JPH04145419A - Second harmonic wave generating element - Google Patents

Abstract

PURPOSE:To improve the second harmonics converting efficiency of a second harmonic generating element by forming a filter on the output side of the element provided with a thin-film waveguide layer formed on its substrate. CONSTITUTION:A slab type waveguide using an LiNbO3 thin film as the waveguide is formed by growing an LiNbO3 solid-solution single crystal thin film containing Mg and Na on a substrate and polishing the thin film to a specular surface. After a Ti waveguide pattern is formed on the waveguide by RF sputtering, etc., the pattern is etched to form a ridge type channel waveguide having a level difference of 1mum. An SHG element is manufactured by polishing both end faces of the waveguide so that light can be made incident on and emitted from the end faces. Then a filter composed of an SiO2 thin film having a thickness of 700Angstrom is formed on one of the end faces by RF sputtering. This element can produce laser light which can selectively fetch second harmonic only, has a high SHG converting efficiency, and is excellent in monochromaticity.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a second harmonic generation element that can selectively extract only second harmonic light and provide laser light with excellent monochromaticity.

(Prior art) The SHG element uses the nonlinear optical effect of an optical crystal material that has a nonlinear optical effect to convert an incident laser beam of wavelength λ into λ
Since the wavelength of the output light is converted to 1/2, the recording density can be increased to 4 by applying it to optical disk memories, CD players, etc.
It can be doubled, and high resolution can be obtained by applying it to laser printers, photolithography, etc.

Conventionally, a bulk single crystal nonlinear optical crystal using a high-power gas laser as a light source has been used as an SHG element. However, in recent years, there has been a strong demand for downsizing of entire devices such as optical disk devices and laser printers, and gas lasers have
Since an external modulator is required for optical modulation and is not suitable for miniaturization, an SHG element that can directly modulate and use a semiconductor laser, which is cheaper and easier to handle than a gas laser, is required. has been done. By the way, when a semiconductor laser is used as a light source, since the output of the semiconductor laser is generally low, ranging from several mW to several tens of mW, there is a demand for an SHO element with a waveguide structure that can obtain particularly high conversion efficiency.

As such an SHG element, Japanese Patent Application Laid-Open No. 6423233
No., LiNb0. A second harmonic generation element is described in which a waveguide is formed on a substrate by proton exchange.

In such a second harmonic generation element, fundamental wavelength light is emitted from the waveguide, and second harmonic light is emitted from the substrate by Cerenkov radiation.

However, such a SHO element using Cerenkov radiation has problems such as the need to make the waveguide thin, making it difficult to guide incident light, and making it difficult to improve efficiency.

For this reason, various second harmonic generation elements that do not utilize Cerenkov radiation have been proposed.

(Problems with conventional technology) However, thin film waveguide type S that does not utilize Cerenkov radiation
In the HG element, the second harmonic light and the fundamental wavelength light that has not been converted to the second harmonic light are simultaneously emitted from the thin film waveguide, so in order to improve the conversion efficiency, the second harmonic light and the second harmonic light must be It is necessary to provide a mechanism to separate the fundamental wavelength light that is not converted into , which increases cost and makes miniaturization difficult, which is not seen in thin-film waveguide type SHG devices that utilize Cerenkov radiation. A new problem arose.

As a result of intensive research, the inventors of the present invention have found that the above-mentioned problem can be solved by forming a filter on the output side of the SHG element, and have completed the present invention.

(Means for Solving the Problem) The present invention provides a second harmonic generation element in which a thin film waveguide layer is formed on a substrate, and a filter is formed on the output side of the second harmonic generation element. This is a second harmonic generation element characterized by the following.

(Function) The second harmonic generation element of the present invention requires that a filter be formed on the output side.

The reason for this is that unnecessary fundamental laser light can be removed from the emitted light and only the necessary second harmonic light can be efficiently extracted.

The filter described in the present invention refers to a filter that selectively does not transmit only fundamental wavelength light, or hardly transmits it.

The transmittance of the fundamental wavelength light of the filter is 0 to 10χ
It is desirable that

Further, the transmittance of the second harmonic light of the filter is 9
It is desirable that it is 0 to 100'&.

Further, the filter may be formed directly on the output end face to form the second filter.
By making adjustments to satisfy the anti-reflection conditions for harmonic light, it is possible to reduce loss due to reflection that occurs at the output end face due to the large difference in refractive index between the lithium niobate single crystal thin film layer and air, and increase the SHG output. can be improved.

The filter may be formed at a position remote from the output end face behind the output end face, or may be fixed on the output end face using a suitable adhesive.

When fixing on the output end face using the adhesive, it is desirable to improve the SHG output by adjusting the refractive index and thickness of the adhesive layer to meet anti-reflection conditions for the second harmonic light.

As the anti-reflection condition, it is desirable that formula (1) is satisfied, and it is preferable that formula (2) is satisfied.

naad*a-λ/4 + mλ/2-(1)n□: refractive index of adhesive d, 6: thickness of adhesive λ: wavelength m of second harmonic light is 0 and natural number nmd=rth s no -- (2) no: refractive index of the adhesive ns: refractive index of the thin film waveguide no refractive index of the two-person radiation medium The above-mentioned filters include colored glass filters, glass substrates coated with interference films, polarized light Films, polarizing plates, etc. can be used.

The reason why the polarizing film or polarizing plate can be used as a filter is that the fundamental wavelength laser light propagates through the waveguide with a TE of 1,000, and the generated second harmonic light propagates in a side mode.
In mode and TM mode, their polarization planes make an angle of 90° to each other, so by utilizing this property,
Only the incident light can be selectively removed using a polarizing film or a polarizing plate.

The filter material includes SiO, MgO,
Oxides such as Z n O, A j2 z Oy, LiNb
O3, LiTa oi, Y3 Gas 01
! , cd.

Composite oxides such as Ga, O, etc., or PMMA, MN
Organic materials such as A can be used, and multilayer thin films made by stacking these can also be used.

Methods for producing the filter include sputtering method, liquid phase epitaxial method, molecular beam epitaxial method, and MBE (Molecular Beam Epitaxial method).
Epitaxial) method, MOCVD (Meta
1 0rganic Chemical VaporD
eposition) method, ion blating method, L
B method, spin code method, dip method, etc. can be used.

The SHG element of the present invention has a single film waveguide layer formed on a substrate, and has a fundamental wave laser light wavelength (7 μm), a film thickness of the yi film waveguide layer (TIIm), a fundamental wave laser light wavelength (7 μm), and a thickness of the yi film waveguide layer (TIIm).
), the ordinary refractive index (no, 1) of the substrate at the wavelength of the fundamental laser light (7 μm), the ordinary refractive index (nov+) of the thin film waveguide layer at the wavelength of the fundamental laser light (7 μm), and the extraordinary refractive index of the substrate at the second harmonic wavelength (λμm/2) 'iR film guiding layer wave layer ordinary refractive index (n,) at s3 and second harmonic wavelength (7 μm/2).

)but, (n*F2 n *S2 or, (n*F2 ns2 λko It is desirable that one of the following relational expressions be satisfied.

However, N in the above formula (A) is (nOF+ne!X) and N2 in the above formula (B) is Unless the structure satisfies either relational expression (A) or (B), the conversion efficiency to second harmonic light will be low (this is because it is not practical).

In particular, in order to obtain high conversion efficiency to second harmonic light, the wavelength of the fundamental laser light (λμm), the thickness of the thin film waveguide layer (Tμm)
), the ordinary refractive index of the substrate (nO3l) at the fundamental laser light wavelength (λμm), the fundamental laser light wavelength (λμm)
) of the thin film waveguide layer (norl - the extraordinary refractive index of the substrate at the second harmonic wavelength (λμm/2) (
The extraordinary refractive index (naFz) of the thin film waveguide layer at the second harmonic wavelength (λμm/2) is (n,
, □ -n, s2) It is preferable to satisfy the following relational expression (Ao), and it is particularly advantageous to satisfy the following relational expression (A'').

λ3 λ3 However, it is preferable that N (n *F2 n @S2 in the above relational expressions (A) and (A'') satisfy the following relational expression (B), and in particular, the following relational expression (B'') should be satisfied. It is advantageous to be satisfied.

λ3 λ3 However, N2 in the above relational expressions (B゛) and (B'') is (nov+ -nos+) Moreover, in the SHO element of the present invention, the optical axis (Z
The angle of incidence (θ) of the fundamental wave laser beam with respect to the axis) is 0±
It is preferably within the range of 15'' or 90±15°.

The reason is that the incident angle (θ) of the fundamental laser beam is
This is because within the above range, the conversion efficiency to the second harmonic is extremely high. It is particularly advantageous for the angle of incidence of the fundamental laser light to be within the range of 0±5'' or 90±5°.

The wavelength (λ) of the fundamental laser beam incident on the SHO element of the present invention is preferably 0.4 to 1.6 μm.

The reason for this is that although it is advantageous for the fundamental wave laser light (λ) to have a wavelength as short as possible, it is practically impossible to generate laser light with a wavelength shorter than 0.4 μm using a semiconductor laser. This is because it is difficult;
On the other hand, when a fundamental laser beam with a wavelength longer than 1.6 μm is used, the wavelength of the second harmonic obtained is 1/2 of the fundamental laser beam, so it can be generated relatively easily by directly using a semiconductor laser. This is because there is no advantage in using the SHG element in the wavelength range where it can be used. The wavelength (λ) of the fundamental laser beam is advantageously 0.6 to 1.3 μm, which makes it relatively easy to operate the semiconductor laser light source, and particularly, 068 to 0.94 am is practically suitable.

The film thickness (T) of the thin film waveguide layer of the SHG element of the present invention is 0.
It is preferable that it is 1-20 micrometers.

The reason is that the film thickness (T) of the single film waveguide layer is 0.1a
This is because if it is thinner than 20 μm, it is difficult to make the fundamental laser beam incident and the incidence efficiency is low, making it difficult to obtain substantially high SHG conversion efficiency.On the other hand, if it is thicker than 20 μm, the optical power density is low, This is because the SHG conversion efficiency becomes low, and in either case, it is difficult to use it as an SHG element. The thickness of the thin film waveguide layer is preferably 0.5 to 10 μm, particularly 1 to 8 μm.
m is practically suitable.

Various optical materials can be used for the substrate and thin film waveguide layer in the present invention, and examples of the thin film waveguide layer include LiNb
O3, α-quartz, KTiOPO.

(KTP), β-B a B20- (BBO), K
E508 ・4H,O(KBs), KH2PO4(K
DP), KDI PO, (KD“P), NH4H2BO
3 (ADP), cs H2AsO4 (CDA), Cs
Dz Ash, (CD” A), RbHz PO.

(RDP), RbHz As O4 (RDA), B
eS○4 ・4H1O1L i CI O, ・3Hz
OSLi10i, α-LiCdBO3, LiB*0s
(LBO), urea, polyparanitroaniline (PPNA)
), polydiacetylene (DCH), 4(N,N-dimethylamino)-3-acetamidonitrobenzene (DAN
), 4~Nitrohenzaldehyde hydrazine (NBA
H), 3-methoxy-4-nitrobenzaldehyde hydrazine, 2-methyl-4-nitroaniline (MNA)
etc., and as a substrate, for example, L i T a O
*, L+Nb():+LiTa0s formed on the substrate
i-film, SiO2, alumina, KTP, BBO1LB○,
KDP and similar compounds such as soda glass, pyreno glass, polymethyl methacrylate (PMMA), etc. can be used.

Materials for the substrate and thin film waveguide layer include NaCr, Mg
By containing different elements such as , Nd, Ti, and V, the refractive index can be adjusted.

By containing Na, Cr, Nd, Ti, etc., the refractive index of the thin film waveguide layer and the substrate can be increased, and by containing the above Mg, V, etc., the thin film waveguide layer, The refractive index of the substrate can be lowered.

As a method for incorporating different elements such as Na, Cr, Mg, Nd, Ti, and V, the raw material and the different elements or different element compounds are mixed in advance, and the mixture is deposited on the substrate by liquid phase epitaxial growth. Method of forming a thin film waveguide layer
It is desirable to use a diffusion method for diffusing different elements such as , Nd, and Ti.

In addition, as a combination suitable for the S)[G element of the present invention, the thin film waveguide layer/substrate is 2-methyl-4-nitroaniline (
MNA)/S i O□; 2-methyl 4-nitroaniline (MNA)/alumina; KTiOPo, (KT
P)/Alumina; β-BaBzO, (BBO)/Flumina; 4-(N, N-tumethylamino)-3~acetamidonitrobenzene (DAN)/SiO□; 4-(N,
N-dimethylamino)-3-acetamidonitrobenzene (DA, N)/polymethyl methacrylate (PMMA);
LiBz Os (LBO)/BBO; LBO/
Alumina; RbH, PO, (RDP)/KH2PO.

(KDP)i polyparanitroaniline (p-PNA)/
Examples include PMMA.

Among the combinations suitable for the SHG element, Li Ta 03 single crystal or LiNb is used as the substrate.
○, L 1Ta03 single crystal thin film formed on a single crystal substrate, LiNb ○ as a thin film waveguide layer.

A combination using the following is preferred.

The reasons for this are that L IN b O3 has a large nonlinear optical constant, small optical loss, and can form a uniform film, and LiTa01 has a large nonlinear optical constant, small optical loss, and can form a uniform film.
iNb0. The crystal structure is similar to that of the LiNb
This is because it is easy to form an O3 film and it is easy to obtain high quality and inexpensive crystals.

When using a LiTa0* single crystal thin film formed on a LiNb○3 single crystal substrate as the substrate, the LiNb
C) The single crystal substrate is preferably of optical grade.

The optical grade LIN b Os single crystal substrate has excellent crystallinity, contains impurities such as iron at 12 ppm or less, has a refractive index distribution of 10-'/cm (locally ≦105) or less, and has a raw material purity of 99.999% or more. refers to something. The LiNb
0. The reason why it is desirable that the single crystal substrate be of optical grade is that LiTa0. By forming a single crystal thin film, it is possible to obtain an optical grade LiTa0. Li on a single crystal thin film
By forming a Nb Ox single crystal, the LiTa
This is because the crystallinity of the 0t single crystal thin film is transferred to the LiNb○3 single crystal, resulting in a thin film waveguide layer with particularly excellent light propagation properties, electro-optic effects, and nonlinear optical effects.

Further, the thickness of the LiTaO3 single crystal thin film is 0.2~
The thickness is preferably 30 μm.

The reason for this is that the thickness of the LiTaO3 single crystal thin film is 0.
If it is thinner than 2 μm, the guided light will leak, and
This is because if it is thicker than 0 μm, the crystallinity will decrease.

The thickness of the L i T a 03 single crystal thin film is particularly 0.
It is preferably between 5 and 10 μm, advantageously between 1 and 5 μm.

In the SHG element of the present invention, it is desirable that the thin film waveguide layer and the substrate are each lattice matched.

The lattice matching means that the lattice constant of the thin film waveguide layer is 99.81 to 100.07% of the lattice constant of the substrate.

The reason why such lattice matching is desirable is that a thin film without lattice distortion or microcracks can be formed.

Furthermore, the SHG element of the present invention has a transmittance of 100% or nearly 100% for fundamental laser light, and does not transmit at all or hardly transmits light with a wavelength of 0.6 μm to less than the fundamental wavelength. Preferably, a selective thin film is formed on the incident end face.

The reason for this is that semiconductor lasers generally emit weak laser light or natural light at peripheral wavelengths in addition to the center wavelength, and light at wavelengths at this frequency is generally unnecessary when used as an SHG element. It is desirable that the transmittance of laser light is 90 to 100%.

Further, the SHG element of the present invention preferably has an anti-reflection coating applied to the incident end face so that the transmittance of the fundamental wave laser beam is 100% or close to 100%.

The transmittance of the fundamental laser beam of the antireflection coating is preferably 90 to 100%.

It is desirable that the antireflection coating material satisfy the following conditions.

n, d, = λ/4 + m λ/2
- (3) n, : Anti-reflection coating material dl : Thickness of anti-reflection coating material λ : Fundamental wave laser beam m is 0 and natural number nt = r77 (4) nl : Reflection Anti-reflection coating material n,: Thickness of the anti-reflection coating material no: Refractive index of the incident medium (generally air).
Oxides such as ZnO, AN2 oi, L 1Nboz
, fluorides such as MgFz, LiTarm, Y3G
Composite oxides such as as○I2, Gd* Gas O+z, etc., or organic substances such as PMMA, MNA, etc. can be used, and multilayer thin films made by stacking these can also be used. Creation methods include sputtering method, liquid phase epitaxial method, etc. method, vapor deposition method, MBE (molecular beam epitaxial +
Mo1ecular Beam Epitaxia
l) method, MOCVD (Metal Organic
Chemical Vapor Deposit
i.

n) method, ion blating method, LB method, spin code method, dip method, etc. are advantageous.

Moreover, the SHG element of the present invention has F! Preferably, a cladding layer is formed on the film waveguide layer.

The reason for this is that by providing the cladding layer on the thin film waveguide layer, the substrate, the thin film waveguide layer, the cladding layer, and the cladding layer become nearly symmetrical with respect to the refractive index. The electric field distribution can be made symmetrical, and even if the thickness of the thin film waveguide layer does not completely match the theoretical phase matching film thickness, the decrease in the output of the second harmonic light can be alleviated. This is because the allowable range of film thickness is wide and an SHG element with high conversion efficiency can be obtained.

In addition, the ground layer acts as a protective layer and can prevent light scattering due to damage to the waveguide layer or adhesion of dust and dust, and can prevent chipping of the waveguide layer, which is a problem when polishing the end face.

(ching) can be completely prevented, and the yield of device fabrication can be significantly improved.

Furthermore, it is desirable that the above-described layers satisfy relational expressions 1) and 2).

n6. , -0.50≦n1lc≦n, , -0,05
---Formula 1) %Formula % ・Formula 2) For every n6, the ordinary refractive index of the substrate at the fundamental laser light wavelength (λμm) noe: The ordinary refractive index of the ground layer at the fundamental laser light wavelength (λμm) nes□: The extraordinary optical refractive index of the substrate at the second harmonic wavelength (λμm/2) is By satisfying equations 1) and 2), the electric field distribution of the second harmonic light and the fundamental laser light can be maximized, and an SHG element with a wide tolerance range of phase matching film thickness and high conversion efficiency can be obtained. This is because it will be done.

In particular, in order to expand the allowable range of phase matching errors in film thickness, it is preferable to satisfy equations 3) and 4).

natI −0,25≦noc≦nos+−0, lO・
- Formula 3) % Formula %) natI: Ordinary refractive index of the substrate at the fundamental laser light wavelength (λμm) noe: Ordinary refractive index of the cladding layer at the fundamental laser light wavelength (λμm) n1lt□: Second harmonic wavelength ( n, c: extraordinary refractive index of the cladding layer at the second harmonic wavelength (Xμm/2); The thickness of the cladding layer of the SHG element of the present invention is 0.
A thickness of 2 to 30 μm is desirable. The reason for this is that if the thickness is less than 0.2 μm, the guided light cannot be confined;
If it is thicker than 0 μm, the crystallinity of the ground layer will be reduced, resulting in poor optical properties, and it will take time to form the ground layer, resulting in reduced productivity.

The cladding layer preferably has a thickness of 0.5 to 10 μm, and has a thickness of 1 to 10 μm.
8 m is suitable.

Various optical materials can be used for the cladding layer in the present invention, such as ZnOlMgO, AL Oi, PMMA, S
iO□, Pyrex glass, soda glass, etc. can be used, and ZnO is particularly suitable.

The SHG device of the present invention is desirably made into a single chip by bonding semiconductor laser devices (bare semiconductor laser chips) so that laser light is incident on the thin film waveguide layer of the SHO device.

It is preferable that the thin film waveguide layer is of a channel type, and in such a form, it is composed of a channel type SHG element and a semiconductor laser element fixed on a protrusion 7. The end face of the light emitting region (laser light is emitted from this end face) and the channel type SH
so that the end faces of the chamfered portions of the G element are close to each other,
It has a structure in which the block, the channel-type SHC, and the substrate of the device are combined, and the radius W and thickness T of the channel portion of the channel-type SHG device, the center line of the semiconductor laser device, and the channel-type SHC deviation ΔX in the width direction of the center line of the chamfered part in the element, deviation ΔZ in the thickness direction, the end face of the light emitting region of the hair tip and the channel name SHO
It is desirable that the distance ΔY between the end faces of the channel portions of the element satisfies the following range.

(W-2) μm/2≦ΔX≦(W-2)ttm/2
0, Ol μm≦ΔY≦4 μm T gm/2≦ΔZ≦T um/2 The reason why such a structure is desirable is that it is easier to handle since there is no need to make complicated adjustments for laser light waveguide. It is.

The deviation ΔX in the width direction between the center line of the semiconductor laser element and the center line of the channel part, the deviation ΔZ in the thickness direction, and the difference between the end face of the light emitting region of the hair chip and the end face of the chamfer part of the chancel type waveguide. The reason why it is desirable for the distance ΔY to satisfy the above range is that within the above range, 50%
This is because the above laser light incidence efficiency can be obtained and it is practical.

By the way, the center line of the hair chip of the semiconductor laser is
It refers to a straight line that is perpendicular to the end face of the light emitting region of the semiconductor laser (that is, from which laser light is emitted) and that simultaneously defines the width and thickness of the light emitting region of the semiconductor laser.

Further, the center line of the channel type waveguide is a straight line that is perpendicular to the end face of the channel portion and that defines the width and thickness of the channel portion at the same time.

The ΔX and ΔZ take positive and negative values, but the state where the center line of the hair chip of the semiconductor laser and the center line of the channel part in the channel type waveguide completely coincide is Δ.
Assuming that X=0 and ΔZ=0, a deviation in a specific direction is defined as positive, and a deviation in the opposite direction to the specific direction is defined as negative.

The ΔY is preferably 0, but considering the difficulty of processing and thermal expansion, the lower limit is preferably 0°01 μm.

Width W and thickness T of the channel portion in the channel-type SHO element, deviation ΔX in the width direction between the center line of the semiconductor laser element and the center line of the channel portion in the chance-type SHG element, deviation ΔZ in the thickness direction, The end face of the light emitting region of the hair tip and the chamfered SHG
It is desirable that the distance ΔY between the end faces of the channel parts of the element satisfies the following range, (W-2)μm/3≦ΔX≦(W-2)μm/30.0
5μm≦ΔY≦2grn Tu m / 3≦ΔZ≦T g m / 3 or (W-2) μm/4≦ΔX≦(W-2) μm/40.1
It is preferable that μm≦ΔY≦0.5 μm T um /4≦ΔZ≦T g m /4.

It is desirable that the width W and thickness T of the channel portion in the channel type SHG element satisfy the following, respectively: 1 μm≦W≦15 μm 0.2 μm≦T≦6Bzm.

The reason for this is that the dimensions of the light emitting part of the semiconductor laser are 1 to 2
This is because, since the thickness is normally 0.1 to 0.4 μm, even higher incidence efficiency can be obtained by using a chancel type waveguide within the above range.

Furthermore, the width W and thickness T of the channel portion preferably satisfy the following conditions: 2 μm≦W≦10 μm, 0.4 am≦T≦4 μm, and preferably satisfy the following conditions: 4 μm≦W≦7 μm, and I μm≦T≦2.5 μm. It is.

It is preferable that the block is a Noricon type block.

This is because the Noricon block has a coefficient of thermal expansion close to that of a semiconductor laser bare chip, so it is resistant to thermal cycles and is easy to process such as chemical etching.

It is preferable that the block and the channel type SHG element are bonded together with an adhesive, and the block and the substrate of the channel type SHG element may be bonded via a fixing plate.

In addition, the bare chimp of the semiconductor laser is bonded 5)
It is desirable that the IG element is enclosed within a puff cage.

The reason for this is that by enclosing it in a pancage, the resistance to mechanical shock can be improved and the life of the semiconductor laser element can be extended.

It is necessary that the package is provided with a window for emitting the second harmonic light to the outside of the pan cage.

It is desirable that the window for emitting the second harmonic light to the outside of the package is provided with a filter as described in the present invention. The reason for this is that unnecessary fundamental wave laser light can be removed from the emitted light and only the necessary second harmonic light can be extracted efficiently while the device remains hermetically sealed.

For this reason, compared to adding a filter inside or outside of a typical sealing window glass, this method simplifies the process, lowers costs, and protects the semiconductor laser element.
Also, it is possible to improve the transmittance of second harmonic light.

Next, examples according to the present invention will be described.

Example ■ (+) By RF sputtering method, Z with a thickness of 0.5-
c) 500mm thick Mg on LiTa03 single crystal substrate
An O thin film was formed, and Mg was diffused into the surface layer of the I-1TaOz single crystal by thermal diffusion. The fundamental laser light wavelength λ is set to 0.
When the thickness is 78 μm, the ordinary refractive index (nosI) of the Mg-diffused LiTa○3 substrate is 2°153, and the second harmonic is λ/2.
The extraordinary refractive index (net2>) of the Mg-diffused LIT a O* substrate was 2.272.

On this substrate, the ordinary refractive index (n
ar, ) is 2.252, and the extraordinary optical refractive index (nor□) at the second harmonic is 2.253.
After growing the x single-crystal thin film, the surface was mirror-polished to create a slab-type waveguide using this LiNb01 thin film as a waveguide.

(2) The thickness of the slab waveguide obtained in (]) was reduced to MK2.23±0.05 μm by ion beam etching.
Adjusted to.

(3) A T1 waveguide pattern was formed on the slab waveguide obtained in (1) and (2) above by phonotrography and RF sputtering, and this was used as a etching mask for ion beam etching. , by removing the Ti etching mask and performing ion beam etching, a width of 10 μm and a film thickness of 2.23 ± 0.05 pm was obtained.
A ridge-type channel waveguide with a step height of 1 μm was fabricated.

(4) Both end faces of the channel-type waveguide obtained in (3) were mirror-polished by puff polishing to enable light input and output from the end faces, and a second harmonic generation element (SHO element) was obtained.

(5) One of both end faces of the channel waveguide obtained in (4) was coated with a thickness of 7 mm by RF sputtering.
00 people created a filter made of SiO□ thin film.

Regarding this SHO element, a wavelength of 0.8
SHC when a 3 am, 40 mW semiconductor laser is incident at an angle of 90” with respect to the crystal axis (Z axis) of a single crystal thin film
When the conversion efficiency was measured, it was 18.5%, indicating a very high efficiency.

Example 2 (1) When the fundamental laser light wavelength (λ) is o and 83 μm, the ordinary refractive index (nail
is 2151, the extraordinary refractive index at the second harmonic (n@$
2) is 2261 and the thickness is 05 [IIl Z cut L
The ordinary refractive index (nov
+ ) is 2.270, and the extraordinary refractive index (n*yz) at the second harmonic wavelength is 2.263. A L JN b Oy single crystal thin film containing 1% Imo solid solution of each of Nd and Na was grown. Afterwards, the surface was mirror-polished, and a slab-type waveguide using this thin film as a waveguide layer was created.

(2) The thickness of the slab waveguide obtained in (1) was reduced to 2.30t by ion beam etching! The thickness was adjusted to 0.03 μm.

(3) The slab waveguide obtained in (1) and (2) above was prepared with a width of 10 μm and a film thickness of 2 by the same method as in (3) of Example 1.
．． A ring-shaped channel waveguide with a width of 3±0.03 μm and a step height of 1 μm was created.

(4) Both end faces of the channel-type waveguide obtained in (3) were mirror-polished by puff polishing to allow light to enter and exit from the end faces.

(5) One of both end faces of the channel waveguide obtained in (4) was coated with a thickness of 590 mm by the RF spanner method.
A filter consisting of a g0Fjl membrane was formed.

Regarding the second SHG element, a wavelength of 0.83
SHO when a μm, 40mW semiconductor laser is incident at an angle of 90° to the crystal axis (Z axis) of a single crystal thin film
When the conversion efficiency was measured, it was 25.6%, indicating a very high efficiency.

(Effects of the Invention) As described above, the second harmonic generation element of the present invention can selectively extract only the second harmonic light and has high SHO conversion efficiency, so it can produce laser light with excellent monochromaticity. can be obtained.

Claims (1)

[Claims] 1. A second harmonic generation element having a thin film waveguide layer formed on a substrate, characterized in that a filter is formed on the output side of the second harmonic generation element. A second harmonic generation element. 2. The second harmonic generation element according to claim 1, wherein the filter is formed directly on the output end face of the second harmonic generation element. 3. The second harmonic generation element has a thin film waveguide layer formed on a substrate, and the wavelength of the fundamental laser beam (λμm) and the film thickness of the thin film waveguide layer (
Tμm), the ordinary refractive index of the substrate at the fundamental laser light wavelength (λμm) (n_O_S_1), the ordinary refractive index of the thin film waveguide layer at the fundamental laser light wavelength (λμm) (n_
O_F_1), the extraordinary refractive index (n_e_s_2) of the substrate at the second harmonic wavelength (λμm/2) and the extraordinary refractive index (n_e_F_2) of the thin film waveguide layer at the second harmonic wavelength (λμm/2) are ( n_O_F_1-n_O_
S_1) > 2, (n_e_F_2-n_e_s_2) 0.02≦(λ+0.1)N_1/λ^3T≦6.0・
...(A) Or (n_O_F_1-n_O_S_1)/(n_e_F_
2-n_e_s_2)≦2, 0.05≦(λ+0
．． 1) The second harmonic generation element according to claim 1, which is expressed by one of the following relational expressions: 1) N_2/λ^3T≦5.0 (B). However, N_1 in the above formula (A) is N_1=(n_e_F_2-n_e_s_2)/(n_
O_F_1−n_e_s_2), and the above formula (
N_2 in B) is N_2=(n_e_F_2-n_e_s_2)/(n_
O_F_1-n_O_S_1).