Optical module

Abstract

This optical module comprises: a semiconductor laser (15) having a light-emitting coupler (15d) that emits rearward laser light (Lb) in conjunction with the emission of forward laser light (Lf) from a front end; and an optical monitor (16) having an optical coupling coupler (16c) that receives and couples the rearward laser light (Lb) emitted from the light-emitting coupler (15d). The semiconductor laser (15) and the optical monitor (16) are superposed so that the light-emitting coupler (15d) and the optical coupling coupler (16c) face each other.

Description

Optical Module

[0001] The present disclosure relates to optical modules.

[0002] One method for increasing the capacity of optical communication systems is the digital coherent communication method. This digital coherent communication method transmits multiple channels by superimposing signals not only on the intensity of light but also on the phase. To extract the optical phase information, the optical interference phenomenon is used, so the wavelengths of both the light source in the transmitter that sends the signal and the local light that becomes the interference light at the receiver that receives the signal must be precisely controlled.

[0003] A single-mode laser is used as the light source. A single-mode laser oscillates at a single wavelength, but the oscillation wavelength and optical output intensity can change due to manufacturing errors and environmental temperature. For this reason, a wavelength locker for wavelength control and an optical intensity monitor are essential in a light source module for digital coherent communication equipped with a single-mode laser. In particular, precise control of the oscillation wavelength to 0.1 nm or less is required. Therefore, Patent Document 1 discloses an optical module that controls the oscillation wavelength of a laser with high precision.

[0004] JP 2003-69130 A Japanese Patent No. 7224555

[0005] The optical module disclosed in Patent Document 1 includes a laser and an etalon. The etalon's transmittance changes depending on the wavelength of the light passing through it. Therefore, the optical module disclosed in Patent Document 1 can transmit rear laser light from the laser through the etalon and monitor the intensity of the rear laser light using a light receiving element. As a result, the optical module disclosed in Patent Document 1 can detect changes in the oscillation wavelength of the laser.

[0006] However, the optical module disclosed in Patent Document 1 requires temperature control elements for both the laser and the etalon, which increases the module size. Furthermore, the optical module disclosed in Patent Document 1 requires multiple components to collimate the light incident on the etalon. Therefore, the optical module disclosed in Patent Document 1 may increase manufacturing costs.

[0007] In contrast, the optical module disclosed in Patent Document 2 includes a planar waveguide optical monitor with the aim of reducing the number of components and achieving miniaturization. In this case, the mounting surface of the base of the optical module is different from the mounting surface of the laser. Therefore, in order to efficiently couple the rear laser light of the laser to the optical monitor, the laser and the optical monitor must be mounted with high precision on their respective mounting surfaces.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an optical module that can efficiently couple rearward laser light emitted from a laser output unit to an optical monitor without providing a mounting surface on the base that is dedicated to the optical monitor.

[0009] The optical module according to the present disclosure comprises a laser output unit having a light emitting coupler that emits rearward laser light in response to the emission of forward laser light from the front end, and an optical monitor having an optical coupling coupler that receives and couples the rearward laser light emitted from the light emitting coupler, and the laser output unit and the optical monitor are superimposed so that the light emitting coupler and the optical coupling coupler face each other.

[0010] According to the present disclosure, the rear laser light emitted from the laser output unit can be coupled to the optical monitor with high efficiency without providing a dedicated mounting surface for the optical monitor on the base.

[0011] FIG. 1 is a longitudinal sectional view of an optical module according to a first embodiment with a cap removed. FIG. 2 is a perspective view of the optical module according to the first embodiment. FIG. 3 is an enlarged view of a main part of FIG. 1. FIG. 4 is a plan view of a state before a semiconductor laser and an optical monitor are stacked on top of each other. FIG. 5 is a plan view of a state before an optical amplifier and an optical monitor are stacked on top of each other in an optical module according to a second embodiment. FIG. 6 is a plan view of an optical module according to a second embodiment with an optical amplifier and an optical monitor stacked on top of each other in an optical module according to the second embodiment. FIG. 7 is an enlarged sectional view of a main part of an optical module according to a third embodiment. FIG. 8 is a plan view of an optical module according to a third embodiment with an optical amplifier and an optical monitor stacked on top of each other in an optical module according to a third embodiment. FIG. 9 is a plan view of an optical module according to a fourth embodiment with an optical amplifier and an optical monitor stacked on top of each other. FIG. 10 is a plan view of an optical module according to a fourth embodiment with an optical amplifier and an optical monitor stacked on top of each other in an optical module according to the fourth embodiment.

[0012] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0013] First Embodiment An optical module according to a first embodiment will be described with reference to FIGS.

[0014] Fig. 1 is a vertical cross-sectional view of the optical module according to the first embodiment with a cap 18 removed, and Fig. 2 is a perspective view of the optical module according to the first embodiment.

[0015] The optical module according to the first embodiment is, for example, an optical module for digital coherent communication. As shown in Figures 1 and 2, the optical module according to the first embodiment includes a stem 11, a temperature regulator 12, a base 13, a semiconductor laser submount (hereinafter referred to as the submount) 14, a semiconductor laser 15, a planar waveguide optical monitor (hereinafter referred to as the optical monitor) 16, a thermistor 17, a cap 18, a window member 19, and a plurality of pins 20. The semiconductor laser 15 constitutes a laser output unit.

[0016] The stem 11 is formed in a disk shape. The stem 11 is made of a conductive material such as a metal material. The stem 11 has a main surface 11a. The main surface 11a is a flat vertical surface and forms a mounting surface for the temperature controller 12. The external shape of the stem 11 may be elliptical, triangular, rectangular, or the like.

[0017] The temperature regulator 12 is fixed to the stem 11. The temperature regulator 12 has a left side surface 12a and a right side surface 12b. The left side surface 12a and the right side surface 12b are arranged parallel to the main surface 11a. Of these, the right side surface 12b is mounted on the main surface 11a.

[0018] The temperature regulator 12 controls the temperatures of the semiconductor laser 15 and the optical monitor 16 via the base 13. Specifically, when a control current is supplied to the temperature regulator 12, the temperature regulator 12 heats or cools the semiconductor laser 15 and the optical monitor 16 depending on the direction of the control current. At this time, when the stem 11 receives heat emitted from the temperature regulator 12, it discharges the heat to the outside. The temperature regulator 12 is, for example, a thermoelectric cooler (TEC) configured using a Peltier element or the like.

[0019] The base 13 is mounted on the left side surface 12a of the temperature controller 12. This base 13 is L-shaped when viewed from the side of the optical module. Therefore, the base 13 has a mounting surface 13a, which is a horizontal surface, and a vertical surface 13b. The mounting surface 13a and the vertical surface 13b are arranged so as to be perpendicular to each other. The base 13 transfers heat generated from the temperature controller 12 to the semiconductor laser 15 and the optical monitor 16. The base 13 is formed, for example, from a metal material with excellent thermal conductivity.

[0020] The submount 14 is mounted on the mounting surface 13a of the base 13. The submount 14 is made of a base made of a dielectric material such as aluminum nitride, on whose surface a metal wiring layer is patterned.

[0021] The semiconductor laser 15 is mounted on the mounting surface 13a of the base 13 via the submount 14. Furthermore, the optical monitor 16 is mounted on the semiconductor laser 15. Details of the mounting of the optical monitor 16 on the semiconductor laser 15 will be described later.

[0022] Therefore, the base 13 conducts heat emitted from the temperature regulator 12 and regulates the temperatures of the semiconductor laser 15 and the optical monitor 16 through the submount 14. At this time, the semiconductor laser 15 and the optical monitor 16, whose temperatures are regulated by the temperature regulator 12, are arranged so as to be stacked on one mounting surface 13a. Therefore, the optical module according to the first embodiment can reduce the area on the mounting surface 13a occupied by the semiconductor laser 15 and the optical monitor 16. As a result, the optical module according to the first embodiment can reduce the size and weight of the base 13.

[0023] The semiconductor laser 15 is a single-wavelength semiconductor laser, or a so-called single-mode laser that oscillates at a single wavelength. The semiconductor laser 15 emits forward laser light Lf from its front end face (emission surface) and backward laser light Lb from its top face. The forward laser light Lf is used for optical communications. The backward laser light Lb is emitted toward the optical monitor 16 and monitored. The optical axes of the forward laser light Lf and the backward laser light Lb are perpendicular to each other.

[0024] The thermistor 17 is provided on the base 13. The thermistor 17 measures the temperature of the heat conducted from the temperature regulator 12 to the semiconductor laser 15 and the optical monitor 16.

[0025] The cap 18 is formed in a cylindrical shape with a lid. The open end of the cap 18 is fixed to the main surface 11a of the stem 11. The cap 18 is provided so as to cover the temperature regulator 12, the base 13, the submount 14, the semiconductor laser 15, the optical monitor 16, and the thermistor 17 from the outside. The cap 18 is formed of, for example, a metal material or a resin material.

[0026] The window member 19 is fitted into the lid portion of the cap 18. The window member 19 condenses and passes the forward laser light Lf emitted from the semiconductor laser 15. The window member 19 is, for example, a flat glass or a lens.

[0027] The multiple pins 20 are electrically connected to the temperature regulator 12, the semiconductor laser 15, and the optical monitor 16. Each pin 20 is supported through the stem 11. In this case, each pin 20 is insulated from the stem 11.

[0028] The optical module according to the first embodiment includes a control unit (not shown). The temperature regulator 12, the semiconductor laser 15, and the optical monitor 16 are controlled by the control unit. The control unit exchanges signals with the temperature regulator 12, the semiconductor laser 15, and the optical monitor 16 via the corresponding pins 20. The control unit also controls the current and voltage to the temperature regulator 12, the semiconductor laser 15, and the optical monitor 16 via the corresponding pins 20, thereby controlling the light intensity and wavelength of the forward laser light Lf emitted from the semiconductor laser 15.

[0029] Next, the mounting of the optical monitor 16 on the semiconductor laser 15 will be described with reference to Fig. 3 to Fig. 5. Fig. 3 is an enlarged view of the main part of Fig. 1. Fig. 4 is a plan view of the semiconductor laser 15 and the optical monitor 16 before they are stacked on top of each other. Fig. 5 is a plan view of the semiconductor laser 15 and the optical monitor 16 after they are stacked on top of each other.

[0030] 3, the semiconductor laser 15 has an upper surface 15a and a lower surface 15b. The upper surface 15a and the lower surface 15b are surfaces located on opposite sides in the thickness direction of the semiconductor laser 15. The optical monitor 16 has an upper surface 16a and a lower surface 16b. The upper surface 16a and the lower surface 16b are surfaces located on opposite sides in the thickness direction of the optical monitor 16.

[0031] The lower surface 15b of the semiconductor laser 15 is mounted on the upper surface of the submount 14. The lower surface 16b of the optical monitor 16 is mounted on the upper surface 15a of the semiconductor laser 15. That is, the lower surface 15b of the semiconductor laser 15 is the mounting surface for the upper surface of the submount 14. The lower surface 16b of the optical monitor 16 is the mounting surface for the upper surface 15a of the semiconductor laser 15.

[0032] 4, the semiconductor laser 15 includes a laser stripe 15c, a light-emitting coupler 15d, a plurality of electrodes 15e and 15f, and a plurality of wiring lines 15g. The laser stripe 15c, the light-emitting coupler 15d, the plurality of electrodes 15e and 15f, and the plurality of wiring lines 15g are provided on the same upper surface 15a.

[0033] The laser stripe 15c emits a forward laser beam Lf. The light-emitting coupler 15d emits a backward laser beam Lb. The light-emitting coupler 15d is connected to the rear end of the elongated laser stripe 15c. In this way, the semiconductor laser 15 includes the light-emitting coupler 15d, so that the backward laser beam Lb can be output from the top surface 15a. The light-emitting coupler 15d is, for example, a grating coupler.

[0034] Electrodes 15e and 15f are arranged around the laser stripe 15c and the light-emitting coupler 15d. The electrodes 15e and 15f constitute laser-side electrodes. The electrode 15e constitutes a laser-side electrode for wire bonding, and the electrode 15f constitutes a laser-side electrode for connection.

[0035] Although details will be described later, electrode 15e is arranged in a range that is not covered by optical monitor 16 when optical monitor 16 is mounted on semiconductor laser 15. Furthermore, electrode 15f is covered by optical monitor 16 when optical monitor 16 is mounted on semiconductor laser 15, and is electrically connected to electrode 16i.

[0036] The lead-out wire 15g electrically connects the electrode 15e to the electrode 15f. As will be described in detail later, the electrode 15f to which the lead-out wire 15g is connected corresponds to the electrode 16i of the optical monitor 16 that is electrically connected to the first optical receiver 16g and the second optical receiver 16h.

[0037] 4, the optical monitor 16 includes an optical coupling coupler 16c, an optical splitter 16d, an optical filter 16e, a heater 16f, a first optical receiver 16g, a second optical receiver 16h, and a plurality of electrodes 16i. The optical coupling coupler 16c, the optical splitter 16d, the optical filter 16e, the heater 16f, the first optical receiver 16g, the second optical receiver 16h, and the plurality of electrodes 16i are provided on the same lower surface 16b. The optical coupling coupler 16c and the optical splitter 16d, the optical splitter 16d and the optical filter 16e, the optical filter 16e and the heater 16f, the heater 16f and the first optical receiver 16g, and the optical splitter 16d and the second optical receiver 16h are connected by optical waveguides (not shown).

[0038] The optical monitor 16 is, for example, a planar waveguide type optical monitor formed by integrating an optical coupling coupler 16c, an optical splitter 16d, an optical filter 16e, a heater 16f, a first photodetector 16g, a second photodetector 16h, a plurality of electrodes 16i, and an optical waveguide on the surface of a silicon (Si) substrate.

[0039] The optical coupler 16c couples the backward laser light Lb that is perpendicularly incident on the lower surface 16b of the optical monitor 16 and transmits it to the optical demultiplexer 16d. The optical coupler 16c is, for example, a grating coupler.

[0040] The optical demultiplexer 16d receives the backward laser light Lb transmitted from the optical coupling coupler 16c, and demultiplexes the received backward laser light Lb into two laser lights.

[0041] The first optical receiver 16g receives one of the laser beams split by the optical splitter 16d and performs photoelectric conversion on the received one of the laser beams. After photoelectric conversion of the one of the laser beams, the first optical receiver 16g outputs a current corresponding to the optical intensity of the one of the laser beams. The first optical receiver 16g converts the optical intensity of the backward laser beam Lb combined by the optical coupling coupler 16c directly into a current, and therefore functions as an optical power monitor for the semiconductor laser 15. Furthermore, the first optical receiver 16g is electrically connected to the corresponding electrode 16i. Therefore, the first optical receiver 16g can output a current corresponding to the optical intensity of one of the laser beams to the electrode 16i.

[0042] The optical filter 16e receives the other laser light branched by the optical branching filter 16d and transmits the other laser light to the second optical receiver 16h via the optical filter 16e. The optical filter 16e, for example, has temperature dependency of the wavelength of light. Therefore, the peak value of the wavelength of the laser light output from the optical filter 16e shifts to the longer wavelength side as the temperature of the optical filter 16e increases. The optical filter 16e is, for example, a ring resonator with a phase shifter or a Mach-Zehnder interferometer with a phase shifter.

[0043] The second photodetector 16h converts the laser light filtered by the optical filter 16e (laser light resonating with the rearward laser light Lb) into a current. At this time, when the wavelength of the rearward laser light Lb changes, the value of the current output from the second photodetector 16h also changes. In addition, the second photodetector 16h is electrically connected to the corresponding electrode 16i. Therefore, the second photodetector 16h can output a current corresponding to the light intensity of the other laser light to the corresponding electrode 16i.

[0044] The electrode 16i is arranged around the optical coupling coupler 16c, the optical splitter 16d, the optical filter 16e, the heater 16f, the first optical receiver 16g, and the second optical receiver 16h. The electrode 16i corresponds to the electrode 15f. The electrode 16i constitutes a monitor-side electrode and a connection monitor-side electrode.

[0045] Therefore, when mounting the optical monitor 16 on the semiconductor laser 15, first, the semiconductor laser 15 is in a state where the upper surface 15a faces upward, and the optical monitor 16 is in a state where the lower surface 16b faces upward, as shown in Fig. 4. Next, as shown in Fig. 4 and Fig. 5, from this state, the optical monitor 16 is turned over so that the upper surface 16a and the lower surface 16b are upside down, and the lower surface 16b is mounted on the upper surface 15a of the semiconductor laser 15.

[0046] At this time, the light emitting coupler 15d and the optical coupling coupler 16c face each other. Therefore, the optical coupling coupler 16c can receive and couple the backward laser light Lb emitted from the light emitting coupler 15d. Furthermore, the electrodes 15f and 16i face each other. The electrodes 15f and 16i are joined to each other using gold bumps, solder bumps, or the like. Therefore, the optical module according to the first embodiment can electrically connect the semiconductor laser 15 and the optical monitor 16.

[0047] Furthermore, because the optical monitor 16 is mounted upside down, it is not possible to perform wire bonding on the electrodes 16i electrically connecting to the first and second optical receivers 16g and 16h, which means that it is not possible to extract a current corresponding to the intensity of the laser light from the electrodes 16i electrically connecting to the first and second optical receivers 16g and 16h.

[0048] However, in the optical module according to the first embodiment, the lead wire 15g connects the electrode 15f electrically connected to the electrode 16i to the electrode 15e that is not covered by the optical monitor 16. Therefore, in the optical module according to the first embodiment, by bonding the wire 30 to the electrode 15e that is not covered by the optical monitor 16, a current corresponding to the optical intensity of the laser light can be extracted from the electrode 15e.

[0049] Therefore, the optical module according to the first embodiment can detect the optical output and oscillation wavelength of the semiconductor laser 15 by measuring the current value output from the first optical receiver 16g and the current value output from the second optical receiver 16h.

[0050] In the optical module disclosed in Patent Document 2, the semiconductor laser and the optical monitor, which are mounted on different mounting surfaces at different positions, must be separated by a distance of several hundred micrometers to prevent contact during mounting. Such mounting hinders the improvement of optical coupling efficiency in the optical monitor. Furthermore, in the optical module disclosed in Patent Document 2, variations in the thickness of the submount and the semiconductor laser, or variations in the emission direction of the backward laser light from the semiconductor laser due to cleavage errors, may occur. In such cases, it becomes difficult for the optical module disclosed in Patent Document 2 to efficiently and stably couple the backward laser light to the optical monitor.

[0051] In contrast, in the optical module according to the first embodiment, the upper surface 15a of the semiconductor laser 15 and the lower surface 16b of the optical monitor 16 are connected so that they face each other and overlap. Therefore, in the optical module according to the first embodiment, the semiconductor laser 15 and the optical monitor 16 can be brought close to each other, for example, to within several tens of micrometers, without having to worry about them touching each other. As a result, the optical module according to the first embodiment can improve the efficiency of optical coupling in the optical monitor 16 without providing the mounting surface of the optical monitor 16 on the base 13.

[0052] As described above, the optical module according to the first embodiment includes the semiconductor laser 15 having the light-emitting coupler 15d that emits backward laser light Lb in response to the emission of forward laser light Lf from the front end, and the optical monitor 16 having the optical coupling coupler 16c that receives and couples the backward laser light Lb emitted from the light-emitting coupler 15d, and the semiconductor laser 15 and the optical monitor 16 are overlapped so that the light-emitting coupler 15d and the optical coupling coupler 16c face each other. Therefore, the optical module according to the first embodiment can efficiently couple the backward laser light Lb emitted from the semiconductor laser 15 to the optical monitor 16 without providing a mounting surface dedicated to the optical monitor on the base 13.

[0053] Furthermore, in the optical module according to the first embodiment, the semiconductor laser 15 and the optical monitor 16 are connected so as to face each other and overlap each other, so that the base 13 can be made smaller and lighter.

[0054] Second Embodiment An optical module according to a second embodiment will be described with reference to FIGS.

[0055] Fig. 6 is a plan view of an optical module according to the second embodiment, showing an optical amplifier 25 and a reflective filter integrated optical monitor (hereinafter referred to as an optical monitor) 26 before they are stacked on top of each other. Fig. 7 is a plan view of an optical module according to the second embodiment, showing an optical amplifier 25 and an optical monitor 26 stacked on top of each other. Note that components having the same functions as those described in the first embodiment are given the same reference numerals, and their description will be omitted.

[0056] The optical module according to the second embodiment includes an optical amplifier 25 and an optical monitor 26 instead of the semiconductor laser 15 and the optical monitor 16 of the optical module according to the first embodiment. The optical amplifier 25 constitutes a laser output unit.

[0057] 6, the optical amplifier 25 has an upper surface 25a and a lower surface 25b. The upper surface 25a and the lower surface 25b are surfaces located on opposite sides in the thickness direction of the optical amplifier 25. The optical monitor 26 has an upper surface 26a and a lower surface 26b. The upper surface 26a and the lower surface 26b are surfaces located on opposite sides in the thickness direction of the optical monitor 26.

[0058] The lower surface 25b of the optical amplifier 25 is mounted on the upper surface of the submount 14. The lower surface 26b of the optical monitor 26 is mounted on the upper surface 25a of the optical amplifier 25. That is, the lower surface 25b of the optical amplifier 25 is the mounting surface that faces the upper surface of the submount 14. The lower surface 26b of the optical monitor 26 is the mounting surface that faces the upper surface 25a of the optical amplifier 25.

[0059] 6, the optical amplifier 25 includes an amplifying stripe 25c, a light output coupler 25d, a plurality of electrodes 25e and 25f, and a plurality of lead-out wires 25g. The amplifying stripe 25c, the light output coupler 25d, the plurality of electrodes 25e and 25f, and the plurality of lead-out wires 25g are provided on the same upper surface 25a.

[0060] The amplifying stripe 25c emits forward laser light Lf. The light emitting coupler 25d emits backward laser light Lb. The light emitting coupler 25d is connected to the rear end of the elongated amplifying stripe 25c. In this way, by having the light emitting coupler 25d, the optical amplifier 25 can output the backward laser light Lb from the top surface 25a. The light emitting coupler 25d is, for example, a grating coupler.

[0061] Electrodes 25e and 25f are arranged around amplifying stripe 25c and light-emitting coupler 25d. Electrodes 25e and 25f constitute laser-side electrodes. Electrode 25e constitutes a laser-side electrode for wire bonding, and electrode 25f constitutes a laser-side electrode for connection.

[0062] Although details will be described later, electrode 25e is arranged in a range that is not covered by optical monitor 26 when optical monitor 26 is mounted on optical amplifier 25. Furthermore, electrode 25f is covered by optical monitor 26 when optical monitor 26 is mounted on optical amplifier 25, and is electrically connected to electrode 26n thereof.

[0063] The lead-out wire 25g electrically connects the electrode 25e to the electrode 25f. As will be described in detail later, the electrode 25f to which the lead-out wire 25g is connected corresponds to the electrode 26n, among the electrodes 16n of the optical monitor 26, that is electrically connected to the first photoreceiver 26k and the second photoreceiver 26l.

[0064] 6, the optical monitor 26 includes an optical coupling coupler 26c, an optical splitter 26d, a first optical filter 26e, a second optical filter 26f, a third optical filter 26g, a first heater 26h, a second heater 26i, a third heater 26j, a first photodetector 26k, a second photodetector 26l, a waveguide-type mirror 26m, and a plurality of electrodes 26n. The optical coupling coupler 26c, the optical splitter 26d, the optical filters 26e-26g, the heaters 26h-26j, the first photodetector 26k, the second photodetector 26l, the waveguide-type mirror 26m, and the plurality of electrodes 26n are provided on the same lower surface 26b. Furthermore, they are connected to each other by optical waveguides (not shown).

[0065] The optical filters 26e to 26g have the same configuration and function, and the heaters 26h to 26j have the same configuration and function.

[0066] The optical monitor 26 is a reflective filter integrated optical monitor formed by integrating, for example, an optical coupling coupler 26c, an optical splitter 26d, optical filters 26e to 26g, heaters 26h to 26j, a first photodetector 26k, a second photodetector 26l, a waveguide mirror 26m, a plurality of electrodes 26n, and an optical waveguide on the surface of a silicon (Si) substrate.

[0067] The optical coupler 26c couples the backward laser light Lb that is perpendicularly incident on the lower surface 26b of the optical monitor 26, and transmits the coupled light to the waveguide mirror 26m via optical filters 26f and 26g and heaters 26i and 26j. The optical coupler 26c is, for example, a grating coupler.

[0068] The waveguide mirror 26m transmits a part of the backward laser light Lb transmitted from the optical coupling coupler 26c.

[0069] The optical splitter 26d receives a portion of the backward laser light Lb transmitted from the waveguide mirror 26m, and splits the received portion of the backward laser light Lb into two laser lights.

[0070] The first optical receiver 26k receives one of the laser beams split by the optical splitter 26d and performs photoelectric conversion on the received one of the laser beams. After photoelectric conversion of the one of the laser beams, the first optical receiver 26k outputs a current corresponding to the optical intensity of the one of the laser beams. The first optical receiver 26k converts the optical intensity of the backward laser beam Lb combined by the optical coupling coupler 26c directly into a current, and therefore functions as an optical power monitor for the optical amplifier 25. Furthermore, the first optical receiver 26k is electrically connected to the corresponding electrode 26n. Therefore, the first optical receiver 26k can output a current corresponding to the optical intensity of the one of the laser beams to the electrode 26n.

[0071] The first optical filter 26e receives the other laser light separated from the optical splitter 26d, and transmits the other received laser light to the second light receiver 26l via the first heater 26h.

[0072] The second photodetector 26l converts the laser light filtered by the first optical filter 26e (laser light resonating with the rearward laser light Lb) into a current. At this time, when the wavelength of the rearward laser light Lb changes, the value of the current output from the second photodetector 26l also changes. In addition, the second photodetector 26l is electrically connected to the corresponding electrode 26n. Therefore, the second photodetector 26l can output a current corresponding to the optical intensity of the other laser light to the corresponding electrode 26n.

[0073] The electrode 26n is arranged around the optical coupling coupler 26c, the optical splitter 26d, the optical filters 26e to 26g, the heaters 26h to 26j, the first light receiver 26k, the second light receiver 26l, and the waveguide mirror 26m. The electrode 26n corresponds to the electrode 25f. The electrode 26n constitutes a monitor-side electrode and a connection monitor-side electrode.

[0074] Therefore, when mounting the optical monitor 26 on the optical amplifier 25, first, the optical amplifier 25 is in a state where the upper surface 25a faces upward, and the optical monitor 26 is in a state where the lower surface 26b faces upward, as shown in Fig. 6. Next, as shown in Fig. 6 and Fig. 7, from this state, the optical monitor 26 is turned over so that the upper surface 26a and the lower surface 26b are upside down, and the lower surface 26b is mounted on the upper surface 25a of the optical amplifier 25.

[0075] At this time, the light emitting coupler 25d and the optical coupling coupler 26c face each other. Therefore, the optical coupling coupler 26c can receive and couple the backward laser light Lb emitted from the light emitting coupler 25d. Furthermore, the electrodes 25f and 26n face each other. The electrodes 25f and 26n are joined to each other using gold bumps, solder bumps, or the like. Therefore, the optical module according to the second embodiment can electrically connect the optical amplifier 25 and the optical monitor 26.

[0076] Furthermore, because the optical monitor 26 is mounted upside down, it is not possible to perform wire bonding on the electrodes 26n electrically connected to the first optical receiver 26k and the second optical receiver 26l. In other words, it is not possible to extract a current corresponding to the optical intensity of the laser light from the electrodes 26n electrically connected to the first optical receiver 26k and the second optical receiver 26l.

[0077] However, in the optical module according to the second embodiment, the lead wire 25g connects the electrode 25f electrically connected to the electrode 26n to the electrode 25e that is not covered by the optical monitor 16. Therefore, in the optical module according to the second embodiment, by bonding the wire 30 to the electrode 25e that is not covered by the optical monitor 26, a current corresponding to the optical intensity of the laser light can be extracted from the electrode 25e.

[0078] Therefore, the optical module according to the second embodiment can detect the optical output and oscillation wavelength of the optical amplifier 25 by measuring the current value output from the first optical receiver 26k and the current value output from the second optical receiver 26l.

[0079] In the optical module according to the second embodiment, the upper surface 25a of the optical amplifier 25 and the lower surface 26b of the optical monitor 26 are connected so as to face each other and overlap each other. Therefore, in the optical module according to the second embodiment, the optical amplifier 25 and the optical monitor 26 can be brought close to each other, for example, to within several tens of micrometers, without having to worry about them touching each other. As a result, the optical module according to the second embodiment can improve the efficiency of optical coupling in the optical monitor 26 without providing the mounting surface of the optical monitor 26 on the base 13.

[0080] As described above, the optical module according to the second embodiment includes the optical amplifier 25 having the light emitting coupler 25d that emits backward laser light Lb in response to the emission of the forward laser light Lf from the front end, and the optical monitor 26 having the optical coupling coupler 26c that receives and couples the backward laser light Lb emitted from the light emitting coupler 25d, and the optical amplifier 25 and the optical monitor 26 are overlapped so that the light emitting coupler 25d and the optical coupling coupler 26c face each other. Therefore, the optical module according to the second embodiment can efficiently couple the backward laser light Lb emitted from the optical amplifier 25 to the optical monitor 26 without providing a mounting surface dedicated to the optical monitor on the base 13.

[0081] Furthermore, in the optical module according to the second embodiment, the optical amplifier 25 and the optical monitor 26 are connected so as to face each other and overlap each other, so that the base 13 can be made smaller and lighter.

[0082] Third Embodiment An optical module according to a third embodiment will be described with reference to FIGS.

[0083] Fig. 8 is an enlarged cross-sectional view of a main part of an optical module according to embodiment 3. Fig. 9 is a plan view of the optical module according to embodiment 3 in a state before the semiconductor laser 15A and the optical monitor 16A are stacked on top of each other. Fig. 10 is a plan view of the optical module according to embodiment 3 in a state where the semiconductor laser 15A and the optical monitor 16A are stacked on top of each other. Note that components having the same functions as those described in embodiment 1 above are assigned the same reference numerals, and descriptions thereof will be omitted.

[0084] As shown in FIG. 8, the optical module according to the third embodiment includes a semiconductor laser 15A and an optical monitor 16A instead of the semiconductor laser 15 and the optical monitor 16 of the optical module according to the first embodiment.

[0085] 9, the semiconductor laser 15A has an upper surface 15a, a lower surface 15b, a laser stripe 15c, a light-emitting coupler 15d, and a plurality of electrodes 15f. The laser stripe 15c, the light-emitting coupler 15d, and a plurality of electrodes 15f are provided on the same upper surface 15a. The semiconductor laser 15A does not have an electrode 15e. The upper surface 15a constitutes one surface or the other surface, and the lower surface 15b constitutes the other surface or one surface.

[0086] The optical monitor 16A has an upper surface 16a, a lower surface 16b, an optical coupling coupler 16c, an optical splitter 16d, an optical filter 16e, a heater 16f, a first optical receiver 16g, a second optical receiver 16h, and a plurality of electrodes 16i and 16j. The optical coupling coupler 16c, the optical splitter 16d, the optical filter 16e, the heater 16f, the first optical receiver 16g, the second optical receiver 16h, and the plurality of electrodes 16j are provided on the same plane, the upper surface 16a. The plurality of electrodes 16i are provided on the same plane, the lower surface 16b.

[0087] The electrode 16i corresponds to the electrode 15f of the semiconductor laser 15A. That is, the electrode 15f and the electrode 16i are connected to each other. The electrode 16j is electrically connected to the first light receiver 16g and the second light receiver 16h. The electrode 16j constitutes a monitor-side electrode and a wire-bonding monitor-side electrode.

[0088] Therefore, when mounting the optical monitor 16A on the semiconductor laser 15A, first, the upper surface 15a of the semiconductor laser 15A faces upward, and the upper surface 16a of the optical monitor 16 also faces upward, as shown in Fig. 9. Next, from this state, the optical monitor 16 slides laterally, so that the lower surface 15b is mounted on the upper surface 15a of the semiconductor laser 15, as shown in Figs.

[0089] At this time, the light emitting coupler 15d and the optical coupling coupler 16c face each other. Therefore, the optical coupling coupler 16c can receive and couple the backward laser light Lb emitted from the light emitting coupler 15d. In addition, the electrodes 15f and 16i face each other. The electrodes 15f and 16i are joined to each other using gold bumps, solder bumps, or the like.

[0090] Furthermore, because the optical monitor 16A is not mounted upside down, the optical module according to the third embodiment allows wires 30 to be easily bonded to the electrodes 16i provided on the upper surface 16a and electrically connected to the first and second optical receivers 16g and 16h. Therefore, the optical module according to the third embodiment can extract a current corresponding to the optical intensity of the laser beam from the electrodes 15e. In other words, the optical module according to the third embodiment can extract a current corresponding to the optical intensity of the laser beam without using the wiring 15g.

[0091] Therefore, the optical module according to the third embodiment can detect the optical output and oscillation wavelength of the semiconductor laser 15A by measuring the current value output from the first optical receiver 16g and the current value output from the second optical receiver 16h.

[0092] In the optical module according to the third embodiment, the upper surface 15a of the semiconductor laser 15A and the lower surface 16b of the optical monitor 16A are connected so that they face each other and overlap. Therefore, in the optical module according to the third embodiment, the semiconductor laser 15A and the optical monitor 16A can be brought close to each other, for example, to within several tens of micrometers, without having to worry about them touching each other. As a result, the optical module according to the third embodiment can improve the efficiency of optical coupling in the optical monitor 16A without providing the mounting surface of the optical monitor 16A on the base 13.

[0093] As described above, the optical module according to the third embodiment includes the semiconductor laser 15A having the light-emitting coupler 15d that emits backward laser light Lb in response to the emission of the forward laser light Lf from the front end, and the optical monitor 16A having the optical coupling coupler 16c that receives and couples the backward laser light Lb emitted from the light-emitting coupler 15d, and the semiconductor laser 15A and the optical monitor 16A are overlapped so that the light-emitting coupler 15d and the optical coupling coupler 16c face each other. Therefore, the optical module according to the third embodiment can efficiently couple the backward laser light Lb emitted from the semiconductor laser 15A to the optical monitor 16A without providing a mounting surface dedicated to the optical monitor on the base 13.

[0094] Furthermore, in the optical module according to the third embodiment, the semiconductor laser 15A and the optical monitor 16A are connected so as to face each other and overlap each other, and therefore the base 13 can be made smaller and lighter.

[0095] Fourth Embodiment An optical module according to a fourth embodiment will be described with reference to FIGS.

[0096] Fig. 11 is a plan view of the optical module according to the fourth embodiment, showing the state before the optical amplifier 25A and the optical monitor 26A are stacked on top of each other. Fig. 12 is a plan view of the optical module according to the fourth embodiment, showing the state after the optical amplifier 25A and the optical monitor 26A are stacked on top of each other. Note that components having the same functions as those described in the first and second embodiments are given the same reference numerals, and their description will be omitted.

[0097] As shown in FIG. 11, the optical module according to the fourth embodiment includes an optical amplifier 25A and an optical monitor 26A instead of the optical amplifier 25 and the optical monitor 26 of the optical module according to the second embodiment.

[0098] 11, the optical amplifier 25A has an upper surface 25a, a lower surface 25b, an amplifying stripe 25c, a light output coupler 25d, and multiple electrodes 25f. The amplifying stripe 25c, the light output coupler 25d, and the multiple electrodes 25f are provided on the same upper surface 25a. The optical amplifier 25A does not have an electrode 25e. The upper surface 25a constitutes one surface or the other surface, and the lower surface 25b constitutes the other surface or one surface.

[0099] The optical monitor 26A has an upper surface 26a, a lower surface 26b, an optical coupling coupler 26c, an optical splitter 26d, a first optical filter 26e, a second optical filter 26f, a third optical filter 26g, a first heater 26h, a second heater 26i, a third heater 26j, a first photodetector 26k, a second photodetector 26l, a waveguide-type mirror 26m, and a plurality of electrodes 26n and 26o. The optical coupling coupler 26c, the optical splitter 26d, the optical filters 26e-26g, the heaters 26h-26j, the first photodetector 26k, the second photodetector 26l, the waveguide-type mirror 26m, and the plurality of electrodes 26o are provided on the same plane, the upper surface 26a. The plurality of electrodes 26n are provided on the same plane, the lower surface 26b.

[0100] The electrode 26n corresponds to the electrode 25f of the optical amplifier 25A. That is, the electrode 25f and the electrode 26n are connected to each other. The electrode 26o is electrically connected to the first optical receiver 26k and the second optical receiver 26l. The electrode 26o constitutes a monitor-side electrode and a wire-bonding monitor-side electrode.

[0101] Therefore, when mounting the optical monitor 26A on the optical amplifier 25A, first, the upper surface 25a of the optical amplifier 25A faces upward, and the upper surface 26a of the optical monitor 26A also faces upward, as shown in Fig. 11. Next, as shown in Fig. 11 and Fig. 12, from this state, the optical monitor 26A slides laterally, so that the lower surface 26b is mounted on the upper surface 25a of the optical amplifier 25A.

[0102] At this time, the light emitting coupler 25d and the optical coupling coupler 26c face each other. Therefore, the optical coupling coupler 26c can receive and couple the backward laser light Lb emitted from the light emitting coupler 25d. In addition, the electrodes 25f and 26n face each other. The electrodes 25f and 26n are joined to each other using gold bumps, solder bumps, or the like.

[0103] Furthermore, because the optical monitor 26A is not mounted upside down, the optical module according to the fourth embodiment allows wires 30 to be easily bonded to the electrodes 26o provided on the upper surface 46a and electrically connected to the first optical receiver 26k and the second optical receiver 26l. Therefore, the optical module according to the fourth embodiment can extract a current corresponding to the optical intensity of the laser light from the electrodes 26o. That is, the optical module according to the fourth embodiment can extract a current corresponding to the optical intensity of the laser light without using the above-mentioned wiring 25g.

[0104] Therefore, the optical module according to the fourth embodiment can detect the optical output and oscillation wavelength of the optical amplifier 25A by measuring the current value output from the first optical receiver 26k and the current value output from the second optical receiver 26l.

[0105] In the optical module according to the fourth embodiment, the upper surface 25a of the optical amplifier 25A and the lower surface 26b of the optical monitor 26A are connected so that they face each other and overlap. Therefore, in the optical module according to the fourth embodiment, the optical amplifier 25A and the optical monitor 26A can be brought close to each other, for example, to within several tens of micrometers, without having to worry about them touching each other. As a result, the optical module according to the fourth embodiment can improve the efficiency of optical coupling in the optical monitor 26A without providing the mounting surface of the optical monitor 26A on the base 13.

[0106] As described above, the optical module according to the fourth embodiment includes an optical amplifier 25A having a light emitting coupler 25d that emits backward laser light Lb in response to emission of forward laser light Lf from the front end, and an optical monitor 26A having an optical coupling coupler 26c that receives and couples the backward laser light Lb emitted from the light emitting coupler 25d, and the optical amplifier 25A and the optical monitor 26A are overlapped so that the light emitting coupler 25d and the optical coupling coupler 26c face each other. Therefore, the optical module according to the fourth embodiment can efficiently couple the backward laser light Lb emitted from the optical amplifier 25A to the optical monitor 26A without providing a mounting surface dedicated to the optical monitor on the base 13.

[0107] Furthermore, in the optical module according to the fourth embodiment, the optical amplifier 25A and the optical monitor 26A are connected so as to face each other and overlap each other, and therefore the base 13 can be made smaller and lighter.

[0108] It should be noted that within the scope of the present disclosure, the embodiments may be freely combined, or any component in each embodiment may be modified, or any component in each embodiment may be omitted.

[0109] The optical module according to the present disclosure is suitable for use in optical modules, etc., because the laser output unit and the optical monitor are overlapped so that the light emitting coupler and the optical coupling coupler face each other, allowing the rearward laser light Lb to be coupled with high efficiency.

[0110] REFERENCE SIGNS LIST 11 stem, 11a main surface, 12 temperature regulator, 12a left side surface, 12b right side surface, 13 base, 13a mounting surface, 13b vertical surface, 14 semiconductor laser submount, 15 semiconductor laser, 15a upper surface, 15b lower surface, 15c laser stripe, 15d light output coupler, 15e, 15f electrodes, 15g wiring line, 16 planar waveguide type optical monitor, 16a upper surface, 16b lower surface, 16c optical coupling coupler, 16d optical splitter, 16e optical filter, 16f heater, 16g first light receiver, 16h second light receiver, 16i, 16j electrodes, 17 thermistor, 18 cap, 19 window member, 20 pin, 25 optical amplifier, 25a upper surface, 25b Lower surface, 25c amplifying stripe, 25d light output coupler, 25e, 25f electrodes, 25g wiring line, 26 reflective filter integrated optical monitor, 26a upper surface, 26b lower surface, 26c optical coupling coupler, 26d optical splitter, 26e first optical filter, 26f second optical filter, 26g third optical filter, 26h first heater, 26i second heater, 26j third heater, 26k first photodetector, 26l second photodetector, 26m waveguide type mirror, 26n, 26o electrodes, 30 wire, Lf forward laser light, Lb backward laser light.

Claims

1. An optical module comprising: a laser output unit having a light emitting coupler that emits a rearward laser light in response to the emission of a forward laser light from a front end; and an optical monitor having an optical coupling coupler that receives and couples the rearward laser light emitted from the light emitting coupler, wherein the laser output unit and the optical monitor are superimposed so that the light emitting coupler and the optical coupling coupler face each other.

2. The optical module according to claim 1, characterized in that: the laser output section has the light emission coupler and multiple laser side electrodes on the same surface; the optical monitor has the optical coupling coupler and multiple monitor side electrodes on the same surface; the multiple laser side electrodes are composed of a multiple connection laser side electrodes covered by the optical monitor and connected to the multiple monitor side electrodes respectively, and a multiple wire bonding laser side electrodes that are not covered by the optical monitor and are not connected to the multiple monitor side electrodes; and the multiple connection laser side electrodes corresponding to the monitor side electrodes connected to the optical receiver of the optical monitor among the multiple connection laser side electrodes are respectively connected to the multiple wire bonding laser side electrodes by wiring.

3. An optical module as claimed in claim 1, characterized in that: said laser output section has said light emission coupler and a plurality of laser side electrodes on the same surface; and said optical monitor has said optical coupling coupler and a plurality of monitor side electrodes, said plurality of monitor side electrodes being comprised of: a plurality of wire bonding monitor side electrodes provided on the surface on which said optical coupling coupler is arranged and connected to a light receiver of said optical monitor; and a plurality of connection monitor side electrodes provided on the surface opposite to the surface on which said optical coupling coupler is arranged and connected to each of said plurality of laser side electrodes.

4. An optical module as claimed in any one of claims 1 to 3, characterized in that it comprises: a stem supporting a temperature regulator which adjusts the temperature of said laser output unit and said optical monitor; and a cap which has a window member through which the forward laser light emitted from said laser output unit passes and is provided on said stem so as to cover said laser output unit and said optical monitor from the outside.

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