Optical device and wavelength variable laser

Abstract

An optical device (10) has, for example, a multimode interference waveguide (11) having a first end portion (11a) in a first direction (D1) and a second end portion (11b) in a direction opposite to the first direction, a first port (p1) in the first end portion offset from a center of a second direction (D2) crossing the first direction toward the second direction, a second port (p2) in the first end portion located on an opposite side from the first port with respect to the center of the second direction, a third port (p3) in the second end portion located at the center of the second direction, and two fourth ports (p4) in the second end portion offset from the third port toward both sides of the second direction. The multimode interference waveguide is configured so that in-phase components of light input to the first port and the second port are coupled at the third port, and opposite-phase components of light input to the first port and the second port are coupled at the two fourth ports.

Description

Technical Field

[0001] This invention relates to optical devices and wavelength-variable lasers. Background Technology

[0002] Previously, wavelength-variable lasers equipped with ring resonators were known (for example, Patent Document 1). In Patent Document 1, a 2×2 multimode interference waveguide (MMI) was provided at the coupling section between the linear waveguide and the ring waveguide.

[0003] Prior art literature

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-093627 Summary of the Invention

[0006] -The problem the invention aims to solve-

[0007] In such optical devices, it is preferable to have minimal optical loss relative to manufacturing errors in the multimode interference waveguide. Furthermore, it is preferable to have a structure that appropriately handles stray light generated in the multimode interference waveguide.

[0008] Therefore, one of the objectives of this invention is, for example, to obtain optical devices and wavelength-variable lasers with further improved structures that can further reduce light loss or more appropriately handle stray light.

[0009] -Methods for solving problems-

[0010] The optical device of the present invention includes, for example, a multimode interference waveguide having a first end in a first direction and a second end in a direction opposite to the first direction; a first port offset from the center of a second direction intersecting the first direction toward the second direction; a second port located on the opposite side of the first end relative to the center of the second direction; a third port located at the center of the second end in the second direction; and two fourth ports offset to both sides of the second end relative to the third port in the second direction. The multimode interference waveguide is configured such that in-phase components of light input to the first port and the second port are coupled at the third port, and out-of-phase components of light input to the first port and the second port are coupled at the two fourth ports.

[0011] The optical device may also have a light processing unit that is optically connected to the fourth port.

[0012] The optical device may also have a third connecting waveguide, one end of which is optically connected to the first port and the other end of which is optically connected to the second port.

[0013] The optical device may also include: a first multimode interference waveguide serving as the multimode interference waveguide; a second multimode interference waveguide serving as the multimode interference waveguide, spaced apart from the first multimode interference waveguide in the opposite direction to the second direction; a first waveguide optically connected to the first port of the first multimode interference waveguide; a curved first connecting waveguide optically connecting the third port of the first multimode interference waveguide to the third port of the second multimode interference waveguide; a curved second connecting waveguide optically connecting the first port of the second multimode interference waveguide to the second port of the first multimode interference waveguide; and a second waveguide optically connected to the second port of the second multimode interference waveguide.

[0014] The optical device may also include a first optical processing unit, which is optically connected to both the fourth port of the first multimode interference waveguide that is closest to the second multimode interference waveguide and the fourth port of the second multimode interference waveguide that is closest to the first multimode interference waveguide.

[0015] The optical device may also include a second optical processing unit, which is optically connected to both the fourth port of the first multimode interference waveguide that is remote from the second multimode interference waveguide and the fourth port of the second multimode interference waveguide that is remote from the first multimode interference waveguide.

[0016] The wavelength-variable laser of the present invention, for example as a filter or a reflector, includes one or more of the aforementioned optical devices.

[0017] -Invention Effects-

[0018] According to the present invention, new optical devices and wavelength-variable lasers can be obtained with further improvements. Attached Figure Description

[0019] Figure 1 This is an illustrative and schematic top view of the optical device according to the first embodiment.

[0020] Figure 2 This is an illustrative and schematic top view of the optical device according to the second embodiment.

[0021] Figure 3 This is an illustrative and schematic top view of the wavelength-variable laser of the third embodiment.

[0022] Figure 4 This is an illustrative and schematic top view of the wavelength-variable laser according to the fourth embodiment.

[0023] Figure 5 This is an illustrative and schematic top view of the wavelength-variable laser according to the fifth embodiment.

[0024] Figure 6 This is an illustrative and schematic top view of the wavelength-variable laser according to the sixth embodiment.

[0025] Figure 7 This is an exemplary and schematic top view of the wavelength-variable laser according to the seventh embodiment.

[0026] Figure 8 This is an illustrative and schematic top view of the wavelength-variable laser according to the eighth embodiment.

[0027] Figure 9 This is an exemplary and schematic top view of the wavelength-variable laser according to the ninth embodiment.

[0028] Figure 10 This is an illustrative and schematic top view of the wavelength-variable laser according to the tenth embodiment. Detailed Implementation

[0029] The following are exemplary embodiments of the present invention. The structure of the embodiments shown below, as well as the effects and results (effects) resulting from such structures, are examples. The present invention can also be implemented using structures other than those disclosed in the following embodiments. Furthermore, according to the present invention, at least one of various effects (including derived effects) obtained by the structure can be obtained.

[0030] The various embodiments shown below have the same structure. Therefore, based on the structure of each embodiment, the same functions and effects based on this same structure can be obtained. Furthermore, in the following, these same structures are sometimes labeled with the same reference numerals, and repeated descriptions are omitted.

[0031] In this specification, ordinal numbers are assigned to distinguish parts, directions, etc., and do not indicate priority or order.

[0032] Furthermore, in each diagram, arrow D1 represents the D1 direction, arrow D2 represents the D2 direction, and arrow Z represents the Z direction. The D1, D2, and Z directions intersect and are orthogonal to each other.

[0033] [First Implementation Method]

[0034] Figure 1This is a top view of the optical device 10 according to the first embodiment. The optical device 10 has a multimode interference waveguide 11 and multiple waveguides 12 and 14 optically connected to the multimode interference waveguide 11 via multiple ports p1 to p4. Waveguides 12 are connected to ports p1, p2, and p3 respectively, and waveguides 14 are connected to two ports p4 respectively.

[0035] The multimode interferometric waveguide 11 has an end 11a in the D1 direction and an end 11b in the opposite direction of the D1 direction. The D1 direction is an example of a first direction. Furthermore, end 11a is an example of a first end, and end 11b is an example of a second end.

[0036] The multimode interferometric waveguide 11 has a port p1 at end 11a that is offset from the center of the D2 direction towards the D2 direction. The D2 direction intersects the D1 direction and is an example of a second direction. Port p1 is an example of a first port.

[0037] The multimode interference waveguide 11 has a port p2 at end 11a that is offset from the center of the D2 direction in the opposite direction to the D2 direction. Port p2 is located on the opposite side of port p1 relative to the center of the D2 direction at end 11a. Port p2 is an example of a second port.

[0038] The multimode interference waveguide 11 has a port p3 located at the center in the D2 direction at end 11b. Port p3 is an example of a third port.

[0039] The multimode interference waveguide 11 of this embodiment is configured as a 1×2 multimode interference waveguide 11 that outputs light input from ports p1 and p2 to port p3. The inventors conducted in-depth research through simulations and experiments, and found that the 1×2 multimode interference waveguide 11 has lower sensitivity to light loss relative to manufacturing errors compared to a 2×2 multimode interference waveguide. This is believed to be because, within the specifications corresponding to the same wavelength of light, the 2×2 multimode interference waveguide has a narrower width in the D2 direction compared to the 1×2 multimode interference waveguide, and correspondingly, the impact of manufacturing errors due to this width is greater. According to a study by the inventors, it was determined that in a 2×2 multimode interference waveguide, when the manufacturing error is ±50 [nm], the light loss increases significantly (e.g., to the extent of 0.6 dB). In contrast, in a 1×2 multimode interference waveguide of approximately the same specifications, even with a manufacturing error of ±100 [nm], the increase in light loss can be suppressed to a lower level (e.g., to the extent of 0.2 dB).

[0040] While this method has the advantage of suppressing light loss, it is known that in a 1×2 multimode interference waveguide 11, opposite phase components of the light input from ports p1 and p2 reach both sides of the end 11b in the D2 direction. These opposite phase components are reflected inside the multimode interference waveguide 11, thus becoming a factor of stray light. Stray light can also be referred to as useless light.

[0041] Therefore, the multimode interference waveguide 11 of this embodiment has ports p4 offset to both sides in the D2 direction relative to port p3 at end 11b. Port p4 is an example of a fourth port. Stray light can be appropriately processed from the waveguide 14 connected to port p4.

[0042] Regarding the multimode interference waveguide 11, the length in the D1 direction, the width in the D2 direction, the side shapes on both sides of the D2 direction, and the shapes of the ends 11a and 11b in the D1 direction are set to ensure that light input to ports p1 and p2 with the same phase is coupled to port p3, and light input to ports p1 and p2 with opposite phase components is coupled to both ports p4.

[0043] As explained above, the multimode interferometric waveguide 11 according to this embodiment has the advantage of suppressing light loss due to processing errors compared to a 2×2 multimode interferometric waveguide. Furthermore, the multimode interferometric waveguide 11 of this embodiment is a more robust structure, thus, for example, it can further reduce individual differences (deviations) in the characteristics of the optical device 10 and further improve the yield rate by setting larger tolerances.

[0044] [Second Implementation]

[0045] Figure 2 This is a top view of the ring resonator 10A according to the second embodiment. The ring resonator 10A is an example of an optical device.

[0046] like Figure 2 As shown, the ring resonator 10A has two multimode interference waveguides 11-1 and 11-2, waveguides 12-1 and 12-2 (12) that are optically connected to the two multimode interference waveguides 11-1 and 11-2 respectively, and waveguides 13-1 and 13-2 (12) that are optically connected to the two multimode interference waveguides 11-1 and 11-2, thus forming a ring resonator.

[0047] Furthermore, the ring resonator 10A includes optical processing units 15-1 and 15-2 (15) for processing stray light from multimode interference waveguides 11-1 and 11-2.

[0048] The two multimode interference waveguides 11-1 and 11-2 have the same structure as the first embodiment described above. Furthermore, the two multimode interference waveguides 11-1 and 11-2 have the same specifications in terms of length in the D1 direction, width in the D2 direction, side shape on both sides in the D2 direction, shape of ends 11a and 11b in the D1 direction, number and position of ports p1 to p4, etc.

[0049] The two multimode interferometric waveguides 11-1 and 11-2 are configured in parallel, extending in the D1 direction and aligned in the D2 direction. Multimode interferometric waveguide 11-2 separates from multimode interferometric waveguide 11-1 in the opposite direction to the D2 direction. Multimode interferometric waveguide 11-1 is an example of a first multimode interferometric waveguide, and multimode interferometric waveguide 11-2 is an example of a second multimode interferometric waveguide.

[0050] The ring resonator 10A of this embodiment has an overall structure that includes two multimode interference waveguides 11, multiple waveguides 12, and multiple optical processing units 15. It has a structure that is symmetrical with respect to a center line (not shown) that extends along the D1 direction and passes through the center in the D2 direction.

[0051] Waveguide 12-1 (12) is optically connected to port p1 of multimode interference waveguide 11-1. Waveguide 12-1 is an example of the first waveguide. Laser Li is input to multimode interference waveguide 11-1 via waveguide 12-1 and port p1.

[0052] Waveguide 13-1 (12) optically connects port p3 of multimode interference waveguide 11-1 to port p3 of multimode interference waveguide 11-2, and is bent into an arc shape with a roughly constant radius of curvature. Waveguide 13-1 is an example of the first connected waveguide.

[0053] Waveguide 13-2 (12) optically connects port p1 of multimode interference waveguide 11-2 to port p2 of multimode interference waveguide 11-1, and is bent into an arc shape with a roughly constant radius of curvature. The radius of curvature of waveguide 13-2 is set to be slightly smaller than that of waveguide 13-1. Waveguide 13-2 is an example of a second connecting waveguide.

[0054] Waveguide 12-2 (12) is optically connected to port p2 of multimode interference waveguide 11-2. Waveguide 12-2 is an example of a second waveguide. Laser Lo is output from multimode interference waveguide 11-2 via port p2 and waveguide 12-1.

[0055] In addition, the multimode interference waveguides 11-1 and 11-2 are optically connected to the optical processing units 15-1 and 15-2 via waveguides 14-1 and 14-2 (14) connected to port p4.

[0056] Optical processing units 15-1 and 15-2 process stray light from multimode interference waveguides 11-1 and 11-2, respectively. Optical processing unit 15-1, for example, is a planar waveguide, which processes stray light by allowing it to diffuse and leak outwards, or by scattering light outwards from the uneven shape formed at the boundary with the outside. Furthermore, optical processing unit 15-2, for example, is a bulk semiconductor or a planar waveguide, which allows stray light to diffuse in two or three dimensions, thereby reducing the power density of the stray light while allowing it to leak outwards.

[0057] from Figure 2 It is known that the optical processing unit 15-1 is optically connected to the two multimode interference waveguides 11-1 and 11-2 via the two adjacent ports p4 of the two ports p4 of the multimode interference waveguides 11-1 and 11-2, and waveguide 14-1. The optical processing unit 15-1 is an example of the first optical processing unit.

[0058] Furthermore, the optical processing unit 15-2 is optically connected to the two multimode interference waveguides 11-1 and 11-2 via the two mutually distant ports p4 of the two ports p4 of the multimode interference waveguides 11-1 and 11-2, and waveguide 14-2. The optical processing unit 15-2 is an example of a second optical processing unit.

[0059] That is, in the ring resonator 10A, the optical processing unit 15-1 is shared in the processing of stray light from the two multimode interference waveguides 11-1 and 11-2, and the optical processing unit 15-2 is shared in the processing of stray light from the two multimode interference waveguides 11-1 and 11-2. With this structure, compared with a structure that has separate optical processing units 15 for each of the four ports p4, advantages such as a simpler and smaller device structure can be obtained.

[0060] Waveguides 14-1 and 14-2 (14) can also be referred to as abandoned optical waveguides. The extension direction of each port p4 of waveguides 14-1 and 14-2 forms an acute angle with the opposite direction of D1. Therefore, stray light reflection can be suppressed at each port p4. In addition, the radius of curvature of waveguide 14-1 is smaller than that of waveguides 13-1 and 13-2. Here, waveguide 14-1 can suppress the increase of stray light leakage caused by bending loss by gradually reducing the radius of curvature along the spiral curve away from port p4, and the radius of curvature is set to be smaller.

[0061] According to this embodiment, through the structure of waveguides 14-1, 14-2 (12) and light processing units 15-1, 15-2 (15), stray light recovered from multimode interference waveguides 11-1, 11-2 can be reflected to a farther distance and is less likely to return to the ring resonator. Therefore, the adverse effects of stray light on the main light in the ring resonator can be suppressed.

[0062] [Third Implementation Method]

[0063] Figure 3 This is a top view of the laser device 100 according to the third embodiment. Figure 3 As shown, the laser device 100 includes a DBR section 20, a ring resonator 10A, a gain section 30, an optical amplifier 40, and a waveguide 102.

[0064] The laser device 100 is a semiconductor laser element, an example of a wavelength-variable laser. The laser device 100 is disposed on a semiconductor multilayer substrate 101. The semiconductor multilayer substrate 101 is configured to have multiple semiconductor layers stacked on a semiconductor substrate to have given functions such as waveguides.

[0065] The DBR section 20, the ring resonator 10A, the gain section 30, the optical amplifier 40, and the waveguide 102 are all made of InP-based semiconductor materials.

[0066] The DBR section 20 has a waveguide (not shown) containing a distributed Bragg-type sampling grating (SG-DBR). The DBR section 20 is an example of a reflector and can also be referred to as a first reflector.

[0067] The ring resonator 10A has the same structure as the ring resonator 10A in the second embodiment described above. The ring resonator 10A functions as a mirror whose reflection characteristics periodically change with respect to the wavelength of light input from the waveguide 102. The ring resonator 10A is an example of a filter or a reflector, and an example of a second reflector.

[0068] The gain section 30 has a waveguide path (not shown) made of an active layer.

[0069] In addition, the optical amplifier 40 has a waveguide path (not shown) made of an active layer.

[0070] In the above structure, the active layer, for example, has a multiple quantum well (MQW) structure comprising GaInAsP-based or AlGaInAs-based semiconductor materials. The passive waveguide is, for example, made of type i GaInAsP-based semiconductor material with a bandgap wavelength of 1300 nm. The waveguide of the SG-DBR structure is, for example, made of GaInAsP-based or AlGaInAs-based semiconductor material, and portions with different refractive indices are periodically arranged to form a diffraction grating.

[0071] Miniature heaters (not shown) are provided in both the DBR section 20 and the ring resonator 10A. These miniature heaters are so-called resistive heating elements that generate heat according to the supply of current. The miniature heaters are provided with wiring structures such as electrodes and conductor layers for supplying current.

[0072] The DBR section 20 and the ring resonator 10A constitute a laser resonator. The DBR section 20 has comb-shaped reflection peaks with frequency intervals periodically according to the reciprocal of the period of the diffraction grating. Since the periods of the DBR section 20 and the ring resonator 10A are different, the laser frequency can be coarsely tuned using a method known as a vernier type. Heating the DBR section 20 by a microheater changes its refractive index, thereby shifting the comb-shaped reflection peaks along the frequency axis. Similarly, heating the ring resonator 10A by a microheater changes its refractive index, also shifting the comb-shaped reflection peaks along the frequency axis.

[0073] The gain section 30 is located between the DBR section 20 and the ring resonator 10A. In other words, the ring resonator 10A is positioned on the opposite side of the DBR section 20 relative to the gain section 30. A pair of separate electrodes (not shown) are provided in the gain section 30. By applying a voltage to the pair of electrodes, current flows through the gain section 30, resulting in optical amplification. This generates laser oscillation.

[0074] Optical amplifier 40 is located on the opposite side of gain section 30 and ring resonator 10A relative to DBR section 20, and is situated between DBR section 20 and end 101a, which serves as the laser emission end. By applying a voltage to optical amplifier 40 via electrodes (not shown), current flows within optical amplifier 40, resulting in optical amplification. Optical amplifier 40 amplifies the laser light output from DBR section 20 via laser oscillation.

[0075] The laser device 100 outputs laser L, amplified by the optical amplifier 40, from end 101a. The laser L emitted from end 101a is the output light of the laser device 100.

[0076] In the laser device 100, the ring resonator 10A has the same structure as in the second embodiment described above, and has the same multimode interference waveguides 11-1 and 11-2 (11) as in the first embodiment described above. Therefore, the laser device 100 according to this embodiment can obtain the effects of the first embodiment and the second embodiment described above.

[0077] [Fourth Implementation Method]

[0078] Figure 4This is a top view of the laser device 100A according to the fourth embodiment. (See attached image.) Figure 4 and Figure 3 In contrast, in this embodiment, a multimode interference waveguide 11, which optically couples the two waveguides 12-1 and 12-2 extending from the ring resonator 10A to the waveguide 102, is provided as the coupler in the same manner as in the embodiment described above. In this case, the same effect as in the embodiment described above can be obtained in this coupler.

[0079] [Fifth Implementation]

[0080] Figure 5 This is a top view of the laser device 100B according to the fifth embodiment. Figure 5 As shown, the laser device 100B of this embodiment, like the laser device 100 of the third embodiment described above, includes a DBR section 20, a ring resonator 10A, a gain section 30, an optical amplifier 40, and a waveguide 102.

[0081] However, in this embodiment, a gain section 30 is optically connected to waveguide 12-1 extending from the ring resonator 10A, and a DBR section 20 and an optical amplifier 40 are optically connected to another waveguide 12-2 extending from the ring resonator 10A. From end face 101c2 to end face 101c1 of the semiconductor laminate substrate 101, the gain section 30, the ring resonator 10A, the DBR section 20, and the optical amplifier 40 are arranged sequentially and optically connected via waveguide 102. Furthermore, a coating with relatively low reflectivity is applied to end face 101c1, and a coating with relatively high reflectivity is applied to end face 101c2. In this case, relative to the gain section 30, the ring resonator 10A and the DBR section 20 function as vernier-type oscillation wavelength selective filters, the DBR section 20 functions as a front reflector, and the end face 101c2 functions as a rear reflector. In this structure, the laser beam output from the structural element between the end face 101c2, which functions as the laser unit, and the DBR unit 20 is amplified by the optical amplifier 40, and laser beam L1 is output from the end face 101a as the output light. On the other hand, a laser beam L2, which is weaker than laser beam L1, is output from the end face 101b of the end face 101c2. Laser beam L2 can also be used as a monitoring light.

[0082] The laser device 100B of this embodiment includes the same ring resonator 10A and multimode interference waveguide 11 as in the above embodiment. Therefore, according to this embodiment, the same effects as in the above embodiment can also be obtained.

[0083] [Sixth Implementation Method]

[0084] Figure 6This is a top view of the laser device 100C according to the sixth embodiment. The laser device 100C has the same structure as the laser device 100B of the fifth embodiment described above. However, as... Figure 6 and Figure 5 As can be seen from the comparison, in this embodiment, a ring mirror 50 is provided as a rear reflector instead of the coating on the end face 101c2.

[0085] The ring mirror 50 has a multimode interference waveguide 11. In this multimode interference waveguide 11, two ports on the opposite side of waveguides 12 and 14 are optically connected via a U-shaped waveguide 16. The structure having such a multimode interference waveguide 11 and waveguide 16 functions as a mirror. Waveguide 16 is an example of a third connecting waveguide.

[0086] Furthermore, the multimode interference waveguide 11 has the same structure as in the embodiment described above. That is, the multimode interference waveguide 11 is configured such that, when a light component of the same phase is input to the two ports (the first port and the second port) connected to the waveguide 16, this same phase component couples at the port (the third port) connected to the waveguide 12; and when a light component of opposite phase is input to the two ports (the first port and the second port) connected to the waveguide 16, this opposite phase component couples at the two ports (the fourth port) connected to the waveguide 14. Additionally, although not shown, the end of the waveguide 14 opposite to the multimode interference waveguide 11 can also be optically connected to the light processing unit 15.

[0087] The laser device 100C in this embodiment also includes the same ring resonator 10A, multimode interference waveguide 11, and waveguide 14 as in the above embodiment. Therefore, according to this embodiment, the same effects as in the above embodiment can also be obtained.

[0088] [Seventh Implementation Method]

[0089] Figure 7 This is a top view of the laser device 100D according to the seventh embodiment. (As shown) Figure 7 As shown, the laser device 100D of this embodiment includes two ring resonators 10A, a gain unit 30, an optical amplifier 40, a broadband mirror 60, and a waveguide 102.

[0090] The broadband mirror 60, for example, has multiple mirror sections that reflect laser light for each different wavelength band. The broadband mirror 60 can be fabricated in the semiconductor multilayer substrate 101 by etching. In this case, the broadband mirror 60 can also be referred to as an etched mirror.

[0091] In this embodiment, from end face 101c2 to end face 101c1, the gain unit 30, two ring resonators 10A connected in series, a broadband mirror 60, and an optical amplifier 40 are arranged sequentially and optically connected via waveguide 102. Furthermore, a coating with relatively low reflectivity is applied to end face 101c1, and a coating with relatively high reflectivity is applied to end face 101c2. In this case, relative to the gain unit 30, the two ring resonators 10A function as vernier-type oscillation wavelength selective filters, the broadband mirror 60 functions as a front reflector, and end face 101c2 functions as a rear reflector. In this structure, the laser output from the structural element between end face 101c2 (which functions as the laser unit) and the broadband mirror 60 is amplified by the optical amplifier 40, and laser L1 is output from end face 101a as the output light. On the other hand, a laser L2, weaker than laser L1, is output from end face 101b of end face 101c2. Additionally, to utilize the vernier effect, the encirclement lengths of the two ring resonators 10A are set to slightly different lengths.

[0092] The laser device 100D in this embodiment also includes the same ring resonator 10A and multimode interference waveguide 11 as in the above embodiment. Therefore, according to this embodiment, the same effects as in the above embodiment can also be obtained.

[0093] [Eighth Implementation Method]

[0094] Figure 8 This is a top view of the laser device 100E according to the eighth embodiment. The laser device 100E has the same structure as the laser device 100D according to the seventh embodiment described above. However, as... Figure 8 and Figure 7 As can be seen from the comparison, in this embodiment, a ring mirror 50 is provided as a rear reflector, replacing the coating on the end face 101c2. The ring mirror 50 has the same structure as in the sixth embodiment described above.

[0095] The laser device 100E in this embodiment also includes the same ring resonator 10A and multimode interference waveguide 11 as in the above embodiment. Therefore, according to this embodiment, the same effects as in the above embodiment can also be obtained.

[0096] [Ninth Implementation Method]

[0097] Figure 9 This is a top view of the laser device 100F according to the ninth embodiment. Figure 9 As shown, the laser device 100F of this embodiment includes two ring resonators 10A, a gain unit 30, an optical amplifier 40, a broadband mirror 60, and a waveguide 102.

[0098] In this embodiment, two ring resonators 10A connected in series and a gain unit 30 are arranged sequentially from end face 101c2 to end face 101c1 and are optically connected via waveguide 102. Furthermore, a coating with relatively low reflectivity is applied to end face 101c1, and a coating with relatively high reflectivity is applied to end face 101c2. In this configuration, end face 101c1 functions as a front reflector relative to the gain unit 30, the two ring resonators 10A function as vernier-type oscillation wavelength selective filters, and end face 101c2 functions as a rear reflector. In this structure, laser L1, generated and amplified by the structural elements between end face 101c2 and end face 101c1 (which function as a laser unit), is output as output light from end face 101a. On the other hand, laser L2, weaker than laser L1, is output from end face 101b of end face 101c2.

[0099] The laser device 100F in this embodiment also includes the same ring resonator 10A and multimode interference waveguide 11 as in the above embodiment. Therefore, according to this embodiment, the same effects as in the above embodiment can also be obtained.

[0100] [Tenth Implementation Method]

[0101] Figure 10 This is a top view of the laser device 100G according to the tenth embodiment. Figure 10 As shown, the laser device 100G of this embodiment includes two ring resonators 10A, a multimode interference waveguide 11, a gain unit 30, and a waveguide 102.

[0102] In the multimode interference waveguide 11, the two ports on the opposite side of waveguides 12 and 14 are optically connected via a U-shaped waveguide 102 (16). The structure of the multimode interference waveguide 11 and waveguide 16 functions as a mirror. Furthermore, the two ring resonators 10A are optically connected in series via waveguide 16.

[0103] The multimode interference waveguide 11 is optically connected to the gain unit 30 via waveguide 102 (12) on the opposite side of waveguide 16. In addition, although not shown, the end of waveguide 14 on the opposite side of multimode interference waveguide 11 can also be optically connected to the optical processing unit 15.

[0104] In this configuration, relative to the gain unit 30, the end face 101c1 functions as a front reflector, the two ring resonators 10A function as vernier-type oscillation wavelength selective filters, and the mirror having the multimode interference waveguide 11 and waveguide 16 functions as a rear reflector. In this structure, the laser L1 generated and amplified by the structural elements including the gain unit 30 (which functions as a laser unit), the multimode interference waveguide 11, and the two ring resonators 10A is output as output light from the end face 101a.

[0105] The laser device 100G of this embodiment also includes the same ring resonator 10A, multimode interference waveguide path 11, and waveguide path 14 as in the above embodiment. Therefore, according to this embodiment, the same effects as in the above embodiment can also be obtained.

[0106] The above embodiments of the present invention have been illustrated, but these embodiments are merely examples and are not intended to limit the scope of the invention. The above embodiments can be implemented in various other ways, and various omissions, substitutions, combinations, and modifications can be made without departing from the spirit of the invention. Furthermore, the specifications of various structures, shapes, etc. (construction, type, orientation, model, size, length, width, thickness, height, quantity, configuration, position, material, etc.) can be appropriately modified for implementation.

[0107] Industrial availability

[0108] This invention can be used in optical devices and wavelength-variable lasers.

[0109] -Explanation of Figure Markers-

[0110] 10… Optical equipment

[0111] 10A… Ring resonator (optical device)

[0112] 11…Multimode interferometric waveguide

[0113] 11-1… Multimode Interferometric Waveguide (First Multimode Interferometric Waveguide)

[0114] 11-2… Multimode interferometric waveguide (Second multimode interferometric waveguide)

[0115] 11a… End (First End)

[0116] 11b… End (Second End)

[0117] 12…waveguide path

[0118] 12-1… Waveguide Path (First Waveguide Path)

[0119] 12-2… Waveguide Path (Second Waveguide Path)

[0120] 13-1… Waveguide Path (First Connecting Waveguide Path)

[0121] 13-2… Waveguide Path (Second Connecting Waveguide Path)

[0122] 14, 14-1, 14-2… Waveguide circuits (discarded optical waveguide circuits)

[0123] 15…Light Processing Department

[0124] 15-1…Light Processing Department (First Light Processing Department)

[0125] 15-2… Light Processing Department (Second Light Processing Department)

[0126] 16… Waveguide Path (Third Connecting Waveguide Path)

[0127] 20…DBR Department

[0128] 30… Gain section

[0129] 40… Optical Amplifier

[0130] 50… Circular mirror (optical device)

[0131] 100, 100A~100G… laser devices (wavelength variable lasers)

[0132] 101…Semiconductor laminate substrate

[0133] 101a, 101b... Ends

[0134] 101c1, 101c2... End faces

[0135] 102…waveguide path

[0136] D1… direction (first direction)

[0137] D2… direction (second direction)

[0138] L, L1, L2, Li, Lo...laser

[0139] p1…port (first port)

[0140] p2…port (second port)

[0141] p3…port (third port)

[0142] p4…port (fourth port)

[0143] Z… direction.

Claims

1. A wavelength-variable laser comprising one or more optical devices, wherein the optical devices serve as filters or reflectors, said optical devices having: A multimode interference waveguide having a first end in a first direction and a second end in the opposite direction to the first direction; The first port is offset from the center of a second direction that intersects the first direction in the first end toward the second direction; The second port is located on the opposite side of the first port relative to the center of the second direction at the first end; The third port is located at the center of the second end in the second direction; Two fourth ports are offset to both sides in the second direction relative to the third port at the second end; The abandoned optical waveguide is optically coupled to one of the fourth ports, and its radius of curvature gradually decreases along a cycloid curve as it moves away from the fourth port. The optical processing unit is optically connected to one of the fourth ports via the discarded optical waveguide; as well as The third connecting waveguide has one end optically connected to the first port and the other end optically connected to the second port. The multimode interference waveguide is a 1×2 multimode interference waveguide, configured such that the in-phase components of the light input to the first port and the second port are coupled at the third port, and the out-of-phase components of the light input to the first port and the second port are coupled at the two fourth ports. The fourth angle difference between the extension direction of the abandoned optical waveguide at the connection position with the fourth port and the opposite direction of the first direction is an acute angle, and The fourth angle difference is greater than the third angle difference between the extension direction at the connection position of the waveguide optically connected to the third port and the opposite direction of the first direction.

2. A wavelength-variable laser comprising one or more optical devices, wherein the optical devices serve as filters or reflectors, said optical devices having: A multimode interference waveguide having a first end in a first direction and a second end in the opposite direction to the first direction; The first port is offset from the center of a second direction that intersects the first direction in the first end toward the second direction; The second port is located on the opposite side of the first port relative to the center of the second direction at the first end; The third port is located at the center of the second end in the second direction; Two fourth ports are offset to both sides in the second direction relative to the third port at the second end; The abandoned optical waveguide is optically coupled to one of the fourth ports, and its radius of curvature gradually decreases along a cycloid curve as it moves away from the fourth port. The optical processing unit is optically connected to one of the fourth ports via the discarded optical waveguide; The first multimode interferometric waveguide serves as the multimode interferometric waveguide; The second multimode interferometric waveguide is provided at a distance from the first multimode interferometric waveguide in the opposite direction to the second direction, and serves as the multimode interferometric waveguide. The first waveguide is optically connected to the first port of the first multimode interference waveguide; The first connecting waveguide, which optically connects the third port of the first multimode interference waveguide to the third port of the second multimode interference waveguide, is curved; The second connecting waveguide optically connects the first port of the second multimode interference waveguide to the second port of the first multimode interference waveguide, and is curved; as well as The second waveguide is optically connected to the second port of the second multimode interference waveguide. The multimode interference waveguide is a 1×2 multimode interference waveguide, configured such that the in-phase components of the light input to the first port and the second port are coupled at the third port, and the out-of-phase components of the light input to the first port and the second port are coupled at the two fourth ports. The fourth angle difference between the extension direction of the abandoned optical waveguide at the connection position with the fourth port and the opposite direction of the first direction is an acute angle, and The fourth angle difference is greater than the third angle difference between the extension direction at the connection position of the waveguide optically connected to the third port and the opposite direction of the first direction.

3. The wavelength-variable laser according to claim 2, wherein, The optical device includes: a first optical processing unit, which is optically connected to both the fourth port of the first multimode interference waveguide that is close to the fourth port of the second multimode interference waveguide and the fourth port of the second multimode interference waveguide that is close to the fourth port of the first multimode interference waveguide.

4. The wavelength-variable laser according to claim 2 or 3, wherein, The optical device includes a second optical processing unit, which is optically connected to both the fourth port of the first multimode interference waveguide that is remote from the second multimode interference waveguide and the fourth port of the second multimode interference waveguide that is remote from the first multimode interference waveguide.

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