TW201413359A - Wavelength conversion element, light source device, and method for manufacturing wavelength conversion element - Google Patents

Abstract

A wavelength conversion element (10) is formed using a ferroelectric crystal (100). The ferroelectric crystal (100) is provided with a plurality of polarization reversal regions (110) at intervals in a first direction (X direction). The interval (L) between the polarization reversal regions (110) is from 6.0 μm to 9.9 μm (inclusive). The width (H) of the polarization reversal regions (110) in a second direction (Y direction) that is perpendicular to the first direction is from 0.01 mm to 1 mm (inclusive).

Description

Wavelength conversion element, light source device, and method of manufacturing wavelength conversion element

The present invention relates to a wavelength conversion element, a light source device, and a method of manufacturing a wavelength conversion element in which a polarization inversion structure is provided in a ferroelectric crystal.

One of the wavelength conversion elements that convert the wavelength of light has a pseudo phase integrator. This wavelength conversion element is a region in which a polarization reversal region is periodically set in a ferroelectric crystal. The polarization inversion region is formed in a region of the ferroelectric crystal to bring the first electrode into contact with the region where the polarization is to be reversed, and the second electrode is in contact with the opposite surface of the ferroelectric crystal. A voltage is applied between the first electrode and the second electrode. Patent Document 1 describes that the length of the first electrode perpendicular to the polarization inversion period is twice or less the thickness of the ferroelectric crystal.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 3884197

In order to improve the quality of the wavelength conversion element, it is necessary to form the polarization inversion region completely as designed. However, as a result of the review by the inventors of the present invention, there is a case where a portion which is not reversed by polarization is generated even after the first electrode. In such a case, the quality of the wavelength conversion element is deviated from the reference, and as a result, the productivity of the wavelength conversion element is lowered.

The present invention has been made in view of the above circumstances, and an object thereof is to improve the productivity of a wavelength conversion element.

According to the invention, the wavelength conversion element is provided with a ferroelectric crystal. The ferroelectric crystal has a complex polarization inversion region periodically disposed along the first direction. The period of the polarization inversion region is 6.0 μm or more and 9.9 μm or less. Further, the width of the polarization inversion region orthogonal to the second direction in the first direction is 0.01 mm or more and 1 mm or less.

According to the present invention, the light source device has a light source that generates laser light having a wavelength of 1020 nm or more and 1200 nm or less, and the wavelength conversion element described above.

The method for producing a wavelength conversion element according to the present invention has the following steps. First, the first surface of the ferroelectric crystal is placed on the first region where the polarization is reversed, so that the plurality of first electrodes are periodically arranged along the first direction, and at the same time as the first of the ferroelectric crystallization. The second electrode is disposed on the second surface of the opposite surface of the surface. Next, by the first electrode and the second electrode A voltage is applied between the poles to form a polarization inversion region. The period of the plurality of first electrodes is 6.0 μm or more and 9.9 μm or less. Further, the width of the first electrode orthogonal to the second direction in the first direction is 0.01 mm or more and 1 mm or less.

According to the method of manufacturing a wavelength conversion element of the present invention, a plurality of wavelength conversion elements are manufactured by repeating the first step and the second step. In the first step, the first electrode is placed on the first surface of the ferroelectric crystal so that the contact portion between the first electrode and the first surface is periodic, and the first electrode is the first of the ferroelectric crystal. The second electrode is disposed on the second surface of the opposite surface of the surface. In the second step, a polarization inversion region is formed by applying a voltage between the first electrode and the second electrode. Next, before the first step and the second step are repeated, the width of the first electrode orthogonal to the second direction in the first direction is changed to prepare a sample of the complex wavelength conversion element. Next, the width of the first electrode used in the first step was determined by investigating the productivity of the polarization inversion region of the plurality of samples.

According to the present invention, the productivity of the wavelength conversion element can be improved.

10‧‧‧ wavelength conversion components

20‧‧‧Light source

30‧‧‧temperature regulating components

32‧‧‧Heat conduction department

40‧‧‧ Temperature Detection Department

42‧‧‧Intensity Detection Department

50‧‧‧Control Department

60‧‧‧Differentiation Department

100‧‧‧Dynamic crystallization

102‧‧‧Band

110‧‧‧Polarization reversal zone

210‧‧‧Insulation film

220‧‧‧1st electrode

222‧‧‧2nd electrode

Fig. 1(a) is a plan view showing a configuration of a wavelength conversion element according to a first embodiment, and Fig. 1(b) is a cross-sectional view taken along line A-A' of Fig. 1(a).

Fig. 2 is a view for explaining a method of manufacturing a wavelength conversion element.

Fig. 3 is a view showing an example of the relationship between the width H of the polarization inversion region and the productivity of the wavelength conversion element.

Fig. 4 is a plan view showing the configuration of a wavelength conversion element according to a second embodiment.

Fig. 5 is a view showing the configuration of a light source device according to a third embodiment.

Fig. 6 is a view showing the configuration of a light source device according to a fourth embodiment.

Fig. 7 is a view showing a modification of Fig. 6.

Hereinafter, embodiments of the present invention will be described using the drawings. In the drawings, the same components are denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

(First embodiment)

Fig. 1(a) is a plan view showing the configuration of the wavelength conversion element 10 according to the first embodiment. Fig. 1(b) is a cross-sectional view taken along line A-A' of Fig. 1(a). The wavelength conversion element 10 is formed using a ferroelectric crystal 100. In the ferroelectric crystal 100, the complex polarization inversion region 110 is periodically set along the first direction (X direction of FIG. 1(a)). The period L of the polarization inversion region 110 is 6.0 μm or more and 9.9 μm or less. Next, the width H of the polarization inversion region 110 orthogonal to the second direction in the first direction (the Y direction in FIG. 1(a)) is 0.01 mm or more and 1 mm or less. So enter If it is done, the quality of the wavelength conversion element will not easily deviate from the reference. The details will be described below.

The ferroelectric crystal 100 is, for example, LiNbO ₃ (lithium niobate) or LiTaO ₃ (lithium niobate) to which Mg (magnesium) is added, and the surface is a +Z plane. The thickness of the ferroelectric crystal 100 is, for example, 0.2 mm or more and 2.0 mm or less. The polarization inversion region 110 is reversely disposed on the wavelength conversion element 10 in plan view. The design value of the width W in the first direction of the polarization inversion region 110 is half of the period L of the polarization inversion region 110. However, because of the inconsistency in the manufacturing process, the width W becomes 45% or more and 55% or less of the period L.

In the present embodiment, the period L of the polarization inversion region 110 is 6.0 μm or more and 9.9 μm or less. Therefore, the wavelength conversion element 10 functions as an element that converts incident light having a wavelength of 1020 nm or more and 1200 nm or less into an emission light having a wavelength of 510 nm or more and 600 nm or less.

FIG. 2 is a view for explaining a method of manufacturing the wavelength conversion element 10. Fig. 2(a) is a plan view, and Fig. 2(b) is a cross-sectional view taken along line A-A' of Fig. 2(a). The method of manufacturing the wavelength conversion element 10 has the following steps. First, the first electrode 220 is disposed on the first surface (for example, the surface) of the ferroelectric crystal 100, and the second electrode 222 is disposed on the second surface (surface opposite to the first surface) of the ferroelectric crystal 100. . The first electrode 220 is in contact only with a region in which the polarization inversion region 110 is formed among the first faces. In other words, the first electrode 220 is disposed such that the contact portion with the first surface is periodic. At this time, the period of the contact portion is 6.0 μm or more and 9.9 μm or less. In addition, the second direction (the Y direction of Fig. 2 (a)) The width of the 1 electrode 220 is 0.01 mm or more and 1 mm or less. Next, a polarization inversion region 110 is formed by applying a voltage between the first electrode 220 and the second electrode 222. The details will be described below.

First, the second electrode 222 is formed on the second surface (in the figure below) of the ferroelectric crystal 100 by, for example, a sputtering method or a vacuum deposition method. The second electrode 222 is, for example, an Al (aluminum) film or a Cr (chromium) film, and has a thickness of, for example, 0.5 μm.

Next, an insulating film 210 is formed on the first surface of the ferroelectric crystal 100 to selectively remove the insulating film 210. Thereby, a region of the first surface of the ferroelectric crystal 100 that is not reversed by polarization is covered with the insulating film 210. The insulating film 210 is, for example, a photoresist film, and may be another insulating film.

Next, the first electrode 220 is formed on the first surface of the ferroelectric crystal 100 and the insulating film 210. The method of forming the first electrode 220 is the same as the method of forming the second electrode 222. Next, a voltage is applied between the first electrode 220 and the second electrode 222. Thereby, the polarization inversion region 110 is formed in the ferroelectric crystal 100. Thereafter, the first electrode 220 and the second electrode 222 are removed, and the insulating film 210 is removed.

Next, the effect of this embodiment will be described. In order to form the polarization inversion region 110 with high precision in the ferroelectric crystal 100 by the voltage application method, not only the crystal composition or the crystal structure of the ferroelectric crystal 100 is uniform, but also the first electrode 220 and the second electrode. The construction of 222 is also preferably uniform. In view of this, the present invention assumes that the width H of the first electrode 220 in the second direction is left-right polarization reversal.

3(a) and (b) show the width of the polarization inversion region 110, that is, the relationship between the width of the portion of the first electrode 220 that is in contact with the ferroelectric crystal 100 and the productivity of the wavelength conversion element 10. An example. In Fig. 3(a), L = 7.38 μm, and in the example shown in Fig. 3 (b), L = 9.52 μm. For the ferroelectric crystal 100, LiNbO ₃ having a thickness of 0.5 mm and MgO was added. Five samples were prepared for each width H. In FIG. 3, the ratio of the area of the polarization inversion region 100 of the contact portion of the first electrode 220 and the ferroelectric crystal 100 is defined as the productivity. That is, when the contact portions are all reversed in polarization, the productivity is 100%. Further, the region to be the polarization inversion region 110 can be confirmed by wet etching the ferroelectric crystal 100.

In any of the examples of (a) and (b) of FIG. 3, when the width H is 2 mm or less, the region where the polarization is not reversed (hereinafter referred to as the non-reverse region) is reduced, and the productivity of the polarization inversion region 110 is improved. In particular, when the width H is 1 mm or less, the productivity is greatly improved, and it exceeds 95%. Further, when the width H is 0.5 mm or less, the non-reversed area does not occur. This tendency was confirmed up to a width of 0.1 mm.

When the width H is 0.05 mm or less, the unreversed region is again generated, and the productivity of the polarization inversion region 110 is slightly reduced. However, when the width is 0.01 mm, the productivity is 95% or more.

As described above, in the present embodiment, before the wavelength conversion element 10 is manufactured, the width H of the portion of the first electrode 220 that is in contact with the ferroelectric crystal 100 is changed to prepare a plurality of samples. Next, using the prepared sample, the relationship between the productivity of the polarization inversion region 110 and the width H was investigated. Connect Based on the result, the width H of the portion of the first electrode 220 that is in contact with the ferroelectric crystal 100 is determined.

When the period L of the polarization inversion region 110 is 6.0 μm or more and 9.9 μm or less, the productivity of the wavelength conversion element 10 is improved when the width H is 0.01 mm or more and 1 mm or less. When the width H is 0.02 mm or more and 0.5 mm or less, the productivity of the wavelength conversion element 10 is further improved. Further, when the width H is 0.1 mm or more and 0.5 mm or less, the productivity of the wavelength conversion element 10 is particularly high.

(Second embodiment)

Fig. 4 is a plan view showing the configuration of the wavelength conversion element 10 according to the second embodiment. The wavelength conversion element 10 according to the present embodiment has the same configuration as the wavelength conversion element 10 according to the first embodiment except that the waveguide 102 is provided.

In detail, the waveguide 102 extends in the first direction (the X direction in FIG. 4). The waveguide 102 is either a back ridge type or a buried type. The polarization inversion structure 110 is provided in the waveguide 102.

According to this embodiment, the same effects as those of the first embodiment can be obtained.

(Third embodiment)

Fig. 5 is a view showing the configuration of a light source device according to a third embodiment. This light source device has a wavelength conversion element 10 and a light source 20. The configuration of the wavelength conversion element 10 is too phased with the first embodiment or the second embodiment. with. The light source 20 emits laser light having a wavelength of 1020 nm or more and 1200 nm or less. The light source 20, for example, produces ultra-wideband laser light. In addition, the light source 20 may also be a laser diode that emits a single wavelength. The light emitted from the light source 20 is incident on the wavelength conversion element 10. The wavelength conversion element 10 emits incident light by wavelength conversion. The wavelength of the emitted light is 510 nm or more and 1200 nm or less. Further, the light emitted from the light source 20 may be guided to the wavelength conversion element 10 by using an optical fiber, and may be guided by an optical component such as a mirror.

In the present embodiment, the light source device further includes a temperature adjustment element 30, a heat conduction portion 32, a temperature detecting portion 40, and a control portion 50. The temperature adjustment element 30 is in contact with the wavelength conversion element 10 through the heat conduction portion 32. The temperature adjustment element 30 has at least one of a heat generating function and a heat absorbing function. The temperature adjustment element 30 has, for example, at least one of a heater and a Peltier element. The heat conduction portion is formed of, for example, a material having high thermal conductivity such as Cu (copper). The temperature detecting unit 40 detects the temperature of the wavelength conversion element 10. The control unit 50 controls the temperature adjustment element 30 based on the detection result of the temperature detecting unit 40. That is, the control unit 50 controls the temperature adjustment element 30 so that the temperature of the wavelength conversion element 10 is within a desired range. The desired temperature is, for example, 25 ° C or more and 80 ° C or less.

According to this embodiment, the productivity of the wavelength conversion element 10 is high. Therefore, the manufacturing cost of the light source device can be reduced. Further, since the light source device includes the temperature adjustment element 30, the temperature detecting unit 40, and the control unit 50, the temperature of the wavelength conversion element 10 can be controlled to a desired range. Wai. Therefore, the wavelength conversion efficiency of the wavelength conversion element 10 can be maintained at a high value.

(Fourth embodiment)

Fig. 6 is a view showing the configuration of a light source device according to a fourth embodiment. This light source device has the same configuration as that of the light source device according to the third embodiment except that the intensity detecting unit 42 is provided instead of the temperature detecting unit 40. Further, in the present embodiment, the light source is an excitation light source having a narrow wavelength and a narrow wavelength such as a laser diode.

The intensity detecting unit 42 detects the intensity of the light emitted by the wavelength conversion element 10. Next, the control unit 50 controls the temperature adjustment element 30 based on the detection result of the intensity detecting unit 42. Specifically, the control unit 50 controls the temperature adjustment element 30 such that the detection result of the intensity detecting unit 42 becomes higher (preferably, it is the largest).

Moreover, as shown in FIG. 7, the light source device according to this embodiment may be provided with the branch portion 60. The branching unit 60 diverges a part of the light emitted from the wavelength conversion element 10 and inputs it to the intensity detecting unit 42.

According to this embodiment, the same effects as those of the third embodiment can be obtained.

(Example 1)

The wavelength conversion element 10 shown in the second embodiment is produced. In this embodiment, the period of the polarization inversion region 110 is as shown in Table 1. Next, five samples were prepared in each cycle. Next, the polarization inversion region 110 is measured. Productivity. This productivity is defined by the same productivity as shown in FIG.

In the present embodiment, the productivity of the polarization inversion region 110 was 95% under all the conditions shown in Table 1. Thereby, when the cycle is 6.0 μm or more and 9.9 μm or less, the productivity of the wavelength conversion element 10 is improved.

(Example 2)

The light source device shown in the third embodiment was produced using the wavelength conversion element 10 produced in the first embodiment. The wavelength of the light emitted from the light source 20 is 1020 nm or more and 1200 nm or less. Table 2 shows the design values of the wavelengths of the light emitted from the wavelength conversion element 10, and the measured values. Further, in the present embodiment, the control unit 50 controls the temperature of the wavelength conversion element 10 to 40 °C.

As shown in Table 2, the wavelength of the light emitted from the wavelength conversion element 10 was almost the same as the design value for all the samples.

The embodiments of the present invention will be described above with reference to the drawings. The embodiment is merely an exemplification of the present invention, and various configurations other than the above may be employed.

110‧‧‧Polarization reversal zone

10‧‧‧ wavelength conversion components

100‧‧‧Dynamic crystallization

Claims (8)

A wavelength conversion element comprising: a ferroelectric crystal, and a complex polarization inversion region periodically disposed along a first direction in the ferroelectric crystal; the period of the polarization inversion region is 6.0 μm or more and 9.9 μm or less, and the width of the polarization inversion region orthogonal to the second direction in the first direction is 0.01 mm or more and 1 mm or less. The wavelength conversion element according to claim 1, wherein the polarization inversion region has a width of 0.1 mm or more and 0.5 mm or less. The wavelength conversion element according to claim 1, further comprising: a waveguide provided in the ferroelectric crystal extending along the first direction; wherein the complex polarization inversion region is provided in the waveguide. A light source device comprising: a light source that emits laser light having a wavelength of 1020 nm or more and 1200 nm or less; and a wavelength conversion element that converts light emitted from the light source; wherein the wavelength conversion element includes: a ferroelectric crystal, and The ferroelectric crystal is a complex polarization inversion region periodically provided along the first direction; the period of the polarization inversion region is 6.0 μm or more and 9.9 μm or less, and is orthogonal to the second direction of the first direction Polarization inversion region The width is 0.01 mm or more and 1 mm or less. A light source device according to claim 4, further comprising: a temperature detecting unit that detects a temperature of the ferroelectric crystal, and a control unit that controls a temperature of the ferroelectric crystal according to a detection result of the temperature detecting unit. A light source device according to claim 4, further comprising: an intensity detecting unit that detects the intensity of the light emitted from the wavelength converting element, and a control for controlling the temperature of the ferroelectric crystallization according to the detection result of the intensity detecting unit unit. A method for producing a wavelength conversion element, comprising: arranging the first electrode on a first surface of a ferroelectric crystal so that a contact portion between the first electrode and the first surface is periodic; a step of disposing a second electrode on a second surface opposite to the first surface of the ferroelectric crystal, and applying a voltage between the first electrode and the second electrode to form a polarization inverse The step of the transition region; the period of the contact portion is 6.0 μm or more and 9.9 μm or less, and the width of the first electrode orthogonal to the second direction in the first direction is 0.01 mm or more and 1 mm or less. A method for producing a wavelength conversion element, comprising: arranging the first electrode on a first surface of a ferroelectric crystal so that a contact portion between the first electrode and the first surface is periodic; a second side opposite to the first surface of the ferroelectric crystal a first step of arranging the second electrode, and a second step of forming a polarization inversion region by applying a voltage between the first electrode and the second electrode; and performing the first step and the In the second step, the plurality of wavelength conversion elements are manufactured, and before the first step and the second step are repeated, the width of the first electrode orthogonal to the second direction in the first direction is changed to form a plurality of the wavelength conversion elements. In the sample, the width of the first electrode used in the first step was determined by investigating the productivity of the polarization inversion region of the plurality of samples.