US5574740A — Deep blue microlaser

Claim 1

Independent Claim 235 words

A laser comprising: an active gain medium comprising a rare earth doped microlaser crystal selected from the group consisting of neodymium-doped yttrium orthovanadate (Nd:YVO 4 ) and neodymium-doped gadolinium orthovanadate (Nd:GdVO 4 ), said gain medium having two opposite faces, one said face being an input face, said gain medium having a polarized emission at the fundamental wavelength of about 912-914 nm when optically pumped; a nonlinear frequency doubling crystal oriented to phase match at about 912-914 nm, thereby defining the polarization orientation and the propagation axis relative to said nonlinear crystal, said nonlinear crystal having two opposite faces, said gain medium and nonlinear crystal being bonded together to form a composite resonant cavity having a propagation axis, said non linear crystal face located opposite to its said face adjacent said gain medium being the output face of said laser; the distance between said input and output faces ranging between about 0.2 mm and 12 mm, the doping concentration of said gain medium ranging between 0.3 and 2.0%; and optical pumping means in effective operative relationship with said gain medium, for pumping said gain medium, frequency-doubling occurring in said composite cavity to generate blue light from the fundamental frequency of said gain medium at about 456-457 nm, said gain medium exhibiting laser action at the 4 F 3/2 → 4 I 9/2 914-nm transition when said gain medium is pumped by said optical pumping means.

Claim 2

Dependent Claim 235 words

A laser comprising: an active gain medium comprising a rare earth doped microlaser crystal selected from the group consisting of neodymium-doped yttrium orthovanadate (Nd:YVO 4 ) and neodymium-doped gadolinium orthovanadate (Nd:GdVO 4 ), said gain medium having two opposite faces, one said face being an input face, said gain medium having a polarized emission at the fundamental wavelength of about 912-914 nm when optically pumped; a nonlinear frequency doubling crystal oriented to phase match at about 912-914 nm, thereby defining the polarization orientation and the propagation axis relative to said nonlinear crystal, said nonlinear crystal having two opposite faces, said gain medium and nonlinear crystal being bonded together to form a composite resonant cavity having a propagation axis, said non linear crystal face located opposite to its said face adjacent said gain medium being the output face of said laser; the distance between said input and output faces ranging between about 0.2 mm and 12 mm, the doping concentration of said gain medium ranging between 0.3 and 2.0%; and optical pumping means in effective operative relationship with said gain medium, for pumping said gain medium, frequency-doubling occurring in said composite cavity to generate blue light from the fundamental frequency of said gain medium at about 456-457 nm, said gain medium exhibiting laser action at the 4 F 3/2 → 4 I 9/2 914-nm transition when said gain medium is pumped by said optical pumping means.

Claim 3

Dependent Claim 15 words

The laser recited in claim 1, wherein said gain medium crystal is a thin etalon.

Claim 4

Dependent Claim 17 words

The laser recited in claim 1, wherein said gain medium is characterized by having broad absorption bands.

Claim 5

Dependent Claim 21 words

The laser recited in claim 1, wherein said gain medium crystal and said frequency doubling crystal are bonded together with epoxy.

Claim 6

Dependent Claim 22 words

The laser recited in claim 1, and further comprising a dielectric spacer between said gain medium crystal and said frequency doubling crystal.

Claim 7

Dependent Claim 18 words

The laser recited in claim 5, wherein said spacer is annular in shape and said dielectric is air.

Claim 8

Dependent Claim 28 words

The laser recited in claim 1, wherein said gain medium crystal etalon has a thickness between said faces ranging between about 0.1 and 2.0 mm mm in length.

Claim 9

Dependent Claim 20 words

The laser recited in claim 1, wherein said gain medium crystal is no more than 2 mm between said faces.

Claim 10

Dependent Claim 20 words

The laser recited in claim 1, wherein said gain medium crystal ranges between 0.1 and 0.6 mm between said faces.

Claim 11

Dependent Claim 68 words

The laser recited in claim 1, wherein said gain medium crystal is made from an etalon of neodymium-doped yttrium orthovanadate (Nd:YVO 4 ) bonded to said nonlinear frequency doubling crystal to form said composite cavity having said input and output faces which are external, opposite, flat, parallel, and polished and which are perpendicular to the propagation axis for phase-matched generation of blue light wavelength of about 457 nm.

Claim 12

Dependent Claim 60 words

The laser recited in claim 10, and further comprising: a dielectric coating on said input face which is highly reflective at the blue light wavelength; and a dielectric coating on said output face which is highly reflective at the fundamental wavelength from which the blue light is generated and said output face is partially transmissive at the blue light wavelength.

Claim 13

Dependent Claim 19 words

The laser recited in claim 11, wherein said output face dielectric coating is 99-80% transmissive of the blue wavelength.

Claim 14

Dependent Claim 32 words

The laser recited in claim 11, wherein said dielectric coatings on both said input and output faces have a low reflectance at 1064 nm, a high gain emission of Nd:YVO 4 .

Claim 15

Dependent Claim 29 words

The laser recited in claim 11, wherein said dielectric coating on both said input and output external faces have a high reflectivity at the fundamental wavelength of ˜914 nm.

Claim 16

Dependent Claim 23 words

The laser recited in claim 11, wherein said input face coating has high transmissivity at the pumping wavelength from said optical pumping source.

Claim 17

Dependent Claim 68 words

The laser recited in claim 1, wherein said gain medium crystal is made from an etalon of neodymium-doped gadolinium orthovanadate (Nd:GdVO 4 ) bonded to said nonlinear frequency doubling crystal to form said composite cavity having said input and output faces which are external, opposite, flat, parallel, and polished and which are perpendicular to the propagation axis for phase-matched generation of blue light wavelength of about 456 nm.

Claim 18

Dependent Claim 18 words

The laser recited in claim 1, wherein said optical pumping means is closely coupled to said gain medium.

Claim 19

Dependent Claim 21 words

The laser recited in claim 17, wherein the output light from said optical pumping means is incident onto said gain medium.

Claim 20

Dependent Claim 17 words

The laser recited in claim 1, wherein said optical pumping means is butt-coupled to said gain medium.

Claim 21

Dependent Claim 43 words

The laser recited in claim 1, and further comprising optical imaging means, wherein said optical pumping means is spaced from said gain medium, the output light from said optical pumping means being optically imaged onto said gain medium by said optical imaging means.

Claim 22

Dependent Claim 28 words

The laser recited in claim 1, wherein said frequency doubling crystal is oriented with respect to the polarized emission from said gain medium to produce Type-I harmonic generation.

Claim 23

Dependent Claim 66 words

The laser recited in claim 21, wherein said frequency doubling crystal is KNbO 3 and wherein said microlaser achieves a Type-I phase match for the fundamental 914-nm wavelength by lasing polarized along the c-axis of said gain medium and orienting the fundamental wavelength that it is polarized in the a-b plane and propagates at ˜44° from the b-axis toward the a-axis of said frequency doubling crystal.

Claim 24

Dependent Claim 27 words

The laser recited in claim 22, wherein said output face has a radius of curvature which is greater than the distance between said input and output faces.

Claim 25

Dependent Claim 65 words

The laser recited in claim 21, wherein said frequency doubling crystal is BBO and wherein said microlaser achieves a Type-I phase match for the fundamental 914-nm wavelength by lasing polarized along the c-axis of said gain medium and orienting the fundamental wavelength such that it is polarized along the b-axis and propagates at ˜25.7° from the c-axis toward the a-axis of said frequency doubling crystal.

Claim 26

Dependent Claim 28 words

The laser recited in claim 1, wherein said composite cavity is formed with said input face adjacent said optical pumping means being flat, said output face being curved.

Claim 27

Dependent Claim 31 words

The laser recited in claim 1, wherein said optical pumping means is close-coupled with said gain medium and emits at a near-infrared wavelength which is strongly absorbed by said gain medium.

Claim 28

Dependent Claim 24 words

The laser recited in claim 26, wherein said optical pumping means is selected from the group consisting of laser diodes and laser diode arrays.

Claim 29

Dependent Claim 39 words

The laser recited in claim 27, wherein said optical pumping means comprises at least one gallium aluminum arsenide (GaAlAs) laser diode which emits light at a wavelength of about 809 nm and which is attached to a heat sink.

Claim 30

Dependent Claim 28 words

A laser recited in claim 1, wherein said composite cavity is formed with said input face adjacent said optical pumping means being curved, said output face being flat.

Claim 31

Dependent Claim 18 words

The laser recited in claim 1, wherein said gain medium crystal is a uniaxial crystal having polarized emission.

Claim 32

Dependent Claim 42 words

The laser recited in claim 1, and further comprising a spectral filter crystal which, when combined with said gain medium crystal, narrows the effective spectral width of the 4 F 3/2 → 4 I 9/2 914 nm transition of said laser output.

Claim 33

Dependent Claim 22 words

The laser recited in claim 31, wherein said spectral filter crystal is bonded between said gain medium and said frequency doubling crystal.

Claim 34

Dependent Claim 25 words

The laser recited in claim 31, wherein said spectral filter is bonded to the face of said frequency doubling crystal opposite to said gain medium.

Claim 35

Dependent Claim 27 words

The laser recited in claim 31, wherein said spectral filter crystal is formed of neodymium-doped gadolinium orthovanadate (Nd:GdVO 4 ), having an absorption wavelength of ˜912 nm.

Claim 36

Dependent Claim 197 words

A laser comprising: an active gain medium microlaser comprising a neodymium-doped yttrium orthovanadate (Nd:YVO 4 ) thin crystal material having a propagation axis, an input face and an opposite face, said gain medium exhibiting laser action at the 4 F 3/2 → 4 I 9/2 914 nm transition to provide a polarized emission at about 914 nm; a nonlinear frequency doubling crystal having an output face and an opposite face, said opposite face of said gain medium being bonded to said opposite face of said doubling crystal to form a composite resonant cavity; the distance between said input and output faces ranging between about 0.2 mm and 12 mm, the doping concentration of said gain medium ranging between 0.3 and 2.0%; and optical pumping means in effective operative relationship with said gain medium to pump with polarized light said gain medium to thereby excite said gain medium to emit at its fundamental wavelength of ˜914 nm which is doubled within said composite cavity to produce blue light output at ˜457 nm, said gain medium having a crystalline structure having a predetermined orientation with respect to the polarization of the optical pumping light applied to said gain medium.

Claim 37

Dependent Claim 197 words

A laser comprising: an active gain medium microlaser comprising a neodymium-doped yttrium orthovanadate (Nd:YVO 4 ) thin crystal material having a propagation axis, an input face and an opposite face, said gain medium exhibiting laser action at the 4 F 3/2 → 4 I 9/2 914 nm transition to provide a polarized emission at about 914 nm; a nonlinear frequency doubling crystal having an output face and an opposite face, said opposite face of said gain medium being bonded to said opposite face of said doubling crystal to form a composite resonant cavity; the distance between said input and output faces ranging between about 0.2 mm and 12 mm, the doping concentration of said gain medium ranging between 0.3 and 2.0%; and optical pumping means in effective operative relationship with said gain medium to pump with polarized light said gain medium to thereby excite said gain medium to emit at its fundamental wavelength of ˜914 nm which is doubled within said composite cavity to produce blue light output at ˜457 nm, said gain medium having a crystalline structure having a predetermined orientation with respect to the polarization of the optical pumping light applied to said gain medium.

Claim 38

Dependent Claim 34 words

The laser recited in claim 35, wherein fundamental laser action on the 4 F 3/2 → 4 I 9/2 914 nm transition in Nd:YVO 4 is such as to provide the 457 nm output.

Claim 39

Dependent Claim 14 words

The laser recited in claim 35, wherein the neodymium doping concentration is about 1.5%.

Claim 40

Dependent Claim 30 words

The laser recited in claim 35, wherein said frequency doubling crystal is oriented with respect to the polarized emission from said gain medium to produce room temperature Type-I harmonic generation.

Claim 41

Dependent Claim 67 words

The laser recited in claim 38, wherein said frequency doubling crystal is KNbO 3 and wherein said microlaser achieves a Type-I phase match for the fundamental 914-nm wavelength by lasing polarized along the c-axis of said gain medium and orienting the fundamental wavelength such that it is polarized in the a-b plane and propagates at ˜44° from the b-axis toward the a-axis of said frequency doubling crystal.

Claim 42

Dependent Claim 65 words

The laser recited in claim 38, wherein said frequency doubling crystal is BBO and wherein said microlaser achieves a Type-I phase match for the fundamental 914-nm wavelength by lasing polarized along the c-axis of said gain medium and orienting the fundamental wavelength such that it is polarized along the b-axis and propagates at ˜25.7° from the c-axis toward the a-axis of said frequency doubling crystal.

Claim 43

Dependent Claim 97 words

The laser recited in claim 35, wherein said composite cavity is formed with said input and output faces which are exterior, opposite, flat, parallel and polished which are perpendicular to said propagation axis for phase matched generation of the blue light, said microlaser further comprising: a dielectric coating on said input face adjacent said optical pumping means which is highly reflective at ˜457 nm and at the fundamental wavelength of ˜914 nm; and a dielectric coating on said output face which is highly reflective at the fundamental wavelength and is partially transmissive at the blue light wavelength.

Claim 44

Dependent Claim 20 words

The laser recited in claim 41, wherein said second face dielectric coating is 99-80% transmissive to the blue light wavelength.

Claim 45

Dependent Claim 19 words

The laser recited in claim 41, wherein said input face dielectric coating is highly transmissive at the pumping wavelength.

Claim 46

Dependent Claim 18 words

The laser recited in claim 35, wherein said optical pumping means is closely coupled to said gain medium.

Claim 47

Dependent Claim 20 words

The laser recited in claim 44, and further comprising imaging means mounted between said crystal and said optical pumping means.

Claim 48

Dependent Claim 17 words

The laser recited in claim 35, wherein said optical pumping means is butt-coupled to said gain medium.

Claim 49

Dependent Claim 28 words

The laser recited in claim 35, wherein said composite cavity is formed with said input face adjacent said optical pumping means being flat, said opposite face being curved.

Claim 50

Dependent Claim 88 words

The laser recited in claim 35, wherein said optical pumping means produces optical radiation at about 809 nm, said gain medium has a neodymium doping concentration of about 1.5%, said frequency doubling crystal is KNbO 3 , said microlaser exhibiting a room-temperature Type-I phase match for the 914-nm wavelength by lasing polarized along the c-axis of said gain medium and orienting the fundamental wavelength such that it is polarized in the a-b plane and propagates at ˜44° from the b-axis toward the a-axis of said frequency doubling crystal.

Claim 51

Dependent Claim 85 words

The laser recited in claim 35, wherein said optical pumping means produces optical radiation at about 809 nm, said gain medium has a neodymium doping concentration of about 1.5%, said frequency doubling crystal is BBO, said microlaser exhibiting a room-temperature Type-I phase match for the 914-nm wavelength by lasing polarized along the c-axis of said gain medium and orienting the fundamental wavelength such that it is polarized along the b-axis and propagates at ˜25.7° from the c-axis toward the a-axis of said frequency doubling crystal.

Claim 52

Dependent Claim 45 words

The laser recited in claim 35, wherein said composite cavity is formed with said input and output faces having dichroic coatings thereon, said coatings on both faces having low reflectivity at 1064 nm and 1340 nm, said input face being adjacent said optical pumping means.

Claim 53

Dependent Claim 17 words

The laser recited in claim 35, wherein said gain medium is characterized by having broad absorption bands.

Claim 54

Dependent Claim 21 words

The laser recited in claim 35, wherein said gain medium crystal and said frequency doubling crystal are bonded together with epoxy.

Claim 55

Dependent Claim 15 words

The laser recited in claim 35, wherein the output of said composite cavity is polarized.

Claim 56

Dependent Claim 17 words

The laser recited in claim 35, wherein said gain medium is a uniaxial crystal having polarized emission.

Claim 57

Dependent Claim 42 words

The laser recited in claim 35, and further comprising a spectral filter crystal which, when combined with said gain medium crystal, narrows the effective spectral width of the 4 F 3/2 → 4 I 9/2 914 nm transition of said laser output.

Claim 58

Dependent Claim 22 words

The laser recited in claim 55, wherein said spectral filter crystal is bonded between said gain medium and said frequency doubling crystal.

Claim 59

Dependent Claim 25 words

The laser recited in claim 55, wherein said spectral filter is bonded to the face of said frequency doubling crystal opposite to said gain medium.

Claim 60

Dependent Claim 27 words

The laser recited in claim 55, wherein said spectral filter crystal is formed of neodymium-doped gadolinium orthovanadate (Nd:GdVO 4 ), having an absorption wavelength of ˜912 nm.

Claim 61

Dependent Claim 194 words

A laser comprising: an active gain medium microlaser comprising a neodymium-doped gadolinium orthovanadate (Nd:GdVO 4 ) thin crystal material having a propagation axis, an input face and an opposite face, said gain medium exhibiting laser action at the 4 F 3/2 → 4 I 9/2 914 nm transition to provide a polarized emission at about 914 nm; a nonlinear frequency doubling crystal having an output face and an opposite face, said gain medium being bonded to one said face of said doubling crystal to form a composite resonant cavity; the distance between said input and output faces ranging between about 0.2 mm and 12 mm, the doping concentration of said gain medium ranging between 0.3 and 2.0%; and optical pumping means in effective operative relationship with said gain medium to pump with polarized light said gain medium to thereby excite said gain medium to emit at its fundamental wavelength of ˜912 nm which is doubled within said composite cavity to produce blue light output at ˜456 nm, said gain medium having a crystalline structure having a predetermined orientation with respect to the optical pumping energy applied to said gain crystal by said gain medium.

Claim 62

Dependent Claim 194 words

A laser comprising: an active gain medium microlaser comprising a neodymium-doped gadolinium orthovanadate (Nd:GdVO 4 ) thin crystal material having a propagation axis, an input face and an opposite face, said gain medium exhibiting laser action at the 4 F 3/2 → 4 I 9/2 914 nm transition to provide a polarized emission at about 914 nm; a nonlinear frequency doubling crystal having an output face and an opposite face, said gain medium being bonded to one said face of said doubling crystal to form a composite resonant cavity; the distance between said input and output faces ranging between about 0.2 mm and 12 mm, the doping concentration of said gain medium ranging between 0.3 and 2.0%; and optical pumping means in effective operative relationship with said gain medium to pump with polarized light said gain medium to thereby excite said gain medium to emit at its fundamental wavelength of ˜912 nm which is doubled within said composite cavity to produce blue light output at ˜456 nm, said gain medium having a crystalline structure having a predetermined orientation with respect to the optical pumping energy applied to said gain crystal by said gain medium.

Claim 63

Independent Claim 127 words

A method for producing blue light by means of a microlaser, said method comprising the steps of: selecting an active gain medium comprising a neodymium-doped rare earth microlaser crystal having two opposite faces, the gain medium displaying strong broad diode absorption bands and polarized emission at ˜914 nm; selecting a nonlinear frequency doubling crystal oriented to phase match at ˜914 nm, the frequency doubling crystal having two opposite faces; bonding together in facing relationship the gain medium crystal and the frequency doubling crystal to form a composite resonant cavity; and optically pumping the gain medium with polarized light energy at a frequency to cause lasing to occur and doubling to the blue within the composite cavity, the output of the composite cavity being polarized blue laser light.

Claim 64

Independent Claim 127 words

A method for producing blue light by means of a microlaser, said method comprising the steps of: selecting an active gain medium comprising a neodymium-doped rare earth microlaser crystal having two opposite faces, the gain medium displaying strong broad diode absorption bands and polarized emission at ˜914 nm; selecting a nonlinear frequency doubling crystal oriented to phase match at ˜914 nm, the frequency doubling crystal having two opposite faces; bonding together in facing relationship the gain medium crystal and the frequency doubling crystal to form a composite resonant cavity; and optically pumping the gain medium with polarized light energy at a frequency to cause lasing to occur and doubling to the blue within the composite cavity, the output of the composite cavity being polarized blue laser light.

Claim 65

Dependent Claim 43 words

The method recited in claim 60, wherein the gain medium is a crystal producing a blue light output from the composite cavity and is selected from the group consisting of neodymium-doped yttrium orthovanadate (Nd:YVO 4 ) and neodymium-doped gadolinium orthovandate (Nd:GdVO 4 ).

Claim 66

Dependent Claim 18 words

The method recited in claim 61, wherein the gain medium crystal is a uniaxial crystal having polarized emission.

Claim 67

Dependent Claim 13 words

The method recited in claim 60, wherein the microlaser operates at room temperature.

Claim 68

Dependent Claim 24 words

The method recited in claim 60, wherein the gain medium emits light at ˜914 nm which is doubled to the blue at ˜457 nm.

Claim 69

Dependent Claim 24 words

The method recited in claim 60, wherein the gain medium emits light at ˜912 nm which is doubled to the blue at ˜456 nm.

Claim 70

Dependent Claim 61 words

The method recited in claim 60, and comprising the further steps of: selecting a spectral filter crystal comprising a neodymium-doped rare earth crystal; bonding the spectral filter crystal to one face of the frequency doubling crystal, the combined effect of the active gain medium, spectral filter crystal and frequency doubling crystal being to narrow the effective output wavelength of the microlaser.

Claim 71

Dependent Claim 22 words

The method recited in claim 60, wherein said spectral filter crystal is bonded between said gain medium and said frequency doubling crystal.

Claim 72

Dependent Claim 25 words

The laser recited in claim 60, wherein said spectral filter is bonded to the face of said frequency doubling crystal opposite to said gain medium.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1999-11-12	2000-05-13	2000-11-12	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	2003-11-12	2004-05-13	2004-11-12	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2007-11-12	2008-05-13	2008-11-12	$7700.00	Window Closed / Lapsed

Deep blue microlaser

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