Low speckle noise monolithic microchip RGB lasers
First Claim
1. A low speckle noise monolithic microchip laser comprising:
- two independent laser sources to produce two fundamental beams linearly polarized with mutually orthogonal polarizations;
a birefringent crystal for tilting propagation direction of one fundamental laser beam with polarization along the principal plane of said birefringent crystal, referred to as e-ray, and for combining said e-ray with another fundamental laser beam with polarization normal to the principal plane of said birefringent crystal, referred to as o-ray, at the output surface; and
a nonlinear optical crystal optically bonded to the birefringent crystal to generate a new wavelength based on sum frequency mixing of the two fundamental laser beams;
wherein;
each independent laser source further comprising a laser gain medium and a pump light;
the two laser gain media are optically bonded each other, both are optically bonded to the birefringent crystal;
the two pump lights are substantially parallel to each other and separated by a distance equal to the birefringent crystal length multiplied by the tangent walk-off angle;
said fundamental laser beams are generated in separate optical cavities with a common portion in the nonlinear optical crystal to eliminate the green problem;
wherein the exterior surface of the first gain medium, where the first pump beam enters, is coated highly reflective to the first fundamental wavelength and highly transmissive to the first pump wavelength;
wherein the exterior surface of the second gain medium, where the second pump beam enters, is coated highly reflective to the second fundamental wavelength and highly transmissive to the second pump wavelength;
the exterior surface of the nonlinear optical crystal is coated highly reflective to at least one of the first and second fundamental wavelengths and is highly transmissive to the converted wavelength via sum frequency mixing;
the interface between the birefringent crystal and the nonlinear optical crystal is coated highly transmissive to the first and second fundamental wavelengths and is highly reflective to the converted wavelength via sum frequency mixing;
wherein each of the two fundamental laser beams possesses at least two longitudinal modes such that the mode intervals of the e-ray and o-ray are different, and the sum frequency mixing between the two fundamental beams is non-degenerate, therefore, at least four longitudinal modes with unequal spacing and a narrowed bandwidth present in the laser output;
wherein;
the two pump lights are split from a single light source via a beam splitter;
wherein;
the polarization of the light from the light source is controlled by a wave plate or other polarization-sensitive elements, or a rotation of a free-space laser diode, or an optic fiber;
wherein;
said beam splitter includes any combination of the following;
polarization dependent elements including mirrors coated with polarization sensitive materials, polarization beam splitter, birefringent crystal, and prisms coated with polarization sensitive materials.
1 Assignment
0 Petitions
Accused Products
Abstract
A method for reducing speckle noise of a monolithic microchip laser with intracavity beam combining and sum frequency mixing is based on time averaging of uncorrelated speckle patterns generated from a large number of independent longitudinal modes and comprises schemes including selection of gain media and nonlinear optical materials to support broadband sum frequency mixing; adoption of gain-conjugated and/or chirped mirrors for flat-top spectra and/or mode phase diversification; multimode laser operation introduced by RF modulation; and multiplication of source modes in frequency mixing process featured with degeneration free and narrowed/uneven intervals. A device and an apparatus for generating low speckle noise red, green, blue lasers adaptable for color display systems are developed based on the inventive method.
69 Citations
8 Claims
-
1. A low speckle noise monolithic microchip laser comprising:
-
two independent laser sources to produce two fundamental beams linearly polarized with mutually orthogonal polarizations; a birefringent crystal for tilting propagation direction of one fundamental laser beam with polarization along the principal plane of said birefringent crystal, referred to as e-ray, and for combining said e-ray with another fundamental laser beam with polarization normal to the principal plane of said birefringent crystal, referred to as o-ray, at the output surface; and a nonlinear optical crystal optically bonded to the birefringent crystal to generate a new wavelength based on sum frequency mixing of the two fundamental laser beams; wherein; each independent laser source further comprising a laser gain medium and a pump light; the two laser gain media are optically bonded each other, both are optically bonded to the birefringent crystal; the two pump lights are substantially parallel to each other and separated by a distance equal to the birefringent crystal length multiplied by the tangent walk-off angle; said fundamental laser beams are generated in separate optical cavities with a common portion in the nonlinear optical crystal to eliminate the green problem; wherein the exterior surface of the first gain medium, where the first pump beam enters, is coated highly reflective to the first fundamental wavelength and highly transmissive to the first pump wavelength; wherein the exterior surface of the second gain medium, where the second pump beam enters, is coated highly reflective to the second fundamental wavelength and highly transmissive to the second pump wavelength; the exterior surface of the nonlinear optical crystal is coated highly reflective to at least one of the first and second fundamental wavelengths and is highly transmissive to the converted wavelength via sum frequency mixing; the interface between the birefringent crystal and the nonlinear optical crystal is coated highly transmissive to the first and second fundamental wavelengths and is highly reflective to the converted wavelength via sum frequency mixing; wherein each of the two fundamental laser beams possesses at least two longitudinal modes such that the mode intervals of the e-ray and o-ray are different, and the sum frequency mixing between the two fundamental beams is non-degenerate, therefore, at least four longitudinal modes with unequal spacing and a narrowed bandwidth present in the laser output; wherein; the two pump lights are split from a single light source via a beam splitter; wherein; the polarization of the light from the light source is controlled by a wave plate or other polarization-sensitive elements, or a rotation of a free-space laser diode, or an optic fiber; wherein; said beam splitter includes any combination of the following;
polarization dependent elements including mirrors coated with polarization sensitive materials, polarization beam splitter, birefringent crystal, and prisms coated with polarization sensitive materials. - View Dependent Claims (4, 5, 6, 7)
-
-
2. A low speckle noise monolithic microchip laser comprising:
-
two independent laser sources to produce two fundamental beams linearly polarized with mutually orthogonal polarizations; a birefringent crystal for tilting propagation direction of one fundamental laser beam with polarization along the principal plane of said birefringent crystal, referred to as e-ray, and for combining said e-ray with another fundamental laser beam with polarization normal to the principal plane of said birefringent crystal, referred to as o-ray, at the output surface; and a nonlinear optical crystal optically bonded to the birefringent crystal to generate a new wavelength based on sum frequency mixing of the two fundamental laser beams; wherein; each independent laser source further comprising a laser gain medium and a pump light; the two laser gain media are optically bonded each other, both are optically bonded to the birefringent crystal; the two pump lights are substantially parallel to each other and separated by a distance equal to the birefringent crystal length multiplied by the tangent walk-off angle; said fundamental laser beams are generated in separate optical cavities with a common portion in the nonlinear optical crystal to eliminate the green problem; wherein the exterior surface of the first gain medium, where the first pump beam enters, is coated highly reflective to the first fundamental wavelength and highly transmissive to the first pump wavelength; wherein the exterior surface of the second gain medium, where the second pump beam enters, is coated highly reflective to the second fundamental wavelength and highly transmissive to the second pump wavelength; the exterior surface of the nonlinear optical crystal is coated highly reflective to at least one of the first and second fundamental wavelengths and is highly transmissive to the converted wavelength via sum frequency mixing; the interface between the birefringent crystal and the nonlinear optical crystal is coated highly transmissive to the first and second fundamental wavelengths and is highly reflective to the convened wavelength via sum frequency mixing; wherein each of the two fundamental laser beams possesses at least two longitudinal modes such that the mode intervals of the e-ray and o-ray are different, and the sum frequency mixing between the two fundamental beams is non-degenerate, therefore, at least four longitudinal modes with unequal spacing and a narrowed bandwidth present in the laser output; wherein; one or more of the cavity mirrors are coated with gain compensation for obtaining flat-top spectra.
-
-
3. A low speckle noise monolithic microchip laser comprising:
-
two or more crystal layers stacked one above one, each layer represents an individual laser, further comprising; two independent laser sources to produce two fundamental beams; a birefringent crystal; and a nonlinear optical crystal to generate a new wavelength based on sum frequency mixing of the two fundamental laser beams; in each laser, at least one fundamental beam is generated by a gain medium that is end-pumped by a pump light; the birefringent crystal is sandwiched in between the gain medium and the nonlinear optical crystal with optical bonding, which forms an independent optical cavity resonated at the fundamental wavelength; wherein; each of the two fundamental laser beams possesses at least two longitudinal modes; one of the fundamental beams is an e-ray in the birefringent crystal and the other is an o-ray such that at the entrance to the birefringent crystal the e-ray and o-ray are substantially parallel and their separation equals the birefringent crystal length multiplied by the tangent walk-off angle; the mode intervals of the e-ray and o-ray are different, thereby, the sum frequency mixing between the two fundamental beams is non-degenerate, therefore, the laser output resultant from the sum frequency mixing possesses at least four longitudinal modes with unequal spacing and a narrowed bandwidth wherein; one or more of the cavity mirrors are coated with gain compensation for obtaining flat-top spectra. - View Dependent Claims (8)
-
Specification