US 5,515,394 AGranted

One dimensional beam expanding cavity for diode-pumped solid-state lasers

OwnerTong Zhanginventor

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Abstract

The pump region (9a-d) in the active medium (1a-d) excited by the pumping source (3a-b) is modeled of a thin layer shape or line shape for the side-pumping, and of a line shape for the end-pumping. The prism beam expander (2) as a mode-expanding device is used to expand TEM.sub.00 mode in one dimension resulting in a highly mode-matched fashion when the mode-expanding is required.

Claims20

Dependent claims

A laser pump/cavity arrangement, which can be used for regular lasers and tunable lasers, comprising:

a laser cavity forming means including an output mirror means and a rear mirror means serving as a light reflector;
a laser material means within said cavity;
a pump source means to provide the relevant pump light for pumping said laser material means;
a gain region within said laser material means;
a pumping coupling optics means placed between said pump source means and said laser material means for coupling the pump light from said pump source means to said laser material means so as to produce said gain region;
and
an one-dimensional beam expander means inserted within said laser cavity between said laser material means and said output mirror means;
wherein
(1) said gain region, which is positioned very close to said rear mirror means, is designed in the shape of a line vertical to the optical axis of said laser cavity in contrast to the commonly-used horizontal line, whereby minimizing or eliminating the spatial hole-burning effect to facilitate single longitudinal mode operation, and whereby resulting in scalable pumping capabilities and in a great reduction of the undesired thermo-optic effects, as well as leading to overcoming the key technical barrier and major limitation on the efficiency and effectiveness of diode lasers as the pump source, and on high power operation for diode end-pumped solid-state lasers;
(2) said one-dimensional beam expander means expands the TEM.sub.00 mode of said laser cavity in the dimension along the line defined by said gain region, whereby to obtain mode-matched pumping and TEM.sub.00 mode operation, and to provide both large and small beam waists in said laser cavity so as to be able to achieve mode-matched pumping and efficient intracavity frequency conversion at the same time;
(3) said pumping coupling optics means includes a collimating lens means for collimating said pump light if said pump light is not collimated light, and an one-dimensional focus lens means for tightly compressing the collimated pump light onto said laser material means for producing said gain region in the shape of a line;
(4) two parameters, line size Y and Z are introduced hereof to designate the two dimensions of the cross section of the line gain region;
said line size Z is defined to be the dimension of said cross section parallel to the optical axis of said laser cavity;
and said line size Y is defined to be the dimension of said cross section along the dimension unexpanded by said beam expander means and perpendicular to the optical axis of said laser cavity;
(5) said line size Y is predetermined to match the TEM.sub.00 mode size of said laser cavity approximately in the unexpanded dimension;
and
(6) based on reducing the spatial hole-burning effect, said line size Z is predetermined to be the value, which is less than a few millimeter and, equivalently and more precisely in the frequency domain in the laser physics, should lead to that the laser oscillation within the laser cavity has an oscillating mode interval equal to or larger than twice that of the free spectral range of the laser cavity.

14 more elements

A laser pump/cavity arrangement is configured with the side-pumping scheme, which can be used for regular lasers and tunable lasers, comprising:

a laser cavity forming means including an output mirror and a rear mirror means serving as a light reflector;
a laser material means within said cavity;
a pump source means to provide the relevant pump light for pumping said laser material means;
a gain region within said laser material means produced by said pump light;
and
an one-dimensional beam expander means inserted within the laser cavity between said laser material means and said output mirror;
wherein
(1) said gain region is designed in the shape of a thin layer, whereby resulting in a) a favorable condition for mode-matched pumping, b) a great flexibility in pump condition and pump arrangement with uniform pump, c) maximizing the absorption of pump power in said gain region thus leading to a high gain, d) scalable pumping capabilities, e) a great reduction of the undesired thermo-optic effects, as well as f) overcoming the key technical barrier and major limitation on the efficiency and effectiveness of diode lasers as the pump source;
(2) the shape and absorption coefficient of said laser material means at the pump wavelength are predetermined in the optimized condition for a) producing said gain region in the shape of a thin layer, b) concentrating the pump power in the central lasing area, c) maximizing the absorption efficiency of said laser material means, and d) obtaining uniform pump;
(3) three parameters, dimension X, Y and Z, are introduced hereof for designating the three dimensions of said gain region;
dimension X is defined to be the size of said gain region along the dimension expanded by said one-dimensional beam-expander means, dimension Y is defined to be the thickness of said gain region, and dimension Z is defined to be the size of said gain region along the optical axis of said laser cavity, respectively;
(4) said one-dimensional beam expander means expands the TEM.sub.00 mode of said laser cavity along said dimension X, whereby to obtain mode-matched pumping and TEM.sub.00 mode operation, and to provide both large and small beam waists in one compact cavity so as to be able to achieve mode-matched pumping and efficient intracavity frequency conversion at the same time;
and
(5) said dimension Y is predetermined to be around 3 millimeter or less so as to match the TEM.sub.00 mode size of said laser cavity approximately in the unexpanded dimension.

11 more elements

A laser pump/cavity arrangement with the side-pumping scheme for diode-pumped solid-state lasers, which can also be used for diode-pumped tunable solid state lasers and diode-pumped laser amplifiers, comprising:

a laser cavity forming means;
a solid-state laser material means within said cavity;
a laser diode means selected from the group consisting of 2-D stacked diode bars and a group of linear array laser diode bars, to provide the relevant pump light for pumping said laser material means;
a gain region within said laser material means;
and
a pumping coupling optics means placed between said pump source means and said laser material means for coupling the pump light from said pump source means to said laser material means so as to produce said gain region;
wherein
(1) said gain region is designed in the shape of a line along the optical axis of the laser cavity, whereby resulting in a) a favorable condition for mode-matched pumping, b) scalable pumping capabilities, c) a large flexibility in pump conditions, and d) overcoming the key technical barrier and major limitation on the efficiency and effectiveness of diode lasers as the pump source;
(2) the absorption coefficient of said laser material means at the pump wavelength is predetermined and large enough for obtaining a short pump depth so as to produce said gain region in the shape of a line whose size is around 2 millimeter or less to match the relevant mode size of said laser cavity;
and
(3) said pumping coupling optics means includes an one-dimensional collimating lens means, such as a group of fiber rod lenses, placed at the front of said laser diode means for collimating the pump light if the pump light is not collimated light, and an one-dimensional focus lens, such as a cylindrical lens, placed at the front of laser material means, whose compressibility is predetermined to be powerful enough for tightly compressing the collimated pump light onto said laser material means, so as to produce said gain region in the shape of a line whose size is around 2 millimeter or less to match the relevant mode size of said laser cavity.

8 more elements

Dependencies are inferred from the claim text.

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Abstract

A laser pump/cavity arrangement, which can be used for regular lasers and tunable lasers, comprising:

a laser cavity forming means including an output mirror means and a rear mirror means serving as a light reflector;
a laser material means within said cavity;
a pump source means to provide the relevant pump light for pumping said laser material means;
a gain region within said laser material means;
a pumping coupling optics means placed between said pump source means and said laser material means for coupling the pump light from said pump source means to said laser material means so as to produce said gain region;
and
an one-dimensional beam expander means inserted within said laser cavity between said laser material means and said output mirror means;
wherein
(1) said gain region, which is positioned very close to said rear mirror means, is designed in the shape of a line vertical to the optical axis of said laser cavity in contrast to the commonly-used horizontal line, whereby minimizing or eliminating the spatial hole-burning effect to facilitate single longitudinal mode operation, and whereby resulting in scalable pumping capabilities and in a great reduction of the undesired thermo-optic effects, as well as leading to overcoming the key technical barrier and major limitation on the efficiency and effectiveness of diode lasers as the pump source, and on high power operation for diode end-pumped solid-state lasers;
(2) said one-dimensional beam expander means expands the TEM.sub.00 mode of said laser cavity in the dimension along the line defined by said gain region, whereby to obtain mode-matched pumping and TEM.sub.00 mode operation, and to provide both large and small beam waists in said laser cavity so as to be able to achieve mode-matched pumping and efficient intracavity frequency conversion at the same time;
(3) said pumping coupling optics means includes a collimating lens means for collimating said pump light if said pump light is not collimated light, and an one-dimensional focus lens means for tightly compressing the collimated pump light onto said laser material means for producing said gain region in the shape of a line;
(4) two parameters, line size Y and Z are introduced hereof to designate the two dimensions of the cross section of the line gain region;
said line size Z is defined to be the dimension of said cross section parallel to the optical axis of said laser cavity;
and said line size Y is defined to be the dimension of said cross section along the dimension unexpanded by said beam expander means and perpendicular to the optical axis of said laser cavity;
(5) said line size Y is predetermined to match the TEM.sub.00 mode size of said laser cavity approximately in the unexpanded dimension;
and
(6) based on reducing the spatial hole-burning effect, said line size Z is predetermined to be the value, which is less than a few millimeter and, equivalently and more precisely in the frequency domain in the laser physics, should lead to that the laser oscillation within the laser cavity has an oscillating mode interval equal to or larger than twice that of the free spectral range of the laser cavity.

14 more elements