Optical devices

Abstract

To provide an optical device capable of improving the plane parallelism of two reflectors or the plane parallelism of a light emitting unit and a reflector.SOLUTION: An optical device includes a first reflector, a second reflector, at least three elastic supports that support the second reflector, and a piezoelectric element provided in each of the at least three elastic supports, and an independent drive signal is supplied to the piezoelectric element of the at least three elastic supports and the at least three elastic supports are elastically deformed independently, thereby changing the plane parallelism of the first and second reflectors.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to an optical device. [Background technology]

[0002] In recent years, advances in research into autonomous driving and driver assistance systems have led to increased interest in automotive radar as a sensing tool. Among these, frequency-modulated continuous wave (FMCW) radars are widely used as radars capable of measuring the distance and relative speed of an object, as well as radars using heterodyne technology to detect weak reflected waves. Developments are underway to improve the directionality of electromagnetic waves and miniaturize antennas. Research is also underway into FMCW LiDAR (Light Detection and Ranging), which replaces electromagnetic waves with laser light to improve directionality, reduce size, and reduce power consumption. The wavelength of the light source for FMCW LiDAR must be swept over time, and a tunable MEMS (Micro Electro Mechanical Systems) laser is known for its ability to change the wavelength by directly modulating the cavity length.

[0003] For example, Patent Document 1 describes a tunable laser that emits tunable radiation light with an output power spectrum and average radiation power over an emission wavelength band having a center wavelength. The tunable laser includes an optical resonator including first and second mirrors, a gain region interposed between the first and second mirrors, an air gap tuning region, and a MEMS drive mechanism for adjusting the air gap, the MEMS drive mechanism having a deformable dielectric membrane that is optically transparent over the wavelength band and attached to a rigid support structure. The MEMS drive mechanism has a membrane stress value in the range of 100 to 1000 MPa. The frequency response of the MEMS drive mechanism has substantially increased damping due to a squeeze film damping effect controlled by a central plate having a diameter greater than 50 μm but not exceeding the actuator diameter. The free spectral range (FSR) of the optical resonator exceeds 5% of the center wavelength. The tunable laser operates in a substantially single longitudinal / lateral mode over the wavelength band. The MEMS drive mechanism has a wavelength tuning frequency response with a 6 dB bandwidth of greater than approximately 1 kHz. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6328112 Summary of the Invention [Problem to be solved by the invention]

[0005] However, conventional MEMS-type tunable lasers have a problem in that if the plane parallelism between the light-emitting part (e.g., a Half-VCSEL element) and the movable reflecting mirror element (e.g., a MEMS mirror) is low, that is, if the plane parallelism between the two reflecting mirrors (the first and second reflecting mirrors) is low, the threshold current for laser emission becomes high. This problem is particularly pronounced in MEMS-type tunable lasers that use electrostatic attraction, and since the precision of the plane parallelism at the time of bonding is fixed, sufficient emission intensity cannot be obtained.

[0006] The present invention has been made based on the above-mentioned concerns, and aims to provide an optical device that can improve the surface parallelism of two reflecting mirrors or the surface parallelism of a light-emitting part and a reflecting mirror. [Means for solving the problem]

[0007] The optical device of this embodiment is an optical device that outputs laser light in which the first reflecting section, an active layer, and a second reflecting section are arranged in this order in a direction perpendicular to the first reflecting section, and has a light emitting section that includes the active layer and the first reflecting section, the second reflecting section, at least three elastic support sections that support the second reflecting section, and a movable reflecting mirror element that includes piezoelectric elements provided on the at least three elastic support sections, and the surface parallelism of the first reflecting section and the second reflecting section is changed by independent elastic deformation of the at least three elastic support sections due to drive signals that are independently supplied to the piezoelectric elements of the at least three elastic support sections. and supplying independent drive signals to the piezoelectric elements of the at least three elastic support parts based on the intensity of the laser light from the optical device, thereby elastically deforming the at least three elastic support parts independently. It is characterized by: The optical device of this embodiment is an optical device that outputs laser light in which the first reflecting section, an active layer, and a second reflecting section are arranged in this order in a direction perpendicular to the first reflecting section, and has a light emitting section including the active layer and the first reflecting section, and a movable reflecting mirror element including the second reflecting section, at least three elastic support sections that support the second reflecting section, and piezoelectric elements provided on each of the at least three elastic support sections, and is characterized in that the surface parallelism of the first reflecting section and the second reflecting section is changed by independent elastic deformation of the at least three elastic support sections due to drive signals independently supplied to the piezoelectric elements of the at least three elastic support sections, and each of the at least three elastic support sections has a plurality of arm sections extending adjacent to each other and a folded section that connects the ends of the plurality of arm sections in the extension direction, and the piezoelectric elements are respectively provided on the plurality of arm sections of the at least three elastic support sections. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an optical device that can improve the surface parallelism of two reflecting mirrors or the surface parallelism of a light emitting section and a reflecting mirror. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a tunable laser according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram illustrating an example of a detailed structure of a Half-VCSEL element. [Figure 3] FIG. 10 is a plan view showing an example of a support structure for a second reflecting mirror. [Figure 4] FIG. 4 is a cross-sectional view taken along line AA in FIG. [Figure 5] 5 is a side view illustrating a driven state of a second reflecting mirror in the support structure of FIGS. 3 and 4. FIG. [Figure 6]FIG. 2 is a diagram showing the relationship between the drive voltage and the cavity length of the tunable laser of the present embodiment. [Figure 7] FIG. 1 is a diagram showing the relationship between the drive voltage and the cavity length of a conventional MEMS tunable laser using electrostatic attraction. [Figure 8] FIG. 10 is a functional block diagram showing a configuration for supplying independent drive signals to piezoelectric elements of three elastic support portions. [Figure 9] 10A and 10B are diagrams illustrating an example of an operation in which different voltages are applied to two connecting parts to tilt a reflecting part. [Figure 10] 10A and 10B are diagrams illustrating an example of the relationship between the displacement of the connecting portion and the inclination obtained when the distance between the connection ends is changed. [Figure 11] FIG. 2 is a diagram illustrating an example of wavelength sweeping by the tunable laser of the present embodiment. [Figure 12] 10 shows the results of a simulation showing the relationship between the length of the gap between the Half-VCSEL element and the second reflector and the oscillation wavelength. [Figure 13] FIG. 2 is a diagram showing a first modified example of the tunable laser of the present embodiment. [Figure 14] FIG. 10 is a diagram showing a second modified example of the tunable laser of the present embodiment. [Figure 15] FIG. 15A is a cross-sectional view of a bonded movable reflector element and half-VCSEL element when tilt is not corrected, and FIG. 15B is a cross-sectional view of a bonded movable reflector element having a second reflector and a movable reflector structure for high-speed driving and a half-VCSEL element. [Figure 16] FIG. 16A is a diagram showing an example of adjusting the tilt of the second reflecting mirror, and FIG. 16B is a diagram showing an example of the relationship of voltage signals applied to piezoelectric elements. [Figure 17] FIG. 10 is a diagram showing an example of an outline of calibration of the surface parallelism between a movable reflecting mirror element and a half-VCSEL element. [Figure 18] 10 is a diagram illustrating an example of the relationship between the phase of a drive signal source and the optical output value of a tunable laser during calibration. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] A tunable laser (optical device) 10 of this embodiment will be described in detail with reference to Figures 1 to 18. In the following description, the X, Y, and Z directions are based on the directions of the arrows drawn in the drawings.

[0011] FIG. 1 is a diagram showing an example of the overall configuration of a tunable laser 10 according to this embodiment.

[0012] The tunable laser 10 has a half-VCSEL (Vertical Cavity Surface Emitting Laser) element 100 as a light emitting unit, a movable reflecting mirror element 200, and a bonding layer 300 for maintaining (defining) the relative positional relationship between the half-VCSEL element 100 and the movable reflecting mirror element 200. The half-VCSEL element 100 and the movable reflecting mirror element 200 have a rectangular shape that extends in the XY plane, and the bonding layer 300 has a rectangular frame shape that connects the peripheral portions of the half-VCSEL element 100 and the movable reflecting mirror element 200 in the XY plane to their upper and lower surfaces in the Z direction.

[0013] The half-VCSEL element 100 has a first reflecting mirror (first reflecting portion) 400, a semiconductor substrate 500, and an anti-reflection film 600, which are layered in this order from top to bottom in the Z direction. The half-VCSEL element 100 has an electrode 101, an electrode 102, and wiring 103 that electrically connects the electrode 101 and the electrode 102.

[0014] The movable reflecting mirror element 200 has a fixed support part 700 in the shape of a rectangular frame extending in the XY plane, and a rectangular second reflecting mirror (second reflecting part) 800 supported in the center of the XY plane of the fixed support part 700. The second reflecting mirror 800 is supported by the fixed support part 700 in a manner that allows it to move towards or away from the first reflecting mirror 400 from a reference opposing position with the first reflecting mirror 400 defined by the bonding layer 300 (the details of which will be described later).

[0015] There is a space between the first reflecting mirror 400 and the second reflecting mirror 800, and this space is filled with a vacuum or gas. An active layer 105 (described later with reference to FIG. 2), which is the light-emitting source of the half-VCSEL device 100, is located between the first reflecting mirror 400 and the second reflecting mirror 800.

[0016] The tunable laser 10 sweeps the wavelength of light emitted by the half-VCSEL element 100, and also changes the distance (gap) G in the Z direction between the first reflecting mirror 400 and the second reflecting mirror 800 to change the oscillation wavelength of the light emitted by the half-VCSEL element 100. In Fig. 1, the upper end of the arrow indicating the distance G is drawn from the second reflecting mirror 800, and the lower end of the arrow indicating the distance G is drawn from a position slightly above the first reflecting mirror 400, but this is for convenience of drawing (it is equivalent to the lower end of the arrow indicating the distance G being drawn from the first reflecting mirror 400). The structure for changing the distance G in the Z direction between the first reflecting mirror 400 and the second reflecting mirror 800 will be described in detail later. A structure for changing (improving) the surface parallelism between the first reflecting mirror 400 and the second reflecting mirror 800 (or the surface parallelism between the half-VCSEL device 100 and the second reflecting mirror 800) will also be described in detail later.

[0017] FIG. 2 is a diagram showing an example of the detailed structure of the half-VCSEL device 100. As shown in FIG.

[0018] The half-VCSEL device 100 has a semiconductor substrate 500 laminated on the upper surface of an anti-reflection film 600. The semiconductor substrate 500 is made of a semiconductor substrate such as an n-GaAs substrate. A first reflecting mirror 400 is laminated on the upper surface of the semiconductor substrate 500.

[0019] The first reflecting mirror 400 constitutes a semiconductor multilayer reflecting mirror having a first semiconductor layer 410, a second semiconductor layer 420, and a third semiconductor layer 430 stacked in this order from top to bottom. The number and arrangement of the semiconductor layers constituting the first reflecting mirror 400 are flexible (not limited to those exemplified here), and various design modifications are possible.

[0020] The semiconductor layers (e.g., the first semiconductor layer 410, the second semiconductor layer 420, and the third semiconductor layer 430) constituting the first reflecting mirror 400 may include, for example, a low-refractive index layer made of n-Al0.9Ga0.1As and a high-refractive index layer made of n-Al0.2Ga0.8As. To reduce electrical resistance, a compositionally graded layer, e.g., 20 nm thick, in which the composition gradually changes from one composition to the other, may be provided between the semiconductor layers (refractive index layers) constituting the first reflecting mirror 400. The thickness of each semiconductor layer (refractive index layer) is preferably set to an optical thickness of λ / 4, including half of the adjacent compositionally graded layer, where λ is the oscillation wavelength. When the optical thickness is λ / 4, the actual thickness D of the layer is D=λ / 4n (where n is the refractive index of the medium of the layer).

[0021] In addition to the first reflecting mirror 400, or as part of the components of the first reflecting mirror 400, an electrode 101, an electrode 102, a wiring 103, a spacer layer 104, an active layer 105, a selective oxidation layer 106, a contact layer 107, an insulating layer 108, a mesa 109, a groove 110, an opening 111, and an opening 112 are formed on the upper surface of the semiconductor substrate 500.

[0022] The spacer layer 104 is, for example, composed of an undoped AlGaInP layer, and is formed at the boundary layer between the semiconductor multilayer reflector of the first reflector 400 and the active layer 105. The portion including the spacer layer 104 and the active layer 105 is also referred to as a resonator structure (resonator region), and its thickness, including half of the adjacent compositionally graded layer, is set to be the optical thickness of one wavelength (λ). The spacer layer 104 is formed in two layers spaced apart in the Z direction, and the active layer 105 is formed between the two spacer layers 104. The active layer 105 is, for example, an active layer with a triple quantum well structure having three quantum well layers and four barrier layers. For example, each quantum well layer is an InGaAs layer, and each barrier layer is an AlGaAs layer.

[0023] The selective oxidation layer 106 is composed of an oxidized region 106A and a non-oxidized region 106B. For example, a selective oxidation layer 106 made of p-AlAs is inserted into the semiconductor multilayer reflector of the first reflector 400 with a thickness of 30 nm. The insertion position can be, for example, within the second pair of high-refractive index layer and low-refractive index layer counting from the spacer layer 104. Note that the selective oxidation layer 106 may include layers such as compositionally graded layers and intermediate layers above and below it; here, the layers that are actually oxidized are collectively referred to as the selective oxidation layer 106.

[0024] The contact layer 107 is made of, for example, a p-GaAs layer, and is formed on the semiconductor multilayer film reflector of the first reflector 400 .

[0025] The mesa 109 and the groove 110 are formed by etching away a portion of the semiconductor multilayer reflector (e.g., the first semiconductor layer 410, the second semiconductor layer 420, and the third semiconductor layer 430) of the first reflector 400, the spacer layer 104, the active layer 105, and the contact layer 107.

[0026] The insulating layer 108 is made of, for example, SiN, SiON, SiO2, or the like, and covers the mesa 109. An opening 111 is formed in the insulating layer 108 to expose a portion of the contact layer 107 of the mesa 109. The opening 111 is formed at a position that overlaps with the non-oxidized region 106B of the selective oxidation layer 106 in plan view.

[0027] An electrode 101 electrically connected to the contact layer 107 through an opening 111 is formed on the insulating layer 108 of the mesa 109. The electrode 101 may be, for example, a laminated film in which titanium (Ti), platinum (Pt), and gold (Au) are laminated in this order from the insulating layer side.

[0028] The insulating layer 108 covers the trench 110. An opening 112 is formed in the insulating layer 108, exposing a portion of the semiconductor substrate 500.

[0029] An electrode 102 electrically connected to the contact layer 107 through the opening 112 is formed on the insulating layer 108 in the groove 110. The electrode 102 may be, for example, a laminated film in which germanium alloy (AuGe), nickel (Ni), and gold (Au) are laminated in this order from the semiconductor substrate 500 side.

[0030] The wiring 103 electrically connects the electrode 101 and the electrode 102. For example, the wiring 103 may be a laminated film in which titanium (Ti), platinum (Pt), and gold (Au) are laminated in this order from the semiconductor substrate 500 side.

[0031] In this embodiment, the Half-VCSEL element 100 is used as the "light-emitting section," but an LD (Laser Diode) or an LED (Light Emitting Diode) can also be used as the "light-emitting section." An EEL (Edge Emitting Laser) can also be used as the "light-emitting section." Furthermore, the "light-emitting section" can be a single light source, or multiple light sources that emit light simultaneously (for example, a VCSEL array light source). In other words, there is a degree of freedom in the specific form of the "light-emitting section," and various design changes are possible.

[0032] However, conventional MEMS-type tunable lasers use electrostatic attraction to modulate the cavity length, i.e., the distance between two parallel mirrors facing each other, which results in insufficient linearity between the drive voltage and the displacement, making it difficult to obtain the desired wavelength. Furthermore, since the initial cavity length cannot be precisely adjusted to an interval that is an integer multiple of the oscillation wavelength during manufacturing, there is a problem in that during oscillation, a high voltage must be applied to the moving part of the mirror to move the mirror until the cavity length satisfies the oscillation conditions.

[0033] The reason why the drive voltage and cavity length of a MEMS-based tunable laser using electrostatic attraction do not have a linear relationship is because the position of the MEMS-side reflector is proportional to the square of the drive voltage. The position of the MEMS-side reflector is determined by the initial gap between the two reflectors when no voltage is applied, as well as the balance between the electrostatic attraction generated by the potential difference and the restoring force of the spring, which is the MEMS's drive mechanism. Increasing the drive voltage increases the electrostatic attraction between the two reflectors, shortening the cavity length. Over a wide voltage range, the mirror displacement deviates from the linear relationship. To solve this issue, one possible method is to pre-distort the drive voltage so that the wavelength change is linear with the drive voltage. However, because the initial inter-mirror gap (1–2 μm) changes due to variations in device manufacturing and temperature changes, ultra-precise initial gap control is difficult. Therefore, a drive voltage pre-distorted under static conditions cannot achieve linear change in the cavity length.

[0034] Furthermore, if the gap between the two reflecting mirrors is displaced to more than one-third of the initial gap, the electrostatic attractive force generated by the potential difference will always exceed the restoring force of the spring that is the MEMS's driving structure, causing a pull-in effect in which the membranes are attracted to each other, preventing the MEMS-based tunable laser from functioning properly. In other words, the mirror driving range of a MEMS-based tunable laser using electrostatic attractive force is limited to less than one-third of the initial gap.

[0035] In this embodiment, we address the above-mentioned issues with MEMS-type tunable lasers using electrostatic attraction as a key technical challenge. We employ a structure in which a piezoelectric element is deposited on a spring as the driving source for the MEMS-side reflector. This structure utilizes the linear relationship between the applied voltage and the volumetric contraction of the piezoelectric element to linearly modulate the resonator length with respect to the voltage. When a voltage is applied to a meander-structure spring connected to the MEMS-side reflector, electrodes are deposited on the spring so that they sandwich the piezoelectric element, and the volume of the piezoelectric element shrinks linearly with the voltage. The meander-structure spring deforms in the perpendicular direction in response to the in-plane stress generated by this contraction. The linear relationship between the stress and deformation of the piezoelectric element is maintained. Furthermore, because the spring is connected to the reflector, a linear relationship is maintained between the spring deformation and the reflector displacement, resulting in the reflector being driven linearly with respect to the voltage. Furthermore, because this relationship does not depend on the initial value of the resonator length, the resonator length can be controlled with high precision for electrostatically driven MEMS.

[0036] More specifically, in this embodiment, an elastic support member 900 that supports the second reflecting mirror 800 and a piezoelectric element 1000 that is provided on the elastic support member 900 are formed on the fixed support member 700 of the movable reflecting mirror element 200, and a drive voltage is applied to the piezoelectric element 1000 to elastically deform the elastic support member 900, thereby changing the distance between the first reflecting mirror 400 and the second reflecting mirror 800 and changing the oscillation wavelength of the light emitted by the Half-VCSEL element 100.

[0037] Here, by integrally forming the first reflecting mirror 400 and the half-VCSEL element 100 as a "first substrate," and by integrally forming the second reflecting mirror 800, the elastic support member 900, and the piezoelectric element 1000 as a "second substrate," it is possible to simplify the configuration of the tunable laser 10. For example, the half-VCSEL element 100 can constitute the "first substrate," and the movable reflecting mirror element 200 can constitute the "second substrate."

[0038] Furthermore, conventional MEMS-type tunable lasers have a problem in that the threshold current for laser emission becomes high due to the low plane parallelism between the light-emitting part (e.g., a Half-VCSEL element) and the movable reflecting mirror element (e.g., a MEMS mirror), i.e., the low plane parallelism between the two reflecting mirrors (first and second reflecting mirrors). This problem is particularly pronounced in MEMS-type tunable lasers that use electrostatic attraction, and since the precision of the plane parallelism at the time of bonding is fixed, sufficient emission intensity cannot be obtained.

[0039] The reason for the decrease in the plane parallelism between the light emitting section (e.g., Half-VCSEL element) and the movable reflecting mirror element (e.g., MEMS mirror) is due to the mounting conditions during device integration. A MEMS-type tunable laser integrates the light emitting section (e.g., Half-VCSEL element) and the movable reflecting mirror element (e.g., MEMS mirror) into a single device, with an air gap between each element. Of the ultra-high reflecting mirrors possessed by each element, the reflecting section on the MEMS side is minutely driven in the direction perpendicular to the element surface while injecting current into the Half-VCSEL, thereby adding a wavelength sweep function to the oscillating light.

[0040] Integration methods are classified into stacking and bonding. Bonding requires a bonding layer to bond the two elements, and the plane parallelism of the two elements changes depending on the film thickness variation and the bonding temperature and pressure. Sputtering and vapor deposition are used to form the bonding layer, but film thickness variations occur depending on the film formation position. Furthermore, heating and pressure are required to bond the bonding layers formed on each element, but these conditions also inevitably vary depending on the position. Therefore, the bonding layer does not deform uniformly after bonding, resulting in film thickness variations and a decrease in the plane parallelism between the light-emitting element (e.g., a Half-VCSEL element) and the movable reflecting mirror element (e.g., a MEMS mirror).

[0041] Laser elements with a cavity perpendicular to the surface, such as Half-VCSELs, can achieve low threshold current, low power consumption, and high output by reducing the loss of light traveling back and forth between the two reflecting mirrors that make up the cavity. Therefore, tunable lasers with the above device structure have had the problem that if there is a problem with the plane parallelism between the elements, i.e., if there is a tilt between the reflecting mirrors, the loss increases accordingly, resulting in a higher threshold current.

[0042] Therefore, in this embodiment, at least three elastic support members (elastic support members 910, 920, and 930 in this embodiment) are provided as elastic support member 900 that supports second reflecting mirror 800, and piezoelectric elements (piezoelectric elements 1010, 1020, and 1030 in this embodiment) are provided on the at least three elastic support members (elastic support members 910, 920, and 930 in this embodiment), respectively. Independent drive signals are supplied to the piezoelectric elements (piezoelectric elements 1010, 1020, and 1030 in this embodiment) of the at least three elastic support members (elastic support members 910, 920, and 930 in this embodiment) to elastically deform the at least three elastic support members (elastic support members 910, 920, and 930 in this embodiment) independently, thereby changing the plane parallelism between first reflecting mirror 400 and second reflecting mirror 800 (plane parallelism between Half-VCSEL element 100 and second reflecting mirror 800).

[0043] That is, in this embodiment, three or more elastic bodies connect the MEMS-side reflector and the chip support, and each elastic body is driven by an independent signal. In this structure, the drive amount of each elastic body is changed independently according to the tilt of the chip, thereby changing the position of the multiple connections between the reflector and the elastic bodies in the direction perpendicular to the chip surface. By constructing the reflector from a highly rigid material, the difference in the position of the connections can be converted into the tilt of the reflector. By utilizing this function, the elastic bodies can be driven to cancel out the tilt between the elements, thereby reducing loss in the resonator structure.

[0044] Fig. 3 is a plan view showing an example of a support structure (support structure for the MEMS-side reflecting mirror) for second reflecting mirror 800. Fig. 4 is a cross-sectional view taken along line AA in Fig. 3.

[0045] 3, second reflecting mirror 800 is supported in a floating state with through-hole 700X interposed in the center of fixed support 700 extending in the XY plane. Connection ends 810, 820, and 830 are formed to protrude from the periphery of second reflecting mirror 800, and linking portions 710, 720, and 730 are formed to protrude from the periphery of second reflecting mirror 800 on fixed support 700. Connection end 810 and linking portion 710 are connected by elastic support portion 910, connection end 820 and linking portion 720 are connected by elastic support portion 920, and connection end 830 and linking portion 730 are connected by elastic support portion 930. The set of elastic support member 910, connecting end 810 and connecting portion 710, the set of elastic support member 920, connecting end 820 and connecting portion 720, and the set of elastic support member 930, connecting end 830 and connecting portion 730 are generally spaced apart at equal angular intervals (180° intervals) in the circumferential direction.

[0046] The elastic support member 910 has a first arm member 911 extending diagonally upward to the right from the connecting member 710, a folded portion 912 folded back from the first arm member 911, and a second arm member 913 extending diagonally downward to the left from the folded portion 912 and connecting to the connecting end 810 (having a meander structure). The left half of the first arm member 911 is provided with a piezoelectric element 1011 and serves as a displacement member 911A that elastically deforms when a drive voltage is applied to the piezoelectric element 1011. The right half of the first arm member 911 is not provided with the piezoelectric element 1011 and serves as a displacement regulating member 911B that does not elastically deform when a drive voltage is applied to the piezoelectric element 1011. The second arm member 913 is provided with a piezoelectric element 1013 and serves as a displacement member 913A that elastically deforms when a drive voltage is applied to the piezoelectric element 1013. As described above, the elastic support member 910 has a first arm member 911 and a second arm member 913 extending adjacent to each other, and a folded portion 912 connecting the ends of the first arm member 911 and the second arm member 913 in the extension direction, and a piezoelectric element 1011 is provided on the first arm member 911, and a piezoelectric element 1013 is provided on the second arm member 913. The piezoelectric elements 1011 and 1013 are provided so as not to be aligned in a direction perpendicular to the extension direction of the first arm member 911 and the second arm member 913. The piezoelectric element 1010 is constituted by a set of the piezoelectric element 1011 and the piezoelectric element 1013.

[0047] The elastic support member 920 has a first arm member 921 extending diagonally downward to the right from the connecting member 720, a folded portion 922 folded back from the first arm member 921, and a second arm member 923 extending diagonally upward to the left from the folded portion 922 and connecting to the connecting end 820 (having a meander structure). The left half of the first arm member 921 is provided with a piezoelectric element 1021 and serves as a displacement member 921A that elastically deforms when a drive voltage is applied to the piezoelectric element 1021. The right half of the first arm member 921 is not provided with the piezoelectric element 1021 and serves as a displacement regulating member 921B that does not elastically deform when a drive voltage is applied to the piezoelectric element 1021. The second arm member 923 is provided with a piezoelectric element 1023 and serves as a displacement member 923A that elastically deforms when a drive voltage is applied to the piezoelectric element 1023. As described above, the elastic support member 920 has a first arm member 921 and a second arm member 923 extending adjacent to each other, and a folded portion 922 connecting the ends of the first arm member 921 and the second arm member 923 in the extension direction, and the piezoelectric element 1021 is provided on the first arm member 921, and the piezoelectric element 1023 is provided on the second arm member 923. The piezoelectric elements 1021 and 1023 are provided so as not to be aligned in a direction perpendicular to the extension direction of the first arm member 921 and the second arm member 923. The piezoelectric element 1020 is constituted by a set of the piezoelectric element 1021 and the piezoelectric element 1023.

[0048] The elastic support member 930 has a first arm member 931 extending leftward from the connecting member 730, a folded portion 932 folded back from the first arm member 931, and a second arm member 933 extending rightward from the folded portion 932 and connecting to the connecting end 830 (having a meander structure). The right half of the first arm member 931 is provided with a piezoelectric element 1031, and serves as a displacement member 931A that elastically deforms when a drive voltage is applied to the piezoelectric element 1031. The left half of the first arm member 931 is not provided with the piezoelectric element 1031, and serves as a displacement regulating member 931B that does not elastically deform when a drive voltage is applied to the piezoelectric element 1031. The second arm member 933 is provided with a piezoelectric element 1033, and serves as a displacement member 933A that elastically deforms when a drive voltage is applied to the piezoelectric element 1033. As described above, the elastic support member 930 has a first arm member 931 and a second arm member 933 extending adjacent to each other, and a folded portion 932 connecting the ends of the first arm member 931 and the second arm member 933 in the extension direction. A piezoelectric element 1031 is provided on the first arm member 931, and a piezoelectric element 1033 is provided on the second arm member 933. The piezoelectric elements 1031 and 1033 are arranged so as not to be aligned in a direction perpendicular to the extension direction of the first arm member 931 and the second arm member 933. The piezoelectric element 1030 is constituted by a set of the piezoelectric element 1031 and the piezoelectric element 1033.

[0049] As shown in FIG. 4, the fixed support portion 700 is constructed by stacking a support layer 730, an oxide insulating layer 740, a silicon active layer 750, and an insulating layer 760 in this order from the lower layer side to the upper layer side in the Z direction.

[0050] The displacement regulating portion 921B and the displacement regulating portion 931B are constructed by laminating a silicon active layer 750 and an insulating layer 760 in order from the lower layer side to the upper layer side in the Z direction (they have a laminated structure that is partially shared with the fixed support portion 700).

[0051] The displacement section 923A (including the piezoelectric element 1023) and the displacement section 933A (including the piezoelectric element 1033) constitute an actuator in which a piezoelectric element 1000 is formed on the upper surface of a silicon active layer 750. The piezoelectric element 1000 is formed by laminating, from the lower layer side to the upper layer side in the Z direction, a lower electrode 1000A, a piezoelectric material 1000B, and an upper electrode 1000C. By applying a drive voltage to the lower electrode 1000A and the upper electrode 1000C, the displacement sections 923A and 933A are elastically deformed. An insulating layer 760 and a protective film 1100 are provided on the upper surface of the piezoelectric element 1000 (upper electrode 1000C).

[0052] In this embodiment, by applying a drive voltage to the piezoelectric elements 1011, 1013, 1021, 1023, 1031, and 1033 to elastically deform the elastic support members 910, 920, and 930, the distance between the first reflecting mirror 400 and the second reflecting mirror 800 (the half-VCSEL element 100 and the second reflecting mirror 800) can be changed, thereby changing the oscillation wavelength of light emitted by the half-VCSEL element 100. That is, second reflecting mirror 800 as a movable reflecting mirror can translate fixed support member 700 and second reflecting mirror 800 as a movable reflecting mirror in the Z direction by taking over the displacement generated by the combination of the meandering structure actuators (piezoelectric elements 1011, 1013, 1021, 1023, 1031, 1033), displacement regulating members 911B, 921B, 931B, and folded members 912, 922, 932 via connecting ends 810, 820, 830. This translation in the Z direction is achieved by applying a drive voltage to lower electrode 1000A and upper electrode 1000C of the actuator to generate a potential difference.

[0053] When a drive voltage (for example, the same voltage) is applied to the piezoelectric element, the volume of the piezoelectric element changes. Because the piezoelectric element and the arm are physically connected, in-plane stress is generated near the piezoelectric element in the arm. The arm, to which stress is applied, undergoes elastic deformation to relieve the stress. In this case, if the arm's XY dimension ratio is made anisotropic and the thickness of the arm in the Z direction is made smaller than its dimensions in the X and Y directions, the arm will predominantly warp in the Z direction, and the piezoelectric element will similarly warp in the Z direction with a specified radius of curvature. The warping of the arm caused by the piezoelectric element is transmitted to the displacement determining section, which does not have a piezoelectric element. The displacement determining section bends in the Z direction due to the effect of gravity, but this is small enough compared to the warping of the piezoelectric element that it can be ignored (equivalent to no elastic deformation).

[0054] FIG. 5 is a side view illustrating the driving state of second reflecting mirror 800 in the support structure of FIGS. 3 and 4. FIG. 5 illustrates an enlarged view of elastic support member 910, but elastic support members 920 and 930 have a similar configuration. In FIG. 5, Z-direction displacement Z1 of folded portion 912 of elastic support member 910 can be achieved by increasing the deflection generated by piezoelectric elements 1011 and 1013 (reducing the radius of curvature), or by lengthening displacement regulating portion 911B of first arm portion 911, or by both. First arm portion 911 is tilted toward folded portion 912 at an angle θ1 from the free state, and immediately after folding back by folded portion 912, second arm portion 913 is tilted at an angle θ2 from the free state (the difference between angle θ1 and angle θ2 is the tilt angle between first arm portion 911 and second arm portion 913). When a piezoelectric element of the same dimensions as first arm portion 911 is formed on second arm portion 913 and driven, the tilt of first arm portion 911 is cancelled. Therefore, at connection end 810 at the end of second arm portion 913, second reflecting mirror 800 as a movable reflecting mirror can be driven in the Z direction while maintaining the parallelism between the XY plane of fixed support portion 700 and second reflecting mirror 800 as a movable reflecting mirror before driving.

[0055] The dimensions on the XY plane of the piezoelectric elements formed on the first arm portion 911 and the second arm portion 913 may or may not be the same. If they are not the same, it is necessary to adjust the voltage applied to each piezoelectric element so that the warping generated in each piezoelectric element portion is the same.

[0056] The drive voltage applied to the piezoelectric element can be a DC voltage, or a sine wave, cosine wave, or triangular wave, which changes over time. Note that, under conditions where the modulation frequency of the voltage and the resonant frequency of the movable reflecting mirror element are separated from each other, the linearity of the displacement amount relative to the voltage is maintained, as described above. Piezoelectric elements are driven by applying a voltage, and there is a linear relationship between the voltage and the generated stress. Furthermore, there is also a linear relationship between the generated stress and the deformation amount of the arm, so there is a linear relationship between the applied voltage and the displacement amount.

[0057] Fig. 6 is a diagram showing the relationship between the drive voltage and the cavity length of the tunable laser 10 of this embodiment, and Fig. 7 is a diagram showing the relationship between the drive voltage and the cavity length of a conventional MEMS-type tunable laser using electrostatic attraction. As shown in Fig. 6, the tunable laser 10 of this embodiment achieves high linearity between the drive voltage and the cavity length. On the other hand, as shown in Fig. 7, in the conventional MEMS-type tunable laser using electrostatic attraction, the linearity between the drive voltage and the cavity length is insufficient due to the fact that the position of the reflecting mirror on the MEMS side is proportional to the square of the drive voltage and the influence of the pull-in effect, in which the films are attracted to each other when the gap between the two reflecting mirrors is displaced to ⅓ or more of the initial gap.

[0058] FIG. 8 is a functional block diagram showing a configuration for supplying independent drive signals (drive voltages) to the piezoelectric elements 1010 to 1030 of the elastic support portions 910 to 930. As shown in FIG.

[0059] As shown in FIG. 8, a drive signal supply unit (drive voltage supply unit) 1200, which is a functional component of a CPU (Central Processing Unit), supplies independent drive signals (drive voltage signals) to the piezoelectric element 1010 (piezoelectric elements 1011, 1013) of the elastic support member 910, the piezoelectric element 1020 (piezoelectric elements 1021, 1023) of the elastic support member 920, and the piezoelectric element 1030 (piezoelectric elements 1031, 1033) of the elastic support member 930, thereby elastically deforming the elastic support members 910, 920, and 930 independently, thereby changing the surface parallelism of the first reflecting mirror 400 and the second reflecting mirror 800 (the surface parallelism of the Half-VCSEL element 100 and the second reflecting mirror 800).

[0060] Among the drive signals (drive voltage signals) supplied to the piezoelectric element 1010 of the elastic support member 910, the drive signal supplying section 1200 may further separate the drive signals (drive voltage signals) supplied to the piezoelectric elements 1011 and 1013.

[0061] Among the drive signals (drive voltage signals) supplied to the piezoelectric element 1020 of the elastic support member 920, the drive signal supplying section 1200 may further separate the drive signals (drive voltage signals) supplied to the piezoelectric elements 1021 and 1023.

[0062] Among the drive signals (drive voltage signals) supplied to the piezoelectric element 1030 of the elastic support member 930, the drive signal supplying section 1200 may further separate the drive signals (drive voltage signals) supplied to the piezoelectric elements 1031 and 1033.

[0063] For example, if a portion of the elastic support members 910, 920, 930 is too close or too far from the first reflecting mirror 800 (Half-VCSEL element 100) compared to the other portions of the elastic support members, the drive signal (drive voltage signal) supplied to the piezoelectric element of that portion of the elastic support member can be made different from the drive signal (drive voltage signal) supplied to the piezoelectric element of the other portions of the elastic support members. This adjusts the attitude of the elastic support members 910, 920, 930 (whether or not to elastically deform, and if so, the degree and direction of elastic deformation, etc.), thereby making it possible to optimally set the surface parallelism between the first reflecting mirror 400 and the second reflecting mirror 800 (the surface parallelism between the Half-VCSEL element 100 and the second reflecting mirror 800).

[0064] The drive signal supply unit 1200 supplies independent drive signals (drive voltage signals) to the piezoelectric elements 1010 (piezoelectric elements 1011, 1013), 1020 (piezoelectric elements 1021, 1023), and 1030 (piezoelectric elements 1031, 1033) of the elastic support units 910, 920, and 930 based on the inclination of the second reflecting mirror 800 relative to the first reflecting mirror 400, thereby elastically deforming the elastic support units 910, 920, and 930 independently, thereby improving the surface parallelism of the first reflecting mirror 400 and the second reflecting mirror 800 (the surface parallelism of the Half-VCSEL element 100 and the second reflecting mirror 800).

[0065] Drive signal supply unit 1200 supplies independent drive signals (drive voltage signals) to piezoelectric elements 1010 (piezoelectric elements 1011 and 1013), piezoelectric elements 1020 (piezoelectric elements 1021 and 1023), and piezoelectric elements 1030 (piezoelectric elements 1031 and 1033) of elastic support units 910, 920, and 930 based on the intensity of light emitted by half-VCSEL element (light-emitting unit) 100, thereby elastically deforming elastic support units 910, 920, and 930 independently, thereby improving the intensity of light emitted by half-VCSEL element (light-emitting unit) 100. There is a degree of freedom in the method for detecting the intensity of light emitted by half-VCSEL element (light-emitting unit) 100, and for example, an external detection device (photodiode) that detects the reflectance of first reflecting mirror 400 and second reflecting mirror 800 can be used.

[0066] The tilt adjustment of second reflecting mirror 800 by drive signal supply unit 1200 can be performed during manufacturing or mounting of tunable laser 10. Alternatively, since tilt adjustment may be required after manufacturing or mounting depending on the surrounding environment (materials and temperature), tilt adjustment of second reflecting mirror 800 by drive signal supply unit 1200 can also be performed as a calibration process at startup or at predetermined time intervals.

[0067] The drive signal supply unit 1200 may be either an internal or external component of the tunable laser 10, and there is a degree of freedom in the specific form thereof (it is not limited to that shown in FIG. 8).

[0068] FIG. 9 is a diagram showing an example of the operation of applying different voltages to two connecting parts to give the reflecting part (second reflecting mirror 800) an inclination θ.

[0069] 9, when one connecting part is displaced in the +z direction and the other connecting part is displaced in the -z direction, the reflecting part (second reflecting mirror 800) tilts by θ relative to when it is not driven. The resulting tilt depends on the displacement Δz of the connecting part and the distance l between the connection ends, and the relationship is θ = arcsin(2 Δz / l).

[0070] Figure 10 shows an example of the relationship between the displacement of the connecting part and the tilt obtained when the distance between the connection ends is changed. By appropriately setting the displacement of the connecting part and the distance between the connection ends, it is possible to absorb the tilt that occurs during mounting (the tilt of the first reflecting mirror 400 and the second reflecting mirror 800). When the same offset voltage is further applied while different voltages are applied to multiple connecting parts, the linearity between the voltage and the displacement described above allows the reflecting part to be driven in the Z direction while maintaining its tilt. Therefore, wavelength sweeping is possible while maintaining the tilt of the reflecting part that is optimal for laser oscillation.

[0071] 11A and 11B are diagrams showing an example of wavelength sweeping by the tunable laser 10 of this embodiment.

[0072] The laser oscillation wavelength of the tunable laser 10 is determined by the emission spectrum (i.e., wavelength distribution) specific to the material composing the active layer 105 and the resonator structure. The resonator structure is determined by the distance G in the Z direction between the first reflecting mirror 400 and the second reflecting mirror 800 and the refractive index and dimensions of the material present between the first reflecting mirror 400 and the second reflecting mirror 800. The active layer 105 emits light in response to a current injected through the electrodes of the half-VCSEL device 100, and the wavelength of the resonant light (oscillation light) changes depending on the distance G in the Z direction between the first reflecting mirror 400 and the second reflecting mirror 800. FIG. 11A illustrates a state in which the resonant light (oscillation light) is directed downward in the Z direction, and FIG. 11B illustrates a state in which the resonant light (oscillation light) is directed upward in the Z direction.

[0073] Since the position of the second reflecting mirror 800 as a movable reflecting mirror element can be changed in the Z direction, the distance G in the Z direction between the first reflecting mirror 400 and the second reflecting mirror 800 can be varied, and the wavelength of the resonant light (oscillation light) can be modulated. In particular, in this embodiment, by devising a support structure for the second reflecting mirror 800 using the elastic support member 900 and the piezoelectric element 1000, the distance G in the Z direction between the first reflecting mirror 400 and the second reflecting mirror 800 can be controlled with high precision. This improves the linearity of the oscillation wavelength relative to the drive voltage, making it possible to obtain light of the desired oscillation wavelength.

[0074] Furthermore, by supplying independent drive signals (drive voltage signals) to the piezoelectric element 1010 (piezoelectric elements 1011, 1013) of the elastic support member 910, the piezoelectric element 1020 (piezoelectric elements 1021, 1023) of the elastic support member 920, and the piezoelectric element 1030 (piezoelectric elements 1031, 1033) of the elastic support member 930, and elastically deforming the elastic support members 910, 920, and 930 independently, it is possible to improve the surface parallelism of the first reflecting mirror 400 and the second reflecting mirror 800 (the surface parallelism of the Half-VCSEL element 100 and the second reflecting mirror 800).

[0075] 12 shows the results of a simulation showing the relationship between the length of the gap between the half-VCSEL element 100 (first reflecting mirror 400) and the second reflecting mirror 800 and the oscillation wavelength. Oscillated light from the half-VCSEL element 100 is emitted from either the first reflecting mirror 400 or the second reflecting mirror 800, whichever has the lower reflectivity. Therefore, the emission direction of the oscillating light from the half-VCSEL element 100 can be adjusted by adjusting the relative magnitude of the reflectivities of the first reflecting mirror 400 and the second reflecting mirror 800. For example, if the reflectivity of the first reflecting mirror 400 is made lower than that of the second reflecting mirror 800, the oscillating light is emitted downward in the Z direction (FIG. 11A), and if the reflectivity of the first reflecting mirror 400 is made higher than that of the second reflecting mirror 800, the oscillating light is emitted upward in the Z direction (FIG. 11B).

[0076] In addition, bonding layers made of a metal multilayer film made of multiple metals are formed on each of the half-VCSEL element 100 (first reflecting mirror 400) and the second reflecting mirror 800. For example, by bonding the bonding layers on each element using atomic diffusion bonding, a space can be secured between the first reflecting mirror 400 and the second reflecting mirror 800. Furthermore, the active layer 105 of the half-VCSEL element 100 is provided in the center of the resonator structure, which is a position corresponding to an antinode in the standing wave distribution of the electric field, so as to obtain a high stimulated emission probability.

[0077] Fig. 13 is a diagram showing a first modified example of the tunable laser 10 of this embodiment. In Fig. 13, multiple half-VCSEL elements 100 are provided for one second reflecting mirror 800. Specifically, three half-VCSEL elements 100X, 100Y, and 100Z adjacent in the X direction on the XY plane are provided for one second reflecting mirror 800. Furthermore, the first reflecting mirror 400, semiconductor substrate 500, and anti-reflection film 600 may be shared by the three half-VCSEL elements 100X, 100Y, and 100Z.

[0078] 13, when current is injected into the three Half-VCSEL elements 100X, 100Y, and 100Z while the reflector (second reflector 800) is tilted, a gradient occurs in the cavity length of each element, which can cause dispersion of the oscillation wavelength. Furthermore, the magnitude of the wavelength dispersion can be controlled by controlling the amount of tilt.

[0079] FIG. 14 is a diagram showing a second modified example of the tunable laser 10 of this embodiment. In FIG. 14, a movable reflecting mirror structure 800X for high-speed operation is added inside a second reflecting mirror 800 serving as a movable reflecting mirror. The length of the gap between the half-VCSEL element 100 (first reflecting mirror 400) and the second reflecting mirror 800, which are bonded via a bonding layer 300, varies depending on the operating environment (e.g., temperature) of the tunable laser 10. The length of this gap change is several micrometers, and the center value of the oscillation wavelength can be fixed by statically driving the meander structure with a voltage that is prepared (set) in advance according to the operating environment (e.g., temperature) of the tunable laser 10. Furthermore, by fixing the center wavelength and displacing the movable reflecting mirror structure 800X for high-speed operation by several tens of nanometers in the Z direction using a modulation signal, the center wavelength can be kept constant regardless of environmental changes, and the oscillation wavelength can be swept over a certain wavelength range. In this way, by providing the second reflecting mirror 800, which is responsible for a relatively large driving range, and the movable reflecting mirror structure 800X, which is responsible for a relatively small driving range (by dividing the functions), it is possible to more accurately control the gap between the Half-VCSEL element 100 (first reflecting mirror 400) and the second reflecting mirror 800. This further improves the linearity of the oscillation wavelength with respect to the driving voltage, making it possible to obtain light with the desired oscillation wavelength.

[0080] Here, as shown in Figure 9 above, if the reflector (second reflector 800) is driven in the Z direction without correcting its tilt, only a portion of the reflected light enters the active layer, resulting in increased loss in the resonator. As a result, laser oscillation becomes difficult in wavelength regions with small gain, narrowing the wavelength sweep width. Therefore, correcting the tilt of the reflector, which can minimize loss during reflection, can achieve effects such as expanding the wavelength sweep width and increasing the light intensity.

[0081] Figure 15A shows a cross-sectional view of a bonded movable reflector element and half-VCSEL element when tilt correction is not performed. One reason for a decrease in the plane parallelism between the movable reflector element and half-VCSEL element is a difference in the thickness of the bonding layer after bonding. This height difference does not necessarily have a single cause; examples include a difference in the thickness of the bonding layer before bonding, or an in-plane distribution of heat and pressure applied to the movable reflector element, half-VCSEL element, and bonding layer during bonding.

[0082] Figure 15B shows a cross-sectional view of a half-VCSEL device bonded to a second reflector and a movable reflector element having a high-speed movable reflector structure. As shown in Figure 15A, when the surface parallelism deteriorates, it can be improved by driving the elastic support members supporting the second reflector and the piezoelectric elements attached to each elastic support member with independent drive signals. Furthermore, by continuously driving the high-speed movable reflector structure over time using a modulation signal while maintaining this voltage, it is possible to simultaneously suppress light reflection loss and rapidly sweep the wavelength.

[0083] FIG. 16A is a diagram showing an example of adjusting the tilt of the second reflecting mirror. When a piezoelectric element on an elastic body connected to the second reflecting mirror is not driven, a tilt α occurs between the normal to the second reflecting mirror when it is driven and when it is not driven, relative to the normal to the second reflecting mirror when it is not driven. Furthermore, the position of a point P on a line extending from the surface of the reflecting mirror along the normal direction when it is not driven changes depending on the drive voltage of the piezoelectric element. For example, by driving multiple piezoelectric elements with independent voltage signals and changing the relative or absolute value difference between the signal values, the tilt α and the position of point P can be controlled.

[0084] FIG. 16B is a diagram showing an example of the relationship between voltage signals applied to piezoelectric elements. Here, an example is shown in which three piezoelectric elements are independently driven by signals A, B, and C. The three voltage values ​​are set so that they vary sinusoidally with respect to the phase. For example, if initial phases phase_ini_A, phase_ini_B, and phase_ini_C are given to each signal, the voltage signal at a certain phase is given by the following equation. Amp indicates amplitude. Voltage_A = Amp*sin(phase + phase_ini_A) Voltage_B = Amp*sin(phase + phase_ini_B) Voltage_C = Amp*sin(phase + phase_ini_C)

[0085] From the above equation, the voltage values ​​of all signals can be calculated by applying a certain phase. Because the voltage applied to the piezoelectric element is proportional to the displacement of the elastic body, setting a certain phase prevents the displacement of each elastic body from being uniform, which controls the tilt α and the position of point P as shown in Figure 16A, and ultimately enables the tilt of the second reflecting mirror to be adjusted with high precision.

[0086] Fig. 17 is a diagram showing an example of an outline of calibration of the surface parallelism between the movable reflecting mirror element and the half-VCSEL element, and Fig. 18 is a diagram showing an example of the relationship between the phase of the drive signal source and the optical output value of the tunable laser during calibration.

[0087] The drive signal source includes a voltage signal source that drives the piezoelectric element in the movable mirror element that constitutes the tunable laser, and a current signal source that injects current into the half-VCSEL element. Sweeping the phase of the voltage signal source while injecting a certain current into the half-VCSEL element changes the tilt of the second mirror. At a certain tilt, the plane between the movable mirror element and the half-VCSEL element approaches parallelism, minimizing loss during light reflection. When loss is small, the intensity of the spontaneously emitted or oscillated light emitted from the tunable laser increases. Therefore, the optical output intensity is maximized at a certain phase of the drive signal source. The photoelectric conversion element generates a voltage corresponding to the intensity of the incident light. By plotting the relationship between the phase value and the optical output intensity using the phase value and voltage value of the drive source or the conversion constant of the photoelectric conversion element (the voltage generated per unit optical output value), and searching for the phase value at which the voltage value (or optical output value) is maximized, the phase condition that indicates a high degree of plane parallelism can be determined. In addition to the optical output value, the use of the oscillation threshold current and slope efficiency, which are used as performance indicators of the tunable laser, enables calibration to optimize each performance. This calibration can be performed not only when starting up a device using this tunable laser, but also when significant changes in external factors such as temperature, humidity, and atmospheric pressure occur, allowing the device to operate while maintaining constant performance. For example, a temperature measurement element (temperature measurement element) is placed near the light source to measure the temperature of the tunable laser or its vicinity during oscillation. The memory unit stores the relationship between the wavelength and optical output value of the tunable laser during oscillation and temperature, for example, as a correlation equation or table, and also stores the relationship between the drive voltage of the piezoelectric element and the amount of change in oscillation wavelength. Based on the measured temperature-wavelength relationship in the memory unit, the processing unit determines a correction voltage that maintains a constant oscillation wavelength or maximizes the optical output value with respect to temperature changes, and the drive signal source drives the piezoelectric element according to that voltage.

[0088] As described above, the optical device of this embodiment includes a first reflecting unit, a second reflecting unit, at least three elastic support members supporting the second reflecting unit, and piezoelectric elements provided on each of the at least three elastic support members. The surface parallelism of the first and second reflecting units (or the surface parallelism of the light-emitting unit and the second reflecting unit) is changed by supplying independent drive signals to the piezoelectric elements of the at least three elastic support members, thereby independently elastically deforming the at least three elastic support members. That is, by using a piezoelectric drive method and supporting the support members and the mirror with a joint having three or more drive units, the tilt of the light-emitting unit (e.g., a half-VCSEL element) and the mirror can be freely adjusted by independently controlling the drive units. This improves the surface parallelism of the two reflecting mirrors (the first and second reflecting mirrors) or the surface parallelism of the light-emitting unit (e.g., a half-VCSEL element) and the reflecting mirror (the second reflecting mirror). As a result, the threshold current of the light-emitting unit can be reduced, thereby improving the emission intensity.

[0089] The present invention is not limited to the above-described embodiment, and various modifications can be made to the present invention. In the above-described embodiment, the size, shape, and function of the components illustrated in the accompanying drawings are not limited to these, and can be modified as appropriate within the scope of the effects of the present invention. In addition, the present invention can be modified as appropriate without departing from the scope of the object of the present invention.

[0090] In the above embodiment, an example has been described in which three elastic support parts for supporting the second reflecting mirror are provided spaced apart around the periphery of the second reflecting mirror, but the number of elastic support parts provided spaced apart around the periphery of the second reflecting mirror is flexible, and various design modifications are possible. For example, four, five, six or more elastic support parts for supporting the second reflecting mirror may be provided spaced apart around the periphery of the second reflecting mirror (as long as at least three are provided).

[0091] In the above-described embodiment, the at least three elastic support members each have a meander structure including two adjacently extending arms and one folded portion connecting the ends of the two arms in the extension direction, and piezoelectric elements are provided on two of the arms. However, the at least three elastic support members may each have a meander structure including three or more adjacently extending arms and two or more folded portions connecting the ends of the three or more arms in the extension direction, and piezoelectric elements may be provided on three or more arms. That is, it is sufficient that the at least three elastic support members each have a plurality of adjacently extending arms and a folded portion connecting the ends of the plurality of arms in the extension direction, and that piezoelectric elements are provided on the plurality of arms of the at least three elastic support members, respectively.

[0092] In the above embodiment, the piezoelectric elements are not aligned in a direction perpendicular to the extension direction of the arms of at least three elastic support parts. However, it is also possible to align the piezoelectric elements in a direction perpendicular to the extension direction of the arms of at least three elastic support parts.

[0093] In the above embodiment, the arm portions of at least three elastic support members each have a displacement regulating portion that does not elastically deform when a drive voltage is applied to a piezoelectric element, and the displacement regulating portion is a portion of the arm portions where no piezoelectric element is provided. However, the displacement regulating portion may also be a portion of the arm portions where a piezoelectric element is provided but where no drive voltage is applied. [Explanation of symbols]

[0094] 10 Tunable laser (optical device) 100 Half-VCSEL element (light-emitting part, first substrate) 200 Movable reflecting mirror element (second substrate) 400 First reflecting mirror (first reflecting portion) 800 Second reflector (second reflecting portion) 900, 910, 920, 930 Elastic support part 911, 921, 931 First arm 911B, 921B, 931B Displacement regulation part 913, 923, 933 Second arm 912, 922, 932 Folded section 1000, 1010, 1011, 1013, 1020, 1021, 1023, 1030, 1031, 1033 Piezoelectric elements 1200 Drive signal supply unit (drive voltage supply unit)

Claims

1. An optical device that outputs laser light, in which the first reflector, an active layer, and a second reflector are arranged in this order in a direction perpendicular to the first reflector, the active layer; the first reflecting portion; a light emitting unit including: the second reflecting portion; At least three elastic support portions that support the second reflecting portion; a piezoelectric element provided on each of the at least three elastic support portions; a movable reflector element including: and changing the surface parallelism of the first reflecting portion and the second reflecting portion by independent elastic deformation of the at least three elastic support portions due to drive signals independently supplied to the piezoelectric elements of the at least three elastic support portions; supplying independent drive signals to the piezoelectric elements of the at least three elastic support portions based on the intensity of the laser light from the optical device, thereby elastically deforming the at least three elastic support portions independently; An optical device characterized by:

2. a first substrate on which the first reflecting portion and the light emitting portion are formed; a second substrate on which the second reflecting portion, the at least three elastic support portions, and the piezoelectric element are formed; 2. The optical device according to claim 1, further comprising:

3. An optical device that outputs laser light, in which the first reflector, an active layer, and a second reflector are arranged in this order in a direction perpendicular to the first reflector, the active layer; the first reflecting portion; a light emitting unit including: the second reflecting portion; At least three elastic support portions that support the second reflecting portion; a piezoelectric element provided on each of the at least three elastic support portions; a movable reflector element including: and changing the surface parallelism of the first reflecting portion and the second reflecting portion by independent elastic deformation of the at least three elastic support portions due to drive signals independently supplied to the piezoelectric elements of the at least three elastic support portions; each of the at least three elastic support portions has a plurality of arm portions extending adjacent to each other and a folded portion connecting end portions of the plurality of arm portions in the extension direction; the piezoelectric elements are provided on the arm portions of the at least three elastic support portions, respectively; An optical device characterized by:

4. the piezoelectric elements are provided so as not to be aligned in a direction perpendicular to the extension direction of the plurality of arm portions of the at least three elastic support portions, 4. The optical device according to claim 3.

5. the plurality of arm portions of the at least three elastic support portions each have a displacement regulating portion that does not elastically deform when a drive voltage is applied to the piezoelectric element; 5. The optical device according to claim 3 or 4.

6. the displacement regulating portion is a portion of the plurality of arms where the piezoelectric element is not provided; 6. The optical device according to claim 5.

7. improving the surface parallelism of the first reflecting portion and the second reflecting portion by independent elastic deformation of the at least three elastic support portions due to drive signals independently supplied to the piezoelectric elements of the at least three elastic support portions based on the inclination of the second reflecting portion relative to the first reflecting portion; 7. The optical device according to claim 1, wherein the optical element is a lens.

8. the at least three elastic support portions are provided spaced apart around the periphery of the second reflecting portion; 8. The optical device according to claim 1, wherein the optical element is a lens.

9. the second reflecting portion includes a movable reflecting mirror structure having a driving range smaller than a driving range of the second reflecting portion; 9. The optical device according to claim 1, wherein the optical element is a lens.

10. a bonding layer that bonds the light emitting section and the movable reflecting mirror element; the movable reflecting mirror element further includes a frame-shaped fixed support portion surrounding the second reflecting portion, the elastic support portion connects the second reflecting portion and the fixed support portion, and supports the second reflecting portion with a through hole interposed between the second reflecting portion and the fixed support portion; The bonding layer is provided at a position overlapping the fixed support portion.

10. The optical device according to claim 1.

11. the piezoelectric element is not provided on the second reflecting portion but on the elastic supporting portion; 11. The optical device according to claim 1.

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