JP5609135B2 - Tunable laser light source - Google Patents

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.

  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) increases the capacity by increasing the number of wavelengths. However, the progress of optical cross-connect by ROADM (Reconfigurable Optical Add / Drop Multiplexing), wavelength routing, etc. 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, good characteristics are obtained as a wavelength tunable light source having no movable part.

  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.

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

  By the way, in a wavelength tunable light source using a ring type optical resonator, since the degree of coupling of the directional coupler that optically couples the ring waveguide and the linear optical waveguide is wavelength-dependent, the wavelength resonance spectrum of the entire optical resonator. There is a problem that distortion occurs in the shape. This distortion is a factor that inhibits stable single mode oscillation and narrows the wavelength variable range. By solving this problem, it is possible to improve the wavelength resonance spectrum and expand the wavelength variable range. It has been desired to propose a new structure for improving the distortion of the wavelength resonance spectrum and to provide a wavelength tunable laser light source capable of covering both the C and L bands with a single light source.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wavelength tunable laser light source capable of realizing a wide wavelength tunable range.

  A wavelength tunable laser light source according to the present invention includes a wavelength tunable resonator including a plurality of wavelength tunable resonance filters capable of moving a wavelength spectrum peak of transmitted light intensity, and light optically connected to the wavelength tunable resonator. A laser that oscillates at a wavelength at which the transmission peaks of the plurality of wavelength tunable resonance filters included in the wavelength tunable resonator coincide with each other, and that allows the transmission peak wavelength to be tuned by external control; and The variable resonator has at least two of the wavelength tunable resonance filters, and the two wavelength tunable resonance filters are configured such that the wavelength dependency of the resonance intensity works complementarily in opposite directions. It is a characteristic.

  ADVANTAGE OF THE INVENTION According to this invention, the wavelength variable laser light source which can implement | achieve the broadband of a wavelength variable range can be provided.

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 plan view showing the characteristics of the waveguide structure of the directional coupler according to Embodiment 1. FIG. 6 is a diagram for explaining the relationship between resonance intensity and wavelength in the first ring-type optical resonator according to the first embodiment. 6 is a diagram for explaining branch characteristics of a directional coupler of a first ring optical resonator according to the first embodiment. FIG. FIG. 6 is a diagram for explaining a relationship between resonance intensity and wavelength in the second ring optical resonator according to the first embodiment. 6 is a diagram for explaining branch characteristics of a directional coupler of a second ring optical resonator according to the first embodiment. FIG. 4 is a graph showing a wavelength spectrum of reflection intensity of the entire wavelength tunable resonator according to the first embodiment. It is a graph which shows the wavelength spectrum of the reflection intensity of the whole wavelength variable resonator in the conventional wavelength variable laser light source. 6 is a schematic plan view showing characteristics of a waveguide structure of a directional coupler according to Embodiment 2. FIG. 10 is a schematic plan view showing the characteristics of the waveguide structure of the directional coupler according to Embodiment 3. FIG.

  The wavelength tunable laser light source of the present invention includes two wavelength tunable resonance filters that can move the wavelength spectrum peak of transmitted light intensity, and an optical amplifier. The wavelength tunable laser light source has a mechanism that oscillates at a wavelength at which the transmission peaks of the two wavelength tunable resonance filters coincide with each other and can tune the transmission peak wavelength by external control. The two wavelength tunable resonance filters are set so that the wavelength dependency of the resonance strength (Q value = wavelength / full width at half maximum of spectrum) works complementarily in the opposite direction. As shown, the wavelength dependence of the resonance strength is reduced.

Specifically, the two wavelength tunable resonance filters are two ring optical resonators configured by a planar optical circuit composed of a ring-shaped optical waveguide and a linear waveguide arranged close to the ring-shaped optical waveguide. Here, the coupling constant and the coupler length of a directional coupler comprising one of the ring-type optical resonators (first ring-type optical resonator) and comprising a linear optical waveguide and a ring-shaped optical waveguide are respectively represented by K _1. , and _{L 1.} The coupling constant and the coupler length of the directional coupler comprising the linear optical waveguide and the ring optical waveguide constituting the other ring optical resonator (second ring optical resonator) are respectively represented by K ₂ , and L _2. At this time, it is characterized in that the following equation (1) is set between K ₁ , K ₂ , L ₁ , and L ₂ .
_{K 2 × L 2 -K 1 ×} L 1 = π × (2n + 1) ··· (1)
(However, n = 0, 1, 2, 3, ...)

  The wavelength tunable laser light source of the present invention is a light source that can change the oscillation wavelength of laser light 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 generally changed by tuning the resonance wavelength of the resonator by external control. In order to increase the wavelength tunable range, a method of expanding the peak wavelength interval in the envelope of the resonance spectrum of the entire resonator by combining a plurality of resonators having different resonance periods is often used.

  However, there is a wavelength dependency in the resonance strength of each resonator (for example, the half-value width of the resonance spectrum peak shape). Therefore, combining the resonators increases the wavelength dependence of the resonance intensity, but in order to control the oscillation wavelength over a wide wavelength range, the resonance having a uniform resonance peak value at a constant wavelength interval. It is desirable to use a vessel. In the present invention, the resonators having wavelength dependence in opposite directions are formed so that the wavelength dependence of the resonance strengths of the plurality of resonators complement each other to form a resonator with less wavelength dependence as a whole. It is combined. Thereby, stable oscillation wavelength control is possible over a wide wavelength range.

  As described above, the wavelength tunable laser light source of the present invention has particularly excellent properties in widening the wavelength variable range and stability of the oscillation wavelength. In the wavelength tunable laser light source of the present invention, the periodic shape of the resonance wavelength spectrum of the optical resonator serving as the wavelength tunable mechanism is uniform over a wide wavelength, and therefore, a wide wavelength tunable operation can be stably performed.

  Therefore, a particularly remarkable effect can be expected for an optical circuit having an optical waveguide characteristic having a large wavelength dependency, such as a silicon fine wire type optical waveguide. That is, the optical resonant circuit, which is a feature of the silicon waveguide, can be downsized without sacrificing the wavelength tunable range, and a compact wavelength tunable light source can be realized. Further, power consumption of the wavelength variable operation can be realized by using the high thermo-optic effect that is a feature of the silicon material without sacrificing the wavelength variable range. Furthermore, the wavelength tunable laser light source of the present invention has a uniform wavelength characteristic over a wide wavelength range because the resonance spectrum of the optical resonator responsible for the wavelength tunable mechanism has a complex wavelength considering the distortion of the resonance period characteristic. No control is required. Therefore, the cost of the control circuit and software can be reduced.

  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.

  In FIG. 1, the wavelength tunable laser light source of this embodiment is a wavelength tunable resonance 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 1. The device 100 and the semiconductor optical amplifier 10 are configured to be hybrid-mounted. Details are described below.

  Specifically, a tunable resonator 100 including a first ring optical resonator 110 and a second ring optical resonator 120 is formed on the SOI substrate 1. The first ring-type optical resonator 110 includes a ring-shaped optical waveguide 12 and linear optical waveguides 14 and 5 that are arranged close to each other so as to be optically coupled to the ring-shaped optical waveguide 12. The directional coupler 4 is constituted by a part of the ring-shaped optical waveguide 12 and a part of the linear optical waveguide 14. A directional coupler 4 is constituted by a part of the ring-shaped optical waveguide 12 and a part of the linear optical waveguide 5.

  On the other hand, the second ring-type optical resonator 120 includes a ring-shaped optical waveguide 13 and linear optical waveguides 15 and 5 arranged close to each other so as to be optically coupled to the ring-shaped optical waveguide 13. A directional coupler 8 is constituted by a part of the ring-shaped optical waveguide 13 and a part of the linear optical waveguide 15. A directional coupler 8 is constituted by a part of the ring-shaped optical waveguide 13 and a part of the linear optical waveguide 5.

  The first ring type optical resonator 110 and the second ring type optical resonator 120 are optically connected by a linear optical waveguide 5. The two linear optical waveguides 14 and 15 are each composed of one optical waveguide by a multiplexer / demultiplexer 9 having a 1 × 2 MMI (Multimode interferometer) structure having one input port end and two output port ends. 16 is optically coupled. The optical waveguide 16 is optically connected to one input / output end of the optical amplifier 10 mounted in a hybrid manner. A mirror having an appropriate reflectance is formed on the other input / output end of the optical amplifier 10 by applying an optical thin film (mirror end face reflection film 11).

  In addition, the effective refractive index of the waveguide is changed by the thermo-optic effect above the ring-shaped optical waveguides 12 and 13 constituting the first ring-type optical resonator 110 and the second ring-type optical resonator 120. The heaters 3 and 7 are arranged respectively. Although the heater is provided in the vicinity of the ring-shaped optical waveguides 12 and 13 here, other than the heater may be used as long as the electrode structure is used for tuning the wavelength characteristics by changing the effective refractive index of the waveguide. Good.

  Here, the directional coupler 4 constituting the first ring optical resonator 110 and the directional coupler 8 constituting the second ring optical resonator 120 will be described in detail with reference to FIG. . FIG. 2 is a schematic plan view showing the characteristics of the waveguide structure of the directional coupler according to the first embodiment. In FIG. 2, an outline of the structure of the coupler portion of the directional coupler 4 constituting the first ring type optical resonator 110 is shown on the left side, and the second ring type optical resonator 120 is shown on the right side. The outline of the structure of the coupler part of the directional coupler 8 is shown.

In the present embodiment, the directional coupler 4 constituting the first ring optical resonator 110 and the directional coupler 8 constituting the second ring optical resonator 120 are as shown in FIG. The coupling constants κ of the coupler section are formed to be equal, but the coupler length difference is set to be π / κ. That is, the length L ₂ of the length L ₁ and the directional coupler 8 of the directional coupler 4 is set so as to satisfy the relationship of _{L 2 -L 1 = π / κ} . This relational expression is obtained when K ₁ = K ₂ = κ and n = 0 in the expression (1). Although details will be described later, the wavelength dependence of the resonance strength can be suppressed by configuring the directional couplers 4 and 8 to be different from each other in this manner.

  Subsequently, an operation mechanism of the wavelength tunable laser light source according to the present embodiment will be described. Stimulated emission light generated by injecting current into the semiconductor optical amplifier 10 propagates through the optical waveguide 16 and is demultiplexed in two directions of the linear optical waveguides 14 and 15 by the multiplexer / demultiplexer 9, respectively. Are guided to the second ring-type optical resonator 110 and the second ring-type optical resonator 120. Only the wavelength components that resonate in common with the respective resonators of the first ring-type optical resonator 110 and the second ring-type optical resonator 120 propagate through the linear optical waveguides 5 in the opposite directions, and then merge again. The light is combined by the waver 9 and guided through the optical waveguide 16. Then, the laser beam returns to the semiconductor optical amplifier 10 and is reflected by the end face mirror (mirror end face reflection film 11) to repeat the same reciprocating wave guide as described above. As a result, laser oscillation occurs, and output light is obtained from one end of the semiconductor optical amplifier 10.

  In addition, the resonance wavelengths of the first ring-type optical resonator 110 and the second ring-type optical resonator 120 can be changed by waveguide heating by the heaters 3 and 7, so that the laser oscillation wavelength can be tuned. It becomes possible to do.

  Here, the mechanism for suppressing the wavelength dependence of the resonance intensity, which is a feature of the present invention, will be described in detail. First, the relationship between the resonance intensity and the wavelength of the first ring-type optical resonator 110 will be described with reference to FIGS. FIG. 3 is a diagram for explaining the relationship between the resonance intensity and the wavelength in the first ring optical resonator according to the first embodiment. FIG. 4 is a diagram for explaining branch characteristics of the directional coupler of the first ring optical resonator according to the first embodiment. FIG. 3 shows the resonance wavelength when the light wave input from the linear optical waveguide 14 propagates through the ring optical waveguide 12 and is output to the linear optical waveguide 5 in the first ring optical resonator 110. The spectrum is shown.

As can be seen from FIG. 3, in the first ring optical resonator 110, the resonance intensity decreases as the wavelength increases, and the sharpness of the periodic spectral shape decreases. This is because the coupling / branching ratio (P / P ₀ ) of the directional coupler 4 constituting the first ring optical resonator 110 increases with respect to the wavelength, as shown in FIG. The main factor is that the confinement of the light wave in the Si core layer becomes weak and the coupling to the adjacent Si core layer increases.

  On the other hand, the relationship between the resonance intensity and the wavelength of the second ring optical resonator 120 will be described with reference to FIGS. FIG. 5 is a diagram for explaining the relationship between the resonance intensity and the wavelength in the second ring optical resonator according to the first embodiment. FIG. 6 is a diagram for explaining branch characteristics of the directional coupler of the second ring optical resonator according to the first embodiment. FIG. 5 shows a resonance wavelength spectrum when the light wave input from the linear optical waveguide 15 propagates through the ring optical waveguide 13 and is output to the linear optical waveguide 5 in the second ring optical resonator 120. Is shown.

As can be seen from FIG. 5, in the second ring optical resonator 120, the resonance intensity increases as the wavelength increases, and the sharpness of the periodic spectral shape increases. This is because, as shown in FIG. 6, the coupling / branching ratio (P / P ₀ ) of the directional coupler 8 constituting the second ring optical resonator 120 decreases with respect to the wavelength. That is, in the second ring optical resonator 120, since the length of the coupler of the directional coupler 8 is set to be longer than the complete coupling length, the coupling branching ratio is the first ring with respect to the wavelength. This is due to the reverse behavior of the type optical resonator 110.

  Here, FIG. 7 shows the wavelength spectrum of the reflected light that propagates through the first ring-type optical resonator 110 and the second ring-type optical resonator 120 configured as described above and returns to the optical waveguide 16 again. . FIG. 7 is a graph showing the wavelength spectrum of the reflection intensity of the entire tunable resonator according to the first embodiment. As can be seen from FIG. 7, the entire wavelength tunable resonator 100 has a spectral envelope having no inclination with respect to the wavelength.

  On the other hand, the wavelength spectrum of the reflected light returning to the optical waveguide 16 in the wavelength tunable laser light source when the second ring optical resonator 120 has the same configuration as that of the first ring optical resonator 110 as in the prior art As shown in FIG. FIG. 8 is a graph showing the wavelength spectrum of the reflection intensity of the entire tunable resonator in the conventional tunable laser light source. As shown in FIG. 8, in the conventional configuration, the envelope of the wavelength spectrum of the reflected light returning to the optical waveguide 16 is greatly inclined with respect to the wavelength, which becomes a factor that narrows the wavelength variable range and inhibits stable oscillation. This problem can be solved by providing asymmetry between the two resonators as shown in the present embodiment.

  As described above, in the present embodiment, one of the directional coupler 4 of the first ring-type optical resonator 110 and the directional coupler 8 of the second ring-type optical resonator 120 is in accordance with the wavelength. The coupler lengths of the directional couplers 4 and 8 are made different so that the optical coupling degree increases and the other optical coupling degree decreases with respect to the wavelength. Thereby, in the entire wavelength tunable resonator 100, the periodic shape of the resonance wavelength spectrum can be made uniform over a wide wavelength range. Therefore, according to the wavelength tunable laser light source of the present embodiment, a broadband wavelength tunable operation can be stably performed.

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. 9 is a schematic plan view showing the characteristics of the waveguide structure of the directional coupler according to the second embodiment. In FIG. 9, an outline of the structure of the coupler portion of the directional coupler 4 constituting the first ring type optical resonator 110 is shown on the left side, and the second ring type optical resonator 120 is shown on the right side. The outline of the structure of the coupler part of the directional coupler 8 is shown. In the present embodiment, only the configurations of the directional couplers 4 and 8 are different from those of the first embodiment, and the other configurations are the same as those of the first embodiment, and thus the description thereof is omitted.

  In the first embodiment, an example will be described in which the coupling strengths are made different by making the lengths of the directional couplers 4 and 8 asymmetric to reduce the envelope slope of the wavelength spectrum of the entire tunable resonator 100. did. In the present embodiment, an example of reducing the envelope inclination of the wavelength spectrum of the entire tunable resonator 100 by making the coupling strengths different by making the coupling constant κ of the directional couplers 4 and 8 asymmetrical. explain.

In the present embodiment, the directional coupler 4 constituting the first ring optical resonator 110 and the directional coupler 8 constituting the second ring optical resonator 120 are, as shown in FIG. Although the lengths of the directional coupler sections are the same, the widths of the silicon core layers (waveguide widths) are set to be different from each other. That is, the coupling constant kappa ₂ binding constants kappa ₁ and the directional coupler 8 of the directional coupler 4, so as to satisfy the relational expression of _{κ 2 = κ 1 + π /} L, the waveguide of the directional coupler 4 The width W ₁ is set wider than the waveguide width W ₂ of the directional coupler 4. This relational expression is obtained when L ₁ = L ₂ = L and n = 0 in the expression (1).

  In a directional coupler having a narrow core layer width, optical coupling occurs in a state exceeding the complete coupling, and wavelength dependence opposite to that of the other directional coupler occurs. As a result, as in the first embodiment, it is possible to reduce the envelope inclination of the wavelength spectrum of the entire tunable resonator 100.

  As described above, in the present embodiment, one of the directional coupler 4 of the first ring-type optical resonator 110 and the directional coupler 8 of the second ring-type optical resonator 120 is in accordance with the wavelength. The waveguide widths of the directional couplers 4 and 8 are made different so that the optical coupling degree increases and the other optical coupling degree decreases with respect to the wavelength. Thereby, in the entire wavelength tunable resonator 100, the periodic shape of the resonance wavelength spectrum can be made uniform over a wide wavelength range. Therefore, according to the wavelength tunable laser light source of the present embodiment, a broadband wavelength tunable operation can be stably performed.

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. 10 is a schematic plan view illustrating the characteristics of the waveguide structure of the directional coupler according to the third embodiment. In FIG. 10, an outline of the structure of the coupler portion of the directional coupler 4 constituting the first ring type optical resonator 110 is shown on the left side, and the second ring type optical resonator 120 is shown on the right side. The outline of the structure of the coupler part of the directional coupler 8 is shown. In the present embodiment, the configuration of the directional couplers 4 and 8 is only different from those of the first and second embodiments, and the other configurations are the same as those of the first and second embodiments, and thus description thereof is omitted. To do.

  In the second embodiment, in order to improve the wavelength spectrum shape of the entire tunable resonator 100, the waveguide widths of the directional couplers 4 and 8 are made different to make the coupling constant κ asymmetric. In the embodiment, an example in which the coupling constant κ is asymmetric by changing the refractive index of the cladding layer covering the waveguide core layer will be described.

In the present embodiment, the directional coupler 4 constituting the first ring optical resonator 110 and the directional coupler 8 constituting the second ring optical resonator 120 are, as shown in FIG. Although the length and width of the directional coupler section are the same, the refractive indexes of the cladding layers covering the silicon core layer are set to be different from each other. That is, the coupling constant kappa ₂ binding constants kappa ₁ and the directional coupler 8 of the directional coupler 4, so as to satisfy the relational expression of _{κ 2 = κ 1 + π /} L, the directional coupler 8, directional A clad layer different from the coupler 4 is formed. Specifically, a silicon oxide film is formed in the directional coupler 4 and a polymer resin is formed in the directional coupler 8 as a cladding layer covering the silicon core layer.

  In the directional coupler 8 using the polymer resin as the cladding layer, the optical coupling is strong because the difference in refractive index between the waveguide core layer and the cladding layer is small, and the optical coupling occurs in a state exceeding the complete coupling length. ing. For this reason, it is set so that the wavelength dependence opposite to that of the light wave branching of the directional coupler 4 having the silicon oxide film as the cladding layer occurs. As a result, as in the first and second embodiments, it is possible to reduce the envelope inclination of the wavelength spectrum of the entire wavelength tunable resonator 100.

  As described above, in the present embodiment, one of the directional coupler 4 of the first ring-type optical resonator 110 and the directional coupler 8 of the second ring-type optical resonator 120 is in accordance with the wavelength. The refractive indexes of the cladding layers covering the waveguide cores of the directional couplers 4 and 8 are made different so that the optical coupling degree increases and the other optical coupling degree decreases with respect to the wavelength. Thereby, in the entire wavelength tunable resonator 100, the periodic shape of the resonance wavelength spectrum can be made uniform over a wide wavelength range. Therefore, according to the wavelength tunable laser light source of the present embodiment, a broadband wavelength tunable operation can be stably performed.

Note that the present invention is not limited to the above-described embodiment, and can be changed as appropriate without departing from the spirit of the present invention. For example, in the above embodiment, the wavelength tunable resonator 100 has been described as including two wavelength tunable resonance filters, the first ring optical resonator 110 and the second ring optical resonator 120. The number of wavelength tunable resonance filters included in the variable resonator 100 is not limited to two, and may be three or more. That is, the wavelength tunable resonator 100 only needs to include at least two wavelength tunable resonance filters configured such that the wavelength dependence of the resonance intensity works complementarily in opposite directions. Thus, for example, a wavelength tunable laser light source having a mechanism in which laser transmission occurs at a wavelength at which the transmission spectrum peaks of the three wavelength tunable resonance filters coincide with each other. May be configured to work complementarily in opposite directions.
Also good.

  In the first to third embodiments, the planar optical circuit constituting the ring optical waveguide is described as an example of an optical circuit having a silicon layer formed on the SOI substrate 1 as a core layer. It may be composed of an optical waveguide having a core layer mainly composed of a silicon oxide film, a silicon nitride film, or a silicon oxynitride film, or may be composed of an optical waveguide of a compound semiconductor material.

  Further, in the first to third embodiments, the case where the heaters are provided on the upper portions of the first ring optical resonator 110 and the second ring optical resonator 120, respectively, has been exemplarily described. Any electrode structure other than a heater may be used as long as the electrode structure is used for tuning the wavelength characteristics by changing the rate. For example, the optical waveguides constituting the first ring optical resonator 110 and the second ring optical resonator 120 may have a structure in which a PIN structure is doped. Then, the laser transmission wavelength may be tuned by changing the resonance peak wavelength by changing the refractive index of the optical waveguide by the electro-optic effect generated by current injection or voltage application to the PIN structure.

  In the first to third embodiments, only one of the coupler length, the coupler width, and the cladding layer covering the waveguide core is made different so that one of the directional couplers 4 and 8 has a wavelength. On the other hand, the optical coupling degree is increased and the other optical coupling degree is decreased with respect to the wavelength. However, the present invention is not limited to this. One of the directional couplers 4 and 8 covers the coupler length, the coupler width, and the waveguide core so that the optical coupling degree increases with respect to the wavelength and the other decreases the optical coupling degree with respect to the wavelength. Any one or more of the cladding layers may be different. Therefore, for example, by making the coupler length and the coupler width different from each other, one may increase the optical coupling degree with respect to the wavelength, and the other may decrease the optical coupling degree with respect to the wavelength. .

1 SOI substrate,
3 Heater,
4 directional coupler,
5 linear optical waveguide,
7 Heater,
8 directional coupler,
9 MUX / DEMUX,
10 Optical amplifier 11 End face reflection film for mirror,
12 Ring-shaped optical waveguide,
13 Ring-shaped optical waveguide,
14 linear optical waveguide 15 linear optical waveguide 16 optical waveguide 100 tunable resonator 110 ring type optical resonator 120 ring type optical resonator

Claims (6)

A wavelength tunable resonator including a plurality of wavelength tunable resonance filters capable of moving a wavelength spectrum peak of transmitted light intensity;
An optical amplifier optically connected to the wavelength tunable resonator;
A laser that oscillates at a wavelength at which the transmission peaks of the plurality of wavelength tunable resonance filters included in the wavelength tunable resonator coincide, and the transmission peak wavelength can be tuned by external control; and
The wavelength tunable resonator has at least two wavelength tunable resonance filters,
The two wavelength tunable resonance filters are configured such that the wavelength dependence of the resonance intensity works complementarily in opposite directions ,
The two wavelength tunable resonance filters are a first ring type optical resonator and a second ring type optical resonator which are constituted by a planar optical circuit comprising a ring-shaped optical waveguide and a linear optical waveguide arranged close to the ring-shaped optical waveguide. And
A directional coupler comprising a part of a linear optical waveguide constituting the first ring optical resonator and a part of the ring optical waveguide, and a linear optical constituting the second ring optical resonator. A directional coupler consisting of a part of a waveguide and a part of a ring-shaped optical waveguide is coupled so that one has an increased optical coupling with respect to the wavelength and the other has a decreased optical coupling with respect to the wavelength. One or more of the length, the coupler width, and the refractive index of the cladding layer covering the waveguide core are different,
The directional coupler constituting the second ring-type optical resonator is set such that the coupling constant and the coupler length of the directional coupler constituting the first ring-type optical resonator are K ₁ and L ₁ , respectively . When the coupling constant and the coupler length of K ₂ and L ₂ are K ₁ , K ₂ , L ₁ and L ₂ ,
_{K 2 × L 2 -K 1 ×} L 1 = π × (2n + 1)
(However, n = 0, 1, 2, 3, ...)
A tunable laser light source characterized in that The planar optical circuit constituting the first ring optical resonator and the second ring optical resonator is an optical circuit having a silicon layer formed on an SOI substrate as a core layer. The tunable laser light source according to claim 1 . A planar optical circuit constituting the first ring-type optical resonator and the second ring-type optical resonator has a core layer mainly composed of a silicon oxide film, a silicon nitride film, or a silicon nitride oxide film. tunable laser light source according to claim 1, characterized in that it is constituted by a waveguide. Wavelength of claim 1, wherein the first ring-type optical resonator and the planar optical circuit constituting the second ring-type optical resonator, characterized in that it is composed of an optical waveguide of a compound semiconductor material Variable laser light source. A heater is installed above each of the first ring-type optical resonator and the second ring-type optical resonator,
The wavelength tunable according to any one of claims 1 to 4 , wherein the laser oscillation wavelength is tuned by changing the refractive index of the optical waveguide by changing the refractive index of the optical waveguide by the thermo-optic effect caused by the heating of the heater. Laser light source. An optical waveguide constituting the first ring optical resonator and the second ring optical resonator has a configuration in which a PIN structure is doped,
5. The wavelength according to claim 4 , wherein the laser oscillation wavelength is tuned by changing the refractive index of the optical waveguide by changing the refractive index of the optical waveguide by an electro-optic effect caused by current injection or voltage application to the PIN structure. Variable laser light source.

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