JPH0514436B2 - - Google Patents
Info
- Publication number
- JPH0514436B2 JPH0514436B2 JP63199357A JP19935788A JPH0514436B2 JP H0514436 B2 JPH0514436 B2 JP H0514436B2 JP 63199357 A JP63199357 A JP 63199357A JP 19935788 A JP19935788 A JP 19935788A JP H0514436 B2 JPH0514436 B2 JP H0514436B2
- Authority
- JP
- Japan
- Prior art keywords
- phase shift
- mode
- semiconductor laser
- distributed feedback
- coupled distributed
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
- 230000010363 phase shift Effects 0.000 claims description 22
- 239000004065 semiconductor Substances 0.000 claims description 14
- 238000010586 diagram Methods 0.000 description 7
- 230000010355 oscillation Effects 0.000 description 6
- 238000005253 cladding Methods 0.000 description 3
- 239000006185 dispersion Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 229910000980 Aluminium gallium arsenide Inorganic materials 0.000 description 2
- 229910001218 Gallium arsenide Inorganic materials 0.000 description 2
- 229910000530 Gallium indium arsenide Inorganic materials 0.000 description 2
- 230000003595 spectral effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 230000005428 wave function Effects 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S5/00—Semiconductor lasers
- H01S5/10—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region
- H01S5/12—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers
- H01S5/124—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers incorporating phase shifts
- H01S5/1246—Construction or shape of the optical resonator, e.g. extended or external cavity, coupled cavities, bent-guide, varying width, thickness or composition of the active region the resonator having a periodic structure, e.g. in distributed feedback [DFB] lasers incorporating phase shifts plurality of phase shifts
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、発振周波数が安定しており、スペク
トル幅の狭い半導体レーザに関するものである。DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor laser having a stable oscillation frequency and a narrow spectrum width.
発振周波数が安定している結合分布帰還型半導
体レーザ（DFBレーザ）の従来例の主要部を第
６図に示す。この第６図に示す構造では、スペク
トル幅を狭くするために共振器長を長くすると、
中心付近の高強度が高くなりすぎて、空間的ホー
ルバーニングを生じモードが不安定になる。これ
を改善するためには、第７図に示す結合位相シフ
ト分布帰還（DFB）構造が有効である。
FIG. 6 shows the main parts of a conventional coupled distributed feedback semiconductor laser (DFB laser) with a stable oscillation frequency. In the structure shown in Fig. 6, when the resonator length is lengthened to narrow the spectral width,
The high intensity near the center becomes too high, causing spatial hole burning and making the mode unstable. In order to improve this, a combined phase shift distributed feedback (DFB) structure shown in FIG. 7 is effective.
しかしながら、前記の従来構造では、発振周波
数とフラツグ周波数との差δが０のモードは、最
低次モードとならず、δ≠０である２つのモード
が最低次モードとなるため、この最低次モードを
抑圧する方法でレーザ動作させなければならない
という問題があつた。
However, in the conventional structure described above, the mode in which the difference δ between the oscillation frequency and the flag frequency is 0 is not the lowest-order mode, but the two modes in which δ≠0 are the lowest-order modes. The problem was that the laser had to be operated in a way that suppressed the
更に、これを改善するために、第８図のように
３箇所の位相シフト量φをλ／４からずらせる構
造が提案されている。ここで、λはレーザ光の波
長である、しかし、この第８図に示す構造では、
δが０にならないため発振周波数がサンプルごと
にバラツクという問題があつた。 Furthermore, in order to improve this problem, a structure has been proposed in which the phase shift amount φ at three locations is shifted from λ/4 as shown in FIG. Here, λ is the wavelength of the laser beam, but in the structure shown in FIG.
Since δ did not become 0, there was a problem that the oscillation frequency varied from sample to sample.
なお、第６図〜第８図において、１１，１３は
例えばInP、AlGaAs等からなるクラツド層、１
２は例えばInGaAs、GaAs等からなる活性層で
ある。 In addition, in FIGS. 6 to 8, 11 and 13 are cladding layers made of, for example, InP, AlGaAs, etc.
2 is an active layer made of, for example, InGaAs or GaAs.
本発明は、前記問題点を解決するためになされ
たものである。 The present invention has been made to solve the above problems.
本発明の目的は、δ＝０のモードが最低次で存
在し、かつモード分布が平坦になる結合分布帰還
型半導体レーザを提供することにある。 An object of the present invention is to provide a coupled distributed feedback semiconductor laser in which the mode of δ=0 exists at the lowest order and the mode distribution is flat.
本発明の前記ならびにその他の目的と新規な特
徴は、本明細書の前述及び添付図面によつて明ら
かになるであろう。 The above and other objects and novel features of the present invention will become apparent from the foregoing of this specification and the accompanying drawings.
前記目的を達成するために、本発明は、３箇所
の位相シフト部位を有する結合分布帰還型半導体
レーザであつて、真中の位相シフト量がλ／４で
あり、両側の位相シフトが０、−１、１を除く−
１と１の間のパラメータｑに対してλ（１＋
ｑ）／４及びλ（１−ｑ）／４であり、かつこの
３箇所の位相シフトにより４分割された各部分の
長さが端から順にＬ（１＋ｄ）／４、Ｌ（１−
ｄ）／４、Ｌ（１−ｄ）／４、Ｌ（１＋ｄ）／４で
あり、但しλはレーザ光の波長、Ｌは半導体レー
ザの全長、ｄは−１と１を除く−１と１の間の数
であることを最も主要な特徴とする。
In order to achieve the above object, the present invention provides a coupled distributed feedback semiconductor laser having three phase shift sites, in which the phase shift amount at the center is λ/4, and the phase shifts at both sides are 0, -. 1, except 1-
λ(1+
q)/4 and λ(1-q)/4, and the length of each portion divided into four by the phase shift at these three locations is L(1+d)/4, L(1-q)/4 in order from the end.
d)/4, L(1-d)/4, L(1+d)/4, where λ is the wavelength of the laser beam, L is the total length of the semiconductor laser, and d is -1 and 1 excluding -1 and 1. The most important feature is that the number is between .
前述の手段によれば、３箇所ある位相シフトを
φ1＝λ（１＋ｑ）／４、φ2＝λ／４、φ3＝λ（１
−ｑ）／４、但し−１＜ｑ＜０、０＜ｑ＜１と
し、この位相シフトで４分割された各部分の長さ
l1、l2、l3、l4をそれぞれl1＝l4＝Ｌ（１＋ｄ）／
４、l2＝l3＝Ｌ（１−ｄ）／４とし、但し−１＜ｄ
＜１と設定することにより、前述のδ＝０のモー
ドが最低次で存在し、かつモード分布が平担にな
る結合分布帰還型半導体レーザを提供することが
できる。
According to the above-mentioned means, the phase shifts at three positions are φ 1 =λ(1+q)/4, φ 2 =λ/4, φ 3 =λ(1
-q)/4, where -1<q<0, 0<q<1, and the length of each portion divided into four by this phase shift
l 1 , l 2 , l 3 , l 4 respectively l 1 = l 4 = L(1+d)/
4, l 2 = l 3 = L(1-d)/4, where -1<d
By setting <1, it is possible to provide a coupled distributed feedback semiconductor laser in which the mode of δ=0 described above exists at the lowest order and the mode distribution is flat.
すなわち、従来の構造はφ1＝φ2＝φ3であり、
前述のｑ＝０の場合のみがこれと重複するが、本
発明ではｑ≠０が特徴である。 That is, the conventional structure is φ 1 = φ 2 = φ 3 ,
Only the case of q=0 described above overlaps with this, but the present invention is characterized by q≠0.
以下、本発明の一実施例を図面を用いて具体的
に説明する。
Hereinafter, one embodiment of the present invention will be specifically described using the drawings.
第１図は、本発明の一実施例の結合分布帰還型
半導体レーザの概略構成を説明するための要部断
面図である。 FIG. 1 is a sectional view of a main part for explaining the schematic structure of a coupled distributed feedback semiconductor laser according to an embodiment of the present invention.
本実施例の結合分布帰還型半導体レーザは、第
１図に示すように、例えばInP、AlGaAs等から
なるクラツド層１とクラツド層３の間に、例えば
InGaAs、GaAs等からなる活性層２が設けられ
ている。そして、位相シフト量がφ1＝λ（１＋
ｑ）／４、φ2＝λ／４、φ3＝λ（１−ｑ）／４で
ある光位相シフト部分３箇所を有し、これに分割
された４つの部分の長がＬ（１＋ｄ）／４、Ｌ（１
−ｄ）／４、Ｌ（１−ｄ）／４、Ｌ（１＋ｄ）／４
であるような結合分布帰還型構造になつている。 As shown in FIG. 1, the coupled distributed feedback semiconductor laser of this embodiment has, for example, a layer between a cladding layer 1 and a cladding layer 3 made of, for example, InP, AlGaAs, etc.
An active layer 2 made of InGaAs, GaAs, etc. is provided. Then, the phase shift amount is φ 1 =λ(1+
q)/4, φ 2 = λ/4, φ 3 = λ(1-q)/4, and the length of the four divided portions is L(1+d). /4, L(1
-d)/4, L(1-d)/4, L(1+d)/4
It has a joint distribution feedback type structure.
一般に、位相シフト部分を有する結合分布帰還
（DFB）構造のモードは、次の結合モード方程式
(1)、(2)を解くことで決定される。 In general, the modes of a coupled distributed feedback (DFB) structure with a phase-shifted part are expressed by the following coupled mode equation:
It is determined by solving (1) and (2).
−dR／dZ＋（α−jδ）Ｒ＝jxS ……(1)
dS／dZ＋（α−jδ）Ｓ＝jxR ……(2)
ここで、Ｒ、Ｓは右進行、左進行の光の波動関
数、ｘは光帰還の強さを表わすパラメータであ
り、結合分布帰還構造の溝の深さに比例する量で
ある。しきい値ゲインαとδは、式(1)及び式(2)を
境界条件のもとで解くことで求まる。-dR/dZ+(α-jδ)R=jxS...(1) dS/dZ+(α-jδ)S=jxR...(2) Here, R and S are the wave functions of light traveling to the right and to the left , x is a parameter representing the strength of optical feedback, and is a quantity proportional to the depth of the groove of the coupled distributed feedback structure. The threshold gains α and δ are found by solving equations (1) and (2) under boundary conditions.
φ1＝φ2＝φ3＝λ／５、ｘ＝2.5の場合のαとδの
関係（分数姿数）の計算結果を第２図に示す。FIG. 2 shows the calculation results of the relationship between α and δ (fractional figure number) in the case of φ 1 =φ 2 =φ 3 =λ/5 and x=2.5.
この場合、最低次（αが最小）のモードはδ≠
０となる。同様な計算を他の様々な構造で行つた
結果、第１図の構造の場合δ＝０にモードが存在
することを発明者は見出した。 In this case, the lowest order (α is the smallest) mode is δ≠
It becomes 0. As a result of performing similar calculations on various other structures, the inventor found that in the structure shown in FIG. 1, a mode exists at δ=0.
第１図の構造の範囲で、δ＝０のモードのαと
それ以外のモードの内の最低次モードとの差Δα
を計算した結果を第３図の点線で等高線として示
した。Δα＜０（斜線領域）は、δ＝０のモードが
最低次にならない領域である。 Within the structure of Figure 1, the difference Δα between α of the mode with δ = 0 and the lowest mode among the other modes
The calculated results are shown as dotted contour lines in Figure 3. Δα<0 (shaded region) is a region where the mode of δ=0 does not become the lowest order.
結合分布帰還構造ではモード分布が平担になる
ため、長共振器構造でも安定になる。モード分布
の平担さは次の関数Ｆで定義できる。 Since the mode distribution becomes flat in the coupled distributed feedback structure, even a long resonator structure becomes stable. The flatness of the mode distribution can be defined by the following function F.
Ｆ＝∫0/L（Ｉ(Z)−I0）2dZ ……(3)
但し、強度Ｉ(Z)＝｜Ｒ｜2＋｜Ｓ｜2であり、I0
は強度Ｉ(Z)の平均値である。ｘを最適にした時の
モード分布の平担さの関数Ｆのｄ及びｑ依存性の
等高線を第３図の実線に示した。最も平担になる
のはｑ＝0.4、ｄ＝０の構造であり、単一位相シ
フトの場合に比べＦは約1/6になる。この構造の
モード分布及び分散関数を第４図及び第５図に示
した。この構造でレーザ動作をさせた時のスペク
トル幅は、長共振器効果により単一位相シフトの
場合と比較して1/5になる。 F=∫ 0/L (I(Z)−I 0 ) 2 dZ ...(3) However, the intensity I(Z)=|R| 2 + |S| 2 , and I 0
is the average value of intensity I(Z). The solid line in FIG. 3 shows the contour lines of the d and q dependence of the function F of the flatness of the mode distribution when x is optimized. The structure with q=0.4 and d=0 is the most flat, and F is about 1/6 of that in the case of a single phase shift. The mode distribution and dispersion function of this structure are shown in FIGS. 4 and 5. When operating a laser with this structure, the spectral width is reduced to 1/5 compared to the case with a single phase shift due to the long cavity effect.
以上の説明からわかるように、本実施例によれ
ば、結合分布帰還構造を用い、モード分布が平担
で長共振器化に対し安定なレーザ実現する際、第
１図に示すような対称性を有する構造にしている
ため、δ＝０のモードで発振するようにできる利
点がある。これは、このレーザをコヒーレント光
伝送システムや光センサシステムなどに用いる
際、発振周波数のバラつきが小さくなりシステム
全体の安定性が増加する利点がある。 As can be seen from the above explanation, according to this example, when realizing a laser with a flat mode distribution and stable against a long cavity by using a coupled distributed feedback structure, the symmetry as shown in FIG. Since the structure has the following, there is an advantage that oscillation can be made in the mode of δ=0. This has the advantage that when this laser is used in a coherent optical transmission system, an optical sensor system, etc., variations in the oscillation frequency are reduced and the stability of the entire system is increased.
以上、本発明を実施例にもとづき具体的に説明
したが、本発明は、前記実施例に限定されるもの
ではなく、その要旨を逸脱しない範囲において
種々変更可能であることは言うまでもない。 Although the present invention has been specifically described above based on Examples, it goes without saying that the present invention is not limited to the above-mentioned Examples, and can be modified in various ways without departing from the gist thereof.
以上、説明したように、本発明によれば、３箇
所の位相シフト部位を有する結合分布帰還型半導
体レーザであつて、真中の位相シフト量をλ／４
にし、両側の位置シフトが０、−１、１を除く−
１と１の間のパラメータｑに対してλ（１＋
ｑ）／４及びλ（１−ｑ）／４にし、かつこの３
箇所の位置シフトにより４分割された各部分の長
さが端から順にＬ（１＋ｄ）／４、Ｌ（１−ｄ）／
４、Ｌ（１−ｄ）／４、Ｌ（１＋ｄ）／４にするこ
とにより、δ＝０のモードが最低次で存在し、か
つモード分布が平担になる結合分布帰還型半導体
レーザを提供することができる。
As described above, according to the present invention, it is a coupled distributed feedback semiconductor laser having three phase shift parts, and the phase shift amount at the center is set to λ/4.
and the position shift on both sides is 0, -1, except 1 -
λ(1+
q)/4 and λ(1-q)/4, and this 3
The length of each part divided into four by shifting the position of the part is L (1 + d) / 4, L (1 - d) / in order from the end.
4. By setting L(1-d)/4 and L(1+d)/4, a coupled distributed feedback semiconductor laser is provided in which the mode of δ=0 exists at the lowest order and the mode distribution is flat. can do.
第１図は、本発明の一実施例の結合分布帰還型
半導体レーザの概略構成を説明するための要部断
面図、第２図は、結合位相シフトDFB構造を４
等分割している３箇所の位相シフト量が等しく
λ／５でｘが2.5である構造の分散関数の図、第
３図は、本発明の構造において構造パラメータ
ｄ、ｑを変化させた時のΔα（点線）及びＦ（実線）
の計算値の等高線図、第４図及び第５図は、本発
明の構造でｄ＝０、ｄ＝0.4の構造のレーザにつ
いてのモード分布及び分散関数の図、第６図は、
従来構造である単一位相シフトDFB構造図、第
７図は、他の従来構造の結合位相シフトDFB構
造図、第８図は、他の従来構造の結合位相シフト
DFB構造図である。
図中、１，３……クラツド層、２……活性層。
FIG. 1 is a sectional view of the main parts for explaining the schematic configuration of a coupled distributed feedback semiconductor laser according to an embodiment of the present invention, and FIG. 2 is a sectional view of a coupled phase shift DFB structure.
Figure 3 is a diagram of the dispersion function of a structure in which the phase shift amount at three equally divided locations is equal to λ/5 and x is 2.5. Δα (dotted line) and F (solid line)
Figures 4 and 5 are contour diagrams of the calculated values of , and Figures 4 and 5 are diagrams of the mode distribution and dispersion function for the laser having the structure of the present invention with d = 0 and d = 0.4, and Figure 6 is
Figure 7 is a diagram of the single phase shift DFB structure of a conventional structure. Figure 7 is a diagram of the combined phase shift DFB structure of another conventional structure. Figure 8 is a diagram of the combined phase shift DFB of another conventional structure.
It is a DFB structure diagram. In the figure, 1, 3... clad layer, 2... active layer.
Claims (1)
還型半導体レーザであつて、真中の位相シフト量
がλ／４であり、両側の位相シフトが０、−１、
１を除く−１と１の間のパラメータｑに対してλ
（１＋ｑ）／４及びλ（１−ｑ）／４であり、かつ
この３箇所の位相シフトにより４分割された各部
分の長さが端から順にＬ（１＋ｄ）／４、Ｌ（１−
ｄ）／４、Ｌ（１−ｄ）／４、Ｌ（１＋ｄ）／４で
あり、但しλはレーザ光の波長、Ｌは半導体レー
ザの全長、ｄは−１と１を除く−１と１の間の数
であることを特徴とする結合分布帰還型半導体レ
ーザ。1 A coupled distributed feedback semiconductor laser having three phase shift sites, in which the phase shift amount in the center is λ/4, and the phase shifts on both sides are 0, -1,
λ for parameter q between −1 and 1 except 1
(1+q)/4 and λ(1-q)/4, and the length of each portion divided into four by the phase shift at these three locations is L(1+d)/4 and L(1-q)/4 in order from the end.
d)/4, L(1-d)/4, L(1+d)/4, where λ is the wavelength of the laser beam, L is the total length of the semiconductor laser, and d is -1 and 1 excluding -1 and 1. A coupled distributed feedback semiconductor laser characterized in that the number is between.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63199357A JPH0247887A (en) | 1988-08-10 | 1988-08-10 | Coupling distribution feedback type semiconductor laser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63199357A JPH0247887A (en) | 1988-08-10 | 1988-08-10 | Coupling distribution feedback type semiconductor laser |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0247887A JPH0247887A (en) | 1990-02-16 |
| JPH0514436B2 true JPH0514436B2 (en) | 1993-02-25 |
Family
ID=16406417
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63199357A Granted JPH0247887A (en) | 1988-08-10 | 1988-08-10 | Coupling distribution feedback type semiconductor laser |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0247887A (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP3186705B2 (en) | 1998-08-27 | 2001-07-11 | 日本電気株式会社 | Distributed feedback semiconductor laser |
| US6574261B2 (en) | 1998-08-27 | 2003-06-03 | Nec Corporation | Distributed feedback semiconductor laser |
| US6946050B2 (en) * | 2003-01-27 | 2005-09-20 | Nike, Llc | Method for flange bonding |
-
1988
- 1988-08-10 JP JP63199357A patent/JPH0247887A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0247887A (en) | 1990-02-16 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| LAPS | Cancellation because of no payment of annual fees |