Multi-wavelength laser device

Abstract

A Mach-Zehnder switch (4) in a multi-wavelength laser device (100) is capable of changing a phase difference between multi-wavelength light passing through a first waveguide and multi-wavelength light passing through a second waveguide, thereby adjusting an output branching ratio of multi-wavelength light output from a first input port to a gain section (2) and multi-wavelength light output from a second input port to an output waveguide (6).

Description

Technical Field

[0001] This invention relates to multi-wavelength laser devices. Background Technology

[0002] Wavelength Division Multiplexing (WDM) technology bundles multiple optical signals of different wavelengths together in a single optical fiber and transmits these signals through the fiber, enabling high-capacity optical transmission in optical communication systems.

[0003] As an example of WDM technology, Patent Document 1 describes a multi-wavelength laser device with an external resonator. This multi-wavelength laser device has an external resonator consisting of a semiconductor gain chip and two mirrors configured to sandwich the semiconductor gain chip, amplifying the light by confining it between the two mirrors. The external resonator includes: a periodic wavelength filter that extracts multi-wavelength light with periodic peak wavelengths from the confined light; and a wavelength splitting filter that outputs multiple optical signals by dividing the multi-wavelength light according to each wavelength.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-85475 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In the external resonator described above, a directional coupler is sometimes used to extract the amplified multi-wavelength light from the external resonator, which extracts the multi-wavelength light from the waveguide within the external resonator. However, the directional coupler has the following problem: due to its wavelength dependence, the output of each peak wavelength in the multi-wavelength light extracted by the directional coupler varies depending on the wavelength.

[0009] The present invention was made to solve the above-mentioned problems and provides a technology that can extract constant multi-wavelength light from an external resonator for each peak wavelength.

[0010] Methods for solving problems

[0011] The multi-wavelength laser device of the present invention comprises: an external resonator that amplifies light; and a first output waveguide that outputs the light amplified by the external resonator. The multi-wavelength laser device further comprises: a semiconductor gain chip; a first Mach-Zehnder switch having a first input port, a second input port, a first output port, and a second output port; and a first waveguide and a second waveguide optically connecting the first and second input ports to the first and second output ports, respectively. The first input port is optically connected to the semiconductor gain chip, and the second input port is optically connected to the first output waveguide; and a loop resonator-type periodic wavelength mirror optically connected to the first and second output ports of the first Mach-Zehnder switch. By partially reflecting the light input from the first Mach-Zehnder switch, multi-wavelength light with periodic peak wavelengths is output to the first Mach-Zehnder switch; and a reflector is provided on the side opposite to the first Mach-Zehnder switch with the semiconductor gain chip as a reference, thereby forming an external resonator together with the semiconductor gain chip and the periodic wavelength reflector, reflecting the light after passing through the semiconductor gain chip toward the semiconductor gain chip. The first Mach-Zehnder switch can change the phase difference between the multi-wavelength light passing through the first waveguide and the multi-wavelength light passing through the second waveguide, thereby adjusting the output branch ratio of the multi-wavelength light output from the first input port to the semiconductor gain chip and the multi-wavelength light output from the second input port to the first output waveguide.

[0012] Invention Effects

[0013] According to the present invention, it is possible to extract multi-wavelength light with constant output from an external resonator, with each peak wavelength being extracted. Attached Figure Description

[0014] Figure 1 This is a block diagram showing the structure of the multi-wavelength laser device 100 according to Embodiment 1.

[0015] Figure 2 This is a schematic diagram showing the structure of the multi-wavelength laser device 100 according to Embodiment 1.

[0016] Figure 3 This is a diagram showing another multi-wavelength laser device with a structure different from the multi-wavelength laser device 100 of Embodiment 1.

[0017] Figure 4 Show Figure 3 The series transmission characteristics of the loop resonator and loop reflector of the Si thin-wire waveguide in another multi-wavelength laser device are shown.

[0018] Figure 5The transmission characteristics of multi-wavelength light from the first input port of the Mach-Zehnder switch to the second input port are shown in the periodic wavelength mirror of the Mach-Zehnder switch and loop resonator type of the multi-wavelength laser device of Embodiment 1.

[0019] Figure 6 This is a block diagram showing the structure of the multi-wavelength laser device in Embodiment 2.

[0020] Figure 7 This is a schematic diagram showing the structure of the multi-wavelength laser device in Embodiment 2.

[0021] Figure 8 This is a schematic diagram showing the structure of the multi-wavelength laser device in Embodiment 3. Detailed Implementation

[0022] Hereinafter, in order to illustrate the present invention in more detail, the embodiments for carrying out the present invention will be described with reference to the accompanying drawings.

[0023] Implementation Method 1

[0024] Figure 1 This is a block diagram showing the structure of the multi-wavelength laser device 100 according to Embodiment 1. Figure 2 This is a schematic diagram illustrating the structure of the multi-wavelength laser device 100 according to Embodiment 1. (As shown...) Figure 1 and Figure 2 As shown, the multi-wavelength laser device 100 includes a reflector 1, a gain unit 2, a phase control unit 3, a Mach-Zehnder switch 4 (first Mach-Zehnder switch), a periodic wavelength reflector 5, and an output waveguide 6.

[0025] The multi-wavelength laser device 100 includes: an external resonator that amplifies light; and an output waveguide 6 (first output waveguide) that outputs the light amplified by the external resonator. The external resonator is composed of a reflector 1, a gainer 2, and a periodic wavelength mirror 5.

[0026] More specifically, the multi-wavelength laser device 100 is an external resonator type multi-wavelength laser device that has a periodic wavelength reflector 5 within an external resonator and is capable of oscillating simultaneously with multiple wavelengths. Furthermore, in Figure 1 and Figure 2 An example is given showing signal light (λ1~λ2) oscillating simultaneously with an N wavelength. N A multi-wavelength laser (N is a positive integer greater than or equal to 2) is used. A gain unit 2 is disposed between the reflector 1 and the periodic wavelength reflector 5 in the multi-wavelength laser device 100. Furthermore, a phase control unit 3 and a Mach-Zehnder switch 4 are disposed in series between the gain unit 2 and the periodic wavelength reflector 5 in the multi-wavelength laser device 100.

[0027] Gain section 2 is a semiconductor gain chip. More specifically, gain section 2 is, for example, a quantum dot gain chip having a quantum dot gain medium.

[0028] The reflector 1 is positioned on the side opposite to the Mach-Zehnder switch 4, with the gain unit 2 as a reference, and together with the gain unit 2 and the periodic wavelength reflector 5, forms an external resonator. The reflector 1 reflects the light that has passed through the gain unit 2 toward the gain unit 2.

[0029] For example, if the gain section 2 is a quantum dot gain chip, the reflection section 1 can also be a cleaved end face of that quantum dot gain chip. However, as the gain section 2, an end face coated with a high-reflectivity film is preferred, for example, compared to such a cleaved end face. The gain section 2 can also be a waveguide element such as a loop mirror or a DBR mirror.

[0030] A phase control unit 3 is disposed between the gain unit 2 and the Mach-Zehnder switch 4. The phase control unit 3 controls the phase of the multi-wavelength light to be transmitted. More specifically, the phase control unit 3 is a component that imparts a phase change to the optical waveguide using thermo-optical effects or the like. Alternatively, the multi-wavelength laser device 100 may not have a phase control unit 3, but it is preferable that the multi-wavelength laser device 100 has a phase control unit 3 to improve the stability of the oscillation wavelength of the external resonator type laser.

[0031] The Mach-Zehnder switch 4 has a first input port, a second input port, a first output port, a second output port, and a first waveguide and a second waveguide optically connecting the first and second input ports to the first and second output ports, respectively. That is, the Mach-Zehnder switch 4 is a Mach-Zehnder type switch with 2×2 input and output ports.

[0032] The first input port of the Mach-Zehnder switch 4 is optically connected to the gain unit 2. More specifically, in embodiment 1, the first input port of the Mach-Zehnder switch 4 is optically connected to the gain unit 2 via the phase control unit 3. The second input port of the Mach-Zehnder switch 4 is optically connected to the output waveguide 6.

[0033] The periodic wavelength reflector 5 is optically connected to the first and second output ports of the Mach-Zehnder switch 4. The periodic wavelength reflector 5 outputs multi-wavelength light with periodic peak wavelengths to the Mach-Zehnder switch 4 by partially reflecting the light input from the Mach-Zehnder switch 4.

[0034] More specifically, in Embodiment 1, the periodic wavelength reflector 5 is an element that reflects only light with periodic peak wavelengths. The periodic wavelength reflector 5 is composed of a 1×2 optical coupler and a loop resonator. Alternatively, the periodic wavelength reflector 5 can also be composed of a 2×2 optical coupler and a loop resonator. The two waveguides branching from the 1×2 optical coupler are respectively positioned close to the loop resonator. The FSR (free spectral range) of the loop resonator of the periodic wavelength reflector 5 is designed to match the wavelength spacing of the desired WDM communication standard. Furthermore, a heater or the like is provided on the waveguide of the loop resonator within the periodic wavelength reflector 5. Thus, by utilizing the thermo-optic effect, the refractive index of the waveguide changes, thereby enabling the periodic wavelength reflector 5 to be configured to adjust the wavelength spacing of the periodic peak wavelengths of the multi-wavelength light to be reflected.

[0035] The function of the Mach-Zehnder switch 4 will be explained in more detail below. The Mach-Zehnder switch 4 can change the phase difference between the multi-wavelength light passing through the first waveguide and the multi-wavelength light passing through the second waveguide, thereby adjusting the output branch ratio of the multi-wavelength light output from the first input port to the gain unit 2 and the multi-wavelength light output from the second input port to the output waveguide 6.

[0036] More specifically, in implementation 1, the Mach-Zehnder switch 4 uses thermo-optical effects to impart a phase difference between the first waveguide and the second waveguide, thereby enabling the output branch ratio to the output waveguide 6 to be controlled with any branch ratio.

[0037] For example, in a Si thin-wire waveguide, optical coupling can be achieved with a desired branching ratio by applying a simple directional coupler. However, directional couplers are inherently wavelength-dependent, and the output of each peak wavelength in the multi-wavelength light extracted by the directional coupler varies depending on the wavelength. On the other hand, in the Mach-Zehnder switch 4, even when a wavelength-dependent directional coupler is applied to the input / output section, the wavelength dependence is reduced for the multi-wavelength light output from the second input port to the output waveguide 6. By adjusting the output branching ratio of the Mach-Zehnder switch 4, the internal losses of the external resonator can be changed. However, the Mach-Zehnder switch 4 is preferably designed so that the output branching ratio is the desired value when no power is applied, in order to reduce the power consumption used to adjust the output branching ratio of the Mach-Zehnder switch 4.

[0038] The operation of the multi-wavelength laser device 100 of Embodiment 1 will now be described. When a current is applied to the gain unit 2, light of a wavelength corresponding to the FSR of the loop resonator of the periodic wavelength mirror 5 resonates between the periodic wavelength mirror 5 and the reflection unit 1. As a result, light of a wavelength with gain exceeding the internal loss is output from the second input port of the Mach-Zehnder switch 4 to the output waveguide 6. Here, light other than light of wavelengths with a fixed interval Δλ passes through the periodic wavelength mirror 5. Therefore, multi-wavelength light with periodic peak wavelengths having a fixed interval Δλ can resonate and oscillate simultaneously.

[0039] Furthermore, by monitoring the multi-wavelength light from the output waveguide 6 and adjusting the output branch ratio of the Mach-Zehnder switch 4 using the method described above, the internal losses of the external resonator in the desired applied current can be minimized, thereby maximizing the output power.

[0040] Furthermore, by utilizing the periodic wavelength reflector 5 and the Mach-Zehnder switch 4, the aforementioned wavelength dependence can be reduced, thus suppressing the deviation in output power for each wavelength of the multi-wavelength laser output.

[0041] In order to illustrate the wavelength dependence reduction effect of the multi-wavelength laser device 100 based on Embodiment 1, a comparison will be made with another multi-wavelength laser device having a different structure from the multi-wavelength laser device 100. Figure 3 This is a diagram showing another multi-wavelength laser device with a structure different from the multi-wavelength laser device 100 of Embodiment 1.

[0042] Figure 3 Another multi-wavelength laser device shown has a structure in which a gain section and a periodic wavelength filter are arranged between two reflectors. Figure 3 The right-hand reflector of the two reflectors reflects a portion of the power of the light after it has passed through the periodic wavelength filter, while allowing the remaining power to pass through. Therefore, the waveguide on the opposite side of the waveguide in this reflector, which is connected to the periodic wavelength filter, functions as an output waveguide.

[0043] For example, in a loop mirror constructed using Si thin-wire waveguides Figure 3 In the case of the right-hand reflector, the directional coupler of the loop reflector is wavelength dependent. Therefore, the output of each peak wavelength in the multi-wavelength light extracted by the directional coupler deviates according to each wavelength.

[0044] The following is about Figure 3 The transmission characteristics of the other multi-wavelength laser device shown are compared with those of the multi-wavelength laser device 100 in Embodiment 1. Furthermore, in the following description, a loop resonator using a Si fine-wire waveguide is used as... Figure 3The periodic wavelength filter of another multi-wavelength laser device shown uses a loop mirror as... Figure 3 The reflective part on the right side of the image. Figure 4 Show Figure 3 The series transmission characteristics of the loop resonator and loop mirror in another multi-wavelength laser device are shown. On the other hand, Figure 5 The diagram illustrates the transmission characteristics of multi-wavelength light from the first input port of the Mach-Zehnder switch 4 to the second input port in the Mach-Zehnder switch 4 and the loop resonator-type periodic wavelength reflector 5 of the multi-wavelength laser device 100 of Embodiment 1. However, in Figure 4 and Figure 5 In all examples, the loop resonator structure is identical. Under the condition that the transmittance of the loop mirror and the branch ratio of the Mach-Zehnder switch are both 50%, the transmission characteristics are calculated through simulation. Figure 4 and Figure 5 In the diagram, the vertical axis represents transmittance (dB), and the horizontal axis represents wavelength (nm).

[0045] Compare Figure 4 The curves shown and Figure 5 The curve shown indicates that, Figure 4 In the curves shown, according to the wavelength dependence of the loop mirror, the transmittance increases with longer wavelengths. On the other hand, in Figure 5 The curves shown exhibit relatively flat transmission characteristics. That is, in the multi-wavelength laser device 100 of Embodiment 1, it is possible to extract multi-wavelength light with constant output peak wavelengths from an external resonator.

[0046] As described above, the multi-wavelength laser device 100 of Embodiment 1 includes: an external resonator that amplifies light; and an output waveguide 6 that outputs the light amplified by the external resonator. The multi-wavelength laser device 100 includes: a gain section 2 serving as a semiconductor gain chip; a Mach-Zehnder switch 4 having a first input port, a second input port, a first output port, a second output port, and a first waveguide and a second waveguide optically connecting the first and second input ports to the first and second output ports, respectively; the first input port being optically connected to the gain section 2, and the second input port being optically connected to the output waveguide 6; and a periodic wavelength mirror 5 connected to the first input port of the Mach-Zehnder switch 4. The output port and the second output port are optically connected. By partially reflecting the light input to the Mach-Zehnder switch 4, multi-wavelength light with periodic peak wavelengths is output to the Mach-Zehnder switch 4. The reflector 1 is set on the side opposite to the Mach-Zehnder switch 4 with reference to the gain section 2. Together with the gain section 2 and the periodic wavelength reflector 5, it forms an external resonator and reflects the light after passing through the gain section 2 toward the gain section 2. The Mach-Zehnder switch 4 can change the phase difference between the multi-wavelength light passing through the first waveguide and the multi-wavelength light passing through the second waveguide. As a result, the output branch ratio of the multi-wavelength light output from the first input port to the gain section 2 and the multi-wavelength light output from the second input port to the output waveguide 6 is adjusted.

[0047] Based on the above structure, by adjusting the output branch ratio of the Mach-Zehnder switch 4, a constant multi-wavelength light with each peak wavelength can be extracted from the external resonator.

[0048] For example, when using the multi-wavelength laser device described in Patent Document 1 for WDM transmission, the oscillation characteristics need to converge within a wavelength grid defined by specifications. In existing multi-wavelength laser devices that can simultaneously oscillate multiple wavelengths of light by placing a periodic wavelength filter within the external resonator of an external resonator-type quantum dot laser, the center wavelength of the periodic wavelength filter varies due to manufacturing errors. Therefore, countermeasures such as temperature control or applying electricity to the resistive component formed on the periodic wavelength filter are required to control the center wavelength. Thus, a wavelength monitoring mechanism for adjusting the oscillation wavelength is necessary. In Patent Document 1, a wavelength splitter filter is connected in series with the periodic wavelength filter within the external resonator, and wavelength adjustment is performed using light passing through the monitoring port of the wavelength splitter filter and light passing through the transmission port of the periodic wavelength filter. However, there is a problem: because the wavelength splitter filter is inserted into the external resonator, the internal loss of the external resonator increases, resulting in a decrease in output power.

[0049] However, according to the structure of the multi-wavelength laser device 100 in Embodiment 1, it is possible to extract multi-wavelength light with constant output peak wavelengths from the external resonator without increasing the internal losses of the external resonator. Moreover, it is also possible to monitor and adjust the peak wavelengths of the extracted multi-wavelength light.

[0050] Implementation Method 2

[0051] In Embodiment 2, the structure for monitoring the output of each peak wavelength of multi-wavelength light will be described.

[0052] Hereinafter, Embodiment 2 will be described with reference to the accompanying drawings. Furthermore, structures having the same functions as those described in Embodiment 1 will be labeled with the same reference numerals, and their descriptions will be omitted. Figure 6 This is a block diagram showing the structure of the multi-wavelength laser device 101 in Embodiment 2. Figure 7 This is a schematic diagram showing the structure of the multi-wavelength laser device 101 in Embodiment 2. (As shown...) Figure 6 and Figure 7 As shown, the multi-wavelength laser device 101, in addition to the structure of the multi-wavelength laser device 100 of Embodiment 1, also includes a second Mach-Zehnder switch 11, an optical coupler 14, a photodetector 15 (first photodetector), multiple loop filters 16, and multiple photodetectors 17 (multiple second photodetectors). Furthermore, Figure 6 and Figure 7 The first Mach-Zehnder switch 10 shown has the same function as the Mach-Zehnder switch 4 described in Embodiment 1.

[0053] The multi-wavelength laser device 101 in Embodiment 2 is an external resonator-type multi-wavelength laser device capable of oscillating simultaneously at multiple wavelengths, with a wavelength monitoring mechanism added to the structure of the multi-wavelength laser device 100 in Embodiment 1. As waveguides, the multi-wavelength laser device 101 also includes an output waveguide 12 (second output waveguide), a monitoring waveguide 13, an output monitoring waveguide 18, and a wavelength monitoring waveguide 19. Furthermore, in Figure 6 and Figure 7 The example illustrates the simultaneous oscillation of signal light with wavelengths N (λ1~λ). N Multi-wavelength laser (N is a positive integer greater than 2).

[0054] The second Mach-Zehnder switch 11 has a first input port, a second input port, a first output port, a second output port, and a first waveguide and a second waveguide optically connecting the first and second input ports to the first and second output ports, respectively. That is, similar to the first Mach-Zehnder switch 10, the second Mach-Zehnder switch 11 is a Mach-Zehnder type switch with 2×2 input / output ports.

[0055] The first input port of the second Mach-Zehnder switch 11 is optically connected to the first Mach-Zehnder switch 10 via the output waveguide 6. The first output port of the second Mach-Zehnder switch 11 is optically connected to the output waveguide 12. The second output port of the second Mach-Zehnder switch 11 is optically connected to the monitoring waveguide 13.

[0056] The second Mach-Zehnder switch 11 can change the phase difference between the multi-wavelength light passing through the first waveguide and the second waveguide of the second Mach-Zehnder switch 11, thereby adjusting the output branch ratio of the multi-wavelength light output from the first output port of the second Mach-Zehnder switch 11 to the output waveguide 12 and the multi-wavelength light output from the second output port to the monitoring waveguide 13. That is, similar to the first Mach-Zehnder switch 10, the second Mach-Zehnder switch 11 can control the power of the multi-wavelength light output from the output port according to an arbitrary output branch ratio by employing a phase difference between the first and second waveguides using thermo-optical effects, etc.

[0057] Optical coupler 14 has an input port optically connected to the second Mach-Zehnder switch 11 via monitoring waveguide 13, a first output port optically connected to the output monitoring waveguide 18, and a second output port optically connected to the wavelength monitoring waveguide 19. That is, optical coupler 14 is a 1×2 optical coupler. Optical coupler 14 branches the multi-wavelength light input from the second Mach-Zehnder switch 11, outputting it to the output monitoring waveguide 18 and the wavelength monitoring waveguide 19, respectively.

[0058] The photodetector 15 is optically connected to the optical coupler 14 via the output monitoring waveguide 18. The photodetector 15 detects multi-wavelength light input from the output monitoring waveguide 18.

[0059] Multiple loop filters 16 are optically connected to wavelength monitoring waveguide 19. More specifically, in embodiment 2, the multiple loop filters 16 are N loop resonators, and wavelength monitoring waveguide 19 is optically connected in series with the N loop resonators.

[0060] Multiple loop filters 16 extract light of a predetermined wavelength from the multi-wavelength light input from the wavelength monitoring waveguide 19. More specifically, in embodiment 2, the multiple loop filters 16 are multiple loop resonators, each configured such that the wavelength of the light to be extracted is a wavelength according to the WDM communication standard, which is a different discard wavelength (λ1, λ2, ..., λ) for each loop resonator. N ).

[0061] Multiple photodetectors 17 are connected to corresponding loop filters in multiple loop filters 16. The multiple photodetectors 17 detect the light extracted by the corresponding loop filters in the multiple loop filters 16.

[0062] Similar to Embodiment 1, the periodic wavelength reflector 5 in Embodiment 2 can adjust the wavelength interval of the periodic peak wavelengths of the multi-wavelength light output to the first Mach-Zehnder switch 10. More specifically, in Embodiment 2, a heater or the like is provided on the waveguide of the loop resonator within the periodic wavelength reflector 5. This causes a change in the refractive index of the waveguide using a thermo-optical effect, thereby enabling the periodic wavelength reflector 5 to adjust the wavelength interval of the periodic peak wavelengths of the multi-wavelength light to be reflected.

[0063] The operation of the multi-wavelength laser device 101 in Embodiment 2 will now be described. When a current is applied to the gain unit 2, resonance occurs between the periodic wavelength reflector 5 and the reflector 1. As a result, light with a wavelength corresponding to the FSR of the loop resonator of the periodic wavelength reflector 5 is generated. Thus, light with a gain exceeding the internal loss is output from the second input port of the first Mach-Zehnder switch 10 to the output waveguide 6. Here, light other than light with wavelengths at fixed intervals Δλ passes through the periodic wavelength reflector 5. Therefore, multi-wavelength light with periodic peak wavelengths at fixed intervals Δλ can resonate and oscillate simultaneously.

[0064] By adjusting the output branch ratio of the second Mach-Zehnder switch 11 using the method described above, multi-wavelength light is directed to pass through the monitoring waveguide 13 (bus waveguide). Next, by monitoring the photodetector 15 and adjusting the branch ratio of the first Mach-Zehnder switch 10 to maximize the current of the photodetector 15, the internal loss of the external resonator is adjusted to achieve the maximum output power under the desired applied current. Thus, the output power of the multi-wavelength laser device 101 can be maximized.

[0065] Next, the wavelength intervals in the periodic wavelength reflectors 5 are adjusted so that the oscillation wavelength of the multi-wavelength laser device 101 is the wavelength according to the WDM standard. The multiple loop filters 16, optically connected to the wavelength monitoring waveguide 19 of Embodiment 2, are designed to discard light of the WDM standard wavelength. Therefore, when the multi-wavelength light output by the multi-wavelength laser device 101, which is an external resonator type laser, has a periodic peak wavelength according to the WDM standard, the multiple photodetectors 17 (in...) Figure 7 The monitoring current of each of the N photodetectors (17) is maximized.

[0066] However, the periodic wavelength interval of the oscillation wavelength of an external resonator-type multi-wavelength laser is typically offset due to manufacturing errors. Here, the offset is adjusted by monitoring multiple photodetectors 17 separately and adjusting the refractive index of the loop resonator of the periodic wavelength reflector 5 by the heater in a manner that maximizes the monitoring current of each detector 17, so that the wavelength interval of the periodic peak wavelengths of the multi-wavelength light reflected by the periodic wavelength reflector 5 is in accordance with the wavelength interval of the WDM standard.

[0067] After the peak wavelength adjustment is completed, there is no need to output light to the monitoring waveguide 13. Therefore, by adjusting the output branch ratio of the second Mach-Zehnder switch 11, the power is branched to the output waveguide 12. Through the above actions, the multi-wavelength laser device 101 of the external resonator type laser has an oscillation wavelength according to the WDM standard, which can maximize the output power of the multi-wavelength light output by the multi-wavelength laser device 101.

[0068] Implementation Method 3

[0069] In Embodiment 3, the structure of the plurality of loop filters 16 described in Embodiment 2 will be explained.

[0070] Hereinafter, Embodiment 3 will be described with reference to the accompanying drawings. Furthermore, structures having the same functions as those described in Embodiment 1 or Embodiment 2 will be labeled with the same reference numerals, and their descriptions will be omitted. Figure 8 This is a schematic diagram showing the structure of the multi-wavelength laser device 102 in Embodiment 3. (As shown...) Figure 8 As shown, the multi-wavelength laser device 102, in addition to the structure of the multi-wavelength laser device 101 of Embodiment 2, also includes a photodetector 20 (third photodetector) and multiple light sources 21.

[0071] The multi-wavelength laser device 102 in Embodiment 3 has the following structure: In the wavelength monitoring mechanism of the multi-wavelength laser device 101 in Embodiment 2, there is an adjustment mechanism for the loop filter 16, which serves as a loop resonator for wavelength monitoring. In Embodiment 2, an embodiment where the loop filter 16 for wavelength monitoring is manufactured according to design was described; however, in Embodiment 3, a structure for adjusting the loop filter 16 when its discard wavelength changes due to manufacturing errors, etc., is described. Furthermore, in Figure 8 The example illustrates the simultaneous oscillation of signal light with wavelengths N (λ1~λ). N (A multi-wavelength laser device.)

[0072] Multiple light sources 21 are optically connected to corresponding loop filters in multiple loop filters 16. The multiple light sources 21 output light of a specified wavelength to their respective loop filters.

[0073] More specifically, in embodiment 3, the plurality of light sources 21 are wavelength-variable laser diodes (TLDs). Each of the plurality of light sources 21 is optically connected to the end opposite to the end of the waveguide of the corresponding wavelength monitoring loop filter 16 connected to the photodetector 17. Here, the connection between the waveguide and the light source 21 can be via end-face coupling of an optical fiber or based on grating couplers. In the case of grating coupler-based coupling, it is particularly preferable to arrange N grating couplers in an array.

[0074] The photodetector 20 detects light output from multiple light sources 21 and light extracted by corresponding loop filters among multiple loop filters 16. More specifically, in embodiment 3, the photodetector 20 is optically connected to the terminal portion of the wavelength monitoring waveguide 19, in which multiple loop filters 16 are arranged in series.

[0075] In Embodiment 3, the multiple loop filters 16 are each capable of adjusting the wavelength of the light to be extracted. More specifically, in Embodiment 3, heaters or the like are provided on the waveguides of the multiple loop filters 16. This causes a change in the refractive index of the waveguide using a thermo-optical effect, thereby enabling the multiple loop filters 16 to be configured to adjust the wavelength of the light to be extracted.

[0076] The operation of the multi-wavelength laser device 102 in Embodiment 3 will now be explained. First, the multi-wavelength laser device 102 in Embodiment 3 will be... Figure 8 The light source 21 of PD1 outputs light at the wavelength to be used in the multi-wavelength laser device 102, that is, the shortest wavelength (or the longest wavelength) λ1 according to the WDM standard, and applies this light to... Figure 8 The loop filter 16 of RR1 is applied to... Figure 8 The light from the loop filter 16 of RR1 reaches the photodetector 20 via the wavelength monitoring waveguide 19. Then, using... Figure 8 The heater of the loop filter 16 in RR1 is heated, and the heater value is adjusted to the maximum value by means of the monitoring current of the photodetector 20.

[0077] Next, make Figure 8 The light source 21 of PD2 outputs light at a wavelength λ2 that is adjacent to the shortest wavelength (or longest wavelength) λ1 according to the WDM standard, which is to be used in the multi-wavelength laser device 102. This light is then applied to... Figure 8 The loop filter 16 of RR2 is applied to... Figure 8 The light from the loop filter 16 of RR2 reaches the photodetector 20 via the wavelength monitoring waveguide 19. Then, using... Figure 8The heater of the loop filter 16 in RR2 is heated, and the heater value is adjusted to the maximum value by means of the monitoring current of the photodetector 20.

[0078] Capable of transmitting signals from wavelength λ3 to wavelength λ N Repeat the same operation as described above, adjusting the wavelength of light extracted by each monitoring wavelength loop filter 16 (from RR1 to RRN). After fixing the heater value of each loop filter 16, the state of the multi-wavelength laser device 102 becomes exactly the same as that of the multi-wavelength laser device 101 in Embodiment 2. Therefore, the following operations can also be performed in the same way as in Embodiment 2.

[0079] Furthermore, it is possible to freely combine the various embodiments, or modify any structural elements of the various embodiments, or omit any structural elements in the various embodiments.

[0080] Industrial availability

[0081] The multi-wavelength laser device of the present invention can extract multi-wavelength light with constant output of each peak wavelength from an external resonator, and therefore can be used in technologies that utilize multi-wavelength light.

[0082] Label Explanation

[0083] 1: Reflector; 2: Gain unit; 3: Phase control unit; 4: Mach-Zehnder switch; 5: Periodic wavelength mirror; 6: Output waveguide; 10: First Mach-Zehnder switch; 11: Second Mach-Zehnder switch; 12: Output waveguide; 13: Monitoring waveguide; 14: Optical coupler; 15: Photodetector; 16: Loop filter; 17: Photodetector; 18: Output monitoring waveguide; 19: Wavelength monitoring waveguide; 20: Photodetector; 21: Light source; 100, 101, 102: Multi-wavelength laser device.

Claims

1. A multi-wavelength laser device comprising: an external resonator that amplifies light; and a first output waveguide that outputs the light amplified by the external resonator, characterized in that, The multi-wavelength laser device has the following features: Semiconductor gain chip; A first Mach-Zehnder switch has a first input port, a second input port, a first output port, a second output port, and a first waveguide and a second waveguide that optically connect the first and second input ports to the first and second output ports, respectively. The first input port is optically connected to the semiconductor gain chip, and the second input port is optically connected to the first output waveguide. A loop resonator-type periodic wavelength reflector is optically connected to the first and second output ports of the first Mach-Zehnder switch. By partially reflecting the light input from the first Mach-Zehnder switch, it outputs multi-wavelength light with periodic peak wavelengths to the first Mach-Zehnder switch. as well as The reflective element, positioned relative to the semiconductor gain chip and opposite to the first Mach-Zehnder switch side, together with the semiconductor gain chip and the periodic wavelength reflector, forms the external resonator, reflecting light passing through the semiconductor gain chip towards the semiconductor gain chip. The first Mach-Zehnder switch can change the phase difference between the multi-wavelength light passing through the first waveguide of the first Mach-Zehnder switch and the multi-wavelength light passing through the second waveguide of the first Mach-Zehnder switch, thereby adjusting the output branch ratio of the multi-wavelength light output from the first input port of the first Mach-Zehnder switch to the semiconductor gain chip and the multi-wavelength light output from the second input port of the first Mach-Zehnder switch to the first output waveguide.

2. The multi-wavelength laser device according to claim 1, characterized in that, The multi-wavelength laser device also has a phase control unit, which is disposed between the semiconductor gain chip and the first Mach-Zehnder switch to control the phase of the multi-wavelength light to be passed.

3. The multi-wavelength laser device according to claim 1, characterized in that, The multi-wavelength laser device also includes a second output waveguide, a monitoring waveguide, an output monitoring waveguide, and a wavelength monitoring waveguide. The multi-wavelength laser device has the following features: A second Mach-Zehnder switch has a first input port, a second input port, a first output port, a second output port, and a first waveguide and a second waveguide of the second Mach-Zehnder switch that optically connect the first and second input ports of the second Mach-Zehnder switch to the first and second output ports of the second Mach-Zehnder switch, respectively. The first input port of the second Mach-Zehnder switch is optically connected to the first Mach-Zehnder switch via the first output waveguide. The first output port of the second Mach-Zehnder switch is optically connected to the second output waveguide. The second output port of the second Mach-Zehnder switch is optically connected to the monitoring waveguide. An optical coupler having an input port optically connected to the second Mach-Zehnder switch via the monitoring waveguide, a first output port optically connected to the output monitoring waveguide, and a second output port optically connected to the wavelength monitoring waveguide, such that multi-wavelength optical branches input from the second Mach-Zehnder switch are respectively output to the output monitoring waveguide and the wavelength monitoring waveguide; A first photodetector, which is optically connected to the optical coupler via the output monitoring waveguide, detects multi-wavelength light input from the output monitoring waveguide; Multiple loop filters are optically connected to the wavelength monitoring waveguide, which extract light of a specified wavelength from the multi-wavelength light input from the wavelength monitoring waveguide. as well as Multiple second photodetectors, each detecting the light extracted by a corresponding loop filter among the multiple loop filters, The second Mach-Zehnder switch can change the phase difference between the multi-wavelength light passing through the first waveguide of the second Mach-Zehnder switch and the multi-wavelength light passing through the second waveguide of the second Mach-Zehnder switch, thereby adjusting the output branch ratio of the multi-wavelength light output from the first output port of the second Mach-Zehnder switch to the second output waveguide and the multi-wavelength light output from the second output port of the second Mach-Zehnder switch to the monitoring waveguide.

4. The multi-wavelength laser device according to claim 3, characterized in that, The periodic wavelength mirror can adjust the wavelength interval of the periodic peak wavelengths of the multi-wavelength light output to the first Mach-Zehnder switch.

5. The multi-wavelength laser device according to claim 3, characterized in that, The multi-wavelength laser device also has: Multiple light sources are optically connected to corresponding loop filters in the multiple loop filters, and output light of a specified wavelength to the corresponding loop filter; as well as The third photodetector detects the light output from the plurality of light sources and extracted by the corresponding loop filter among the plurality of loop filters.

6. The multi-wavelength laser device according to claim 5, characterized in that, The multiple loop filters can each adjust the wavelength of the light to be extracted.

7. The multi-wavelength laser device according to any one of claims 1 to 6, characterized in that, The semiconductor gain chip has a quantum dot gain medium.

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