JP2010087472A - Variable-wavelength laser light source, and method for driving the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable-wavelength laser light source which can expand a variable-wavelength range with a relatively simple structure. <P>SOLUTION: The variable-wavelength laser light source includes: a variable-wavelength resonator 1 which has a first input port, a second input port, and an output port, and can shift a wavelength spectrum peak of an intensity of transmitted light; a first semiconductor optical amplifier 11 one end of which is optically connected to the first input port of the variable-wavelength resonator 1; a second semiconductor optical amplifier 12 one end of which is optically connected to the second input port of the variable-wavelength resonator 1 and which has a different gain wavelength spectrum from the first semiconductor optical amplifier 11; and a dielectric multilayer film 18 which is formed on the end surface of the output port of the variable-wavelength resonator 1 and has a predetermined transmission factor and reflection factor. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a light source used for optical communication, optical information processing, optical interconnection, and the like, and more particularly to a wavelength tunable laser light source having a wavelength tunable function and a driving method thereof.

  In recent years, Internet traffic has increased rapidly, and technology for expanding communication capacity has also been developed in response to this. Wavelength division multiplexing (WDM) is intended to increase the capacity by increasing the number of wavelengths. Therefore, expansion of communication capacity with more flexibility is being actively studied. In this method, wavelength resources are not only used for capacity expansion, but are also actively used for improving network functions. The expansion of the communication capacity and the enhancement of the functions of the communication system enable the provision of a low-cost and highly secure communication service in relation to each other. A tunable laser is one of the key devices important in constructing such a communication system.

  In conventional wavelength division multiplexing systems, a plurality of fixed wavelength light sources having a fixed wavelength interval are arranged side by side, and the cost of maintenance management backup light sources (for the number of wavelengths) is particularly large, which hinders cost reduction of the system. It was a factor. By applying the wavelength tunable light source, the types of the light sources can be integrated into one, so that the reduction of the system cost is greatly advanced. In addition, a wavelength tunable light source having a high switching speed is an indispensable element for realizing a new network function even in wavelength routing.

  As a wavelength tunable light source capable of covering the C (Conventional) band or the L (Long) band, a movable MEMS mirror is used. Non-Patent Document 1 is published by Berger et al. Although the wavelength tunable light source of Non-Patent Document 1 shows relatively good light output characteristics, there are concerns about its practicality in terms of manufacturing cost and impact resistance. A DBR laser with improved mode stability and further integrated with a modulator is shown in FIG. Although reported in Non-Patent Document 2 by Mason et al., There are problems in terms of cost reduction and reliability.

  On the other hand, a tunable light source using a planar optical circuit (PLC) as an external resonator is relatively easy to manufacture and does not have a movable part like MEMS. Therefore, it is excellent in terms of production yield and reliability (particularly vibration resistance) and is considered suitable for mass production, and several configurations have been proposed at present. As a configuration using a ring-type external resonator and a semiconductor amplifier, H.K. Reported in Non-Patent Document 3 by Yamazaki et al. According to the report of Non-Patent Document 3, as a wavelength variable light source having no movable part, good characteristics are obtained in terms of wavelength variable range, light output, and the like.

Optical Communication, 2001. ECOC'01.27th European Conference on Volume 2,30 P.E. 198-199 IEEE Photonics Letters Volume 11 Number 6, 1999 P.I. 638-640 30th European Conference on Optical Communication 2004, th4.2.3

  However, in the wavelength variable light source having the configuration proposed in Non-Patent Document 3, the wavelength variable range is determined by the wavelength variable range of the ring-type external resonator and the gain band of the semiconductor amplifier. For this reason, there is a limitation in the configuration in order to perform wavelength tuning over a wide range with high output.

  In a high-density wavelength division multiplexing (DWDM) system for optical communication, a communication wavelength band is mainly divided into a C band and an L band, and a large number of wavelength signal lights are assigned to a wavelength range of about 40 nm. Currently, many tunable lasers are being developed based on a wavelength range of 40 nm. However, there are few wavelength tunable lasers having a wavelength tunable range of 80 nm or more that can cover both C and L bands with a single light source. Further, in the CWDM (Coarse WDM) system in which the signal light wavelength is set at intervals of about 20 nm, a wider range of wavelength variation is required.

  The present invention has been made to solve the above problems, and provides a wavelength tunable laser light source capable of expanding the wavelength tunable range with a relatively simple configuration, and a driving method thereof. For the purpose.

  A wavelength tunable laser light source according to the first aspect of the present invention includes a first input port, a second input port, and an output port, and a wavelength tunable filter capable of moving a wavelength spectrum peak of transmitted light intensity; A first optical amplifier having one end optically connected to the first input port; a second optical amplifier having one end optically connected to the second input port and having a gain wavelength spectrum different from that of the first optical amplifier; And an optical mirror provided on the end face of the output port and having a predetermined reflectance and transmittance.

  A wavelength tunable laser light source driving method according to the second aspect of the present invention is the above-described wavelength tunable laser light source driving method, wherein the first optical amplifier and the second light are selected according to a desired wavelength. It is characterized in that current is injected into one of the amplifiers and at the same time no current is injected into the other.

  According to the present invention, it is possible to provide a wavelength tunable laser light source capable of expanding the wavelength tunable range with a relatively simple configuration and a driving method thereof.

2 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to Embodiment 1. FIG. FIG. 3 is a schematic diagram illustrating a state of a resonance path of a light wave when one optical amplifier is driven in the wavelength tunable laser light source according to the first embodiment. 6 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to Embodiment 2. FIG. FIG. 5 is a schematic diagram showing a state of a resonance path of a light wave when one optical amplifier is driven in the wavelength tunable laser light source according to the second embodiment. 6 is a schematic diagram illustrating a schematic configuration of a wavelength tunable laser light source according to Embodiment 3. FIG. FIG. 10 is a schematic diagram illustrating a state of a resonance path of a light wave when one optical amplifier is driven in the wavelength tunable laser light source according to the third embodiment. 6 is a schematic diagram illustrating a schematic configuration of a wavelength tunable laser light source according to Embodiment 4. FIG. 6 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to Embodiment 5. FIG. 10 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to Embodiment 6. FIG.

  The wavelength tunable laser light source of the present invention includes a wavelength tunable external resonator that can move the wavelength spectrum peak of transmitted light intensity, and a gain medium that can vary the gain spectrum. The wavelength is varied by changing both the loss spectrum of the external resonator and the gain spectrum of the gain medium.

  That is, both the variable wavelength external resonator having a periodic transmission spectrum and the variable gain function configured to selectively change the wavelength distribution of the gain are used for controlling the oscillation wavelength. As a result, the wavelength variable range can be increased as compared with the control using only the variable external resonator as proposed so far.

  Specifically, the wavelength tunable laser light source of the present invention includes an external resonator having at least two or more input ports and one or more output ports, and at least two or more connected to the input ports of the external resonator. Gain medium. At this time, it is preferable to use two types of gain media having different gain wavelength spectra. Thereby, the wavelength band of laser oscillation can be divided into a short wave side and a long wave side. Therefore, as compared with the conventional case where only one type of gain medium is used, a large gain intensity can be obtained over a wide band, and high-power laser oscillation can be realized.

  The external resonator has a small variable amount, but can perform wavelength control with high accuracy. On the other hand, the gain variable function cannot perform fine and high-precision control, but can change the gain by a large variable amount. For this reason, the external resonator can be used for fine adjustment of the wavelength, and the variable gain function can be used for coarse adjustment of the wavelength. As described above, by using the external resonator and the gain variable function in combination, the wavelength variable range is large and the wavelength variable operation with high accuracy is possible.

  Here, the wavelength tunable laser light source of the present invention can have a simple configuration in which two types of gain media are connected in parallel to an external resonator as described above. For these two types of gain media, a system is used in which one of them is driven while the other is not driven, but functions as an absorption passive region. Therefore, it is not necessary to control a particularly complicated gain medium, and the wavelength control of laser oscillation can be easily performed.

  The wavelength tunable laser light source of the present invention can use a ring type optical waveguide as the wavelength tunable resonator and two semiconductor amplifiers having different gain spectra as the gain variable medium. By forming the ring-type waveguide and the two semiconductor amplifiers on the same compound semiconductor substrate, it is possible to realize a monolithically integrated wavelength tunable laser function on one chip. Therefore, complicated module assembly at the time of hybrid formation is not required, and cost reduction can be achieved.

  Thus, the wavelength tunable laser light source of the present invention can change the oscillation wavelength of the laser beam to be output by electrical drive control. Usually, the laser light source is composed of a gain medium and a resonator. In particular, in a tunable laser light source, the oscillation wavelength is mostly changed by tuning the resonance wavelength of the resonator by external control. A resonator generally has transmission or reflection characteristics having a certain wavelength period. Therefore, the tuning range is limited to the wavelength period interval near the peak of the gain wavelength distribution of the gain medium. Even if the wavelength period interval of the resonator is expanded by some method, the optical output is determined according to the gain distribution, so that the optical output is reduced as the tuning range is expanded.

  On the other hand, the wavelength tunable laser light source of the present invention employs a system that includes two gain media having different gain wavelength distributions and selectively drives each gain medium according to the oscillation wavelength band to be output. This makes it possible to expand the wavelength variable range without sacrificing the light output.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. For the sake of clarification, duplicate explanation is omitted as necessary. In addition, what attached | subjected the same code | symbol in each figure has shown the same element, and description is abbreviate | omitted suitably.

Embodiment 1 FIG.
The configuration of the wavelength tunable laser light source according to the first embodiment of the present invention will be described in detail with reference to FIG. FIG. 1 is a schematic diagram illustrating a schematic configuration of a wavelength tunable laser light source according to the first embodiment. The wavelength tunable laser light source according to the present embodiment includes a wavelength tunable resonator using a planar optical circuit in which a silicon layer is a core layer and an upper silicon oxide film is a cladding layer on an SOI (Silicon on Insulator) substrate 10; It has a configuration in which a semiconductor optical amplifier is hybrid-mounted. Details are described below.

  In FIG. 1, the wavelength tunable laser light source includes a wavelength tunable resonator 1, and a first semiconductor optical amplifier 11 and a second semiconductor optical amplifier 12 that are connected in parallel to the wavelength tunable resonator 1, respectively. Yes. The wavelength tunable resonator 1 is capable of moving the wavelength spectrum peak of transmitted light intensity, and is also referred to as a wavelength tunable external resonator or a wavelength tunable filter. The wavelength tunable resonator 1 has two input ports and one output port. In the present embodiment, the tunable resonator 1 includes a ring resonator 2 in which a plurality of ring optical waveguides are optically coupled, and optically via the ring resonator 2 and the optical waveguide. And a 3 dB multiplexer / demultiplexer 16 connected thereto.

  Specifically, the first ring-type optical waveguide 21 and the second ring-type optical waveguide 22 are arranged close to the SOI substrate 10 so as to be optically coupled with a predetermined strength. The first ring optical waveguide 21 and the second ring optical waveguide 22 are disposed adjacent to each other along the waveguide direction. The second ring-type optical waveguide 22 has a slightly different peripheral length from the first ring-type optical waveguide 21 and has a different optical path length. A heater 23 for changing the refractive index of the waveguide is formed in a part of the first ring type optical waveguide 21. Similarly, a heater 24 for changing the refractive index of the waveguide is formed in a part of the second ring type optical waveguide 22. The heaters 23 and 24 are positioned in a range where the temperature of the core layer of the waveguide can be changed, such as above, below, or beside the ring optical waveguide. Here, heaters 23 and 24 are disposed above the first ring optical waveguide 21 and the second ring optical waveguide 22, respectively. In addition, although the case where the heater is provided in the vicinity of the ring type optical waveguide has been described, an electrode structure other than the heater may be used as long as the electrode structure is used for tuning the wavelength characteristics by changing the refractive index of the waveguide.

  Thus, the ring resonator 2 is configured by the first ring optical waveguide 21 and the second ring optical waveguide 22. The ring resonator 2 is a double ring resonator in which two ring optical waveguides are arranged in close proximity to each other in cascade.

  The second ring-type optical waveguide 22 is disposed close to the optical waveguide 20 so as to be optically coupled. Both ends of the optical waveguide 20 are connected to the input optical waveguide 15 of the 3 dB multiplexer / demultiplexer 16. The output end of the output optical waveguide 17 of the 3 dB multiplexer / demultiplexer 16 is provided with a dielectric multilayer film 18 so as to have a predetermined reflectance. The dielectric multilayer film 18 becomes an optical mirror (semi-mirror) having a predetermined reflectance and transmittance suitable for causing laser oscillation in the wavelength tunable resonator 1 and allowing the laser to be output to the outside. . Here, the dielectric multilayer film 18 is applied so as to have a reflectance of 20%, for example.

  Thus, the wavelength tunable resonator 1 is provided with the 3 dB multiplexer / demultiplexer 16 having two input port ends and one output port end. Hereinafter, the 3 dB multiplexer / demultiplexer 16 having two input port ends and one output port end is referred to as a 2 × 1 3 dB multiplexer / demultiplexer 16. The 2 × 1 3 dB multiplexer / demultiplexer 16 is formed so as to be optically connected to the second ring optical waveguide 22 of the ring resonator 2 via the optical waveguide 20. The output optical waveguide 17 of the 3 dB multiplexer / demultiplexer 16 becomes the output port of the wavelength tunable resonator 1. A dielectric multilayer film 18 which is an optical mirror having a predetermined reflectance and transmittance is provided on the end face of the output port. The portion of the optical waveguide 20 that is coupled to the second ring optical waveguide 22 is formed in a straight line.

  On the other hand, the optical waveguide 19 is disposed close to the first ring optical waveguide 21 of the ring resonator 2 so as to be optically coupled. At both ends of the optical waveguide 19, two semiconductor amplifiers (first semiconductor optical amplifier 11 and second semiconductor optical amplifier 12) having different gain spectra are disposed so as to be optically coupled to each other. That is, the optical waveguide 19 is optically connected to the first semiconductor optical amplifier 11 at one end and the second semiconductor optical amplifier 12 at the other end, and optically coupled to the first ring optical waveguide 21. It is formed to do. The optical waveguide 19 serves as two input ports of the wavelength tunable resonator 1. The portion of the optical waveguide 19 that is coupled to the first ring optical waveguide 21 is formed in a straight line.

  The first semiconductor optical amplifier 11 has a gain spectrum on the short wave side, and is provided so as to be optically coupled to one input port of the wavelength tunable resonator 1. The second semiconductor optical amplifier 12 has a gain spectrum on the long wave side and is provided so as to be optically joined to the other input port of the wavelength tunable resonator 1. The first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12 are optically connected to each other via an optical waveguide 19. Further, highly reflective films 13 and 14 are formed on the opposite end faces of the first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12, respectively.

  Next, the operation mechanism of the wavelength tunable laser light source according to the present embodiment will be described in detail with reference to FIG. FIG. 2 is a schematic diagram showing a state of a resonance path of a light wave when one of the optical amplifiers is driven in the wavelength tunable laser light source according to the first embodiment. FIG. 2A is a schematic diagram showing the oscillation operation in the long wave band, and FIG. 2B is a schematic diagram showing the oscillation operation in the short wave band.

  The second semiconductor optical amplifier 12 having a long-waveband gain spectrum is turned on (a state in which a driving current is injected), and the first semiconductor optical amplifier 11 having a short-wave gain spectrum is turned off (a driving current is reduced). FIG. 2 (a) shows the path of the light wave when it is in a state of not being injected.

  Among the wavelength spectrum components of the stimulated emission light output from the second semiconductor optical amplifier 12, the components that resonate with both the first ring-type optical waveguide 21 and the second ring-type optical waveguide 22 are indicated by dotted lines. Propagate such a route. That is, from the second semiconductor optical amplifier 12, the optical waveguide 19, the first ring optical waveguide 21, the second ring optical waveguide 22, the optical waveguide 20, the input optical waveguide 15, and the 3 dB multiplexer / demultiplexer 16 are sequentially provided. It propagates to the output optical waveguide 17 via. Then, a part of the stimulated emission light propagated on the semi-reflective end face made of the dielectric multilayer film 18 is reflected, and returns to the second semiconductor optical amplifier 12 through the reverse path again. That is, laser oscillation occurs in the resonance path 41 indicated by the dotted line of the wavelength tunable resonator 1.

  On the other hand, components of the stimulated emission light output from the second semiconductor optical amplifier 12 that do not resonate with the first ring-type optical waveguide 21 and the second ring-type optical waveguide 22 are non-resonant as indicated by the one-dot chain line. Propagates through the resonance path 42. That is, the light is input from the second semiconductor optical amplifier 12 to the first semiconductor optical amplifier 11 via the optical waveguide 19. At this time, the first semiconductor optical amplifier 11 is in an OFF state, and the input non-resonant component is absorbed and does not return to the second semiconductor optical amplifier 12.

  Therefore, in this operation, laser oscillation occurs due to the gain distribution on the long wave side, and the wavelength variation in the long wave band is a double ring type resonance composed of the first ring type optical waveguide 21 and the second ring type optical waveguide 22. This is possible within the free spectrum range (FSR) of the instrument.

  On the other hand, the first semiconductor optical amplifier 11 having the gain spectrum in the short wave band is turned on (the state in which the drive current is injected), and the second semiconductor optical amplifier 12 having the gain spectrum on the long wave side is turned off. FIG. 2B shows a lightwave path when the drive current is not injected.

  Among the wavelength spectrum components of the stimulated emission light output from the first semiconductor optical amplifier 11, the component that resonates with both the first ring optical waveguide 21 and the second ring optical waveguide 22 is indicated by a dotted line. Propagate such a route. That is, from the first semiconductor optical amplifier 11, the optical waveguide 19, the first ring-type optical waveguide 21, the second ring-type optical waveguide 22, the optical waveguide 20, the input optical waveguide 15, and the 3 dB multiplexer / demultiplexer 16 are sequentially provided. It propagates to the output optical waveguide 17 via. Then, a part of the stimulated emission light propagated on the semi-reflecting end face made of the dielectric multilayer film 18 is reflected, and returns to the first semiconductor optical amplifier 11 along the reverse path again. That is, laser oscillation occurs in the resonance path 43 indicated by the dotted line of the wavelength tunable resonator 1.

  On the other hand, in the stimulated emission light output from the first semiconductor optical amplifier 11, components that do not resonate with the first ring-type optical waveguide 21 and the second ring-type optical waveguide 22 are non-resonant as shown by the one-dot chain line. Propagates through the resonance path 44. That is, the light is input from the first semiconductor optical amplifier 11 to the second semiconductor optical amplifier 12 via the optical waveguide 19. At this time, the second semiconductor optical amplifier 12 is in an OFF state, and the input non-resonant component is absorbed and does not return to the first semiconductor optical amplifier 11.

  Therefore, in this operation, laser oscillation occurs due to the gain distribution on the short wave side, and the wavelength tunability in the short wave band is a double ring type resonance consisting of the first ring type optical waveguide 21 and the second ring type optical waveguide 22. This is possible within the range of the FSR of the instrument.

  As described above, the wavelength tunable laser light source of the present embodiment changes both the gain spectrum of the first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12 and the loss spectrum of the wavelength tunable resonator 1. Thus, the wavelength is varied. That is, in addition to the wavelength tunability by the wavelength tunable resonator 1, the wavelength tunability by two semiconductor optical amplifiers is newly used for wavelength control of laser oscillation. Thereby, the selection range of the wavelength of the light to output can be made wider. At this time, in the present embodiment, the first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12 are selectively driven according to the oscillation wavelength band to be output. This makes it possible to expand the wavelength variable range without sacrificing the light output. The first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12 may be controlled so as to drive one according to a desired wavelength and not drive the other while driving one. No complicated control is required.

  As described above, in the present embodiment, the first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12 having different gain wavelength spectra are connected to the wavelength tunable resonator 1 in parallel. The gain variable function obtained by selectively driving the first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12 is combined with the wavelength variable resonator 1 to control the wavelength of laser oscillation. . Thereby, it is possible to widen the selection range of the wavelength of the light to be output in spite of a simple configuration. In addition, a large gain intensity can be obtained over a wide band, and high-power laser oscillation can be realized. This is because both the wavelength tunable resonator 1 that can change the peak position of the loss spectrum within a predetermined range and the gain variable function that can greatly change the gain spectrum shape, particularly the peak position of the gain spectrum, can be used. This is because the wavelength tunable range is large and high output wavelength tunability can be realized by using the control. Furthermore, while the wavelength tunable resonator 1 is used for fine adjustment of the wavelength, the two semiconductor optical amplifiers can be used for coarse adjustment of the wavelength as a gain variable medium having a large variable amount. Therefore, highly accurate wavelength variable operation is possible.

  In this embodiment, the case where the 2 × 1 3 dB multiplexer / demultiplexer 16 is used has been described as an example. However, the 2 × 2 3 dB multiplexer having two input port ends and two output port ends is used. A duplexer can also be used. In the case of using a 2 × 2 3 dB multiplexer / demultiplexer, one of the two output port ends is subjected to antireflection processing, and the other output port end is provided with a high reflection mirror. Alternatively, instead of the high reflection mirror, a 1 × 2 3 dB multiplexer / demultiplexer having one input port end and two output port ends connected to each other may be provided. That is, non-reflection processing is applied to one output port end of the 2 × 2 3 dB multiplexer / demultiplexer, and two output port ends of the 1 × 2 3 dB multiplexer / demultiplexer are mutually connected to the other output port end. You may provide the loop mirror which consists of the connected closed loop-shaped waveguide. The loop mirror composed of the closed loop waveguide formed by the 1 × 2 3 dB multiplexer / demultiplexer functions as if it is a high reflection mirror.

Embodiment 2. FIG.
The configuration of the wavelength tunable laser light source according to the second embodiment of the present invention will be described with reference to FIG. FIG. 3 is a schematic diagram showing a schematic configuration of the wavelength tunable laser light source according to the second embodiment.

  In the present embodiment, the tunable resonator 1 having a configuration different from that of the first embodiment is provided in the tunable laser light source. Specifically, the wavelength tunable resonator 1 according to the present embodiment includes a ring resonator 2 in which a plurality of ring optical waveguides are optically coupled, and optical via the ring resonator 2 and the optical waveguide. And an optical switch 52 connected thereto. That is, instead of the 3 dB multiplexer / demultiplexer 16 of the first embodiment, an optical switch 52 is formed in this embodiment. Since other configurations are the same as those in the first embodiment, description thereof is omitted. In the present embodiment, similarly to the first embodiment, the wavelength tunable resonator 1 having two input ports and one output port includes a first semiconductor optical amplifier 11 and a second semiconductor optical amplifier 11 having different gain wavelength spectra. The semiconductor optical amplifiers 12 are connected in parallel.

  In FIG. 3, 2 × 2 having two input port ends and two output port ends so as to be optically connected via the second ring-type optical waveguide 22 and the optical waveguide 20 of the ring-type resonator 2. The optical switch 52 is provided. Specifically, both ends of the optical waveguide 20 disposed so as to be optically coupled to the second ring optical waveguide 22 of the ring resonator 2 are two input optical waveguides of the optical switch 52. 15 are connected to each other. Of the two output optical waveguides of the optical switch 52, the output end of at least one of the output optical waveguides 17 is provided with a dielectric multilayer film 18 so as to have a predetermined reflectance. Here, the dielectric multilayer film 18 is applied so as to have a reflectance of 20%, for example. The output optical waveguide 17 provided with the dielectric multilayer film 18 serves as an output port of the wavelength tunable resonator 1.

  A heater 51 for changing the refractive index of the waveguide is formed above the optical waveguide constituting the optical switch 52.

  Next, the operation mechanism of the wavelength tunable laser light source according to the present embodiment will be described in detail with reference to FIG. FIG. 4 is a schematic diagram showing a state of a resonance path of a light wave when one of the optical amplifiers is driven in the wavelength tunable laser light source according to the second embodiment. FIG. 4A is a schematic diagram showing the oscillation operation in the long wave band, and FIG. 4B is a schematic diagram showing the oscillation operation in the short wave band.

  The second semiconductor optical amplifier 12 having a long-waveband gain spectrum is turned on (a state in which a driving current is injected), and the first semiconductor optical amplifier 11 having a short-wave gain spectrum is turned off (a driving current is reduced). FIG. 4 (a) shows the path of the light wave when it is in a state of not being injected.

  Among the wavelength spectrum components of the stimulated emission light output from the second semiconductor optical amplifier 12, the components that resonate with both the first ring-type optical waveguide 21 and the second ring-type optical waveguide 22 are indicated by dotted lines. Propagate such a route. That is, the optical switch 52 is sequentially passed from the second semiconductor optical amplifier 12 through the optical waveguide 19, the first ring optical waveguide 21, the second ring optical waveguide 22, the optical waveguide 20, and the input optical waveguide 15. Propagate to. In the optical switch 52, the path is adjusted by the heater 51 so that the light is output to the output optical waveguide 17 on the side where the dielectric multilayer film 18 is provided. That is, the path of the optical switch 52 is adjusted in accordance with the semiconductor optical amplifier on the side where the drive current is injected so that the output optical waveguide 17 on the side where the dielectric multilayer film 18 is provided can obtain a desired optical output. Is switched. Thereafter, a part of the stimulated emission light propagated on the semi-reflecting end face made of the dielectric multilayer film 18 is reflected, and returns to the second semiconductor optical amplifier 12 through the reverse path again. That is, laser oscillation occurs in the resonance path 61 indicated by the dotted line of the wavelength tunable resonator 1.

  On the other hand, components of the stimulated emission light output from the second semiconductor optical amplifier 12 that do not resonate with the first ring-type optical waveguide 21 and the second ring-type optical waveguide 22 are non-resonant as indicated by the one-dot chain line. Propagates through the resonance path 62. That is, the light is input from the second semiconductor optical amplifier 12 to the first semiconductor optical amplifier 11 via the optical waveguide 19. At this time, the first semiconductor optical amplifier 11 is in an OFF state, and the input non-resonant component is absorbed and does not return to the second semiconductor optical amplifier 12.

  Therefore, in this operation, laser oscillation occurs due to the gain distribution on the long wave side, and the wavelength variation in the long wave band is a double ring type resonance composed of the first ring type optical waveguide 21 and the second ring type optical waveguide 22. This is possible within the range of the FSR of the instrument.

  On the other hand, the first semiconductor optical amplifier 11 having the gain spectrum in the short wave band is turned on (the state in which the drive current is injected), and the second semiconductor optical amplifier 12 having the gain spectrum on the long wave side is turned off. FIG. 4B shows a light wave path when the drive current is not injected.

  Among the wavelength spectrum components of the stimulated emission light output from the first semiconductor optical amplifier 11, the component that resonates with both the first ring optical waveguide 21 and the second ring optical waveguide 22 is indicated by a dotted line. Propagate such a route. That is, the optical switch 52 is sequentially passed from the second semiconductor optical amplifier 12 through the optical waveguide 19, the first ring optical waveguide 21, the second ring optical waveguide 22, the optical waveguide 20, and the input optical waveguide 15. Propagate to. In the optical switch 52, the path is adjusted by the heater 51 so that the light is output to the output optical waveguide 17 on the side where the dielectric multilayer film 18 is provided. That is, the path of the optical switch 52 is adjusted in accordance with the semiconductor optical amplifier on the side where the drive current is injected so that the output optical waveguide 17 on the side where the dielectric multilayer film 18 is provided can obtain a desired optical output. Is switched. Thereafter, a part of the stimulated emission light propagated on the semi-reflecting end face made of the dielectric multilayer film 18 is reflected, and returns to the first semiconductor optical amplifier 11 along the reverse path again. That is, laser oscillation occurs in the resonance path 63 indicated by the dotted line of the wavelength tunable resonator 1.

  On the other hand, in the stimulated emission light output from the first semiconductor optical amplifier 11, components that do not resonate with the first ring-type optical waveguide 21 and the second ring-type optical waveguide 22 are non-resonant as shown by the one-dot chain line. It propagates through the resonance path 64. That is, the light is input from the first semiconductor optical amplifier 11 to the second semiconductor optical amplifier 12 via the optical waveguide 19. At this time, the second semiconductor optical amplifier 12 is in an OFF state, and the input non-resonant component is absorbed and does not return to the first semiconductor optical amplifier 11.

  Therefore, in this operation, laser oscillation occurs due to the gain distribution on the short wave side, and the wavelength tunability in the short wave band is a double ring type resonance consisting of the first ring type optical waveguide 21 and the second ring type optical waveguide 22. This is possible within the range of the FSR of the instrument.

  As described above, in the present embodiment, the variable wavelength resonator 1 having a configuration in which the ring type resonator 2 is combined with the optical switch 52 is used. By using the optical switch 52 instead of the 3 dB multiplexer / demultiplexer 16, it is possible to avoid the 3 dB excess loss that occurs in principle in the 3 dB multiplexer / demultiplexer 16. Therefore, the internal excess loss of the wavelength tunable resonator 1 can be reduced in the wavelength tunable laser light source. Further, the same effects as those of the first embodiment can be obtained.

Embodiment 3 FIG.
A configuration of a wavelength tunable laser light source according to the third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to the third embodiment.

  In the present embodiment, the tunable resonator 1 having a configuration different from that of the first embodiment is provided in the tunable laser light source. Specifically, the wavelength tunable resonator 1 of the present embodiment includes a ring resonator 3 in which a plurality of ring optical waveguides are optically coupled, and optical via the ring resonator 3 and the optical waveguide. And a 3 dB multiplexer / demultiplexer 16 connected to each other. Unlike the ring resonator 2 of the first embodiment having two ring optical waveguides, the ring resonator 3 of the present embodiment has three ring optical waveguides (first ring optical waveguide 31, first ring optical waveguide 31). 2 ring type optical waveguides 32 and a third ring type optical waveguide 33). That is, instead of the ring type resonator 2 of the first embodiment, in this embodiment, the ring type resonator 3 is formed, and other configurations are the same as those of the first embodiment. Is omitted. In the present embodiment, similarly to the first embodiment, the wavelength tunable resonator 1 having two input ports and one output port includes a first semiconductor optical amplifier 11 and a second semiconductor optical amplifier 11 having different gain wavelength spectra. The semiconductor optical amplifiers 12 are connected in parallel.

  Specifically, as shown in FIG. 5, the SOI substrate 10 includes a second ring-type optical waveguide 32 and a third ring-type optical waveguide 33 that are optically coupled to the first ring-type optical waveguide 31. They are arranged close to each other so as to be optically coupled through the waveguide 37. The optical waveguide 37 is formed in a straight line. The optical waveguide 37 includes a second ring optical waveguide 32 and a third ring optical waveguide 33 at positions symmetrical to each other with respect to the optical proximity coupling position with the first ring optical waveguide 31. Optical proximity bonding. The second ring-type optical waveguide 32 and the third ring-type optical waveguide 33 are slightly different in peripheral length from the first ring-type optical waveguide 31 and have different optical path lengths.

  A heater 34 for changing the refractive index of the waveguide is formed in a part of the first ring-type optical waveguide 31. Similarly, the heater 35 for changing the refractive index of the waveguide is changed to a part of the second ring type optical waveguide 32, and the refractive index of the waveguide is changed to a part of the third ring type optical waveguide 33. The heater 36 for making it form is each formed. The heaters 34, 35, and 36 are located in a range in which the temperature of the core layer of the waveguide can be changed, such as above, below, or beside the ring optical waveguide. Here, heaters 34, 35, and 36 are disposed above the ring-type optical waveguides, respectively. In addition, although the case where the heater is provided in the vicinity of the ring type optical waveguide has been described, an electrode structure other than the heater may be used as long as the electrode structure is used for tuning the wavelength characteristics by changing the refractive index of the waveguide.

  Thus, in the present embodiment, the ring resonator 3 in which three ring optical waveguides are optically connected to each other via the linear optical waveguide 37 is used. An optical waveguide 38 is disposed close to the second ring optical waveguide 32 of the ring resonator 3 so as to be optically coupled. Further, the optical waveguide 39 is disposed close to the third ring optical waveguide 33 of the ring resonator 3 so as to be optically coupled. The optical waveguides 38 and 39 are both connected to the 2 × 1 3 dB multiplexer / demultiplexer 16 and serve as input optical waveguides for the 3 dB multiplexer / demultiplexer 16. Similar to the first embodiment, a dielectric multilayer film 18 is applied to the output end of the output optical waveguide 17 of the 3 dB multiplexer / demultiplexer 16 so as to have a predetermined reflectance. Here, the dielectric multilayer film 18 is applied so as to have a reflectance of 20%, for example. The portion of the optical waveguide 38 that is coupled to the second ring type optical waveguide 32 and the portion of the optical waveguide 39 that is coupled to the third ring type optical waveguide 33 are linearly formed.

  On the other hand, the optical waveguide 19 is disposed close to the first ring optical waveguide 31 of the ring resonator 3 so as to be optically coupled. As in the first embodiment, two semiconductor amplifiers (first semiconductor optical amplifier 11 and second semiconductor optical amplifier 12) having different gain spectra are optically coupled to both ends of the optical waveguide 19, respectively. Is arranged. The portion of the optical waveguide 19 that is coupled to the first ring optical waveguide 31 is formed in a straight line.

  Next, the operation mechanism of the wavelength tunable laser light source according to the present embodiment will be described in detail with reference to FIG. FIG. 6 is a schematic diagram showing a state of a resonance path of a light wave when one optical amplifier is driven in the wavelength tunable laser light source according to the third embodiment. FIG. 6A is a schematic diagram showing the oscillation operation in the long wave band, and FIG. 6B is a schematic diagram showing the oscillation operation in the short wave band.

  The second semiconductor optical amplifier 12 having a long-waveband gain spectrum is turned on (a state in which a driving current is injected), and the first semiconductor optical amplifier 11 having a short-wave gain spectrum is turned off (a driving current is reduced). FIG. 6 (a) shows the path of the light wave when it is not injected.

  Of the wavelength spectrum components of the stimulated emission light output from the second semiconductor optical amplifier, the components that resonate with both the first ring-type optical waveguide 31 and the third ring-type optical waveguide 33 are indicated by dotted lines. Propagation through various routes. That is, the second semiconductor optical amplifier 12 is sequentially passed through the optical waveguide 19, the first ring optical waveguide 31, the optical waveguide 37, the third ring optical waveguide 33, the optical waveguide 39, and the 3 dB multiplexer / demultiplexer 16. Then, it propagates to the output optical waveguide 17. Then, a part of the stimulated emission light propagated on the semi-reflective end face made of the dielectric multilayer film 18 is reflected, and returns to the second semiconductor optical amplifier 12 through the reverse path again. That is, laser oscillation occurs in the resonance path 81 indicated by the dotted line of the wavelength tunable resonator 1.

  On the other hand, components of the stimulated emission light output from the second semiconductor optical amplifier that do not resonate with the first ring-type optical waveguide 31 and the third ring-type optical waveguide 33 are non-resonant as indicated by the alternate long and short dash line. Propagate path 82. That is, the light is input from the second semiconductor optical amplifier 12 to the first semiconductor optical amplifier 11 via the optical waveguide 19. At this time, the first semiconductor optical amplifier 11 is in an OFF state, and the input non-resonant component is absorbed and does not return to the second semiconductor optical amplifier 12.

  Therefore, in this operation, laser oscillation occurs due to the gain distribution on the long wave side, and the wavelength variation of the long wave band is a double ring resonator composed of the first ring optical waveguide 31 and the third ring optical waveguide 33. This is possible within the range of FSR.

  On the other hand, the first semiconductor optical amplifier 11 having a short-waveband gain spectrum is turned on (a state in which a drive current is injected), and the second semiconductor optical amplifier 12 having a long-wave gain spectrum is turned off ( FIG. 6B shows the path of the light wave when the drive current is not injected.

  Among the wavelength spectrum components of the stimulated emission light output from the first semiconductor optical amplifier 11, the component that resonates with both the first ring type optical waveguide 31 and the second ring type optical waveguide 32 is indicated by a dotted line. Propagate such a route. That is, the first semiconductor optical amplifier 11 is sequentially passed through the optical waveguide 19, the first ring optical waveguide 31, the optical waveguide 37, the second ring optical waveguide 32, the optical waveguide 38, and the 3 dB multiplexer / demultiplexer 16. Then, it propagates to the output optical waveguide 17. Then, a part of the stimulated emission light propagated on the semi-reflecting end face made of the dielectric multilayer film 18 is reflected, and returns to the first semiconductor optical amplifier 11 along the reverse path again. That is, laser oscillation occurs in the resonance path 83 indicated by the dotted line of the wavelength tunable resonator 1.

  On the other hand, components of the stimulated emission light output from the first semiconductor optical amplifier 11 that do not resonate with the first ring-type optical waveguide 31 and the second ring-type optical waveguide 32 are non-resonant as indicated by a one-dot chain line. Propagates through the resonance path 84. That is, the light is input from the first semiconductor optical amplifier 11 to the second semiconductor optical amplifier 12 via the optical waveguide 19. At this time, the second semiconductor optical amplifier 12 is in an OFF state, and the input non-resonant component is absorbed and does not return to the first semiconductor optical amplifier 11.

  Therefore, in this operation, laser oscillation occurs due to the gain distribution on the short wave side, and the wavelength variation of the short wave band is a double ring resonator composed of the first ring type optical waveguide 31 and the second ring type optical waveguide 32. This is possible within the range of FSR.

  As described above, in the present embodiment, the ring resonator 3 in which the ring optical waveguides are optically coupled via the linear optical waveguide 37 is used. Thereby, the optical coupling between the ring type optical waveguides can be eliminated. That is, the optical coupling in the wavelength tunable resonator 1 is unified to the optical coupling between the ring type optical waveguide and the linear optical waveguide. Here, when the wavelength tunable resonator 1 includes the optical coupling between the ring type optical waveguides and the optical coupling between the ring type optical waveguide and the linear optical waveguide, each coupling strength has a certain level. It is necessary to set the relationship, and stricter manufacturing control is required from the viewpoint of manufacturing accuracy. In the present embodiment, the wavelength tunable resonator 1 is unified to optical coupling between the ring optical waveguide and the linear optical waveguide, so that the optical coupling between each linear optical waveguide and the ring optical waveguide is integrated. The strength can be set the same in each part. Therefore, the manufacturing control can be made easier. Further, the same effects as those of the first embodiment can be obtained.

  Note that Embodiment 3 can be used in combination with Embodiments 1 and 2 as appropriate. That is, in the present embodiment, the case where the 2 × 1 3 dB multiplexer / demultiplexer 16 is used in combination with the ring resonator 3 having three ring optical waveguides has been described as an example, but the present invention is not limited thereto. It is not something. The optical switch 52 shown in the second embodiment may be used in combination with the ring resonator 3 having three ring optical waveguides. A 2 × 2 3 dB multiplexer / demultiplexer may be used in combination.

Embodiment 4 FIG.
A configuration of a wavelength tunable laser light source according to the fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to the fourth embodiment. In the present embodiment, an example of a wavelength tunable laser light source that enables miniaturization of the wavelength tunable resonator 1 having two ring optical waveguides and a 3 dB multiplexer / demultiplexer as main components will be described.

  In the present embodiment, the tunable resonator 1 having a configuration different from that of the first embodiment is provided in the tunable laser light source. Since other configurations are the same as those in the first embodiment, description thereof is omitted. That is, in the present embodiment, similarly to the first embodiment, the wavelength tunable resonator 1 having at least two input ports and one output port includes the first semiconductor optical amplifier 11 having different gain wavelength spectra. The second semiconductor optical amplifier 12 is connected in parallel.

  In FIG. 7, the wavelength tunable resonator 1 according to the present embodiment includes a ring resonator 120 in which two ring optical waveguides having different peripheral lengths are optically connected to each other via an optical waveguide, and the ring resonator 120. And a 3 dB multiplexer / demultiplexer 117 optically connected to each other.

  Specifically, in the SOI substrate 10, the optical waveguide 125 is disposed adjacent to each other so as to be optically coupled to each of the first ring optical waveguide 121 and the second ring optical waveguide 122. That is, one optical waveguide 125 is disposed close to each of the first ring optical waveguide 121 and the second ring optical waveguide 122, whereby the first ring optical waveguide 121 and the second ring optical waveguide 125 are disposed. The optical waveguide 122 is optically connected to each other. The second ring-type optical waveguide 122 has a slightly different peripheral length from the first ring-type optical waveguide 121, and is different in optical path length.

  As in the first embodiment, heaters 123 and 124 for changing the refractive index of the waveguide are formed in the vicinity of the first ring optical waveguide 121 and the second ring optical waveguide 122, respectively. In addition, as long as the electrode structure is used for tuning the wavelength characteristics by changing the refractive index of the waveguide, a material other than the heater may be used. As described above, the ring resonator 120 is configured by the first ring optical waveguide 121 and the second ring optical waveguide 122 that are optically coupled via the optical waveguide 125.

  In the ring resonator 120, a 2 × 2 3 dB multiplexer / demultiplexer 117 having two input port ends and two output port ends is disposed in close proximity so as to be optically coupled. That is, the first ring optical waveguide 121 and the second ring optical waveguide 122 are arranged close to each other so as to be optically coupled to the two output optical waveguides 118 and 119 of the 3 dB multiplexer / demultiplexer 117, respectively. Has been. On the other hand, the input optical waveguides 115 and 116 of the 3 dB multiplexer / demultiplexer 117 have one ends of two semiconductor optical amplifiers (first semiconductor optical amplifier 11 and second semiconductor optical amplifier 12) having different gain spectra, respectively. Are optically connected. Accordingly, the two input optical waveguides 115 and 116 of the 3 dB multiplexer / demultiplexer 117 serve as input ports of the wavelength tunable resonator 1. As in the first embodiment, high reflection films (high reflection dielectric films) 13 and 14 are provided on the opposite end surfaces of the first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12, respectively. It has become.

  Further, an optical waveguide for extracting light wave power is disposed in close proximity to a part of the optical waveguide 125 that optically connects the two ring-type optical waveguides. Here, the optical multiplexer / demultiplexer 131 is disposed close to the optical waveguide 125 so as to be optically coupled. An optical antireflection film (not shown) is applied to end faces of the output optical waveguides 132 and 133 of the optical multiplexer / demultiplexer 131 (output optical waveguide ends 134 and 135, respectively).

  Next, an operation mechanism of the wavelength tunable laser light source according to the present embodiment will be described. When either the first semiconductor optical amplifier 11 having the short-wave gain spectrum or the second semiconductor optical amplifier 12 having the long-wave gain spectrum is driven, the signal is output from the driven semiconductor optical amplifier. The stimulated emission light is branched into two by a 3 dB multiplexer / demultiplexer 117. In each of the light waves branched by the 3 dB multiplexer / demultiplexer 117, only the wavelength component resonating with the first ring optical waveguide 121 and the second ring optical waveguide 122 is again 3 dB multiplexed / divided via the optical waveguide 125. Return to Waver 117. Then, the feedback is made to the driven semiconductor optical amplifier.

  Since a highly reflective film is added to one end of the semiconductor optical amplifier, a light wave having a specific wavelength reciprocates between the wavelength tunable resonator 1 including the ring resonator 120 and the semiconductor optical amplifier. As a result, laser oscillation occurs. The laser oscillation light is partially coupled to the optical multiplexer / demultiplexer 131 and output from the optical waveguide end face 135 to the outside. The oscillation wavelength can be tuned by the heaters 123 and 124 that are added to the first ring-type optical waveguide 121 and the second ring-type optical waveguide 122 and change the effective refractive index of the waveguide.

  By adopting the above configuration, in this embodiment, the wavelength tunable resonator 1 having two ring optical waveguides and a 3 dB multiplexer / demultiplexer 117 as main components can be reduced in size. Further, the same effects as those of the first embodiment can be obtained.

Embodiment 5 FIG.
The configuration of the wavelength tunable laser light source according to the fifth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to the fifth embodiment. In the present embodiment, an example of a wavelength tunable laser light source having a configuration in which a 2 × 2 directional coupler type switch is added to the fourth embodiment as means for improving the output light intensity will be described.

  In the present embodiment, the tunable resonator 1 having a configuration different from that of the fourth embodiment is provided in the tunable laser light source. Since other configurations are the same as those in the fourth embodiment, description thereof is omitted. That is, in the present embodiment, as in the fourth embodiment, the wavelength tunable resonator 1 having at least two input ports and one output port includes the first semiconductor optical amplifier 11 having different gain wavelength spectra. The second semiconductor optical amplifier 12 is connected in parallel.

  In FIG. 8, the wavelength tunable resonator 1 of the present embodiment includes a ring resonator 120 in which two ring optical waveguides having different peripheral lengths are optically connected to each other via an optical waveguide, and the ring resonator 120. And a 2 × 2 3 dB multiplexer / demultiplexer 117 optically connected to each other, and a 2 × 2 optical switch 150 having two input port ends and two output port ends.

  Specifically, the optical waveguide 125 is formed on the SOI substrate 10 so as to be optically coupled to each of the first ring optical waveguide 121 and the second ring optical waveguide 122, as in the fourth embodiment. The ring resonator 120 is configured by being arranged close to each other. Also, the first ring optical waveguide 121 and the second ring optical waveguide 122 are arranged close to each other so as to be optically coupled to the two output optical waveguides 118 and 119 of the 3 dB multiplexer / demultiplexer 117, respectively. Has been. The input optical waveguides 115 and 116 of the 3 dB multiplexer / demultiplexer 117 have one ends of two semiconductor optical amplifiers (first semiconductor optical amplifier 11 and second semiconductor optical amplifier 12) having different gain spectra, respectively. Are optically connected.

  In the present embodiment, the other ends of the two semiconductor optical amplifiers (first semiconductor optical amplifier 11 and second semiconductor optical amplifier 12) are connected to the two input optical waveguides 151 and 152 of the optical switch 150, respectively. Has been. The optical switch 150 is a Mach-Zehnder optical switch including two 3 dB multiplexers / demultiplexers 153 and 157, two optical waveguides 154 and 155, and a phase shifter 156. As an example of the phase shifter 156, a heater may be used as in the second embodiment. Of the two output optical waveguides 158 and 159 of the optical switch 150, the output end of at least one of the output optical waveguides is provided with a dielectric multilayer film (dielectric film) (not shown) so as to have a predetermined reflectance. . Here, a dielectric film having an optical reflectivity of about 5% to 10% is applied to the output optical waveguide end 160 of the output optical waveguide 158, for example. The output optical waveguide end 160 provided with the dielectric film becomes an output port of the wavelength tunable resonator 1.

  Next, an operation mechanism of the wavelength tunable laser light source according to the present embodiment will be described. When either the first semiconductor optical amplifier 11 having the short-wave gain spectrum or the second semiconductor optical amplifier 12 having the long-wave gain spectrum is driven, the signal is output from the driven semiconductor optical amplifier. The stimulated emission light propagates through the ring resonator 120 and returns again to the semiconductor optical amplifier on the side where only a specific wavelength light component is driven.

  Further, the phase of the stimulated emission light guided from the driven semiconductor optical amplifier to the 3 dB multiplexer / demultiplexer 153 of the optical switch 150 is guided by the phase shifter 156 so as to be guided to the output optical waveguide end 160. Then, a part of the light wave component reflected at the output optical waveguide end 160 returns again to the driven semiconductor optical amplifier. Thus, an optical resonator is formed between the ring resonator 120 and the output optical waveguide end 160 across the driven semiconductor optical amplifier, and laser oscillation occurs, and the output light is output to the output optical waveguide. It is output from the waveguide end 160. The tunable wavelength band of the laser oscillation light is appropriately selected by operating only one of the two semiconductor optical amplifiers (the first semiconductor optical amplifier 11 and the second semiconductor optical amplifier 12) having different gain wavelength bands. It is possible.

  With the above configuration, the output light intensity can be improved in the present embodiment. Further, the same effects as those of the first and fourth embodiments can be obtained.

Embodiment 6 FIG.
The configuration of a wavelength tunable laser light source according to the sixth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a schematic diagram showing a schematic configuration of a wavelength tunable laser light source according to the sixth embodiment. In this embodiment, an example of a wavelength tunable laser light source in which an optical modulator that converts an electric signal into an optical signal is integrated will be described.

  In FIG. 9, the tunable resonator 1 according to the present embodiment includes a ring resonator 120 in which two ring optical waveguides having different peripheral lengths are optically connected to each other via the optical waveguide, and the ring resonator 120. And a 2 × 2 3 dB multiplexer / demultiplexer 117 optically connected to each other.

  Specifically, the optical waveguide 125 is formed on the SOI substrate 10 so as to be optically coupled to each of the first ring optical waveguide 121 and the second ring optical waveguide 122, as in the fourth embodiment. The ring resonator 120 is configured by being arranged close to each other. Also, the first ring optical waveguide 121 and the second ring optical waveguide 122 are arranged close to each other so as to be optically coupled to the two output optical waveguides 118 and 119 of the 3 dB multiplexer / demultiplexer 117, respectively. Has been. In addition, heaters 123 and 124 for changing the effective refractive index of the waveguide are formed above the first ring-type optical waveguide 121 and the second ring-type optical waveguide 122, respectively.

  In this embodiment, one end of each of the semiconductor optical amplifier 111 and the optical modulator 112 is optically connected to the input optical waveguides 115 and 116 of the 3 dB multiplexer / demultiplexer 117. A high reflection film 113 is added to the other end of the semiconductor optical amplifier 111. On the other hand, an antireflection film 114 is added to the other end of the optical modulator 112.

  Next, an operation mechanism of the wavelength tunable laser light source according to the present embodiment will be described. When the semiconductor optical amplifier 111 is driven, the stimulated emission light output from the semiconductor optical amplifier 111 propagates through the input optical waveguide 115 and is branched in two directions by the 3 dB multiplexer / demultiplexer 117. The light waves branched by the 3 dB multiplexer / demultiplexer 117 propagate only through the output optical waveguides 118 and 119, respectively, and only light waves having wavelength components that resonate with the first ring optical waveguide 121 and the second ring optical waveguide 122, respectively. However, it passes through the output optical waveguides 118 and 119 and returns to the 3 dB multiplexer / demultiplexer 117 again. Then, a part of the light waves are input to the optical modulator 112 after propagating through the input optical waveguide 116. Other light wave components propagate through the input optical waveguide 115, return to the semiconductor optical amplifier 111, and are reflected by the high reflection film 113.

  In other words, in this embodiment, a laser wave is oscillated by the reciprocation of the light wave between the high reflection film 113 and the ring resonator 120 via the semiconductor optical amplifier 111, and a part of the oscillation light is optically modulated. It is configured to pass through the device 112 and output to the outside.

  As described above, the wavelength tunable laser light source according to the present embodiment includes the ring resonator 120 in which two ring optical waveguides having different peripheral lengths are optically connected to each other via the optical waveguide, and the ring resonator 120 A wavelength tunable resonator 1 including a 2 × 2 3 dB multiplexer / demultiplexer 117 optically connected, and a semiconductor optical amplifier 111 and an optical modulator 112 connected in parallel to the wavelength tunable resonator 1 are provided. Has been. Thereby, the optical modulator 112 can be integrated in the same form as the semiconductor optical amplifier 111. Therefore, the mounting process can be shared and the cost can be reduced.

  The above description describes the embodiment of the present invention, and the present invention is not limited to the above embodiment. Moreover, those skilled in the art can easily change, add, and convert each element of the above embodiment within the scope of the present invention.

1 wavelength tunable resonator, 2, 3 ring resonator, 10 substrate,
11 first semiconductor optical amplifier, 12 second semiconductor optical amplifier,
13, 14 highly reflective film, 15 input optical waveguide,
16 3 dB multiplexer / demultiplexer, 17 output optical waveguide,
18 Dielectric multilayer film, 19, 20 Optical waveguide,
21 first ring-type optical waveguide, 22 second ring-type optical waveguide,
23, 24 heater, 31 first ring type optical waveguide,
32 second ring-type optical waveguide, 33 third ring-type optical waveguide,
34, 35, 36 heater, 37, 38, 39 optical waveguide,
41 resonant path, 42 non-resonant path,
43 resonant path, 44 non-resonant path,
51 heater, 52 optical switch,
61 resonant path, 62 non-resonant path,
63 resonant path, 64 non-resonant path,
81 resonant path, 82 non-resonant path,
83 resonant path, 84 non-resonant path,
111 semiconductor optical amplifier, 112 optical modulator,
113 light reflection film, 114 antireflection film,
115, 116 input optical waveguide, 117 3 dB multiplexer / demultiplexer,
118, 119 output optical waveguide, 120 ring resonator,
121, 122 ring type optical waveguide, 123, 124 heater,
125 optical waveguide, 131 optical multiplexer / demultiplexer,
132, 133 output optical waveguide, 134, 135 output optical waveguide end,
150 optical switch, 151, 152 input optical waveguide,
153 3 dB multiplexer / demultiplexer, 154, 155 optical waveguide,
156 phase shifter, 157 3 dB multiplexer / demultiplexer,
158, 159 output optical waveguide, 160 output optical waveguide end

Claims (16)

A tunable filter having a first input port, a second input port, and an output port, and capable of moving a wavelength spectrum peak of transmitted light intensity;
A first optical amplifier having one end optically connected to the first input port;
A second optical amplifier having one end optically connected to the second input port and having a gain wavelength spectrum different from that of the first optical amplifier;
A wavelength tunable laser light source comprising: an optical mirror provided on an end face of the output port and having a predetermined reflectance and transmittance.   The first optical amplifier and the second optical amplifier are semiconductor optical amplifiers having different gain peak wavelengths, and are integrated on the same substrate as the wavelength tunable filter configured by a planar optical circuit. Tunable laser light source.   3. The wavelength tunable laser light source according to claim 2, wherein the first optical amplifier, the second optical amplifier, and the wavelength tunable filter are formed of a compound semiconductor material and monolithically integrated on the same substrate. The wavelength tunable filter is
A ring resonator in which two ring optical waveguides having different perimeters are arranged in close proximity to each other;
A 3 dB multiplexer / demultiplexer having two input port ends and one output port end;
Two input port ends of the 3 dB multiplexer / demultiplexer are connected to each other by an optical waveguide disposed so as to be optically coupled to one ring optical waveguide of the ring resonator,
A half mirror having a predetermined reflectance is provided at the output port end of the 3 dB multiplexer / demultiplexer,
One end of each of the first optical amplifier and the second optical amplifier is connected to each other by an optical waveguide disposed so as to be optically coupled to the other ring optical waveguide of the ring resonator,
High reflection mirrors are provided at the other ends of the first optical amplifier and the second optical amplifier,
The electrode structure for tuning the wavelength characteristic by changing the refractive index of the waveguide is provided in the vicinity of each of the two ring optical waveguides of the ring resonator. The wavelength tunable laser light source according to any one of the above. The wavelength tunable filter is
A second ring-type optical waveguide and a second peripheral length different from that of the first ring-type optical waveguide, optically connected to each other at positions symmetrical to each other via the first ring-type optical waveguide and the linear optical waveguide. A ring resonator having a ring optical waveguide and a third ring optical waveguide;
A 3 dB multiplexer / demultiplexer having two input port ends and one output port end;
One input port end of the 3 dB multiplexer / demultiplexer is optically connected to one end of an optical waveguide disposed in close proximity so as to be optically coupled to the second ring optical waveguide,
The other input port end of the 3 dB multiplexer / demultiplexer is optically connected to one end of an optical waveguide disposed in close proximity so as to be optically coupled to the third ring optical waveguide,
A half mirror having a predetermined reflectance is provided at the output port end of the 3 dB multiplexer / demultiplexer,
One end of each of the first optical amplifier and the second optical amplifier is connected to each other by an optical waveguide disposed so as to be optically coupled to the first ring optical waveguide,
High reflection mirrors are provided at the other ends of the first optical amplifier and the second optical amplifier,
An electrode structure for tuning a wavelength characteristic by changing a refractive index of the waveguide is provided in the vicinity of each of the first ring optical waveguide, the second ring optical waveguide, and the third ring optical waveguide. The tunable laser light source according to claim 1, wherein the tunable laser light source is a light source. The wavelength tunable filter is
A ring resonator in which two ring optical waveguides having different perimeters are arranged in close proximity to each other;
A 3 dB multiplexer / demultiplexer having two input port ends and two output port ends,
Two input port ends of the 3 dB multiplexer / demultiplexer are connected to each other by an optical waveguide disposed so as to be optically coupled to one ring optical waveguide of the ring resonator,
A high reflection mirror is provided at one output port end of the 3 dB multiplexer / demultiplexer,
The other output port end of the 3 dB multiplexer / demultiplexer is subjected to antireflection treatment,
One end of each of the first optical amplifier and the second optical amplifier is connected to each other by an optical waveguide disposed so as to be optically coupled to the other ring optical waveguide of the ring resonator,
High reflection mirrors are provided at the other ends of the first optical amplifier and the second optical amplifier,
The electrode structure for tuning the wavelength characteristic by changing the refractive index of the waveguide is provided in the vicinity of each of the two ring optical waveguides of the ring resonator. The wavelength tunable laser light source according to any one of the above. The wavelength tunable filter is
A second ring-type optical waveguide and a second peripheral length different from that of the first ring-type optical waveguide, optically connected to each other at positions symmetrical to each other via the first ring-type optical waveguide and the linear optical waveguide. A ring resonator having a ring optical waveguide and a third ring optical waveguide;
A 3 dB multiplexer / demultiplexer having two input port ends and two output port ends,
One input port end of the 3 dB multiplexer / demultiplexer is optically connected to one end of an optical waveguide disposed in close proximity so as to be optically coupled to the second ring optical waveguide,
The other input port end of the 3 dB multiplexer / demultiplexer is optically connected to one end of an optical waveguide disposed in close proximity so as to be optically coupled to the third ring optical waveguide,
A high reflection mirror is provided at one output port end of the 3 dB multiplexer / demultiplexer,
The other output port end of the 3 dB multiplexer / demultiplexer is subjected to antireflection treatment,
One end of each of the first optical amplifier and the second optical amplifier is connected to each other by an optical waveguide disposed so as to be optically coupled to the first ring optical waveguide,
High reflection mirrors are provided at the other ends of the first optical amplifier and the second optical amplifier,
An electrode structure for tuning a wavelength characteristic by changing a refractive index of the waveguide is provided in the vicinity of each of the first ring optical waveguide, the second ring optical waveguide, and the third ring optical waveguide. The tunable laser light source according to claim 1, wherein the tunable laser light source is a light source.   The high reflection mirror provided at one output port end of the 3 dB multiplexer / demultiplexer has another input port end and two output port ends connected to each other. The tunable laser light source according to claim 6 or 7, wherein the tunable laser light source is a loop mirror composed of a closed-loop waveguide constituted by: The wavelength tunable filter is
A ring resonator in which two ring optical waveguides having different perimeters are optically connected to each other via the optical waveguide;
A 3 dB multiplexer / demultiplexer having two input port ends and two output port ends,
Each of the two output port ends of the 3 dB multiplexer / demultiplexer is disposed adjacent to each other so that each of the two ring optical waveguides of the ring resonator is optically coupled,
A portion of the optical waveguide that optically connects the two ring-type optical waveguides of the ring-type resonator, is disposed close to the optical waveguide for taking out the light wave power so as to be optically coupled;
One end of each of the first optical amplifier and the second optical amplifier is optically connected to two input port ends of the 3 dB multiplexer / demultiplexer,
High reflection mirrors are provided at the other ends of the first optical amplifier and the second optical amplifier,
The electrode structure for tuning the wavelength characteristic by changing the refractive index of the optical waveguide is provided in the vicinity of each of the two ring optical waveguides of the ring resonator. The wavelength tunable laser light source according to any one of the above. The wavelength tunable filter is
A ring resonator in which two ring optical waveguides having different perimeters are arranged in close proximity to each other;
An optical switch having two input port ends and two output port ends,
Two input port ends of the optical switch are connected to each other by an optical waveguide arranged so as to be optically coupled to one ring optical waveguide of the ring resonator,
At least one of the two output port ends of the optical switch is provided with a half mirror having a predetermined reflectance.
One end of each of the first optical amplifier and the second optical amplifier is connected to each other by an optical waveguide disposed so as to be optically coupled to the other ring optical waveguide of the ring resonator,
High reflection mirrors are provided at the other ends of the first optical amplifier and the second optical amplifier,
The electrode structure for tuning the wavelength characteristic by changing the refractive index of the waveguide is provided in the vicinity of each of the two ring optical waveguides of the ring resonator. The wavelength tunable laser light source according to any one of the above. The wavelength tunable filter is
A second ring-type optical waveguide and a second peripheral length different from that of the first ring-type optical waveguide, optically connected to each other at positions symmetrical to each other via the first ring-type optical waveguide and the linear optical waveguide. A ring resonator having a ring optical waveguide and a third ring optical waveguide;
An optical switch having two input port ends and two output port ends,
One input port end of the optical switch is optically connected to one end of an optical waveguide that is disposed in close proximity so as to be optically coupled to the second ring optical waveguide,
The other input port end of the optical switch is optically connected to one end of an optical waveguide that is disposed in close proximity so as to be optically coupled to the third ring optical waveguide,
At least one of the two output port ends of the optical switch is provided with a half mirror having a predetermined reflectance.
One end of each of the first optical amplifier and the second optical amplifier is connected to each other by an optical waveguide disposed so as to be optically coupled to the first ring optical waveguide,
High reflection mirrors are provided at the other ends of the first optical amplifier and the second optical amplifier,
An electrode structure for tuning a wavelength characteristic by changing a refractive index of the waveguide is provided in the vicinity of each of the first ring optical waveguide, the second ring optical waveguide, and the third ring optical waveguide. The tunable laser light source according to claim 1, wherein the tunable laser light source is a light source. The wavelength tunable filter is
A ring resonator in which two ring optical waveguides having different perimeters are optically connected to each other via the optical waveguide;
A 3 dB multiplexer / demultiplexer having two input port ends and two output port ends;
An optical switch having two input port ends and two output port ends,
Each of the two output port ends of the 3 dB multiplexer / demultiplexer is disposed adjacent to each other so that each of the two ring optical waveguides of the ring resonator is optically coupled,
One end of each of the first optical amplifier and the second optical amplifier is optically connected to two input port ends of the 3 dB multiplexer / demultiplexer,
Two input port ends of the optical switch are optically connected to the other ends of the first optical amplifier and the second optical amplifier,
At least one of the two output port ends of the optical switch is provided with a half mirror having a predetermined reflectance,
The electrode structure for tuning the wavelength characteristic by changing the refractive index of the optical waveguide is provided in the vicinity of each of the two ring optical waveguides of the ring resonator. The wavelength tunable laser light source according to any one of the above. A method of driving a wavelength tunable laser light source according to any one of claims 1 to 9,
A method of driving a wavelength tunable laser light source, wherein current is injected into one of the first optical amplifier and the second optical amplifier according to a desired wavelength, and no current is injected into the other. . A driving method of a wavelength tunable laser light source according to any one of claims 10 to 12,
According to a desired wavelength, current is injected into one of the first optical amplifier and the second optical amplifier, and at the same time, no current is injected into the other.
Wavelength variable, characterized in that the path of the optical switch is switched in accordance with the optical amplifier on the side where current is injected so that a desired optical output can be obtained at the output port end provided with the half mirror Driving method of laser light source. A tunable filter capable of moving the wavelength spectrum peak of transmitted light intensity;
An optical amplifier and an optical modulator respectively connected in parallel to the wavelength tunable filter,
A wavelength tunable laser light source in which the optical modulator is integrated on the same substrate as the wavelength tunable filter and the optical amplifier. The wavelength tunable filter is
A ring resonator in which two ring optical waveguides having different perimeters are optically connected to each other via the optical waveguide;
A 3 dB multiplexer / demultiplexer having two input port ends and two output port ends,
Each of the two output port ends of the 3 dB multiplexer / demultiplexer is disposed adjacent to each other so that each of the two ring optical waveguides of the ring resonator is optically coupled,
One end of the optical amplifier is optically connected to one of two input port ends of the 3 dB multiplexer / demultiplexer, and one end of the optical modulator is optically connected to the other.
The other end of the optical amplifier is provided with a high reflection mirror,
The other end of the light modulator is provided with an antireflection film,
The electrode structure for tuning the wavelength characteristic by changing the refractive index of the optical waveguide is provided in the vicinity of each of the two ring optical waveguides of the ring resonator. Tunable laser light source.

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