amplification of the first reflected light field. The optica amplifier inserted in the sample reflected light field is different from the source so that the effect of the light source may be regulated independent of the degree of amplification. In particular when using the apparatus in coherent optical FMCW reflectometry certain safety regulations for the power density towards the sample has to be observed to reduce the risk of damages to the sample under examination, such as biological tissue. The apparatus may be used for a variety of purposes, in particular for obtaining optical biopsies of transparent as well as non-transparent tissues.

Optical amplification in coherent optical frequency modulated continuous wave reflectometry

The present invention relates to an apparatus and a method for optical coherence reflectometry, in particular for optical coherence tomography. The invention particularly relates to the route of the light field in the sample arm. The reflected light field in the sample arm is amplified before being received by a combining means, said combining means being capable of receiving the reflected light field from the sample arm as well as the second reflected light field from the reference arm. Thereby, it is possible to direct substantially all light energy in the sample arm to the combining means, and to obtain fully the utilisation of the amplification of the reflected light field since preferably only the reflected light field is amplified by the optical amplifier. This leads to an improved signal-to-noise ratio (SNR) whereby an increase of the maximal penetration depth is obtained. Thereby, the apparatus is useful for obtaining optical biopsies of transparent as well as non-transparent tissues as well as new technical fields wherein the increased SNR allows the use of the present apparatus.

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Tølløse, Denmark

Peter Eskil Andersen