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US 2004/0071179 A1Published application
Optical resonant frequency converter
AssigneeNLG New Laser Generation GmbH
InventorsEckhard Zanger, Manfred Salzmann
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AssigneeNLG New Laser Generation GmbH
InventorsEckhard Zanger, Manfred Salzmann
Estimating the term…
The invention concerns an optical resonant frequency converter comprising two mirrors and a non-linear crystal in a ring resonator arrangement for converting laser radiation into frequency-doubled radiation. Because of the refractive effect of the prism-shaped, non-linear crystal two mirrors are sufficient to form a ring resonator with a total of three optical elements. A suitable choice of the orientation of the crystal axes in relation to the laser beam direction reduces scatter in the crystal. In one embodiment the entry surface of the crystal is at the Brewster angle while the exit surface is perpendicular to the beam and has an antireflection coating. In another embodiment the converted beam is coupled out through a polarisation beam splitter layer on one of the crystal surfaces. In a further embodiment the crystal surfaces are cylindrically curved. That produces an elliptical beam profile in the crystal, which reduces the walk-off effect.
An optical resonant frequency converter comprising a ring resonator which includes a first mirror, a second mirror and a non-linear crystal with an entry surface and an exit surface which are so arranged that a light wave can pass into the non-linear crystal in the form of a first laser beam through the entry surface and can issue therefrom again through the exit surface, wherein the light wave is partially converted in the non-linear crystal into a second light beam of a different frequency, characterised in that the normal to the entry surface of the non-linear crystal is approximately at the Brewster angle relative to the light wave incident into the crystal and the incident light wave is polarised parallel to the resonator plane, the exit surface of the non-linear crystal is antireflectively coated both for the frequency of the first and also the second laser beam and the normal to the exit surface is at an angle of less than 15 degrees relative to the light wave issuing from the crystal.
An optical resonant frequency converter including a ring resonator comprising a first mirror, a second mirror and a non-linear crystal with an entry surface and an exit surface which are so arranged that formed in the ring resonator is a light wave which circulates in a resonator plane and which passes into the non-linear crystal as a first laser beam through the entry surface and issues therefrom again through the exit surface and which is partially converted in the non-linear crystal into a second laser beam which is at a higher frequency than the first laser beam, characterised in that the normal to the entry surface of the non-linear crystal is approximately at the Brewster angle relative to the light wave incident into the crystal, the normal to the exit surface of the non-linear crystal is approximately at the Brewster angle relative to the light wave issuing from the crystal, the light wave circulating in the ring resonator is polarised parallel to the resonator plane, the exit surface of the non-linear crystal is provided with a polarisation beam splitter layer which is substantially transparent for the frequency of the first laser beam and reflecting for the frequency of the second laser beam, the non-linear crystal has a third surface which is antireflectively coated for the frequency of the second laser beam and the second laser beam is reflected at the polarisation beam splitter layer and issues from the non-linear crystal through the third surface.
An optical resonant frequency converter comprising a ring resonator which includes a first mirror, a second mirror and a critically phase-matched non-linear crystal having an entry surface and an exit surface which are not parallel to each other, which are so arranged that formed in the ring resonator is a circulating light wave which passes into the non-linear crystal as a first laser beam through the entry surface and issues therefrom again through the exit surface and which is partially converted in the non-linear crystal into a second laser beam which is at a higher frequency than the first laser beam, characterised in that the crystallographic axes of the non-linear crystal are so oriented relative to the direction of the incident light wave that the square of the effective non-linear coefficient is near to or equal to the maximum value in respect of its angle dependency and that the non-linear crystal scatters as small a part as possible of the incident light wave in the direction opposite to the direction of propagation of the incident light wave.
An optical resonant frequency converter comprising a ring resonator which includes a first mirror, a second mirror and a critically phase-matched non-linear crystal having an entry surface and an exit surface which are so arranged that formed in the ring resonator is a light wave which circulates in a resonator plane and which passes into the non-linear crystal as a first laser beam through the entry surface and issues therefrom again through the exit surface and which is partially converted in the non-linear crystal into a second laser beam which is at double the frequency of the first laser beam, characterised in that at least one of the two surfaces of the non-linear crystal has a cylindrical curvature, wherein the axes of symmetry of said cylinder surfaces lie in the resonator plane, at least one of the two mirrors has a cylindrical curvature, wherein the axes of symmetry of said cylinder surfaces are perpendicular to the resonator plane, the principal section plane of the non-linear crystal is perpendicular to the resonator plane and the beam cross-section of the light wave in the non-linear crystal is of an elliptical shape whose longer semiaxis is in the principal section plane of the non-linear crystal.
Dependencies are inferred from the claim text.