JP2005136119A - Sapphire window material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To facilitate alignment work of the propagating direction of light in a window material with the C-axis direction of the window material. <P>SOLUTION: In a sapphire window material, the window material of a hermetically sealed vessel 5 which holds a semiconductor laser element 4 is formed of a sapphire. When the window material 1 is fixed to the hermetically sealed vessel, the C-axis direction of the window material is set obliquely at the angle of a formula (1) α=sin<SP>-1</SP>(sinθ/n(λ)) to a normal of an optical surface of the window material, where θ is the oblique angle of the window material in a direction perpendicular to an optical path direction of an emitting light from the semiconductor laser element, and n(λ) is the refractive index of the window material to the wavelength λ of the emitted light, and a marking is formed on the window material so that the rear surface and the front surface of the window material in a direction of the optical path become different appearances. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a window member used in an airtight sealed container that accommodates a semiconductor laser element.

  In the field of optical communication, which has been remarkably developed in recent years, in order to reliably propagate the light excited from the semiconductor laser element, the hermeticity of the hermetic container that houses the semiconductor laser element is regarded as important. When the inside of the hermetically sealed container is in a high-temperature and high-humidity state, the electrode part of the semiconductor laser element accommodated therein deteriorates, and moisture that has entered the inside condenses to cause optical characteristics of the semiconductor laser element. This is because the lifetime of the semiconductor laser element cannot be guaranteed.

  By the way, the hermetic sealing container serves to optically couple an internal semiconductor laser element and an optical fiber, which is a propagation path component of light emitted from the semiconductor laser element, using a lens. In order to realize such an optical system while ensuring the hermeticity of the hermetic sealing container, a light transmission type window material is used for the hermetic sealing container.

For such a window material, sapphire is suitable because of its excellent light transmission and high strength, and the basic structure of a case of an airtight sealed container using sapphire as the window material and its manufacturing method are disclosed. (For example, see Patent Document 1).
JP 08-148594 A (page 3-4, FIG. 1)

  FIG. 9 is a side sectional view of the above-described casing structure. The frame 100 is made of a metal material such as an Fe—Ni—Co alloy or an Fe—Ni alloy, and is made of silver brazing or the like so as to surround the mounting portion 101a on which the semiconductor laser element 4 is mounted on the upper surface of the base 101. Joined through brazing material.

  Further, the frame body 100 is provided with a through hole 100a on a side portion thereof, and a cylindrical fixing member 102 is attached to the through hole 100a. The fixing member 102 is inserted into the inner space so that the optical fiber 103 faces the semiconductor laser element 4 so that optical coupling can be performed between the optical fiber 103 and the semiconductor laser element 4.

  Further, the end portion of the fixing member 102 located inside the frame 100 is formed obliquely with a predetermined angle, and an inclined angle θ (exit from the semiconductor laser element 4) is formed on the inclined surface as shown in FIG. The window material 1 made of sapphire is fixed with an inclination angle with respect to a direction perpendicular to the optical path direction X of the incident light. As a result, the reflected light reflected from the surface of the window material 1 can be prevented from returning to the semiconductor laser element 4, and the oscillation of the light of the semiconductor laser element 4 can be prevented from becoming unstable and the oscillation operation can be kept stable. I can do it.

  In addition, such a single crystal of sapphire is formed by a conventionally known single crystal pulling method such as the Czochralski method or the Bernoulli method, and the pulled sapphire has a crystal plane orientation with respect to the pulling direction (C-axis direction). Is cut and polished in a vertical direction so as to be [0001], and is made into a predetermined plate shape.

  However, sapphire has a predetermined refractive index for light emitted from the semiconductor laser element 4. Further, since sapphire having a crystal plane orientation of [0001] is obliquely fixed to the end face of the fixing member 102, when the emitted light passes through the window material 1 and is optically coupled to the optical fiber 103, the emitted light is transmitted through the window. Birefringence occurs inside the material 1, and only a part of the light is optically coupled to the optical fiber 103. As a result, the optical coupling efficiency to the optical fiber 103 is deteriorated, and the transmission efficiency of the emitted light is also deteriorated. In addition, a phase difference occurs between the lights separated by birefringence, and due to this phase difference, the extinction ratio originally set for the window material 1 is also lowered.

を満足するように固定することによって、スネルの法則に従って屈折する出射光の窓材１内部における伝搬方向と、窓材１のＣ軸方向とを一致させて、光の複屈折を生じさせない、即ち光の偏光面が回転しないようにする窓材固定構造が提案されている。サファイアのように一軸性の単結晶では、光の伝搬方向とＣ軸方向とを一致させると複屈折は起きなくなり、光の偏光面が回転することなく維持される。 In order to solve these disadvantages, the inclination angle of the window member 1 with respect to the direction perpendicular to the optical path direction X of light is θ, the angle formed by the optical path direction X and the C-axis direction of sapphire is θ1, and the output of the semiconductor laser device 4 is When the refractive index of the window material 1 with respect to the wavelength λ of the incident light is n (λ), the window material 1 is

Is fixed so that the propagation direction of the outgoing light refracted according to Snell's law in the window material 1 and the C-axis direction of the window material 1 coincide with each other, so that no birefringence of light occurs. A window material fixing structure that prevents the polarization plane of light from rotating has been proposed. In a uniaxial single crystal such as sapphire, birefringence does not occur when the light propagation direction coincides with the C-axis direction, and the polarization plane of light is maintained without rotating.

  When birefringence is prevented in this way, all light is optically coupled to the optical fiber 103 as it is. As a result, the optical coupling efficiency to the optical fiber 103 is improved and the transmission efficiency is excellent. It can be. Further, since the propagation direction and the C-axis direction coincide with each other, a phase difference due to birefringence does not occur, and it is possible to prevent a reduction in the extinction ratio of the window material 1.

  However, when attaching the window material, even if it is attempted to make the light propagation direction inside the window material coincide with the C-axis direction of the window material, the C-axis direction cannot be visually confirmed. It was difficult to fix the window material. Therefore, it is necessary to transmit light while applying the window material to the fixed portion and to find the optimum position while confirming the change in the phase difference caused by the birefringence, which complicates the work and takes time. Further, even if the optimum position is derived, the temporary fixing has to be performed once at that position, and the work process becomes redundant.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a window material for a hermetically sealed container that can easily match the light propagation direction inside the window material with the C-axis direction of the window material. It is to provide.

の角度で斜めに設定されると共に、前記光の光路方向における前記窓材の裏面と表面とで異なる外観となるようにマーキングが形成されることを特徴とする窓材である。 According to a first aspect of the present invention, in the window material of the hermetic sealing container containing the semiconductor laser element, the window material is formed of sapphire and the window material is fixed to the hermetic sealing container. When the inclination angle of the window material with respect to the direction perpendicular to the optical path direction of the light emitted from the semiconductor laser element is θ, and the refractive index of the window material with respect to the wavelength λ of the light is n (λ) , The C-axis direction of the window material is normal to the optical surface of the window material,

The window material is characterized in that markings are formed so as to have different appearances on the back surface and the front surface of the window material in the optical path direction of the light.

  According to the window material of the present invention, since the marking is formed so that the back surface and the front surface of the window material have different appearances in the optical path direction of light, the C-axis direction is oblique to the normal line of the optical surface of the window material. It becomes possible to fix the window material set to 1 to the hermetically sealed container without making a mistake on both sides. By making the appearance different between the back surface and the front surface by marking, it is possible to visually determine the inclination direction of the C axis with respect to the normal line. Further, by setting the inclination angle between the optical surface and the C axis in advance so that the light propagation direction inside the window material coincides with the C axis direction, the optimum positioning of the window material where no light birefringence occurs is determined. Becomes easier. As a result, the mounting accuracy of the window material can be easily increased, and the work can be simplified and the work time can be shortened.

  Hereinafter, the window material for an airtight container according to the present invention will be described with reference to FIGS. 1 is a plan view of a window member used in an airtight sealing container for housing a semiconductor laser device, FIG. 2 is a left side view of the window member of FIG. 1, and FIG. 3 is a window of FIGS. It is a fragmentary sectional side view which shows the state which fixed the material to the airtight sealing container typically. In addition, the same number is attached | subjected to the same location as the conventional airtight sealing container shown in FIG.9 and FIG.10, and the overlapping description is abbreviate | omitted or simplified and described.

  The window material 1 according to the present invention is formed of a single crystal of sapphire, and its C-axis direction is relative to the normal H of the optical surfaces 1a and 1b of the window material 1 as indicated by an arrow C in FIG. The angle is set so as to be inclined by the angle α. FIG. 4 shows a unit cell diagram showing the plane orientation of the sapphire single crystal of the window material 1. Sapphire has a rhombohedral structure, but can be approximated by a hexagonal system as shown in this figure.

に設定される。法線Ｈに対しＣ軸方向を角度αを以て斜めに設定して窓材１を形成し、更に、傾斜角θで斜めに気密封止容器５の一端にこの窓材１を固定したとき、光学面1aで屈折して窓材１内部を伝搬する光の伝搬方向とＣ軸方向とを一致させることが出来る（図３参照）。つまり、

を満足するように、気密封止容器５の斜めに傾斜している一端に窓材１が取り付けられる。但し、θ１は光の光路方向（矢印Ｘ）とサファイアのＣ軸方向（矢印Ｃ）とが成す角度である。窓材１は、Au-Snロウ材によって気密封止容器５に接合される。 Sapphire is formed by a conventionally known single crystal pulling method such as Czochralski method or Bernoulli method. Further, the sapphire single crystal is cut by tilting it by an angle α with respect to the C plane ([0001] plane) perpendicular to the C-axis direction (arrow C) (the cut plane 6 is indicated by hatching in FIG. 4). The window material 1 is formed into optical surfaces 1a and 1b by cutting into a shape and polishing the cut surface 6. By tilting the cut surface 6 with respect to the C-axis direction by an angle α, the normal line of the cut surface 6 is also tilted with respect to the C-axis direction by an angle α. In addition, the direction which forms the cut surface 6 which inclines only the angle (alpha) with respect to a C-axis direction (arrow C) can be set arbitrarily, and FIG. 4 is only an example. At this time, the inclination angle α in the C-axis direction with respect to the normal line of the cut surface 6 is the optical path direction of the light emitted from the semiconductor laser element 4 when the window material 1 is fixed to the end face of the hermetic sealing container 5 from FIG. When the inclination angle of the window member 1 with respect to the direction perpendicular to the arrow X direction is θ, and the refractive index of the window member 1 with respect to the wavelength λ of the light is n (λ),

Set to When the window material 1 is formed by setting the C-axis direction obliquely with respect to the normal H at an angle α, and the window material 1 is fixed to one end of the hermetic sealing container 5 at an inclination angle θ, The propagation direction of the light refracted on the surface 1a and propagating through the window material 1 can be matched with the C-axis direction (see FIG. 3). That means

The window material 1 is attached to one end of the hermetic sealing container 5 that is inclined obliquely. Here, θ1 is an angle formed by the optical path direction of light (arrow X) and the sapphire C-axis direction (arrow C). The window material 1 is joined to the hermetically sealed container 5 by an Au—Sn brazing material.

  With the above configuration, the light emitted from the semiconductor laser element 4 is optically coupled to an optical fiber (not shown) without causing birefringence during transmission through the window material 1. As a result, when the optical coupling efficiency to the optical fiber is improved, the light transmission efficiency is improved. Furthermore, since birefringence is prevented, a birefringence phase difference does not occur, and a reduction in the extinction ratio of the window material 1 can be prevented.

  When the deviation angle from the set angle α is γ, the effect appears as sin γ. When γ is 3 degrees or less, the influence can be reduced to about 5%, and when γ is 0.5 degrees or less, the influence can be made 1% or less. Since the shift angle γ directly affects the extinction ratio of the window material 1, it is preferable to suppress γ: 0.2 degrees or less.

  Two orientation flats 2 and 3 are formed on the window material 1. The first orientation flat 2 is formed in a direction perpendicular to the cut surface 6. The formation surface of the orientation flat 2 is not particularly defined. The second orientation flat 3 is formed in a direction perpendicular to the orientation flat 2. As shown in FIG. 1, the orientation flat 3 is set to have a size different from that of the orientation flat 2, and the second orientation flat 3 is smaller than the first orientation flat 2.

  By forming two orientation flats 2 and 3 having different sizes in this way, as shown in FIG. 1, when the window material 1 is viewed from the optical path direction of the light, the orientation flat 3 is located on either side of the orientation flat 2. As can be said, the appearance of the window member 1 in the light path direction can be formed differently on the back surface and the front surface. Accordingly, since the orientation flats 2 and 3 can be marked so that the front and back sides of the window material 1 can be visually confirmed, the light propagation direction inside the window material 1 coincides with that at the stage of cutting the pulled single crystal. In addition, the window material 1 in which the C-axis direction is set obliquely with respect to the normal H with respect to the normal line H can be fixed to the hermetic sealing container 5 without making a mistake in the front and back sides. Accordingly, it is possible to easily increase the accuracy of attaching the window material 1 to the hermetic sealing container 5 and to simplify the operation and shorten the operation time.

となる。角度βの目安として、α×βが90以下で影響ｅを５％程度に納めることが可能となり、α×βが16以下で前記影響ｅを１％以下にすることが出来る。例えば、角度α：４度の場合、影響ｅを１％以下にするためには、数５よりβを４度以下とすることが必要になる。通常、傾斜角度αは８度程度なので、前記回転による影響ｅを１％程度に軽減するには角度βは約３度程度と導出される。 Further, the mounting accuracy in the rotation direction about the normal line H of the window material 1 is set by inclining the C-axis direction with respect to the normal line H as described above. Rotation that has an effect. Therefore, as shown in FIG. 1, it is desirable that the deviation angle β between the C-axis projection direction (arrow T) and the projection line t in the inclination direction of the window material 1 is small. The effect e of the deviation angle β on the extinction ratio is

It becomes. As a guideline for the angle β, it is possible to make the influence e about 5% when α × β is 90 or less, and to make the influence e 1% or less when α × β is 16 or less. For example, in the case where the angle α is 4 degrees, in order to make the influence e 1% or less, β needs to be 4 degrees or less from Equation 5. Since the inclination angle α is usually about 8 degrees, the angle β is derived to be about 3 degrees in order to reduce the influence e caused by the rotation to about 1%.

  In the present embodiment, an example in which two orientation flats are formed as markings for discriminating the front and back surfaces of the window material has been described, but the present invention can be variously modified based on its technical idea, for example, as shown in FIG. Two notches 7 and 8 having different sizes may be marked.

  Alternatively, as shown in FIGS. 6 and 7, one orientation flat 2 is formed on the window material 1, and the chamfering 2a is applied only to the optical surface 1a side of the orientation flat 2 as a marking for discriminating the front and back of the window material 1. Alternatively, as shown in FIG. 8, laser marking 9 may be applied only to the optical surface 1a. Furthermore, as another form of marking, an AR coat may be applied only on one of the two optical surfaces 1a and 1b, and this may be used as a marking for discriminating the front and back of the window material.

  By applying the window material of the present invention to the semiconductor laser element hermetically sealed container of an optical module used in optical communication, birefringence can be prevented and the extinction ratio of the window material can be easily improved.

The top view of the window material used for the airtight sealing container for a semiconductor laser element accommodation. The left view of the window material of FIG. The partial sectional side view which shows typically the state which fixed the window material of FIG.1 and FIG.2 to the airtight sealing container. The unit cell figure which shows the surface orientation of the sapphire single crystal of a window material. The top view which shows the window material in which the marking for back-and-front discrimination of another form was formed. (a) The top view which shows the window material in which the marking for back-and-front discrimination of another form was formed. (b) The top view which looked at the window material of the figure (a) from another optical surface. The left view of the window material of Fig.6 (a). (a) The top view which shows the window material in which the marking for back-and-front discrimination of another form was formed. (b) The top view which looked at the window material of the figure (a) from another optical surface. The sectional side view which shows the housing structure of the conventional airtight sealing container. The figure for demonstrating the relationship with the C-axis direction of the cylindrical fixing member currently fixed to the airtight sealing container shown in FIG. 9, and the sapphire which forms a window material.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Window material 2, 3 Orientation flat 4 Semiconductor laser element 5 Airtight sealing container 6 Cut surface 7, 8 Notch 9 Laser marking

Claims (1)

In the window material of the hermetically sealed container containing the semiconductor laser element,
When the window material is formed of sapphire and the window material is fixed to the hermetic sealing container, an inclination angle of the window material with respect to a direction perpendicular to an optical path direction of light emitted from the semiconductor laser element is θ. And when the refractive index of the window material with respect to the wavelength λ of the light is n (λ), the C-axis direction of the window material is normal to the optical surface of the window material,

The window material is characterized in that the marking is formed so as to be different from the back surface and the front surface of the window material in the light path direction.

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