JP2010147284A - Wavelength-variable laser device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength-variable laser device which can narrow the spreading of the spectrum line width of laser beam emitted from a wavelength-variable laser chip by suppressing the oscillation of an MEMS movable mirror. <P>SOLUTION: In a wavelength-variable laser device, a wavelength-variable laser chip having an MEMS movable mirror is housed in an airtight package having a glass window and a liquid is enclosed in the interior. The wavelength-variable laser device has stabilizing means for lessening a variation in internal pressure in the airtight package. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a wavelength tunable laser device, and more particularly, to performance improvement of a wavelength tunable laser device suitable for an optical measuring instrument, gas analysis, a fiber sensor light source, an optical communication light source, and the like.

  FIG. 5 is a configuration diagram showing an example of a wavelength tunable laser device using a wavelength tunable laser chip having a conventional MEMS movable mirror. In FIG. 5, the wavelength tunable laser device includes a wavelength tunable laser chip 1 in which the wavelength of the emitted light changes according to the applied voltage E1, a lens 2 that converges the emitted light from the wavelength tunable laser chip 1, and a wavelength tunable for the user. An optical fiber 3 that outputs light from the laser chip 1 and a voltage circuit 4 that applies a voltage to the wavelength tunable laser chip 1 are configured.

  First, the configuration of the wavelength tunable laser chip 1 will be described. The wavelength tunable laser chip 1 includes an InP substrate 101 and an SOI (Silicon on Insulator) substrate 107.

  A multilayer mirror 103 is crystal-grown on one surface of the InP substrate 101, an active layer 104 is crystal-grown on the surface of the multilayer mirror 103, and an electrode 105 is formed on the surface excluding the central portion of the active layer 104. Has been. An electrode 102 is formed on the other surface of the InP substrate 101.

  The SOI substrate 107 is obtained by stacking an insulating layer 107b and a silicon layer 107c on a silicon substrate 107a. A recess is formed by polishing the surface of the silicon layer 107c, and a movable mirror 109 is provided in the recess. In addition, a silicon crystal is grown on portions of the silicon layer 107c facing both ends of the InP substrate 101, and a spacer 106 is formed. An electrode 108 is formed on the surface of the silicon layer 107 c including the spacer 106.

  On the other hand, by removing the central portion of the surface of the silicon substrate 107a until it reaches the insulating layer 107b by anisotropic etching or isotropic etching, a quadrangular pyramid-shaped laser light extraction port 110 is formed. An electrode 111 is formed on the outer periphery of the laser beam extraction port 110.

  Further, selective etching is performed on the insulating layer 107b to partially remove the insulating layer 107b. As a result, a space formed by the thickness of the insulating layer 107b is formed, and the silicon layer 107c functions as a diaphragm. Hereinafter, the silicon layer 107c is also referred to as a diaphragm.

  The wavelength tunable laser chip 1 is formed by aligning and bonding the electrode 105 of the InP substrate 101 and the electrode 108 formed on the surface of the spacer 106 of the SOI substrate 107. Thereby, a space formed by the film thickness of the spacer 106 and the electrodes 105 and 108 is formed between the InP substrate 101 and the SOI substrate 107. Diaphragm 107c and movable mirror 109 are displaced in the space formed on both surfaces thereof.

  Further, the laser light extraction port 110 is arranged so that the movable mirror 109, the lens 2 for condensing the laser, and the optical fiber 3 are aligned on the center line of the optical axis of the emitted laser light.

  A first DC power supply E1 is connected between the electrodes 108 and 111 formed on both surfaces of the SOI substrate 107, and a second electrode is formed between the electrode 102 formed on the InP substrate 101 and the electrode 108 formed on the SOI substrate 107. DC power supply E2 is connected.

  The multilayer mirror 103, the active layer 104, and the movable mirror 109 constitute an optical resonator. Since the electrodes 108 and 111 formed on both surfaces of the SOI substrate 107 are insulated by the insulating layer 107b, the voltage of the DC power source E1 that displaces the diaphragm 107c provided with the movable mirror 109 can be controlled.

  In such a configuration, current is injected into the active layer 104 by applying the output voltage of the second DC power source E2 between the electrode 102 formed on the InP substrate 101 and the electrode 108 formed on the SOI substrate 107. Electrons contained in the active layer 104 are excited and light is emitted. This output light is reflected between the movable mirror 109 and the multilayer mirror 103 to cause laser oscillation. That is, the excitation method by current injection is adopted. The laser output light is incident on the optical fiber 3 via the lens 2.

  The oscillation wavelength of the emitted laser light is determined by the distance between the movable mirror 109 and the multilayer mirror 103. That is, by applying the voltage E1 between the electrodes 108 and 111 formed on both surfaces of the SOI substrate 107, the movable mirror 109 is displaced together with the diaphragm 107c by the electrostatic force according to the voltage E1, and the multilayer mirror 103 is The distance between them changes, and the oscillation wavelength of the laser light can be changed. Further, by providing the quadrangular pyramid-shaped laser light extraction port 110 in the SOI substrate 107, the laser light can be efficiently taken into the lens 2 and the optical fiber 3.

  Patent Document 1 relates to a surface-emitting laser that can efficiently put laser light emitted from a surface-emitting laser into an optical fiber and reduce loss.

JP 2007-173550 A

  However, in the wavelength tunable laser device using the wavelength tunable laser chip 1 having the conventional MEMS movable mirror as shown in FIG. 5, the spectrum of the laser light emitted from the wavelength tunable laser chip 1 is vibrated because the MEMS movable mirror vibrates. There is a problem that the line width (wavelength fluctuation) becomes wide (large). When the spectral line width of the laser beam is widened, for example, the measurement accuracy of the optical measuring device is lowered, which is not preferable.

  The present invention solves the above-mentioned problems, and by suppressing the vibration of the MEMS movable mirror, the spread of the spectral line width of the laser light emitted from the wavelength tunable laser chip can be narrowed, and optical measurement is performed. An object of the present invention is to provide a wavelength tunable laser apparatus that can be used for applications where the broadening of the spectral line width is a problem.

In order to achieve the above object, claim 1 of the present invention provides:
In a wavelength tunable laser device in which a wavelength tunable laser chip having a MEMS movable mirror is housed in an airtight package having a glass window, and liquid is sealed inside,
The airtight package has a stabilizing means for reducing fluctuations in internal pressure.

Claim 2 is the wavelength tunable laser device according to claim 1,
The stabilizing means is a space formed by using a rubber-like elastic body as a partition.

Claim 3 is the wavelength tunable laser device according to claim 1,
The stabilizing means is a hollow ball formed of a rubber-like elastic body.

Claim 4 is the wavelength tunable laser device according to any one of claims 1 to 3,
The sealed liquid has an insulating property.

  With this configuration, vibration of the MEMS movable mirror of the wavelength tunable laser chip can be suppressed, and the spread of the spectral line width of the laser light output from the wavelength tunable laser apparatus can be suppressed.

  The wavelength tunable laser device of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of the present invention. In FIG. 1, a hermetic pin 6 is inserted into a hole of the stem 5, and the space between the stem 5 and the hermetic pin 6 is sealed with a sealing glass 7.

  Mounted on the hermetic pin 6 is a first spacer 8 to which a partition made of a rubber-like elastic body (hereinafter referred to as a rubber sheet 9) is attached, and a wavelength tunable laser chip 1 having a MEMS movable mirror similar to FIG. The second spacer 10 is attached so as to overlap.

  A stepped recess is formed on one surface of the first spacer 8, and a partition made of a rubber sheet 9 is joined so as to close the stepped recess. On the other surface, a recess having an opening surface wider than the wavelength tunable laser chip 1 mounted on the second spacer 10 is formed.

  The second spacer 10 is formed in an equal size so that the outer circumferences coincide with each other in a state where it is overlapped with the first spacer 8. On the surface of the second spacer 10 facing the first spacer 8, there is formed a recess for mounting the wavelength tunable laser chip 1 shown in FIG. A hole having a size overlapping with the opening of the laser beam extraction port 110 of the wavelength tunable laser chip 1 is provided at the center of the recess.

  A cap 11 formed so as to enclose the first spacer 8 and the second spacer 10 attached to the hermetic pin 6 so as to overlap each other is attached to the stem 5 so as to constitute an airtight package. . An opening for taking out laser light is provided in the central portion of the main plane of the cap 11, and a recess is formed in the inner surface of the outer periphery, and a glass window 12 is joined to the recess.

  In the wavelength tunable laser device thus hermetically packaged, the liquid 13 is sealed in all the space portions other than the space portion 14 of the stepped recess of the first spacer 8 closed by the rubber sheet 9. .

  FIG. 2 is a process diagram showing an example of a manufacturing process of the wavelength tunable laser device shown in FIG. First, as shown in (a), the hermetic pin 6 is inserted into the hole of the stem 5 and the space between the stem 5 and the hermetic pin 6 is sealed with a sealing glass 7.

  Next, as shown in (b), the rubber sheet 9 is joined while aligning with the stepped recess of the first spacer 8.

  Then, as shown in (c), a first spacer 8 in which a partition made of a rubber sheet 9 is joined to a stepped recess to a hermetic pin 6 inserted into a hole of the stem 5 and sealed with a sealing glass 7. Are inserted and joined so that the partition wall made of the rubber sheet 9 faces the stem 5.

  Next, as shown in (d), the wavelength tunable laser chip 1 of FIG. The first and second spacers 8 and 10 are made of ceramic, for example.

  Thereafter, as shown in (e), the second spacer 10 with the wavelength tunable laser chip 1 bonded to the recess is inserted into the hermetic pin 6 so that the wavelength tunable laser chip 1 faces the first spacer 8. Join.

  Subsequently, as shown in (f), the glass window 12 is joined while aligning the position with the concave portion of the cap 11.

  Then, as shown in (g), the cap 11 having the glass window 12 bonded to the recess is included so as to enclose the first spacer 8 and the second spacer 10 attached to the hermetic pin 6. It is attached to the stem 5 and bonded and fixed.

  The wavelength tunable laser device that is hermetically packaged can be assembled through the steps up to here. Further, in the wavelength tunable laser device of the present invention, the stepped concave portion of the first spacer 8 that is blocked by the rubber sheet 9 is used. The liquid 13 is sealed in the entire space other than the space 14.

  In sealing the liquid 13, for example, the liquid 13 is injected from a hole of the stem 5 (not shown) in a vacuum atmosphere to close the hole of the stem 5, but the liquid 13 may be sealed by other methods.

  Here, as the liquid 13, for example, an insulating material such as silicon oil is used.

  The liquid 13 sealed in the space of the wavelength tunable laser device functions to suppress the vibration of the movable mirror 109 and the vibration of the diaphragm 107c of the wavelength tunable laser chip 1. By suppressing the vibration of the diaphragm 107c, the expansion of the spectral line width can be reduced.

  Even if the liquid 13 is sealed in the optical path portion of the optical resonator of the wavelength tunable laser chip 1 composed of the multilayer mirror 103, the active layer 104, and the movable mirror 109, even if shaking due to an external impact occurs. Since the vibration is suppressed by the liquid 13, the vibration of the diaphragm 107c can be reduced.

  In addition, when the liquid 13 such as silicon oil is enclosed in the hermetic package provided with the glass window 12, the enclosed liquid 13 may expand due to a rise in temperature to increase the internal pressure, and the glass window 12 may be broken. Further, when the temperature is lowered, bubbles are generated by the contraction of the liquid 13, and there is a possibility that the laser beam is blocked.

  Therefore, in the present invention, the partition of the rubber sheet 9 is provided in order to absorb and reduce the change in internal pressure due to the expansion and contraction of the liquid 13 based on the temperature change.

  The rubber sheet 9 is made of a fluoro rubber material such as Viton (registered trademark) which is a stable material in the liquid 13 having high chemical resistance and heat resistance.

  In this way, by absorbing the internal pressure change due to the expansion and contraction of the liquid 13 with a soft material such as the rubber sheet 9, the vibration of the MEMS movable mirror 109 of the wavelength tunable laser chip 1 can be suppressed. The spread of the spectral line width of the output laser light can be suppressed.

  FIG. 3 is a block diagram showing another embodiment of the present invention, and the same reference numerals are given to portions common to FIG. The difference from FIG. 1 is that the partition wall of the first spacer 8 forming the space portion 14 uses a hollow rubber ball 15 instead of the rubber sheet 9.

  By providing the hollow rubber ball 15 inside the liquid 13 as shown in FIG. 3, the internal pressure change due to the expansion and contraction of the liquid 13 can be absorbed and reduced as in FIG.

  Further, by using the hollow rubber ball 15, the stepped portion of the stepped recess for joining the rubber sheet 9 as a partition to the first spacer 8 becomes unnecessary, and the structure of the first spacer 8 is simplified. it can.

  Then, by absorbing and reducing the internal pressure change due to the expansion and contraction of the liquid 13 with the hollow rubber ball 15, the vibration of the MEMS movable mirror 109 of the wavelength tunable laser chip 1 can be suppressed similarly to FIG. The spread of the spectral line width of the laser beam output from the variable laser device can be suppressed.

  FIG. 4 is a process diagram showing another embodiment of the fabrication process of the wavelength tunable laser device shown in FIG. 3, and the same reference numerals are given to portions common to FIG. A difference from FIG. 2 is that a hollow rubber ball 15 is provided in place of the rubber sheet 9 joined as a partition wall to the first spacer 8 shown in FIG.

  In this way, by absorbing and reducing the internal pressure change due to the expansion and contraction of the liquid 13 with a soft material such as the hollow rubber ball 15, the vibration of the MEMS movable mirror 109 of the wavelength tunable laser chip 1 can be suppressed. Narrowing of the spectral line width of output light in the wavelength tunable laser chip 1 can be realized.

  As described above, according to the present invention, it is possible to realize a wavelength tunable laser device that can suppress the vibration of the MEMS movable mirror of the wavelength tunable laser chip, and can suppress the spread of the spectral line width of the output laser light. It is suitable for an optical device, gas analysis, fiber sensor light source, optical communication light source, and the like.

It is a block diagram which shows one Example of this invention. It is process drawing which shows one Example of the manufacturing process of the wavelength tunable laser apparatus of FIG. It is a block diagram which shows the other Example of this invention. It is process drawing which shows the other Example of the manufacturing process of the wavelength tunable laser apparatus of FIG. It is a block diagram which shows an example of the wavelength tunable laser apparatus using the wavelength tunable laser chip which has the conventional MEMS movable mirror.

Explanation of symbols

1 Wavelength Tunable Laser Chip 5 Stem 6 Hermetic Pin 7 Sealing Glass 8 First Spacer 9 Rubber Sheet 10 Second Spacer 11 Cap 12 Glass Window 13 Liquid 14 Space 15 Rubber Ball

Claims (4)

In a wavelength tunable laser device in which a wavelength tunable laser chip having a MEMS movable mirror is housed in an airtight package having a glass window, and liquid is sealed inside,
A wavelength tunable laser device comprising a stabilizing means for reducing fluctuations in internal pressure inside the hermetic package.   2. The wavelength tunable laser device according to claim 1, wherein the stabilizing means is a space formed by using a rubber-like elastic body as a partition wall.   2. The wavelength tunable laser device according to claim 1, wherein the stabilizing means is a hollow ball formed of a rubber-like elastic body.   The wavelength tunable laser device according to claim 1, wherein the sealed liquid has an insulating property.