JP6274488B2 - Multi-wavelength light source device and multi-wavelength light source system - Google Patents

Description

  The present invention relates to a multi-wavelength light source device and a multi-wavelength light source system using the same, and more particularly to a multi-wavelength light source device using a photonic crystal and a multi-wavelength light source system using the same.

Conventionally, a multi-wavelength light source device that emits a plurality of types of light having different wavelengths has been proposed (see, for example, Patent Document 1).
Examples of this type of multi-wavelength light source device include a combination of a semiconductor laser and a wavelength conversion element and a combination of a plurality of laser light sources having different oscillation wavelengths.

JP 2011-66028 A

  However, in the above-described multi-wavelength light source device, it is necessary to combine a semiconductor laser and a wavelength conversion element, or to use a plurality of semiconductor lasers.

  The present invention has been made in view of the above reasons, and a multi-wavelength light source device and a multi-wavelength light source system using the multi-wavelength light source device that can be reduced in size while being capable of emitting a plurality of types of light having different wavelengths. The purpose is to provide.

(1) A multi-wavelength light source device according to the present invention as seen from a certain point of view includes a multi-wavelength light source device having a laminated structure having an active layer composed of a semiconductor substrate and a light-emitting material dispersed in the semiconductor substrate. The stacked structure has a first photonic crystal region that constitutes a two-dimensional photonic crystal and a first photonic crystal region that is adjacent to both sides in the width direction and cannot propagate through the first photonic crystal region. A plurality of first waveguide regions in which a part of the light in the wavelength band can propagate the light in the second wavelength band, and the light corresponding to the energy difference between the electron levels capable of optical transition in the light emitting material The wavelength is included in the high state density wavelength band of the second wavelength band, and at least two high state density wavelength bands of the plurality of first waveguide regions are different from each other.

According to this configuration, the wavelength of light corresponding to the energy difference between two electron levels capable of optical transition in the luminescent material is included in the high state density wavelength band of the second wavelength band. As a result, in the luminescent material, a so-called parcel effect that promotes optical transition between two electron levels accompanied by emission of light having a wavelength included in the high state density wavelength band can be generated. Laser light having the oscillation wavelength as the oscillation wavelength can be generated by enhancing the light of the wavelength included in the band. And the multi-wavelength light source which radiate | emits at least 2 types of laser beams from which an oscillation wavelength differs can be implement | achieved because at least two high state density wavelength bands of several 1st waveguide area | regions mutually differ. Therefore, a plurality of types of laser beams having different oscillation wavelengths can be easily integrated and miniaturized as compared with multi-wavelength light sources that are individually emitted from the corresponding laser light source elements.
In addition, in the light-emitting material, as the light of the wavelength included in the high state density wavelength band is enhanced by the Parcel effect, laser oscillation at the oscillation wavelength included in the high state density wavelength band is likely to occur. That is, since laser light can be obtained with a relatively low excitation density, power consumption can be reduced.

(2) In the multi-wavelength light source device according to the present invention, the second wavelength band and the high state density wavelength band in each of the plurality of first waveguide regions may be different from each other.
According to this configuration, the high state density wavelength bands in the plurality of first waveguide regions are different from each other, whereby the wavelengths of light enhanced by the parcel effect in the plurality of first waveguide regions are different from each other. Therefore, a plurality of types of laser beams having different wavelengths can be emitted.
Further, in each of the plurality of first waveguide regions, a part of the light emitted from the other first waveguide regions can be prevented from entering the first waveguide region. Generation of return light noise can be suppressed.

(3) Further, in the multi-wavelength light source device according to the present invention, the photonic crystal region has a period in a direction that penetrates in the thickness direction of the multilayer structure and is orthogonal to the thickness direction of the multilayer structure in the multilayer structure. The first wavelength band, the second wavelength band, and the high state density wavelength band are respectively a hole interval and a plurality of holes. It may be determined based on at least one of the size of and the thickness of the laminated structure.
According to this configuration, the first wavelength band, the second wavelength band, and the high frequency band are changed by changing at least one of the hole interval of the plurality of holes, the size of each of the plurality of holes, and the thickness of the laminated structure. Since the state density wavelength band can be changed, the design of the first wavelength band, the second wavelength band, and the high state density wavelength band can be facilitated.

(4) In the multi-wavelength light source device according to the present invention, the stacked structure further includes an optical transmission unit that transmits all of the light generated in the plurality of first waveguide regions, and the optical transmission A second photonic crystal region that constitutes a two-dimensional photonic crystal, and a second photonic crystal region adjacent to both sides in the width direction of the third wavelength band that cannot propagate through the second photonic crystal region. And a second waveguide region capable of propagating light in the fourth wavelength band, wherein the plurality of first waveguide regions are connected in parallel to the second waveguide region, and the fourth wavelength band is It may include all the high state density wavelength bands of each of the plurality of first waveguide regions.
According to this configuration, since the fourth wavelength band includes all the high state density wavelength bands of each of the plurality of first waveguide regions, the optical transmission unit is generated in each of the plurality of first waveguide regions. Since all the laser light can be transmitted, wavelength division multiplexing communication can be realized.

(5) Moreover, in the multi-wavelength light source device according to the present invention, the high state density wavelength band of any one of the plurality of first waveguide regions is the second wavelength of the other first waveguide region. It may be present on the shorter wavelength side than the band.
According to this configuration, the high state density wavelength band of any one of the plurality of first waveguide regions is present on the shorter wavelength side than the second wavelength band of the other first waveguide regions. Laser light emitted from any one of the plurality of first waveguide regions cannot enter another first waveguide region. Thereby, generation | occurrence | production of the return light noise in another 1st waveguide area | region can be suppressed.

(6) In the multiwavelength light source device according to the present invention, the second photonic crystal region penetrates in the thickness direction of the stacked structure in the stacked structure and is orthogonal to the thickness direction of the stacked structure. The third wavelength band and the fourth wavelength band are defined as the interval between the plurality of holes, the size of each of the plurality of holes, and the stacking. It may be determined based on at least one of the thicknesses of the structures.
According to this configuration, the third wavelength band and the fourth wavelength band are changed by changing at least one of the interval between the plurality of holes, the size of each of the plurality of holes, and the thickness of the laminated structure. Therefore, the design of the third wavelength band and the fourth wavelength band can be facilitated.

(7) Further, in the multi-wavelength light source device according to the present invention, the plurality of first waveguide regions are coupled in series, and at least one of the high state density wavelength bands of the plurality of first waveguide regions is May exist in the second wavelength band of the first waveguide region.
According to this configuration, since the high state density wavelength band of at least one of the plurality of first waveguide regions exists within the second wavelength band of the other first waveguide region, the plurality of first waveguide regions Light generated in at least one first waveguide region can propagate in other first waveguide regions. Therefore, the structure of the multi-wavelength light source device can be simplified.

(8) Further, in the multi-wavelength light source device according to the present invention, the plurality of first waveguide regions are arranged so that the high state density wavelength band gradually moves toward the longer wavelength side in one arrangement direction thereof. And any one of the plurality of first waveguide regions includes the high state density wavelength band of the first waveguide region adjacent to the side opposite to the one arrangement direction side. It may be a thing.
According to this configuration, the second wavelength band of any one of the plurality of first waveguide regions has a high state density of the first waveguide region adjacent to the side opposite to the one arrangement direction side. By including the wavelength band, it is possible to transmit the laser light generated in the first waveguide region adjacent to the side opposite to the one arrangement direction side to the one arrangement direction side.

(9) In the multi-wavelength light source device according to the present invention, the high state density wavelength band of any one of the plurality of first waveguide regions is adjacent to the side opposite to the one arrangement direction side. It may be present on the longer wavelength side of the first waveguide region than the second wavelength band.
According to this configuration, the laser light emitted from any one of the plurality of first waveguide regions cannot enter the first waveguide region adjacent to the side opposite to the one arrangement direction side. Thereby, generation | occurrence | production of the return light noise in a 1st waveguide area | region can be suppressed.

(10) In the multiwavelength light source device according to the present invention, the light emitting material may be composed of a plurality of quantum dots.
According to this configuration, since laser oscillation can be generated at a relatively low excitation density in the active layer of the stacked structure, power consumption can be reduced.

(11) Further, in the multi-wavelength light source device according to the present invention, the plurality of quantum dots have a size distribution, and the size distribution has a wavelength band of light emitted from the plurality of quantum dots. It may be set so as to include all of the high state density wavelength bands of the respective waveguide regions.
According to this configuration, since the plurality of quantum dots have a size distribution, the wavelength band of the light emitted from the plurality of quantum dots is reduced due to the quantum size effect of the light emitted from the single quantum dot. It spreads over a wider wavelength band than the wavelength band. The size distribution is set so that the wavelength bands of the light emitted from the plurality of quantum dots include all of the high state density wavelength bands of the plurality of first waveguide regions. Laser light having an oscillation wavelength included in the high state density wavelength band of each waveguide region can be obtained. Therefore, for example, manufacture can be facilitated as compared to a multi-wavelength light source having different active layers for each of a plurality of oscillation wavelengths.

(12) A multi-wavelength light source system according to the present invention viewed from another viewpoint is the multi-wavelength light source device according to any one of (1) to (11) above, and the plurality of first leads of the multi-wavelength light source device. An excitation light source that irradiates each waveguide region with excitation light.
According to this configuration, since it is not necessary to provide means for exciting the first waveguide region in the multi-wavelength light source device itself, the structure of the multi-wavelength light source device can be simplified.

(13) In the multi-wavelength light source system according to the present invention, a plurality of the excitation light sources may be provided for each of the plurality of first waveguide regions.
According to this configuration, it is possible to generate laser light on which different signals are superimposed for each of the plurality of first waveguide regions, so that wavelength division multiplexing communication can be realized.

(14) Further, in the multi-wavelength light source system according to the present invention, the excitation light source may sequentially irradiate each of the plurality of first waveguide regions with excitation light in a time division manner. .
According to this configuration, the number of pumping light sources that is smaller than the number of the plurality of first waveguide regions can be provided, so that the number of components and the size of the multi-wavelength light source system can be reduced.

(15) The multi-wavelength light source device according to the present invention may further include a plurality of electrodes provided for each of the plurality of first waveguide regions of the stacked structure.
According to this configuration, an excitation light source is not required as compared with a configuration in which each of the plurality of first waveguide regions is optically excited, so that the configuration can be simplified and downsized.

(16) In the multi-wavelength light source device according to the present invention, the laminated structure is injected from one of the two electrodes into a region between two adjacent electrodes of the plurality of electrodes. You may have a current block layer which suppresses that an electric current flows into the said 1st waveguide area | region corresponding to another electrode.
According to this configuration, the current injected from one of the two adjacent electrodes is restricted from flowing into the first waveguide region corresponding to the other electrode. Therefore, it is possible to suppress interference between signals superimposed on the laser light emitted from the first waveguide region corresponding to each of the two adjacent electrodes.

  According to the present invention, it is possible to provide a multi-wavelength light source device capable of downsizing while allowing a plurality of types of light having different wavelengths to be emitted, and a multi-wavelength light source system using the same.

About the sample which concerns on Embodiment 1, (a) is a perspective view, (b) is a top view, (c) is an arrow view of the cross section fractured | ruptured by the A1-A1 line in (a). (A) is a figure which shows the result of having calculated the group velocity dispersion | distribution of the light in the waveguide area | region WG of the sample which concerns on Embodiment 1, (b) is in the waveguide area | region of the sample which concerns on Embodiment 1. FIG. It is a figure which shows the result of the transmittance | permeability measurement of light. (A) is a figure which shows the result of the transmittance | permeability measurement in the waveguide area | region of the sample which concerns on Embodiment 1, (b) is a void | hole space | interval in the waveguide area | region of the sample which concerns on Embodiment 1. It is a figure which shows the relationship with a transmission zone | band. It is a figure which shows the result of having measured the normalization light emission intensity of the light at the time of carrying out optical excitation of the waveguide area | region of the sample which concerns on Embodiment 1. FIG. 6 is a schematic diagram for explaining a carrier relaxation process in a waveguide region of a sample according to Embodiment 1. FIG. It is a figure which shows the result of having calculated the group velocity dispersion | distribution in the waveguide area | region WG of the sample concerning Embodiment 1. FIG. (A) is a figure which shows the result of having measured the light emission intensity | strength at the time of photoexciting the waveguide area | region of the sample which concerns on Embodiment 1, (b) is the light emission intensity in a peak position about (a). It is a figure which shows the normalized light emission intensity obtained by normalizing. It is a figure which shows the relationship between the peak wavelength of the light emission intensity spectrum obtained by the measurement of light emission intensity, and a space | interval of holes about the sample which concerns on Embodiment 1. FIG. It is a figure which shows the emission spectrum obtained when the high intensity excitation is performed about the sample which concerns on Embodiment 1. FIG. The multi-wavelength light source device which concerns on Embodiment 1 is shown, (a) is a top view, (b) is an arrow line view of the cross section fractured | ruptured by the B1-B1 line | wire in (a). FIG. 5 is an operation explanatory diagram of the multi-wavelength light source device according to the first embodiment. It is a schematic sectional drawing in each manufacturing process of the multiwavelength light source device concerning Embodiment 1. 3 is a partial SEM photograph of the multi-wavelength light source device according to the first embodiment. 6 is a plan view of a multi-wavelength light source device according to Embodiment 2. FIG. FIG. 6 is an operation explanatory diagram of the multi-wavelength light source device according to the second embodiment. It is a schematic block diagram of the multiwavelength light source device which concerns on Embodiment 3. FIG. It is a perspective view which shows a part of multiwavelength light source device which concerns on Embodiment 4. FIG. It is sectional drawing which shows a part of multiwavelength light source device which concerns on Embodiment 4. FIG. It is a schematic sectional drawing in each manufacturing process of the multiwavelength light source device concerning Embodiment 4. It is a schematic sectional drawing in each manufacturing process of the multiwavelength light source device concerning Embodiment 4. It is a schematic block diagram of the multiwavelength light source system which concerns on a modification. It is a schematic sectional drawing in each manufacturing process of the multiwavelength light source device which concerns on a modification. It is the result of having investigated the polarization characteristic of the light emitted from a waveguide area about the sample concerning Embodiment 1 when the waveguide area of a sample is optically excited. It is a schematic block diagram of the multiwavelength light source system which concerns on a modification.

<Embodiment 1>
<1> About the research result which became the motive of this invention First, the research result which became the motive of this invention is demonstrated. The inventors have studied optical characteristics of a sample including a photonic crystal.

<1-1> Configuration of Sample FIG. 1 shows a sample according to the present embodiment, (a) is a perspective view, (b) is a plan view, and (c) is broken along line A1-A1 in (a). It is an arrow view of a cross section.
The sample 1 includes a semiconductor substrate 15, a bridge layer 16, and a laminated structure 10.
The semiconductor substrate 15 is composed of, for example, a GaAs substrate.
The bridge layer 16 is made of, for example, an Al _y Ga _1-y As (y = 0.53) mixed crystal. The bridge layer 16 is formed such that a gap 16 a is interposed between the semiconductor substrate 15 and the laminated structure 10.
The laminated structure 10 includes three active layers 13 and four intermediate layers 14. The laminated structure 10 is formed with a plurality of holes 11 penetrating in the thickness direction. The thickness (slab thickness) of this laminated structure 10 is set to about 240 nm, for example.
The active layer 13 has a structure in which quantum dots (light emitting material) formed of InAs are dispersed in a base material formed of, for example, In _x Ga _1-x As (x = 0.2). The thickness of the active layer 13 is set to about 3 nm, for example. The intermediate layer 114 is made of, for example, GaAs and has a thickness of, for example, about 50 nm. The plurality of quantum dots have a size distribution. For example, the height and the particle size are distributed within the ranges of 2 to 7 nm and 30 to 70 nm, respectively.
The intermediate layer 14 is composed of a GaAs layer.

The holes 11 are periodically arranged in a triangular lattice pattern in the region PC other than the strip-shaped waveguide region WG in the laminated structure 10. For example, holes having a radius r1 are periodically arranged at intervals (hereinafter referred to as “hole intervals”) a1. In this region PC, regions having different refractive indexes are periodically arranged in a direction perpendicular to the thickness direction of the sample 1 to form a so-called two-dimensional photonic crystal. Specifically, a part composed of air and a part composed of a semiconductor having a refractive index of about 3 to 4 times the refractive index of air are periodically arranged.
That is, the laminated structure 10 includes a waveguide region WG and a region PC (hereinafter referred to as “photonic crystal region”) that forms a two-dimensional photonic crystal adjacent to both sides in the width direction of the waveguide region WG. ,have.

<1-2> Analysis Results In the photonic crystal region PC of the laminated structure 10, a photonic band gap is formed, and a first wavelength band corresponding to the photonic band gap (hereinafter, “non-transmission band”). Light) cannot propagate. On the other hand, in the waveguide region WG of the multilayer structure 10, light in the second wavelength band (hereinafter referred to as “transmission band”) included in the non-transmission band can propagate (transmit).
This is due to the presence of a photonic band in a region corresponding to the photonic band gap of the photonic crystal region PC in the group velocity dispersion of light in the waveguide region WG.

  FIG. 2A is a diagram illustrating a result of calculation of group velocity dispersion of light in the waveguide region WG of the sample 1 according to the present embodiment, and FIG. 2B is a sample according to the present embodiment. It is a figure which shows the result of the transmittance | permeability measurement of the light in 1 waveguide region WG. 2A shows light propagating in the TE mode in the longitudinal direction of the waveguide region WG (the light whose amplitude direction is perpendicular to the thickness direction of the sample 1 and parallel to the width direction of the waveguide region W). ) Shows the calculation results.

In the calculation of the group velocity dispersion of light in the waveguide region WG, for example, a calculation method called a three-dimensional FDTD method is adopted. The main parameters used in this calculation include the radius r1 of the holes 11 in the photonic crystal region PC, the hole interval a1, the slab thickness, and the like.
As shown in FIG. 2A, in the waveguide region WG, a transmission band in which light can exist is formed in a non-transmission band in which light cannot exist in the photonic crystal region PC.
In fact, as shown in FIG. 2B, the inventors have obtained the knowledge that the light transmittance in the waveguide region WG increases in the wavelength band corresponding to the transmission band obtained from the calculation result. .

Further, the inventors have obtained knowledge about the change in the transmission band of the sample 1 when the hole interval a1 in the photonic crystal region PC is changed.
FIG. 3A is a diagram illustrating a result of light transmittance measurement in the waveguide region WG of the sample 1 according to the present embodiment, and FIG. 3B is a photonic of the sample 1 according to the present embodiment. It is a figure which shows the relationship between the space | interval a1 in crystal | crystallization area | region PC, and the transmission band in waveguide area | region WG.
As shown in FIG. 3 (a), the inventors have obtained the knowledge that the transmission band shifts to the long wave side when the hole interval a1 in the photonic crystal region PC is increased from 321 nm to 357 nm. . In FIG. 3A, for example, it is assumed that a wavelength band in which the transmittance is −35 dB or more is defined as a transmission band. In this case, as shown in FIG. 3B, the transmission band moves to the longer wavelength side as the hole interval a1 increases.

  That is, the inventors have found that the transmission band of the waveguide region WG can be controlled by changing the hole interval a1 in the photonic crystal region PC adjacent to both sides in the width direction of the waveguide region WG. Have gained.

By the way, the density of states of light in the waveguide region WG becomes higher as the group velocity is lower in the light propagating through the waveguide region WG. Here, the group velocity of light in the waveguide region WG is expressed by the following formula (1).

Here, ω represents the frequency of light, Kx represents the wave number of light, and vg represents the group velocity of light. As shown in Equation (1), the lower the group velocity, the smaller the change in the frequency of light with respect to the change in wave number. That is, the lower the group velocity, the greater the density (state density) of light having different wave numbers that exists per unit frequency.
Therefore, the inventors estimated the wavelength band of light (hereinafter referred to as “high state density wavelength band”) in which the state density is increased from the shape of the photonic band in the waveguide region WG.
Incidentally, the spontaneous emission rate of light emitted from the waveguide region WG is expressed by the following formula (2).

Here, A is the spontaneous emission rate, ρ (ω) is the light state density, and coeff is a coefficient reflecting the probability of optical transition in the waveguide region WG.
As shown in Equation (2), the spontaneous emission rate A increases as the light density of states increases. The inventors have defined the wavelength band of light at which the spontaneous emission rate is a predetermined magnitude or more as the high state density wavelength band.
As shown in FIG. 2 (a), the high state density wavelength band is an area surrounded by an ellipse (area where the frequency ω is in the vicinity of ω1, ω2, ω3, hereinafter referred to as “low group velocity area”) P1, P2. , P3 corresponding to the wavelength band.
Here, the inventors, in the quantum dots dispersed in the active layer 13, when the wavelength of light corresponding to the energy difference between the electron levels capable of optical transition is included in the high state density wavelength band, We thought that the light emitted from the quantum dots was enhanced by the parcel effect. In order to verify this point, the inventors measured the intensity spectrum of light emitted from the waveguide region WG when the waveguide region WG of the sample 1 was optically excited.

  FIG. 4A is a schematic diagram illustrating a method for measuring the intensity spectrum of light emitted from the waveguide region WG when the waveguide region WG of the sample 1 according to the present embodiment is optically excited. FIG. 4B is a diagram showing a result of measuring the normalized emission intensity of light in the waveguide region WG when the waveguide region WG of the sample 1 according to the present embodiment is optically excited. FIG. 4C shows the result of measuring the intensity spectrum of light emitted from the sample when the sample not having the photonic crystal region PC is photoexcited.

As shown in FIG. 4A, in the measurement of the intensity spectrum, the intensity spectrum of light emitted in the longitudinal direction of the waveguide region WG (hereinafter referred to as “horizontal intensity spectrum”) and the thickness direction of the sample 1 are used. The intensity spectrum of the light emitted from the light (hereinafter referred to as “vertical intensity spectrum”) was measured. In FIG. 4B, the horizontal intensity spectrum is represented by “H” and the vertical intensity spectrum is represented by “V”.
As shown in FIG. 4C, the intensity spectrum of the light emitted from the sample when the sample not having the photonic crystal region PC is photoexcited reflects the size distribution of the quantum dots, and the wavelength band of 1120 nm to 1330 nm. It has a broad shape.
On the other hand, as shown in FIG. 4B, when the waveguide region WG of the sample 1 is optically excited, the horizontal intensity spectrum H of the light emitted from the waveguide region WG is 2 near the wavelengths λ1 and λ3. Two peaks “Peak1” and “Peak3” are generated. Also in the vertical intensity spectrum V, one peak “Peak2” occurs in the vicinity of the wavelength λ2.
The wavelength bands in the vicinity of the wavelengths λ1, λ2, and λ3 substantially coincide with the high state density wavelength bands (P1, P2, and P3 in FIG. 2 (see FIG. 2)) in the waveguide region WG.

FIG. 5 is a schematic diagram for explaining a carrier relaxation process in the waveguide region WG of the sample 1 according to the present embodiment.
In the quantum dots dispersed in the active layer 13, the electron levels are discretized by a so-called three-dimensional quantum size effect of electrons. The plurality of quantum dots dispersed in the active layer 13 has a size distribution. For example, a plurality of quantum dots have different particle sizes from b1 to b4. And the electronic level in a some quantum dot changes according to the difference in this particle size b1-b4. In each quantum dot, when an electron makes an optical transition from a higher electron level to a lower one between two electron levels, light corresponding to an energy difference between the two electron levels is emitted. discharge.

For example, in a quantum dot with a particle size of b3, the light accompanying the optical transition of electrons from the lowest electron level on the conduction band side to the electron level on the valence band side, and the second lowest electron level on the conduction band side And light accompanying the optical transition of electrons from the valence band to the electron level on the valence band side. In the quantum dot having the particle size b4, it is assumed that light accompanying the optical transition of electrons from the lowest electron level on the conduction band side to the electron level on the valence band side is emitted.
The inventors, for example, have a wavelength corresponding to an energy difference between optical levels capable of optical transition in quantum dots having particle diameters b3 and b4 included in the high state density wavelength band in the waveguide region WG. Furthermore, it is considered that the oscillator strength between the electron levels has increased. That is, it is considered that the emission intensity is enhanced by the parcel effect in any of the plurality of quantum dots dispersed in the active layer 13.
For example, the wavelength of light corresponding to the energy difference E (ω1), E (ω3) (E (λ1), E (λ3)) between optical levels capable of optical transition in a quantum dot having a particle size b3 is a waveguide. It is equal to the wavelengths λ1 and λ3 included in the high state density band of the region WG. Further, the wavelength of light corresponding to the energy difference E (ω2) (E (λ2)) between the electron levels capable of optical transition in the quantum dot having the particle size b3 is equal to the wavelength λ2.

Incidentally, the shape of the photonic band in the waveguide region WG depends on the structure of the photonic crystal in the photonic crystal region PC, that is, the hole interval a1 and the hole radius r1. Therefore, when the hole interval a1 in the photonic crystal region PC is changed, the shape of the photonic band in the waveguide region WG changes, and accordingly, the position of the high state density wavelength band also changes.
Therefore, the inventors tried to change the wavelength of the enhanced light by changing the position of the high state density wavelength band by changing the gap interval a1 in the photonic crystal region PC.

FIG. 6 is a diagram illustrating a result of calculation of group velocity dispersion in the waveguide region WG of the sample 1 according to the present embodiment. Here, the calculation was performed by changing the gap interval a1 in the photonic crystal region PC. In FIG. 6, (a) is the calculation result when the gap interval is 330 nm, (b) is the gap interval 339 nm, (c) is the gap interval 348 nm, and (d) is the calculation result when the gap interval is 357 nm. Indicates.
As shown in FIG. 6, when the hole interval a1 becomes longer, the wavelengths λ2 (1), λ2 (2), λ2 (3), λ2 (4), λ1 corresponding to the high state density wavelength band of the waveguide region WG are obtained. It was found that (1), λ1 (2), λ1 (3), and λ1 (4) become longer. Here, frequencies ω2 (1), ω2 (2), ω2 (3), ω2 (4), ω1 (1), ω1 (2), ω1 (3) corresponding to the high state density wavelength band of the waveguide region WG. ), Ω1 (4) becomes shorter.

FIG. 7A is a diagram showing a result of measuring an intensity spectrum of light emitted from the waveguide region WG when the waveguide region WG of the sample according to the present embodiment is optically excited, and FIG. It is a figure which shows the intensity spectrum obtained by normalizing with the intensity | strength in a peak position about (a). Here, the measurement was performed on “Peak2” in FIG.
As shown in FIGS. 7A and 7B, high state density wavelength bands (for example, λ2 (1), λ2 (2), λ2 (3), λ2 (4)) obtained from the calculation results shown in FIG. ), It was found that a peak of the intensity spectrum occurred. And it turned out that the said peak position moves to a long wavelength side, so that the space | interval a1 of a hole becomes long.

In addition, the inventors investigated the relationship between the wavelengths of the peaks “Peak1” and “Peak3” other than the peak “Peak2” of the intensity spectrum and the hole interval a1.
FIG. 8 is a diagram showing the relationship between the peak wavelength of the emission intensity spectrum obtained by the measurement of the emission intensity and the void interval for the sample according to this embodiment. Here, the calculated value corresponds to the wavelength corresponding to the low group velocity region of the photonic band obtained from the calculation of the group velocity dispersion in the waveguide region WG of the sample 1 according to the present embodiment.
It has been found that the wavelengths of the other peaks “Peak1” and “Peak3” also move to the longer wavelength side as the hole interval a1 becomes longer.

  As described above, the inventors change the structure of the photonic crystal in the photonic crystal region PC, that is, the position of the transmission band and the high state density wavelength band by changing the hole interval a1 and the hole radius r1. The knowledge that it can be changed was obtained.

Furthermore, the inventors have also demonstrated that laser oscillation occurs when the excitation intensity at the time of exciting the waveguide region WG of the sample 1 is increased to some extent.
FIG. 9 is a diagram illustrating an intensity spectrum of light emitted from the waveguide region when the waveguide region WG is optically excited with high excitation intensity for the sample 1 according to the present embodiment.
As shown in FIG. 9, in the sample 1, it was found that if the waveguide region WG is optically excited with a certain high excitation intensity, a narrow spectrum specific to laser oscillation can be obtained. It was also found that this oscillation wavelength exists in the wavelength band of light emitted from the quantum dots dispersed in the active layer 13 and in the high state density wavelength band in the sample 1.
In other words, the inventors of the multilayer structure 10 having the photonic crystal region PC and the waveguide region WG increase the oscillation wavelength included in the high state density wavelength band by increasing the excitation intensity of the waveguide region WG to some extent. The knowledge that the laser beam which it has can be obtained was acquired.

<2> Multi-wavelength light source device Next, the multi-wavelength light source device devised by the inventors based on the knowledge described in <1> will be described.
10A and 10B show the multi-wavelength light source device 101 according to the present embodiment, where FIG. 10A is a plan view, and FIG. 10B is a cross-sectional view taken along line B1-B1 in FIG.
The multi-wavelength light source device 101 includes a laminated structure 110, a bridge layer 116, and a semiconductor substrate 115.
The semiconductor substrate 115 is made of, for example, a GaAs substrate.
The bridge layer 116 is made of, for example, Al _y Ga _1-y As (y = 0.53) mixed crystal. The bridge layer 116 is formed such that a gap 116 a is interposed between the semiconductor substrate 115 and the laminated structure 110.

The laminated structure 110 has a plurality of regions AR1 to AR4 that generate light in different wavelength bands. Each of the plurality of regions AR1 to AR4 includes photonic crystal regions (first photonic crystal regions) PC1 to PC4 and waveguide regions (first waveguide regions) WG1 to WG4.
Here, the photonic crystal regions PC1 to PC4 constitute a two-dimensional photonic crystal. The waveguide regions WG1 to WG4 are part of light in a non-transmission band (first wavelength band) in which the photonic crystal regions PC1 to PC4 are adjacent to both sides in the width direction and cannot propagate through the photonic crystal regions PC1 to PC4. Light in the transmission band (second wavelength band) can propagate.

The laminated structure 110 is composed of three active layers 113 and four intermediate layers 114. The thickness (slab thickness) t of the laminated structure 110 is set to about 240 nm, for example.
The active layer 113 has a structure in which quantum dots formed of InAs are dispersed in a semiconductor substrate formed of, for example, In _x Ga _1-x As (x = 0.2). The thickness of the active layer 113 is set to about 3 nm, for example. Thus, since the active layer 113 has a structure in which a plurality of quantum dots are dispersed, laser oscillation can be generated at a relatively low excitation density in the active layer 113 of the stacked structure 110. Reduction can be achieved.
The plurality of quantum dots have a size distribution. The size distribution is set so that the wavelength bands of light emitted from the plurality of quantum dots dispersed in the active layer 113 include all of the high state density wavelength bands of the four regions AR1 to AR4. Yes. Specifically, the particle diameters of the plurality of quantum dots are distributed in a range of, for example, a height of 2 to 7 nm and a diameter of 30 to 70 nm. Furthermore, each quantum dot has a plurality of emission peaks by having discrete levels. Thereby, the intensity spectrum of the light emitted from the plurality of quantum dots has a broad shape over the wavelength band 1120 nm to 1330 nm.
The intermediate layer 114 is made of, for example, GaAs and has a thickness of, for example, about 50 nm.

The photonic crystal regions PC1 to PC4 penetrate through the stacked structure 110 in the thickness direction of the stacked structure 110 and are periodically arranged in a triangular lattice pattern in a direction perpendicular to the thickness direction of the stacked structure 110. This is a region where the holes 11 are formed.
The non-transmission band, the transmission band, and the high state density wavelength band in the waveguide regions WG1 to WG4 are the gap interval a2 of the plurality of holes 111, the size of the holes 111 (hole radius r2), and the laminated structure. It is determined based on a thickness of 110 (slab thickness). Specifically, as described in <1> above, the longer the hole interval a2, the more the entire transmission band and the entire high state density wavelength band are located on the long wavelength side.
Thereby, by changing at least one of the hole interval a2, the hole radius r2, and the thickness of the laminated structure 110, the non-transmission band, the transmission band, and the high state density wavelength band in each of the waveguide regions WG1 to WG4 are changed. Can be changed. Therefore, the design of the non-transmission band, the transmission band, and the high state density wavelength band in each of the waveguide regions WG1 to WG4 can be facilitated.

  In addition, the laminated structure 110 has a region (light transmission unit) AR5 that transmits all of the laser beams generated in the four regions AR1 to AR4. This region AR5 is composed of a photonic crystal region (second photonic crystal region) PC5 and a waveguide region (second waveguide region) WG5. Here, the photonic crystal region PC5 constitutes a two-dimensional photonic crystal. In addition, the waveguide region WG5 is adjacent to the photonic crystal region PC5 on both sides in the width direction, and part of the transmission band (fourth wavelength band) of the non-transmission band (third wavelength band) that cannot propagate through the photonic crystal region PC5. (Wavelength band) light can propagate.

The photonic crystal region PC5 also penetrates the stacked structure 110 in the thickness direction of the stacked structure 110, and a plurality of voids periodically arranged in a triangular lattice pattern in a direction perpendicular to the thickness direction of the stacked structure 110. This is a region where the hole 111 is formed.
The non-transmission band and the transmission band in the waveguide region WG5 are determined based on the hole interval a2 of the plurality of holes 111, the size of the holes 111 (hole radius r2), and the thickness of the multilayer structure 110. Yes. Specifically, as described in <1> above, the longer the hole interval a2, the more the entire transmission band is located on the long wavelength side.
Thereby, the non-transmission band and the transmission band in the waveguide region WG5 can be changed by changing at least one of the hole interval a2, the hole radius r2, and the laminated structure 110. Therefore, the design of the non-transmission band and the transmission band in the waveguide region WG5 can be facilitated.

By the way, in the multi-wavelength light source device 101, in each of the areas AR1 to AR4, the wavelength of light corresponding to the energy difference between the electron levels capable of optical transition in at least one of the plurality of quantum dots in the active layer 113. However, the hole interval a2 and the hole radius r2 are set so as to be included in the high state density wavelength band. Here, the “high state density wavelength band” means a wavelength band of light in which the spontaneous emission rate is a predetermined magnitude or more in the waveguide regions WG1 to WG4.
Specifically, it is assumed that the wavelength band of light emitted from a plurality of quantum dots is 1120 nm to 1330 nm. That is, the wavelength of light corresponding to the energy difference between the electron levels capable of optical transition in the plurality of quantum dots is dispersed within the range of 1120 nm to 1330 nm. On the other hand, the high-density wavelength bands of the four regions AR1 to AR4 are, for example, near 1215 nm (λ1 (1)), near 1240 nm (λ1 (2)), near 1255 nm (λ1 (3)), 1290 nm ( It is set in the vicinity of λ1 (4)).

Further, the hole interval a2 of the holes 111 and the hole radius r2 of the holes 111 are different from each other in the four regions AR1 to AR4. Thereby, the transmission band and the high state density wavelength band of the regions AR1 to AR4 are different from each other.
As described above, the high state density wavelength bands in the four regions AR1 to AR4 are different from each other, so that the wavelengths of light enhanced by the parcel effect in the four regions AR1 to AR4 are different from each other. Accordingly, a plurality of types of laser beams having different wavelengths can be emitted from each of the four regions AR1 to AR4. Further, in each of the four regions AR1 to AR4, part of the light emitted from the other regions can be prevented from entering the waveguide regions WG1 to WG4, so that the return light noise in the waveguide regions WG1 to WG4 Can be suppressed.
Here, in the regions AR1 to AR4, when the center wavelengths of the high state density wavelength bands in the waveguide regions WG1 to WG4 are λ1 (1), λ1 (2), λ1 (3), and λ1 (4), The hole interval a2 and the hole radius r2 are set so that the relational expression (3) is established.

Further, the hole interval a2 and the hole radius r2 in the area AR5 are set so that the relational expression expressed by the following expression (4) is established.

Here, the lower limit of the transmission band in the waveguide region WG5 of the region AR5 is λ15t, and the upper limit is λ15c.
As shown in Expression (4), the transmission band of the waveguide region WG5 in the region AR5 is set to include all the high state density wavelength bands of the four regions AR1, AR2, AR3, and AR4. Thereby, all the laser beams generated in each of the four regions AR1, AR2, AR3, AR4 can propagate through the waveguide region WG5 in the region AR5, so that wavelength division multiplexing communication can be realized.

FIG. 11 is an operation explanatory diagram of the multi-wavelength light source device 101 according to the present embodiment. Here, in FIGS. 10A to 10D, the oscillation wavelength of the laser light generated in each of the waveguide regions WG1 to WG4 of the regions AR1 to AR4 and the four light propagation paths PA1, PA2, and PA3 in FIG. , PA4, the transmission band of light propagating along each.
The space | intervals in the photonic crystal regions PC1, PC2, PC3, PC4 in the regions AR1, AR2, AR3, AR4 are set to 330 nm, 339 nm, 348 nm, 357 nm, for example. And the space | interval of holes in the photonic crystal region PC5 in the region AR5 is set to 330 nm, for example.

As shown in FIG. 11A, the transmission band of the area AR1 (lower limit λ11t upper limit λ11c) and the transmission band of the area AR5 (lower limit λ15t upper limit λ15c) match.
As shown in FIG. 11B, the high state density wavelength band of the area AR1 (wavelength band in the vicinity of the wavelength λ1 (1)) exists on the shorter wavelength side than the transmission bands λ12t to λ12c of the other area AR2. Accordingly, light that has reached the waveguide region WG5 in the region AR5 through the light propagation path PA1 cannot enter the waveguide region WG2 in the region AR2. Further, the high state density wavelength band of the area AR2 (wavelength band near the wavelength λ1 (2)) is located slightly on the short wave side from the center of the transmission band (lower limit λ15t upper limit λ15c) of the area AR5.

  As shown in FIG. 11 (c), the high state density wavelength bands of the areas AR1 and AR2 (wavelength bands near the wavelengths λ1 (1) and λ1 (2)) are larger than the transmission bands λ13t to λ13c of the other areas AR3. Present on the short wavelength side. As a result, light that has reached the waveguide region WG5 in the region AR5 through the light propagation paths PA1 and PA2 cannot enter the waveguide region WG3 in the region AR3. Further, the high state density wavelength band of the area AR3 (wavelength band near the wavelength λ1 (3)) is located slightly longer than the center of the transmission band of the area AR5 (lower limit λ15t upper limit λ15c).

  As shown in FIG. 11D, the high state density wavelength bands (wavelength bands near the wavelengths λ1 (1), λ1 (2)) of the regions AR1, AR2, AR3 are larger than the transmission bands λ14t to λ14c of the region AR4. Present on the short wavelength side. As a result, the light that has propagated through the light propagation paths PA1 to PA3 and reached the waveguide region WG5 in the region AR5 cannot enter the waveguide region WG4 in the region AR4. Further, the high state density wavelength band of the area AR1 (wavelength band near the wavelength λ1 (1)) is located near the band end on the long wave side of the transmission band of the area AR5 (lower limit λ15t upper limit λ15c).

  As described above, in the multi-wavelength light source device 101, the high state density wavelength band of any one of the four regions AR1 to AR4 (for example, the region AR1) is higher than the transmission band of the other region (for example, the region AR2). Is also present on the short wavelength side. Accordingly, since the laser light emitted from the area AR1 cannot enter the waveguide area WG2 in the other area AR2, generation of return light noise in the waveguide area WG2 in the area AR2 can be suppressed.

<3> Manufacturing Method of Multiwavelength Light Source Device Next, a manufacturing process of the multiwavelength light source device 101 according to the present embodiment will be described.
FIG. 12 is a cross-sectional view of an incomplete product in each manufacturing process of the multi-wavelength light source device 101 according to the present embodiment. Note that FIG. 12 is a schematic diagram, and the thickness of each layer shown in FIG. 12 does not reflect the actually measured dimensions.
First, as shown in FIG. 12A, a sacrificial layer 156 is formed on a semiconductor substrate 115 by an epitaxial growth method, and thereafter, four intermediate layers 114 and three active layers 113 are formed on the sacrificial layer 156. The laminated structure 110 is formed by an epitaxial growth method. Here, the sacrificial layer 156 is formed of an Al _y Ga _1-y As (y = 0.53) mixed crystal. The thickness of the sacrificial layer 156 is set to 2 μm, for example.
As an epitaxial growth method for forming the sacrificial layer 156, for example, an MOCVD (Metal Organic Chemical Vapor Diposition) method or an MBE (Molecular Beam Epitaxy) method may be employed. When employing the MBE method, the growth conditions may be set, for example, to a growth temperature of 560 ° C. and an arsenic pressure of 1 × 10 ⁻⁵ Torr.
In addition, as an epitaxial growth method when forming the laminated structure 110, an MBE method is adopted. The growth conditions may be set such that the growth temperature is 450 ° C. and the arsenic pressure is 3 × 10 ⁻⁶ Torr.

Next, as illustrated in FIG. 12B, a resist mask 121 having a plurality of holes 121 a is formed on the stacked structure 110 using an electron beam lithography technique.
Specifically, after applying a photoresist (not shown) on the laminated structure 110, electron beam irradiation (EB exposure) is performed on the photoresist. Here, the electron beam is irradiated to a region where the resist mask 121 is to be formed (a region other than the region corresponding to the hole 121a). And the photoresist of the part which is not irradiated with an electron beam is removed by being immersed in a developing solution. Next, the resist solution 121 is formed by removing the developer by washing with water and subsequently performing heat treatment (post-bake treatment and baking treatment).

  Subsequently, as shown in FIG. 12C, a part of the laminated structure 110 and the sacrificial layer 156 is etched by the reactive ion etching (RIE) method using the resist mask 121 as a mask. Here, for example, CCl2F2 or the like may be used as the etching gas. Thereafter, if the resist mask 121 is removed by O 2 (oxygen) asher or the like, a structure as shown in FIG. 12D is obtained.

  Next, as shown in FIG. 12E, the sacrificial layer 156 is partially removed by wet etching to complete the multi-wavelength light source device 101 including the bridge layer 116 having the gap 116a. . Here, for example, BHF (buffered hydrofluoric acid) or the like may be used as the etching solution.

FIG. 13 is an SEM photograph of a part of the multi-wavelength light source device 101 according to this embodiment.
As shown in FIG. 13, the multi-wavelength light source device 101 in which a plurality of holes 111 are formed in a laminated structure 110 composed of three active layers 113 and four intermediate layers 114 is manufactured by the above-described manufacturing method. It can be seen that it can be manufactured. It can also be seen that a gap 116 a is formed between the laminated structure 110 and the semiconductor substrate 115.

<4> Summary After all, in the multi-wavelength light source device 101 according to the present embodiment, the wavelengths λ1 (1) to λ1 (4) are included in the high state density wavelength band of the transmission band (second wavelength band). Here, the wavelengths λ1 (1) to λ1 (4) are the light corresponding to the energy difference between two electron levels capable of optical transition in at least one of the plurality of quantum dots dispersed in the active layer 113. Is the wavelength.
Thereby, in the quantum dot, a so-called parcel effect in which an optical transition between two electron levels accompanied by emission of light having a wavelength included in the high state density wavelength band can be generated. Accordingly, it is possible to enhance the light of the wavelengths λ1 (1) to λ1 (4) included in the high state density wavelength band.
And the multi-wavelength light source 101 which radiate | emits four types of laser beams from which an oscillation wavelength differs can be implement | achieved because the high state density wavelength bands of four area | regions AR1-AR4 mutually differ. Therefore, the areas AR1 to AR4 can be easily integrated and the size can be reduced as compared with a multi-wavelength light source in which a plurality of types of laser light having different oscillation wavelengths are emitted from the corresponding laser light source elements. .

  Further, in the quantum dot, as the light of the wavelength included in the high state density wavelength band is enhanced by the Parcel effect, laser oscillation at the oscillation wavelength included in the high state density wavelength band is likely to occur. That is, since laser light can be obtained with a relatively low excitation density, power consumption can be reduced.

Furthermore, in the multi-wavelength light source device 101 according to the present embodiment, since the plurality of quantum dots have a size distribution, the wavelength band of light emitted from the plurality of quantum dots is single due to the quantum size effect. It spreads in a wider wavelength band than the wavelength band of light emitted from the quantum dots. The size distribution is set so that the wavelength bands of light emitted from the plurality of quantum dots include all of the high state density wavelength bands of the four regions AR1 to AR4. Thereby, it is possible to obtain laser beams having the oscillation wavelengths λ1 (1) to λ1 (4) included in the high state density wavelength bands of the four regions AR1 to AR4. Therefore, for example, manufacture can be facilitated as compared with a multi-wavelength light source having different active layers for each of the four oscillation wavelengths λ1 (1) to λ1 (4).
Further, in the multi-wavelength light source device 101 according to the present embodiment, the size distribution can be increased to widen the wavelength band of light emitted from a plurality of quantum dots. In this case, since the interval between the high state density wavelength bands of each of the four regions AR1 to AR4 can be increased, the wavelength variable range of the laser light emitted from the multi-wavelength light source 101 can be expanded.

<Embodiment 2>
FIG. 13 is a plan view of the multi-wavelength light source device 201 according to this embodiment.
The basic structure of the multi-wavelength light source device 201 is the same as that of the multi-wavelength light source device 101 according to the first embodiment. The multi-wavelength light source device 201 is different from the multi-wavelength light source device 101 according to the first embodiment in the arrangement of the holes 111 in plan view. In addition, about the structure similar to Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably.

In the multi-wavelength light source device 201, the hole interval a2 of the holes 111 and the hole radius r2 of the holes 111 are different from each other in the four regions (regions) AR21 to AR24. The waveguide regions (first waveguide regions) WG21 to WG24 of the four regions AR21 to AR24 are coupled in series. Photonic crystal regions PC21 to PC24 are arranged adjacent to the waveguide regions WG21 to WG24.
The hole interval a2 and the hole radius r2 in the regions AR21, AR22, AR23, AR24 are set so that the relational expressions expressed by the following expressions (5) and (6) are satisfied.


Here, λ21 (1), λ21 (2), λ21 (3), and λ21 (4) are laser beams generated in the waveguide regions WG21, WG22, WG23, and WG24 in the regions AR21, AR22, AR23, and AR24, respectively. Indicates the oscillation wavelength. Further, the lower limits of the transmission bands in the waveguide areas WG21, WG22, WG23, and WG24 of the areas AR21, AR22, AR23, and AR24 are λ21t, λ22t, λ23t, and λ24t, and the upper limits are λ21c, λ22c, λ23c, and λ24c.

That is, as shown in Expression (5), the four regions AR21 to AR24 are arranged in one arrangement direction (the propagation direction of light propagating in the light propagation path PA in FIG. 14, hereinafter referred to as “light propagation path PA direction”). In other words, the high state density wavelength band is gradually moved to the longer wavelength side. The high state density wavelength band of one of the four regions AR21 to AR24 (for example, the region AR21) is shorter than the high state density wavelength band of the region (for example, the region AR22) adjacent to the light propagation path PA direction side. Exists on the side.
Further, as shown in Expression (6), at least one high state density wavelength band of the four regions AR21 to AR24 exists in the transmission band of the other region.

  FIG. 15 is an operation explanatory diagram of the multi-wavelength light source device 201 according to the present embodiment. Here, FIG. 14 shows the oscillation wavelength of the laser light generated in each of the waveguide regions WG21 to WG24 in each of the regions AR21 to AR24, and the transmission band of light propagating through the light propagation path PA in FIG.

The wavelength of the laser light generated in the waveguide region WG21 of the region AR21 is located within the transmission bands of the regions AR22, AR23, AR24 (the lower limit λ22t upper limit λ22c band, the lower limit λ23t upper limit λ23c band, the lower limit λ24t upper limit λ24c band). To do. Accordingly, the laser light generated in the waveguide region WG21 propagates through the waveguide regions WG22, WG23, WG24 of the three regions AR22, AR23, AR24.
The wavelength of the laser light generated in the waveguide region WG22 in the region AR22 is located in the transmission bands of the regions AR23 and AR24 (the lower limit λ23t upper limit λ23c band and the lower limit λ24t upper limit λ24c band). However, the high state density wavelength band of the region AR22 exists on the longer wavelength side than the transmission bands λ21t to λ21c of the region AR21 adjacent to the side opposite to the light propagation path PA direction side. Accordingly, the laser light generated in the waveguide region WG22 propagates to the waveguide regions WG23 and WG24 in the two regions AR23 and AR24, but cannot propagate to the waveguide region WG21 in the region AR21.

The wavelength of the laser light generated in the waveguide region WG23 in the region AR23 is located in the transmission band of the region AR24 (the lower limit λ24t upper limit λ24c band). However, the high state density wavelength band of the area AR23 exists on the longer wavelength side than the transmission band (band of the lower limit λ22t upper limit λ22c) of the area AR22 adjacent to the side opposite to the light propagation path PA direction side. Accordingly, the laser light generated in the waveguide region WG23 propagates to the waveguide region WG24 in the region AR24, but cannot propagate to the waveguide regions WG21 and WG22 in the regions AR21 and AR22.
However, the high state density wavelength band of the area AR24 exists on the longer wavelength side than the transmission band (band of the lower limit λ23t upper limit λ23c) of the area AR23 adjacent to the side opposite to the light propagation path PA direction side. Accordingly, the laser light generated in the waveguide region WG24 cannot propagate to the waveguide regions WG21, WG22, WG23 of the three regions AR21, AR22, AR23.

  As described above, in the multi-wavelength light source device 201, the four regions AR21 to AR24 are arranged so that the high state density wavelength band gradually moves to the longer wavelength side in the light propagation path PA direction. The transmission band (second wavelength band) of the area AR22 (AR23, AR24) includes the high state density wavelength band of the area AR21 (AR22, AR23) adjacent to the side opposite to the light propagation path PA direction side. .

  Thereby, in the area AR22 (AR23, AR24), the laser light generated by the AR21 (AR22, AR23) adjacent to the side opposite to the light propagation path PA direction side can be transmitted to the light propagation path PA direction side. it can.

  Eventually, in the multi-wavelength light source device 201 according to the present embodiment, the high state density wavelength band in the area AR21 exists in the transmission bands of the areas AR22 to AR24, so that the light generated in the area AR21 is in each of the areas AR22 to AR24. It can propagate through the waveguide regions WG22 to WG24. Therefore, the structure of the multi-wavelength light source device 201 can be simplified.

  Further, in the multi-wavelength light source device 201, the area AR22 (AR23, AR24) has an area AR21 (AR22, AR24) adjacent to the side of the area AR22 (AR23, AR24) opposite to the light propagation path PA direction side. It exists on the longer wavelength side than the transmission band of AR23). Thereby, the laser light emitted from the region AR22 (AR23, AR24) enters the waveguide region WG21 (WG22, WG23) of the region AR21 (AR22, AR23) adjacent to the side opposite to the light propagation path PA direction side. Can not. Therefore, it is possible to suppress the occurrence of return light noise in the waveguide region WG21 (WG22, WG23) in the region AR21 (AR22, AR23).

<Embodiment 3>
FIG. 16 is a schematic configuration diagram of a multi-wavelength light source system 301 according to the present embodiment.
The multi-wavelength light source system 301 according to the present embodiment uses the multi-wavelength light source device 101 described in the first embodiment.
The multi-wavelength light source system 301 has a function of optically exciting the waveguide regions WG1 to WG4 of the respective regions AR1 to AR4 of the multi-wavelength light source device 101.
The multi-wavelength light source system 301 includes a multi-wavelength light source device 101, four excitation light sources 311A to 311D, and scanning lenses 313A to 313D corresponding to the respective excitation light sources 311A to 311D.

Excitation light sources 311A-311D are comprised from laser light sources, such as a semiconductor laser, for example. And each of excitation light source 311A-311D outputs a laser beam based on the control signals Data1-Data4 input from the outside.
The scanning lenses 313A to 313D condense the light emitted from the excitation light sources 311A to 311D onto a part of the waveguide regions WG1 to WG4 of the regions AR1 to AR4 of the multi-wavelength light source device 101.

  After all, in the multi-wavelength light source system 301 according to the present embodiment, it is not necessary to provide means for exciting the waveguide regions WG1 to WG4 in the multi-wavelength light source device 101 itself, so that the structure of the multi-wavelength light source device 101 is simplified. be able to.

In the multi-wavelength light source system 301, excitation light sources 311A to 311D are provided for each of the plurality of regions AR1 to AR4.
As a result, it is possible to generate laser light on which different signals are superimposed for each of the four areas AR1 to AR4, so that wavelength multiplexing communication can be realized.

<Embodiment 4>
FIG. 17 is a perspective view illustrating a part of the multi-wavelength light source device 401 according to the present embodiment, and FIG. 18 is a cross-sectional view illustrating a part of the multi-wavelength light source device 401 according to the present embodiment.
The multi-wavelength light source device 401 according to the present embodiment has substantially the same configuration as the multi-wavelength light source device 101 according to the first embodiment. The multi-wavelength light source device 401 is different from the multi-wavelength light source device 101 according to the first embodiment in that it mainly includes four electrodes 417 and a current blocking layer 420. Here, the four electrodes 417 are provided for each of the waveguide regions WG1 to WG4 included in each of the four regions AR1 to AR4 of the multilayer structure 410.

The multi-wavelength light source device 401 includes a semiconductor substrate 415, a bridge layer 416, a laminated structure 410, and an electrode 422.
The semiconductor substrate 415 is composed of, for example, a GaAs substrate having a conductivity type of N type.
The bridge layer 416 is formed of, for example, an Al _y Ga _1-y As (y = 0.53) mixed crystal having an N conductivity type. The bridge layer 416 is formed such that a gap 116 a is interposed between the semiconductor substrate 115 and the laminated structure 110.
The electrode 422 is made of, for example, Ti / Au or the like, and is formed so as to cover the entire surface of the semiconductor substrate 415 opposite to the bridge layer 416 side.

  As shown in FIG. 18, the laminated structure 410 includes a first cladding layer 418, three active layers 113, two intermediate layers 114, a second cladding layer 419, a current blocking layer 420, and contacts. A layer 421 and four electrodes 417 are provided. In the laminated structure 410, a plurality of holes 11 penetrating in the thickness direction are formed.

The first cladding layer 418 is composed of, for example, an N-type GaAs layer. Here, for example, Si may be used as the N-type impurity.
The active layer 113 has a structure in which quantum dots formed of InAs are dispersed in, for example, an In _x Ga _1-x As (x = 0.2) layer.
The intermediate layer 114 is composed of, for example, a GaAs layer.
The second cladding layer 419 is made of, for example, a P-type GaAs layer. Here, for example, Be may be used as the P-type impurity.

The current block layer 420 is composed of, for example, an N-type GaAs layer. The current blocking layer 420 is provided in a region between two adjacent electrodes 417 in the laminated structure 410. In the current blocking layer 420, when a bias is applied between the four electrodes 417 and the electrode 422, a depletion layer is formed in a part near the boundary between the current blocking layer 420 and the second cladding layer 419. . Thereby, the inflow of the current injected from one of the two adjacent electrodes 417 to the waveguide region corresponding to the other electrode 417 is restricted. Therefore, it is possible to suppress interference between signals superimposed on laser beams emitted from the waveguide regions corresponding to the two adjacent electrodes 417, respectively.
The contact layer 421 is composed of, for example, a P-type GaAs layer. The impurity concentration of the contact layer 421 is higher than the impurity concentration of the second cladding layer 419.
The electrode 417 is made of a metal material such as Ti / Au, and is provided above the contact layer 421. The electrode 417 is in ohmic contact with the contact layer 421 having a high impurity concentration.

  In the multi-wavelength light source device 401, by having the current blocking layer 420, most of the current injected from the electrode 417 flows only into the corresponding waveguide region, and diffusion to other waveguide regions is suppressed. Yes.

Next, a method for manufacturing the multi-wavelength light source device 401 according to this embodiment will be described.
19 and 20 are cross-sectional views of the unfinished product in each manufacturing process of the multi-wavelength light source device 401 according to the present embodiment. In addition, about the structure similar to Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably. 19 and 20 are schematic diagrams, and the thickness of each layer shown in FIGS. 19 and 20 does not reflect the actual measurement dimensions.
As shown in FIG. 19A, first, a sacrificial layer 456 is formed on a semiconductor substrate 415 by an epitaxial growth method. Thereafter, a first cladding layer 418, three active layers 113, an intermediate layer 114, a second cladding layer 419, and a contact layer 421 are sequentially formed on the sacrificial layer 456 by an epitaxial growth method.

Then, a silicon oxide mask 511 that covers a region where the electrode 417 is to be formed is formed on the contact layer 421 by using an electron beam lithography technique and an etching technique.
Subsequently, regions other than the silicon oxide mask 511 in the contact layer 421 are removed by wet etching.
Thereafter, the current blocking layer 420 is formed so as to be embedded in a region other than the silicon oxide mask 511 by an epitaxial growth method. At this time, the MOCVD method is employed as the epitaxial growth method.
Then, after forming the current blocking layer 420, the silicon oxide mask 511 is removed.

  After that, as shown in FIG. 19C, a resist mask 512 is formed on the contact layer 421 using an electron beam lithography technique to cover a region other than the region where the electrode 417 is to be formed. The method for forming the resist mask 512 is the same as the method for forming the resist mask 121 described in Embodiment 1.

Next, as shown in FIG. 19D, a metal layer 457 is formed. Here, as a method of forming the metal layer 457, for example, a vapor deposition method or a sputtering method may be employed.
Subsequently, a portion other than the electrode 417 in the metal layer 457 is removed together with the resist mask 512 using a lift-off technique. The removal of the resist mask 512 is performed by, for example, an O 2 (oxygen) asher.

  Thereafter, as shown in FIG. 20A, a resist mask 121 having a plurality of holes 121a is formed on the electrode 417 and the contact layer 421 by using a photolithography technique. The formation method of the resist mask 121 is the same as the formation method of the resist mask 121 described in the first embodiment.

  Subsequently, as shown in FIG. 20B, the stacked structure 410 and a part of the sacrificial layer 456 are etched by the reactive ion etching (RIE) method using the resist mask 121 as a mask. Here, the laminated structure 410 includes the first and second cladding layers 418 and 419, the active layer 113, the intermediate layer 114, the current blocking layer 420, and the contact layer 421 as described above. Thereafter, the resist mask 121 is removed by O 2 (oxygen) asher or the like.

Next, as shown in FIG. 20C, a bridge layer 416 is formed by removing a part of the sacrificial layer 456 by etching using a wet etching method.
Thereafter, after polishing the semiconductor substrate 415, as shown in FIG. 20D, an electrode 422 is formed on the opposite side of the semiconductor substrate 415 from the electrode 417 side, whereby the multi-wavelength light source device 401 is completed. Here, as a method for forming the electrode 422, for example, an evaporation method or a sputtering method may be employed.

  As a result, the multi-wavelength light source device 401 according to the present embodiment can excite the waveguide regions WG1 to WG4 of the four regions AR1 to AR4 by current injection from the electrode 417. Therefore, compared with the configuration in which the waveguide regions WG1 to WG4 in the regions AR1 to AR4 are optically pumped, the multiwavelength light source system using the multiwavelength light source device 401 is simplified and miniaturized as much as an excitation light source is unnecessary. Can do.

<Modification>
(1) In the first and second embodiments, examples in which the transmission band and the high state density wavelength band are different from each other in the areas AR1 to AR4 of the multiwavelength light source device 101 and the areas AR21 to AR24 of the multiwavelength light source apparatus 201 have been described. However, the transmission band and the high state density band are not necessarily limited to different configurations. For example, in the four regions AR1 to AR4 (AR21 to AR24), the two transmission bands and the high state density band may be the same, and may be configured differently from the other transmission bands and the high state density band.

(2) In the first and second embodiments, in the stacked structure 110, the photonic crystal regions PC1 to PC4 (PC21 to PC24) and the waveguide regions WG1 to WG4 (WG21 to WG24) are arranged in two dimensions in parallel. The example provided is described. However, the photonic crystal region and the waveguide region are not necessarily limited to the configuration provided in parallel in two dimensions. For example, the waveguide region may be three-dimensionally surrounded by the photonic crystal region.

For example, a waveguide region having an active layer in which quantum dots are dispersed is formed in a photonic crystal region in which a plurality of semiconductor wires made of the same material as the intermediate layer 114 according to the first embodiment are stacked in a lattice shape. It may be a thing.
Here, for example, the photonic crystal region is extended on a plurality of semiconductor wires arranged so as to be parallel to each other two-dimensionally, in a direction perpendicular to the extending direction of these wires, and arranged so as to be parallel to each other A basic structure is a structure in which a plurality of semiconductor wires are overlapped. The photonic crystal region has a structure in which a plurality of the basic structures are stacked in a direction perpendicular to the plane on which the semiconductor wires in the basic structure are arranged.

(3) In the third embodiment, the example of the multi-wavelength light source system 301 including the excitation light sources 311A to 311D for each of the areas AR1 to AR4 of the multi-wavelength light source device 101 has been described. However, the excitation light source is not necessarily provided separately for each of the areas AR1 to AR4. For example, a configuration in which one excitation light source sequentially irradiates excitation light in time division to the waveguide regions WG1 to WG4 of the regions AR1 to AR4 may be employed.

FIG. 21 is a schematic configuration diagram of a multi-wavelength light source system 601 according to this modification. In addition, about the structure similar to Embodiment 3, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably.
The multi-wavelength light source system 601 includes a multi-wavelength light source device 101, one excitation light source 611, a galvano mirror 612, and a scanning lens 613.
Here, the light emitted from the excitation light source 611 is reflected by the galvano mirror 612, passes through the scanning lens 613, and is condensed on any one of the waveguide regions WG 1 to WG 4 of the multi-wavelength light source device 101. The
Then, by changing the angle of the galvanometer mirror 612, the position where the light emitted from the excitation light source 611 is condensed is changed.

  According to the present configuration, the number of pumping light sources 611 smaller than the number (four) of the areas AR1 to AR4 can be provided, so that the number of parts of the multi-wavelength light source system 601 can be reduced and the size can be reduced. Can be achieved.

In the multi-wavelength light source system 601 according to this modification, the interval between two adjacent waveguide regions in the multi-wavelength light source device 101 can be narrowed (for example, about 3 μm). Further, the distance between the galvanometer mirror 612 and the multi-wavelength light source device 101 can be made longer than the interval between two adjacent waveguide regions. Then, when the waveguide regions WG1 to WG4 in the regions AR1 to AR4 are sequentially optically excited, the swing angle of the galvano mirror 612 can be made relatively small.
For example, the interval between the galvanometer mirror 612 and the multi-wavelength light source device 101 is set to 5 mm. In this case, when the place to be optically excited is changed from one of the two adjacent waveguide regions to the other, the angle of the galvanometer mirror 612 need only be changed by about 0.03 °.

  Thus, according to this configuration, for example, when the waveguide regions WG1 to WG4 in the regions AR1 to AR4 are sequentially optically excited (swept), the dynamic range of the swing angle of the galvanometer mirror 612 can be made relatively small. it can. Therefore, it is possible to shorten the time (sweep time) required for sequentially optically exciting all the waveguide regions WG1 to WG4.

(4) In the fourth embodiment, the example in which the current blocking layer 420 and the contact layer 421 of the multi-wavelength light source device 401 are formed by the epitaxial growth method has been described. However, the current blocking layer 420 and the contact layer 421 are not necessarily limited to those formed by the epitaxial growth method. For example, the current blocking layer 420 and the contact layer 421 may be formed by an ion implantation method.

FIG. 22 is a cross-sectional view of an incomplete product in each manufacturing process of the multi-wavelength light source device 801 according to this modification. In addition, about the structure similar to Embodiment 4, the same code | symbol is attached | subjected and description is abbreviate | omitted suitably. Further, FIG. 22 is a schematic diagram, and the thickness of each layer shown in FIG. 22 does not reflect the actually measured dimension.
As shown in FIG. 22A, first, as in the first embodiment, a sacrificial layer 456, a first cladding layer 418, three active layers 113, and an intermediate layer 114 are formed on a semiconductor substrate 415 by an epitaxial growth method. . Then, a second cladding layer 819 is formed on the active layer 113 located farthest from the semiconductor substrate 415 by an epitaxial growth method.
Next, a silicon oxide mask 911 covering a region other than a region where the electrode 417 is to be formed is formed on the second cladding layer 819 using an electron beam lithography technique and an etching technique.
Subsequently, impurity ions are implanted from the silicon oxide mask 911 into a region where the electrode 417 is to be formed by ion implantation. Here, for example, Be ions are implanted as P-type impurity ions. Thereafter, the contact layer 821 is formed by activating the impurities by performing heat treatment. Then, the silicon oxide mask 911 is removed using, for example, buffered hydrofluoric acid.

Next, as shown in FIG. 22B, a silicon oxide mask 912 covering the region where the electrode 417 is to be formed is formed on the contact layer 821 by using an electron beam lithography technique and an etching technique.
Subsequently, impurity ions are implanted into the region other than the region where the electrode 417 is to be formed from the silicon oxide mask 912 by ion implantation. Here, for example, Si ions are implanted as N-type impurity ions. Thereafter, by applying heat treatment, the impurity is activated and the current blocking layer 820 is formed. Then, the silicon oxide mask 912 is removed.

  Next, as shown in FIG. 22C, a resist mask 121 having a plurality of holes 121a is formed on the electrode 417 and the contact layer 421 by using a photolithography technique.

Thereafter, by performing the same process as the manufacturing direction described in the fourth embodiment, a multi-wavelength light source device 801 having a laminated structure 810 as shown in FIG. 22D is completed.
Here, the laminated structure 810 includes a first cladding layer 418, three active layers 113, two intermediate layers 114, a second cladding layer 819, a contact layer 821, a current blocking layer 820, and an electrode 417. And.

  According to this configuration, since the current blocking layer 820 is formed by an ion implantation method, the manufacturing method can be simplified as compared with a configuration in which the current blocking layer is formed by an epitaxial growth method.

In this modification, the example in which the current blocking layer 820 is formed by implanting N-type impurity ions has been described. However, the implanted ions are not limited to N-type impurity ions. The current blocking layer 820 may be formed by proton injection.
Specifically, hydrogen ions are implanted from the silicon oxide mask 912 into a region other than the region where the electrode 417 is to be formed, and then heat treatment is performed.

(5) Further, the inventors have investigated the polarization characteristics of the light emitted from the sample 1 when the waveguide region WG is optically excited with respect to the sample 1 according to the first embodiment.
FIG. 23 shows the result of examining the polarization characteristics of the light emitted from the sample 1 when the waveguide region WG is optically excited with respect to the sample 1 according to the first embodiment.
In FIG. 23, (a-1) is a waveguide in which the polarizer is disposed opposite to the sample 1 in the thickness direction of the sample 1 and the polarization angle of the polarizer is changed as shown in (a-2). It is the result of measuring the intensity spectrum of the light emitted in the thickness direction of the sample 1 from the region WG. Here, with respect to the polarization angle of the polarizer, the direction orthogonal to the longitudinal direction of the waveguide region WG is 0 °, and the direction parallel to the longitudinal direction of the waveguide region WG is 90 °.
In (b-1), as shown in (b-2), the polarizer is placed opposite to the sample 1 in the longitudinal direction of the waveguide region WG, and the polarization angle of the polarizer is changed. It is the result of measuring the intensity spectrum of the light emitted from the region WG in the longitudinal direction of the waveguide region WG. Here, with respect to the polarization angle of the polarizer, the direction orthogonal to the thickness direction of the sample 1 is 0 °, and the direction parallel to the thickness direction of the sample 1 is 90 °.

From the result shown in FIG. 23A-1, the light emitted from the waveguide region WG in the direction orthogonal to the thickness direction of the sample 1 is linearly polarized in the direction orthogonal to the longitudinal direction of the waveguide region WG. I understand that. Further, from the result shown in FIG. 21 (b-1), it is understood that the light emitted from the waveguide region WG in the longitudinal direction of the waveguide region WG is linearly polarized in the direction orthogonal to the thickness direction of the sample. .
Therefore, the inventors have devised a multi-wavelength light source system that combines the multi-wavelength light source device 101 described in Embodiment 1 and an optical switch element.

FIG. 24 is a schematic configuration diagram of a multi-wavelength light source system 701 according to this modification.
The multi-wavelength light source system 701 includes a multi-wavelength light source device 101, an optical switch element 711, and a control unit 712. Here, the optical switch element 711 can be switched between a state where light incident from the multi-wavelength light source 101 is transmitted and a state where light is not transmitted. The control unit 712 performs switching control for switching the optical switch element 711 to one of the two states.
The optical switch element 711 includes first and second polarizing plates 711a and 711b, and a polarization direction variable element 711c interposed between the first and second polarizing plates 711a and 711b.
The first polarizing plate 711a is disposed on the multi-wavelength light source 101 side of the optical switch element 711, and transmits light polarized in the first polarization direction PL1 perpendicular to the thickness direction of the multilayer structure 110 of the multi-wavelength light source 101.
The second polarizing plate 711b is disposed on the side opposite to the multi-wavelength light source 101 side of the optical switch element 711, and polarizes light polarized in the second polarization direction PL2 parallel to the thickness direction of the laminated structure 110 of the optical switch element 711. Make it transparent. That is, the polarization direction of the light that can be transmitted through the second polarizing plate 711b is shifted by 90 ° with respect to the polarization direction of the light that can be transmitted through the first polarizing plate 711a.

The polarization direction variable element 711c is composed of, for example, an element using a nematic liquid crystal, a Faraday rotation element, or the like, and is interposed between the first polarizing plate 711a and the second polarizing plate 711c. Then, the polarization direction variable element 711c causes the controller 712 to change the polarization direction of the light polarized in the first polarization direction PL1 to the second polarization direction PL2, and the polarization direction of the light polarized in the first polarization direction PL1. The state is switched to a state in which the polarization direction is other than the second polarization direction PL2.
Here, the polarization direction variable element 711c switches to one of the two states according to the change in the electric field applied from the control unit 712.

  The control unit 712 has a function of changing the electric field applied to the polarization direction variable element 711c of the optical switch element 711. The control unit 712 changes the electric field applied to the polarization direction variable element 711c of the optical switch element 711 to switch the optical switch element 711 between a state where light incident from the multi-wavelength light source 101 is transmitted and a state where it is not transmitted. .

  According to this configuration, both the excitation intensity of the waveguide regions WG1, WG2, WG3, and WG4 of the regions AR1, AR2, AR3, and AR4 of the multi-wavelength light source device 101 and the polarization angle of the polarizing element 711 are controlled. Thus, the amount of light emitted from the multi-wavelength light source system 701 can be controlled. Accordingly, since the control parameters of the multi-wavelength light source system 701 can be increased, it is possible to finely control the amount of light emitted from the multi-wavelength light source system 701.

(6) In the above embodiments and modifications, examples have been described in which the active layers 13 and 113 of the laminated structures 10, 110, 410, and 810 have quantum dots as light emitting materials. However, the light emitting material is not limited to quantum dots, and may be constituted of, for example, a quantum well structure or a quantum wire structure.
When the active layers 13 and 113 have a quantum well structure, the thickness of the well layer may be distributed. If the active layers 13 and 113 are quantum wires, the widths may be distributed.
According to this configuration, since laser oscillation can be generated at a relatively low excitation density in the active layer of the stacked structure, power consumption can be reduced.

<Appendix>
The technical scope of the present invention is not limited to the scope described in the above embodiment and the above modification. Various modifications or improvements can be added to the embodiment and the modified examples. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention. For example, a multi-wavelength light source device having an active layer in which quantum dots made of InAs are dispersed has been described, but quantum dots made of other materials (for example, gallium nitride (GaN) or zinc oxide (ZnO) materials) A multi-wavelength light source device having an active layer in which is dispersed.

  The present invention is suitable for a multi-wavelength light source used for optical communication. Further, it is also suitable as a multi-wavelength light source having a high-speed sweep property used in SS-OCT which is one of medical imaging techniques. It is also effective as a light source for an optical integrated circuit.

1 Sample 10, 110, 410, 810 Laminated structure 11, 111, 121a Void 13, 113 Active layer 14, 114 Intermediate layer 15, 115, 415 Semiconductor substrate 16, 116, 416 Bridge layer 16a, 116a Void 101, 201 , 401, 801 Multi-wavelength light source device 121 Resist mask 156, 456 Sacrificial layer 301, 601, 701 Multi-wavelength light source system 311A, 311B, 311C, 311D, 611 Excitation light source 313A, 313B, 313C, 313D, 613 Scan lens 417, 422 Electrode 418 First cladding layer 419, 819 Second cladding layer 420, 820 Current blocking layer 421, 821 Contact layer 457 Metal layer 511, 911, 912 Silicon oxide mask 512 Resist mask 612 Galvano mirror 71 1 optical switch element 712 controller r1, r2 hole radius a1, a2 hole interval AR1, AR2, AR3, AR4, AR5, AR21, AR22, AR23, AR24 region PC1, PC2, PC3, PC4, PC5, PC21, PC22 , PC23, PC24 Photonic crystal region WG1, WG2, WG3, WG4, WG5, WG21, WG22, WG23, WG24 Waveguide region PA1, PA2, PA3, PA4 Light propagation path

Claims (11)

Comprising a laminated structure having an active layer and the intermediate layer, the laminated structure includes a first photonic crystal region constituting the two-dimensional photonic crystal, said first photonic crystal regions on both sides in the width direction adjacent and then the photonic crystal region can not propagate a portion of the first waveguide region a plurality of light capable propagation of the second wavelength band of light in the first wavelength band, light propagating in the plurality of first waveguide region An optical transmission unit capable of propagating
In the active layer , the wavelength of light corresponding to the energy difference between the electron levels capable of optical transition is included in the high state density wavelength band of the second wavelength band ,
The plurality of first waveguide regions are provided in parallel and include at least two first waveguide regions including one first waveguide region and another first waveguide region,
The optical transmission unit is
A second photonic crystal region constituting a two-dimensional photonic crystal;
A second waveguide region in which the second photonic crystal region is adjacent to both sides in the width direction and a part of the fourth wavelength band light that cannot propagate through the second photonic crystal region can propagate. When,
Have
The plurality of first waveguide regions provided in parallel are connected to the second waveguide region,
A center wavelength of the high state density wavelength band in each of the plurality of first waveguide regions is included in the fourth wavelength band, and a center wavelength of the high state density wavelength band in the other first waveguide regions is Than the center wavelength of the high state density wavelength band in the one first waveguide region is on the longer wavelength side in the fourth wavelength band,
The short wavelength side end of the second wavelength band in the other first waveguide region is within the fourth wavelength band than the short wavelength side end of the second wavelength band in the one first waveguide region. Multi-wavelength light source device on the long wavelength side . The multi-wavelength light source device according to claim 1, wherein the second wavelength band and the high state density wavelength band in each of the plurality of first waveguide regions are different from each other. The photonic crystal region is a region in the stacked structure in which a plurality of holes penetrating in the thickness direction of the stacked structure and periodically parallel to the direction perpendicular to the thickness direction of the stacked structure are formed. And
The first wavelength band, the second wavelength band, and the high state density wavelength band are at least one of a hole interval of the plurality of holes, a size of each of the plurality of holes, and a thickness of the multilayer structure. The multi-wavelength light source device according to claim 1, which is determined based on The high state density wavelength band of any one of the plurality of first waveguide regions exists on a shorter wavelength side than the second wavelength band of the other first waveguide regions . The multi-wavelength light source device according to any one of the above. The second photonic crystal region is formed with a plurality of holes penetrating in the thickness direction of the multilayer structure and periodically parallel to a direction perpendicular to the thickness direction of the multilayer structure in the multilayer structure. Area,
The third wavelength band and the fourth wavelength band are determined based on at least one of a hole interval of the plurality of holes, a size of each of the plurality of holes, and a thickness of the multilayer structure. The multi-wavelength light source device according to claim 4 . The multiwavelength light source device according to any one of claims 1 to 5 , wherein the active layer includes a plurality of quantum dots. The plurality of quantum dots have a size distribution;
The size distribution is set so that a wavelength band of light emitted from the plurality of quantum dots includes all of the high state density wavelength bands of the plurality of first waveguide regions. The multi-wavelength light source device according to any one of 6 . The multi-wavelength light source device according to any one of claims 1 to 7 ,
An excitation light source that irradiates excitation light to each of the plurality of first waveguide regions of the multi-wavelength light source device. The multi-wavelength light source system according to claim 8 , wherein a plurality of the excitation light sources are provided for each of the plurality of first waveguide regions. The multi-wavelength light source system according to claim 9 , wherein the excitation light source sequentially irradiates each of the plurality of first waveguide regions with excitation light in a time division manner. Multi-wavelength light source apparatus according to any one of claims 1 to 7, further comprising a plurality of electrodes provided for each of the plurality of first waveguide region of the laminated structure.